Size, demography, ownership profiles, and identification rate of the owned dog population in central Italy.

The One Health paradigm recognizes that information on infectious diseases, zoonosis and related predictors in animal populations is essential. Pets live in close contact with humans and interact with wild animals, but the lack of reliable information on pet population size, demography and ownership profiles is a constant worldwide. Reliable data must be made available in order to address proper public health policies regarding the design of surveillance plans, the management of canine welfare and stray dog phenomenon, the control of dog behaviour-related problems, and the livestock/wildlife endangerment. Dog identification & registration (I&R) have become mandatory in most European countries in recent years, but the process is far from being widely accomplished, thus resulting in an underestimation of the real canine population. To date, data on the completeness of Dog Registries is very limited. A cross-sectional survey through 630 face-to-face questionnaires was performed with the aim of investigating the dog population size, demography, ownership profiles, and the I&R rate in central Italy. Logistic regression models investigated risk factors with the following outcome variables: dog presence into the Dog Registry, veterinary care frequency, and dog ownership. The present study identified that the dog population is higher than previously reported in Italy and in Europe, whilst lower compared to countries with a poor Human Development Index (a statistic composite index of life expectancy, education, and per capita income indicators used by United Nation). Almost half of the interviewed people (47%) owned at least one dog, totalling 315 dogs. The mean number of dogs per household was 0.7 and 1.5 per dog-owning household. The Bayesian model estimated 481,294 (95% CI: 470,860-491,978) dogs (90 dogs/km2; human:dog ratio 9.0, 95% CI: 8.8-9.2) suggesting that a high density of people does not limit the dog ownership. Dogs resulted predominant among pets. The majority of dogs were males, crossbred, acquires as a gift, lived in rural areas, outdoors and attended a veterinary visit 1-2 times per year. The percentage of neutered dogs were higher in females (55%) than in males (8%). Only 75.3% (95% CI: 73.6-76.9) of the dogs were correctly identified and registered. The Dog Registry completeness increased during the first decades after its establishment, but no improvement has been made afterwards. The dogs correctly identified and registered were more likely to be purebred, neutered, lived in urban areas and visited a veterinarian frequently. Several strategies are recommended to encourage I&R, including promoting responsible dog ownership, engaging private veterinarians and dog breeders, and establishing an effective control system. The present study identified also that the dog source and the kind of feeding were variables associated with the veterinary care frequency. Owning a dog was associated with living in rural areas and the presence of children. The present study reported the poor presence of reliable predictors for the dog ownership. This is the first study to provide an estimate of the canine population abundance, characteristics, and ownership profiles in a European large metropolitan area.

Introduction

The One Health paradigm recognizes that standardized and complete information on infectious diseases, zoonoses and risk factors related to their spatial and temporal distributions in pet population is essential [1]. Pet dogs and cats live in close contact with humans and can interact with other pets and wild animals. Therefore, the knowledge of animal populations in terms of size, demographic characteristics, and ownership profiles is a key tool of the whole process. While in livestock species rules on the identification, the registration and related information on abundance, descriptive records (sex, age, breed, owners, etc) and informative systems to manage these data have been developed on a large-scale basis, the lack of information in pet populations is a constant worldwide.

Canine population size

Several papers have been published on owned dog population estimates. Some studies measured the human:dog ratio (HDR), some estimated the percentage of dog-owning households (HH) or the mean number of dogs per HH and others calculated the regression coefficient for predictors [2]. The World Health Organization (WHO) estimated a HDR between 6 and 10 in American and European countries and a ratio varying from 7 to 10 in ‘developing countries’ [3, 4]. Pets are widely present in European HH and their numbers show a growing trend. The number of dogs estimated by the pet food industry in Europe is 85,184,000 [5]. The same source assessed 7,002,000 pet dogs in Italy (i.e. HDR 8.6), while the Italian Ministry of Health recorded 11,753,180 dogs (i.e. HDR 5) [6].

Identification & registration rate: Dog Registry

In most European countries, dog identification and registration (I&R) have become mandatory in recent years [7]. Nevertheless, while identification is performed on an individual basis, registration in a central accessible database (a Dog Registry–DR) is not compulsory in some countries or not implemented effectively in others. Consequently, the completeness of DRs is far from being achieved [7] and little data are published on this topic. To date, reliable data on the dog population abundance are provided by industry or ad hoc surveys rather than managed within an institutional framework [1]. In Italy, since 1991, every owned dog and stray dog caught by the competent authorities must be identified by an electronic transponder (microchip) and registered in a DR (Framework Law 281/1991). The main aim of the law was to contrast the phenomenon of abandoning dogs. Both private and public veterinarians have access to the DR and they can visualize or manage data of both the animals and owners (e.g. sex, age, breed, address, owner, transfer, date of birth/death, etc.). Since the DR establishment, many information campaigns have been organised toward the general population through radio, newspaper, social media, leaflet and advertising posters. The I&R costs are affordable (about 15€).

The accuracy of the DR is uncertain because there is no active control on dog I&R. Most of stakeholders think that the only purpose of the DR is the reunification of lost dogs with their owners, underestimating the epidemiological relevance of population abundance assessment. The rabies vaccination campaigns in 2008 in Veneto Region (north Italy) and the public health activities in the 2016 earthquake emergency (central Italy) indicated that many dogs were not registered and not identified [8]. A previous study carried out to assess the completeness of the DR in a densely populated area of Rome found that only 75% of the dogs were registered [9]. These findings show that the real owned population is likely underestimated in DRs. Therefore, a periodic assessment of the DR completeness is appropriate and factors influencing owners to register a dog are worth investigating.

Canine population demography

Information on demography of dog population are underprovided despite the relevance in public health and industrial fields. Demography is essential for the investigation, management and control of several disease and health issues to be addressed by private veterinarians and public health authorities. The dog breed and the living environment can represent risk factors for the susceptibility of transmissible diseases and degenerative or neoplastic diseases [10]. These factors can be supposed to be related to aggressive behaviour responsible of the dog biting phenomenon and its consequences, such as human and animal injuries and rabies vaccination [11]. Furthermore, the role of dogs as sentinel animals for environmental hazards is particularly important in comparative medicine [12]. The age structure of the dog population can be useful for the private sector to predict which health and commercial services to provide and for public health authorities to predict costs of surveillance and control plans. Additionally, there is very little published information about pet veterinary care. Determinants of the veterinary visit frequency need to be assessed and evaluated, because pet access to veterinary assistance is an essential factor in improving animal health and welfare.

Ownership profiles

A few studies reported reliable predictors for the dog ownership worldwide and there is only one published study in Italy [13-17]. The responsible ownership, defined by the World Animal Health Organisation (OIE) as “the situation whereby a person accepts and commits to perform various duties according to the legislation in place and focused on the satisfaction of the behavioural, environmental and physical needs of a dog and to the prevention of risks (aggression, disease transmission or injuries) that the dog may pose to the community, other animals or the environment” has been recognised by the WHO and the OIE as the main strategy to manage pet population health and welfare [3, 18]. Therefore, collecting data on the owners’ attitude and characteristics has an impact on strategies that can be applied to monitor and enhance individual and community animal health.

The aims of this study were to estimate the canine owned population size, to evaluate the rate of identification and registration into the DR, to study the demography of the owned dog population, and to identify the human factors influencing the dog ownership.

Materials and methods

Study area and survey

The study area was Rome province, covering 5,363 Km2 with a population of 4,331,856 inhabitants (population density: 807.7/Km2). It consists of a metropolis (Rome, 2,839,042 inhabitants) and 120 municipalities surrounded by farmed lands and wooded areas located between the coast and inland territories [19]. The average elevation is 269 meters above sea level and the annual average temperature is 14.5° C. The use of the land was mainly (49%) aimed at agricultural activities, 37% was covered by forest and pastures, 10% was represented by urban area and 4% was classified as another use [20].

Questionnaires data were collected in a District of the Rome province called “Rome 6”. It covers 726.7 Km2 with a population of 539,445 inhabitants. It is located between the Tyrrhenian coast and inland territories. The survey was carried out during weekdays between the months of July and December 2013 in the waiting rooms of 4 General Health Care Centres of the National Health System. A systematic sampling was performed by selecting one in every four person amongst the general diagnostic patients. Survey participation was requested within the framework of a research project on human and animal tumours managed by the Ministry of Health. More details were described in a published study [21].

Two different sample sizes were calculated for the different aims of the research. To calculate the required sample size for the evaluation of the DR, an expected prevalence of 75%, a standard error of 5% and a confidence level of 90% were assumed, resulting in 203 questionnaires to be administered to people owning at least one dog. The expected prevalence was intended as the percentage of dog correctly identified and registered into the DR, which resulted 75% in a study performed in a close area [9].

The required sample size for the study of the dog demography and ownership profiles was 664, assuming a 5% of standard error, an unknown prevalence (i.e. 50%) and a 99% of confidence level.

Questionnaire design

A cross-sectional survey on pet ownership through a face-to-face questionnaire was performed. A detailed description of the survey methodology is provided in a previously published study and in the supporting information [21]. Each person selected for the interview was asked whether they resided in the study area and then provided with information on the survey. The participants were asked whether they owned a dog and/or other pets, the number of owned pets, the characteristics of the owned dog (sex, neutering, breed, age), the source of the dog (born in house, found, gift, adopted from a shelter, purchased), the kind of environment the dog usually lived in (urban/rural area, mainly outdoor/indoor), the kind of feeding (homemade, commercial, mixed), the annual average veterinary care frequency (never, 1–2 times a year, 3 or more times), the number of family members, the presence of children, and the status of identification and registration of the dog into the DR. The final section of the questionnaire collected the personal information of the participant (gender, age, marital status, education level, occupation, habitat–i.e. urban/rural area). In order to have a conservative approach, the presence into the DR was considered as a dichotomous variable where the answer “do not know” was considered as “no”. The definition of the dog ownership was based on the respondent’s definition. Interviewers emphasized the care provided in terms of regular feeding and health status. The physical restriction of the animal was not taken into consideration.

Data analysis

The information gathered during the survey was entered into an ad hoc Microsoft Access® database (Microsoft Office® 2003). All variables were reported as absolute frequency and percentage (%).

A Bayesian approach was adopted to estimate the size of the canine population based on dogs registered in the DR. Based on data from a similar previous investigation [9], a beta distribution (α1 = 287, α2 = 98) was used as a prior to determine the probability that a dog was correctly registered, while the likelihood function was modelled using the data from the present study as a binomial distribution (s = 183, n = 315). Since the beta prior is conjugate to a binomial likelihood, the resulting posterior distribution was a beta distribution with parameters α’1 = α1 + s and α’2 = α2 + n–s, respectively [22]. Then, we used a simple model to calculate the mean and 95% confidence intervals (CI) of the dog population size in Rome province: where P is a random value generated from a beta distribution with the mentioned parameters (R 3.6.1, rBeta 2009 v 1.0 package, 100,000 iterations) and Nreg is the number of registered dogs in the DR (362,277).

Data regarding the DR were collected from the Regional DR Database [23]. In order to eliminate the bias of possible dogs deaths not reported, the animals over the age of 16 years were not counted.

The effect of the exposure variables on three outcome variables (presence of a dog into the DR, frequency of veterinary visit and owning of a dog) was analysed using logistic regression models. Risk factors with a bivariate p value ≤0.25 were included in a multivariable stepwise logistic model [24]. Chi square test and phi coefficient were used to evaluate a possible multicollinearity among risk factors that were significantly associated with the outcomes. The absence of plausible interactions among variables were tested in all regression models. In logistic regression analyses with DR and veterinary care considered as outcome variables (Tables 2 and 3), the HH was included in order to ensure the independence of observations (i.e. an owner owning more than one dog having the same behaviour or attitude with all the dogs). In the logistic regression analysis regarding dog ownership profiles (Table 4), the outcome variable was represented by the owner and not by the dog, avoiding the overrepresentation of HHs with more than one dog.

Table 2

Descriptive, univariable and multivariable logistic analysis of characteristics associated with dogs registered in the Dog Registry in central Italy in 2013.

Dog Registry
	No/Do not know (N = 182)(%)	Yes (N = 130)(%)	Univariable analysis OR (95% CI)	Multivariable model OR (95% CI)
Sex
Male	78 (60)	86 (47)	-
Female	54 (40)	96 (53)	1.6 (1.0–2.6)*
Missing	1	0
Age (years)
≤2	36 (29)	43 (24)	-
2.1–8	52 (42)	99 (56)	1.5 (0.9–2.7)
>8	37 (30)	34 (19)	0.7 (0.4–1.4)
Missing	6	6
Breed
Crossbred	78 (61)	83 (47)	-	-
Purebred	50 (39)	93 (53)	1.7 (1.1–2.8)*	1.7 (1.0–2.8)*
Missing	2	6
Source
Born in house	7 (6)	10 (6)	-
Found	31 (25)	33 (18)	0.7 (0.3–2.2)
Adopted	9 (7)	18 (10)	1.5 (0.4–5.2)
Gift	68 (54)	77 (43)	0.8 (0.3–2.2)
Purchased	10 (8)	42 (23)	2.9 (0.9–9.6)
Missing	5	1
Neutering
No	102 (78)	115 (63)	-	-
Yes	28 (22)	67 (37)	2.1 (1.3–3.6)*	1.9 (1.0–3.3)*
Missing	0	0
Feeding
Homemade	14 (11)	8 (4)	-
Commercial	38 (29)	78 (43)	3.6 (1.4–9.3)**
Mixed	77 (60)	96 (53)	2.2 (0.9–5.5)
Missing	1	0
Veterinary visit
Never	18 (14)	11 (6)	-	-
1–2 times	89 (69)	88 (48)	1.6 (0.7–3.6)	1.4 (0.6–3.1)
3 or more times	22 (17)	83 (46)	6.2 (2.5–15.0)***	4.9 (1.9–12.3)***
Missing	1	0
Habitat
Urban	33 (26)	79 (44)	-	-
Rural	96 (74)	102 (56)	0.4 (0.3–0.7)***	0.4 (0.2–0.7)***
Missing	1	1
Living environment
Indoors	26 (21)	49 (30)	-
Outdoors	95 (79)	117 (70)	0.7 (0.4–1.1)
Missing	9	16
Family member
1	4 (3)	8 (4)	-
2	24 (19)	33 (18)	0.7 (0.2–2.5)
≥3	99 (78)	140 (77)	0.7 (0.2–2.4)
Missing	3	1
Children
No	81 (64)	114 (63)	-
Yes	46 (36)	68 (37)	1.0 (0.7–1.7)
Missing	3	0

*p<0.05;

**p<0.01;

***p<0.001

LR = -181.68 (p<0.001)

Table 3

Descriptive, univariable and multivariable logistic analysis of characteristics associated with the dog veterinary care in central Italy in 2013.

Veterinary visit per year
	Never (N = 29)(%)	1 or more times (N = 283) (%)	Univariable analysis OR (95% CI)	Multivariable model OR (95% CI)
Sex
Male	13 (68)	143 (51)	-
Female	6 (32)	139 (49)	1.8 (0.8–4.1)
Missing	0	1
Age (years)
≤2	3 (16)	73 (27)	-
2.1–8	6 (32)	141 (52)	0.9 (0.3–2.6)
>8	10 (53)	59 (22)	0.4 (0.1–1.1)
Missing	0	10
Breed
Crossbred	13 (68)	141 (51)	-
Purebred	6 (32)	134 (49)	2.5 (1.0–5.8)*
Missing	0	8
Source
Born in house	6 (20)	11 (4)	-	-
Found	7 (23)	58 (21)	5.2 (1.4–19.4)**	5.8 (1.5–23.0)**
Adopted	5 (17)	23 (8)	2.5 (0.6–10.0)	2.5 (0.6–10.8)
Gift	11 (37)	135 (49)	6.7 (2.1–21.6)***	7.3 (2.2–24.8)**
Purchased	1 (3)	51 (3)	27.8 (3.0–254.9)**	28.3 (2.9–279.7)**
Missing	0	5
Neutering
No	15 (79)	194 (69)	-
Yes	4 (21)	89 (31)	1.4 (0.6–3.5)
Missing	0	0
Feeding
Homemade	4 (24)	15 (5)	-	-
Commercial	3 (16)	113 (40)	13.2 (3.4–50.4)***	14.2 (3.5–57.7)***
Mixed	12 (63)	155 (55)	4.0 (1.4–11.2)*	5.1 (1.7–15.3)*
Missing	0	0
Habitat
Urban	3 (16)	104 (37)	-
Rural	16 (84)	178 (63)	0.7 (0.3–1.5)
Missing	0	1
Living environment
Indoors	6 (24)	69 (26)	-
Outdoors	19 (76)	194 (74)	0.9 (0.3–2.3)
Missing	7	20
Dog registry
No/Do not know	10 (53)	111 (39)	-
Microchip/Tattoo	9 (47)	171 (61)	2.5 (1.1–5.5)*
Missing	0	1
Family member
1	0 (0)	11 (4)	-
2	3 (16)	54 (19)	1.6 (0.2–17.2)
≥3	16 (84)	215 (77)	0.8 (0.1–6.3)
Missing	0	3
Children
No	9 (47)	180 (64)	-
Yes	10 (53)	101 (36)	0.6 (0.3–1.3)
Missing	0	2
Cat
No	17 (59)	186 (66)
Yes	12 (41)	97 (34)	0.7 (0.3–1.6)
Missing	0	0
Other pet
No	27 (93)	251 (89)
Yes	2 (7)	32 (11)	1.7 (0.4–7.6)
Missing

*p<0.05;

**p<0.01;

***p<0.001

LR = -80.85 (p<0.001)

Table 4

Descriptive, univariable and multivariable logistic analysis of characteristics associated with dog ownership in central Italy in 2013.

Dog owners
	No (N = 243)(%)	Yes (N = 212)(%)	Univariable analysis OR (95% CI)	Multivariable model OR (95% CI)
Gender
Male	104 (45)	78 (37)	-
Female	128 (55)	133 (63)	1.4 (0.9–2.0)
Missing	11	1
Age (years)
≤19	3 (1)	2 (1)	-
20–29	18 (8)	24 (11)	2.0 (0.3–13.2)
30–39	35 (15)	34 (16)	1.4 (0.2–9.3)
40–49	48 (20)	52 (25)	1.6 (0.3–10.1)
50–59	55 (23)	58 (27)	1.5 (0.2–9.8)
≥60	80 (33)	42 (20)	0.8 (0.1–4.9)
Missing	4	0
Marital status
Single/Separated/Widowed	71 (31)	68 (33)	-
Married	157 (69)	138 (67)	0.9 (0.6–1.4)
Missing	15	6
Education level
Primary school	21 (9)	20 (10)	-
Middle school	68 (31)	60 (30)	0.9 (0.4–1.8)
High school	110 (50)	89 (45)	0.8 (0.4–1.7)
University	22 (10)	29 (15)	1.4 (0.6–3.1)
Missing	22	14
Occupation
Home working	122 (53)	89 (43)	-
Office	74 (32)	77 (38)	1.4 (0.9–2.2)
Other	34 (15)	39 (19)	1.5 (0.9–2.7)
Missing	13	7
Habitat
Urban area	129 (65)	93 (45)	-	-
Rural area	70 (35)	116 (55)	2.3 (1.5–3.4)***	2.1 (1.5–3.3)***
Missing	44	3
Family member
1	16 (8)	10 (5)	-
2	73 (36)	44 (21)	1.0 (0.4–2.3)
≥3	112 (56)	154 (74)	2.2 (1.0–5.0)
Missing	42	4
Children
No	147 (74)	126 (60)	-	-
Yes	52 (26)	83 (40)	1.8 (1.2–2.8)**	1.9 (1.2–2.9)**
Missing	44	3
Cat
No	194 (80)	146 (69)	-
Yes	49 (20)	66 (31)	1.8 (1.2–2.7)**
Missing	0	0
Other pet
No	226 (93)	193 (91)	-
Yes	17 (7)	19 (9)	1.3 (0.7–2.6)
Missing	0	0

*p<0.05; *p<0.01;

***p<0.001;

LR = -267.32 (p<0.001)

The likelihood ratio chi square test (LRT) for goodness of fit was calculated to compare the final model with full models. A two-tailed p value <0.05 was considered statistically significant. All statistical analyses were performed by Stata/SE version 12 for Windows (StataCorp LP, TX, USA).

Results

A total of 630 people were interviewed, the answer rate was 76% and 455 people were considered in the analyses because they resided in the study area. The total number of interviewed people and their family members was 1,297. The mean number of persons per HH was 2.9, higher than the Italian mean, 2.4 [19].

Overall, 244 (53%) interviewed people did not have dogs while 212 (47%) owned at least one dog. Of these, 140 (66%) owned one dog, 53 (25%) two dogs, 13 (6%) three dogs, 6 (3%) four or more dogs, totalling 315 dogs. Among these, 183 (58%) were correctly identified and registered into the DR. The mean number of dogs per HH was 0.7 and 1.5 per dog-owning HH.

At the time of the survey, 362,277 dogs were registered in the DR (N). The model estimated that the mean number of dogs relative to the province of Rome was 481,294 (95% CI: 470,860–491,978), 90 dogs/km2 and the HDR was 9.0 (95% CI: 8.8–9.2). Considering this estimate, 75.3% (362,277/481,294; 95% CI: 73.6–76.9) of the dogs living in Rome province were correctly registered into the DR.

The overall median age was 5.0 years (Q1 = 2.0; Q3 = 8.0) and it was similar in males (median = 5.0; Q1 = 2.0; Q3 = 8.8) and females (median = 5.0; Q1 = 2.0; Q3 = 8.0). The age distribution of the dog population showed a moderately different shape for sex (Fig 1).

Fig 1

Dog population pyramid by sex, identification and registration (I&R) into the Dog Registry.

The majority of dogs were males (52%; male:female ratio: 1.1), not neutered, crossbred, acquired as a gift, living in a rural area, mainly outdoors, fed mixed food, attended a veterinary visit 1–2 times per year and were registered in the DR (Table 1). The percentage of neutered animals was 8% and 55% of males and females, respectively.

Table 1

Demographic characteristics of enrolled dogs based on a survey in central Italy in 2013.

		N	%	Missing
Sex	Male	164	52.1	0
	Female	151	47.9
Overall neutering	No	219	69.5	0
	Yes	96	30.5
Neutered females	No	68	45.0
	Yes	83	55.0
Neutered males	No	151	92.1
	Yes	13	7.9
Breed	Crossbred	164	53.2	8
	Purebred	144	46.8
Source	Born in house	17	5.5	6
	Found	64	20.7
	Gift	148	47.9
	Adopted	28	20.7
	Purchased	52	16.8
Habitat	Urban area	113	56.8	4
	Rural area	199	63.8
Living environment	Indoors	75	35.2	28
	Outdoors	213	74.0
Feeding	Homemade	22	7.1	3
	Commercial	117	37.5
	Mixed	173	55.4
Veterinary visit	Never	29	9.3	3
	1–2 times	178	57.1
	3 or more times	105	33.7
Dog Registry	Microchip	172	55.1	3
	Tattoo	10	3.2
	No	100	32.1
	Do not now	30	9.6

The descriptive analysis showed that the majority of dogs registered in the DR were female, adult, purebred, acquired as a gift, not neutered, fed commercial food, lived in a rural area mainly outdoors, attended a veterinary visit at least once a year, lived in a family with 3 or more members and without children.

The registration into the DR was considered to explore its potential association with exposure variables (Table 2). A significant association was found for sex and kind of feeding in the univariable analysis. In the multivariable model, findings revealed that being a purebred dog, neutered, with intensive veterinary care, and living in an urban area were predictors of the presence into the DR. HH was found to have no effect on the outcome variable (p = 0.07).

Taking into consideration the average veterinary care, the descriptive analysis showed that dogs visiting a veterinarian at least once a year were mainly males, adult, crossbred, acquired as a gift, not neutered, lived in rural areas and outdoors, registered in the DR and commonly fed commercial or mixed food (Table 3). In the logistic regression analyses, a significant association was found for the breed and the presence into the DR in the univariable analysis while multivariable model confirmed the dog source and the kind of feeding as predictors. HH was found to have no effect on the outcome variable (p = 0.432).

Exploring the ownership profiles, the descriptive analysis showed that the majority of dog owners were females, married or long term committed, with a middle educational level, working from home, lived in a numerous family, in a rural area and had no other pets. Of the 212 people owning a dog, 31% also owned a cat and 9% owned a pet different from a cat, such as birds, fish or turtles.

The ownership of a dog was then considered to explore its potential association with exposure variables (Table 4). A significant association was found with the presence of a cat in the univariable analysis. In the multivariable model, habitat and the presence of children were confirmed as predictors of the dog ownership.

There was no multicollinearity between the independent variables. In the regression models, interaction terms were not significant.

Discussion

The present study investigated the dog population size, demography, ownership profiles and the I&R rate in the biggest Italian metropolitan area. Reliable data must be available and regularly updated to address proper policies by competent authorities in a public health concept. The prevention of zoonotic disease including rabies, leishmaniasis, echinococcosis, the design of surveillance plans, the management of livestock predation, wildlife endangerment, owned-wildlife canine population bond, behaviour-related problems (aggressiveness, barking noise, dog-to-human bite), and the impact on canine welfare, are all issues that can be efficiently driven only if the population size, demography and their trends are known and trustworthy. Furthermore, the size and the demography of the canine population is important for many stakeholders: private veterinarians, pet products manufacturers, insurance companies and researchers [25]. Consistent information is crucial to calculate canine diseases incidence, for the possible use of dogs as sentinel animals (e.g. environmental contaminants) and to predict the future population dynamic.

The lack of reliable, centralised and official information leads to the use of surveys to estimate the dog population. Several methods can be implemented to collect data in cross-sectional procedures: mailed, door-to-door, telephone surveys. Most of them are subject to a representativeness bias. The approach used in the present paper, a face-to-face questionnaire, though costly and time-consuming, improves the precision of the estimates limiting the selection, non-response and the measurement biases [2]. Biases were also minimised recruiting respondents within the framework of a research project on human and animal tumours and not directly on the dog ownership. Interviews were performed to general people in Health Care Centres while attending for the booking, the payment or routine diagnostic exams. As the Italian Health Care System provides comprehensive coverage to all citizens, routine diagnostic exams are performed in the Health Care Centres homogenously among age, sex and socio-economic levels. For these reasons, the sampled population was assumed representative of the general population [21].

This research has some limitations. Rome is a province with a large population and a human density, limiting the generalizability of our findings to the rest of the country. Additionally, the a priori probability distribution used in the Bayesian approach was conducted in a limited part of the Rome province [9]. The interviewed people could not be the responsible of the dog management in the HH and this could limit the relation between their characteristics and the dog I&R. Finally, the stray dog population was not considered in this study.

Different indices are used in pet population studies and they are not consistent with each other. The human to dog ratio, the percentage of HHs owning a dog, the mean dog per HH, the number of dogs per km2 are frequently used, together with capture-recapture or Bayesian methods to infer the absolute population size [26]. In the present studies, all the possible indices were calculated and presented to enhance the precision of the estimates [27] and to help researchers to compare results with other studies worldwide.

Dogs are popular in Italy and the findings of the present study confirmed an extensive presence of the dog among human population. The percentage of respondents having a dog was 47%, much higher than previous findings in Italy (33%, 25%) and in Europe (39%, 31%), but lower if compared to countries with a poor Human Development Index (a statistic composite index of life expectancy, education, and per capita income indicators used by United Nation) (65%, 51%) [14,16,17,28-30]. Interestingly, taking in consideration other indices depicts a different pattern. The findings of the present study denoted a massive presence of dogs with 90 dogs/km2 (34 and 46 in previous studies in central and northern Italy, respectively [17, 28]). In contrast, due to a high human density, the HDR (9.0) was the highest (i. e. a relative low number of dogs) if compared with what is reported worldwide (in some cases calculated by the authors from data present in published studies). A HDR ranging from 3 to 5 was found in Brazil, Mexico and in an Italian Province close to Rome [17, 27, 29]. A HDR from 5.4 to 5.8 was reported in 3 studies performed in northern Italy [28, 31, 32] while a score close to 6.0 in UK and in Guatemala [16, 30]. These findings reported a large number of dogs in an area with a high density of people, suggesting that the dog ownership is very popular and anthropogenic pressure seems not to limit it. The wide base of the pyramid (Fig 1) indicates that the population size will likely not decrease. Surprisingly, the mean dog of dog-owning HH reported in the present study (1.5) was almost identical to that reported worldwide (1.3÷1.6), suggesting the number of dogs in an HH can be a constant [14, 16, 17, 30, 32]. Interestingly, the people owning a dog (47%) were more common than the people owning a cat (29%) in the study area [21]. Our findings confirm the previous reports of dog predominance in companion animals [14, 17, 28, 32].

Italy was probably the first country in the world to make dog I&R compulsory in 1991 [7]. Public and private veterinarians are obliged to register new born puppies, owner and address changes and to remove dogs in case of death. Recently, other European countries are implementing DRs, while no DRs are required in the rest of the world [7]. The dog I&R framework in European countries is lagging behind from both a legislative and an operative point of view [7]. In this process, the assessment of the completeness of the I&R systems is a critical requirement.

Researchers exploring the completeness of the DR in Italy found that it varied from 51% in 2004, 55% in 2005 to 71% and 75% in 2011 [9, 17, 28, 32]. As expected, the awareness in dog I&R increased in the first decade after its establishment, but no improvement has been made since as demonstrated in the latest studies. The Bayesian approach used in this study estimated that almost one fourth of living dogs were undetectable. In the DR, the substantial underestimation of the real population was 33%. Interestingly, almost all the non I&R dogs visited a veterinary clinic at least once a year (Table 2), indicating that private veterinarians do not play their role in the I&R control and should be included in the process to enhance the completeness of the DR. Furthermore, it is worth noting that the proportion of dogs with no I&R was homogenously distributed among the age classes (Fig 1), suggesting that the completeness of the DR is not likely to automatically improve in the future, unless further actions are taken.

In the present study, the majority of I&R dogs were purebred dogs, likely because of the owners’ awareness of tracing a dog in case an animal become lost. From the analysis of sex, neutering and habitat, it emerged that a dog was less likely identified and registered if male, not neutered and lived in a rural environment. These findings may be explained by owners’ wanting to avoid the responsibility of an unwanted litter, or the consequence of potential car accidents and dog biting that could be caused by owned traceable dogs.

Several strategies can be suggested to encourage I&R. Firstly, promoting the responsible dog ownership among the general population [3, 18]. Secondly, enforcing private veterinarians and dog breeders to be an active and co-operative part of the system. Thirdly, establishing an effective monitoring system by competent authorities. Finally, introducing incentives to enhance DR and fines towards owners who do not identify or register dogs.

In the present study, the sex ratio favoured male dogs. This diversity is a constant in all similar studies worldwide [17, 27, 29, 31, 32]. Dog owners may believe that male dogs are preferable because they do not produce unwanted puppies, do not attract free roaming dogs during oestrus and can serve as guard dogs, especially those living in rural areas [30].

The overall proportion of neutered dogs in the present study was much greater than the proportion reported in another Italian province [17]. The proportion of neutered female dogs (55%) was significantly higher than males (8%) and it is worth noting that this was the highest rate reported in all the studies considered, except Ireland [14, 17, 29, 30, 33]. In contrast, only 8% of male dogs were neutered, a percentage identical to that observed from Slater et al [17], but far lower than the trend recorded in other European countries, which is close to 30% [14, 33]. It is possible that there was a cultural resistance to the dog male castration in the owners of the present study. Another hypothesis was the intention of preserving the protective behaviour in guard dogs in rural areas, but more causes should be investigated. However, educational efforts and economic incentives could be implemented to increase the percentage of neutering in order to reduce the stray dog population, to decrease the risk of sex-related diseases (tumours and pyometra) and the impact of sex-related undesirable behaviour (bites, noises, roaming, aggressiveness), also considering that more than two third of the animals lived in rural areas and outdoors.

The proportion of purebred dogs in the present study was 47%, a proportion comparable to what reported by other studies in different years in Italy [17, 28] suggesting that this ratio is rather constant over time and geographical areas.

From the analysis of the dog source, it emerged that almost half the dogs were acquired as a gift (i.e. without being payed), followed by one fifth of dogs found (a stray animal being adopted) and purchased. A percentage less than 10% of dogs were adopted and born in house. A previous Italian study showed similar results, while an Irish study found a higher proportion of dogs purchased and similar proportion of dogs adopted [14, 17]. The findings of the present study indicated the lack of a relevant trade of dogs, also if the possibility of puppies imported illegally that are likely not going to be I&R should not be overlooked. Moreover, the presence of a significant stray dog population was confirmed (21% of dogs were found) and this finding revealed the urgency to take measures to enhance the low percentage of dogs’ adoption from shelters.

The findings of the present study showed almost one dog out of 10 did not attend regularly an annual veterinary visit. It is possible to assume that this population is not subjected to those veterinary cares commonly performed on an annual basis such as vaccination, deworming and health check-up. Data from literature indicates that the proportion of dogs not visited by a veterinarian yearly vary remarkably among the different world areas. Investigations conducted in a central Italian region and in the USA reported a percentage comparable to our findings (11% and 9%, respectively) [17, 34]. Prata found that only 2.7% of pets were not taken to a veterinarian in Portugal during the past year [35]. These values are in contrast with those from studies from Brazil and New Zealand which reported that almost one third of pets did not receive veterinary cares during a one-year period [13, 36]. Pet owners can abstain from regularly taking the pet to a veterinarian for many reasons such as costs, inadequate understanding of the need, negative feelings about subjecting the animal to stress during transportation and examination [17, 35].

In the multivariable analysis, we found that two variables, namely source and kind of feeding, were statistically associated with the outcome. Owners who purchased dogs definitely tend to take more care for the health of their dog. Since the cost of veterinary care seems to be one of the most important concerns for dog owners, it is plausible that people who chose to purchase a dog might have a favourable economic condition, being more prone to spend for veterinary cares. Our findings also suggest that dogs totally or partially fed with commercial feed were more likely to be visited by a veterinarian than those adopting a homemade diet. There are possible motivations to explain this result. Commercial food is more expensive than homemade, owners who spent more money for the food had also more economic means for veterinary care. Moreover, dogs with health problems are usually on a diet with commercial products for medical reasons (overweight, allergic or kidney problem, etc…) and they need frequent veterinary visits to check the health status.

Several studies investigated dog ownership profiles in different countries [13–17, 35, 37]. Differently from these studies, the present study reported the poor presence of reliable predictors for the dog ownership. Only living in rural areas and the presence of children in the HH were associated with the dog ownership. Living in rural areas seems an important predictor since it was identified as a significant factor by several authors [14, 16, 37]. It is possible that people consider important for the dog’s well-being having enough space at their disposal and, consequently, they are more prone to own a pet when it can access outdoors. As other authors, we found that the presence of children was associated with the dog ownership. People can consider owning a pet beneficial for children, so it is reasonable that family decision of owning a dog is positively influenced by their presence in the HH [14, 15]. However, this speculation seems to be in contrast with the results from other investigations that showed a negative correlation between dog ownership and presence of children aged less than 10 years or pre-schoolers [15, 16]. It is possible that the age of the children in the HH can influence this choice. Young children need more care than school-aged children and consequently their parents could prefer not to own a dog because they do not have enough time for its needs. Moreover, older children can likely convince their parents regarding acquiring a dog influencing the family decision of owning a dog [14, 15]. Interestingly, dog owners were also more likely to own a cat than people not owning a dog. Cats were popular in the study area [21], showing that the cohabitation of dogs and cats is not considered as a concern, as already demonstrated by Downes et al. but different to the results of Murray et al [14, 16]. The findings of the present study showed few risk factors identified among the studied variables. Therefore, the determinants of the dog ownership were almost unpredictable and not associated to social, economic or cultural factors.

In conclusion, this is the first study to provide an estimate of numbers and characteristics of a canine population and its ownership in a large metropolitan area of Europe. The results of the present study may be of use to plan monitoring of zoonosis, canine diseases and welfare, to manage the stray dog phenomenon, and to help investigate human-dog interactions in a public health perspective.

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9 Jun 2020

PONE-D-20-13213

Size, demography, ownership profile and identification rate of the owned dog population in central Italy

PLOS ONE

Dear Dr. Carvelli,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Your manuscript was reviewed by two experts in the field, who have both made some suggestions for modifications prior to acceptance

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We look forward to receiving your revised manuscript.

I wish you all the best with your revisions.

Hope you are keeping safe and well in these difficult times.

Kind regards,

Simon Clegg, PhD

Academic Editor

PLOS ONE

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Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

Reviewer #2: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: Yes

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Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Regarding availability of all data. The authors state that all data is available in the manuscript itself. I think that the journal is looking for raw data.

This manuscript attempts to better understand and clarify some important information about the dog population in the region around Rome. Part of the challenge is that there are at least 4 objectives: 1. estimate the owned dog population size and demographics; 2. Determine the proportion of dogs not registered with the national registry and see if there are variable which predict this; 3. Predictors of annual veterinary care; 4. Predictors of dog ownership. And the authors spend a lot more time on #2 than the others in both the intro and discussion. The justification and recommendations are rather superficial and simplistic even though the authors are clearly passionate about this topic.

The manuscript is hampered by the need for English language editing. It is quite wordy and repetitive regardless. I would suggest that the authors organize the manuscript according to the 4 objectives, particularly in the methods, results and discussion.

I have some specific comments below; however, the manuscript requires extensive revisions to integrate the 4 objectives as well as in organization, language and clarity of content before I will dive in row by row. The comments I’ve included here are examples of some of the lack of critical thinking and clarity and I hope will help the authors in their revision.

The introduction is focused on identification and registration, an important issue for the reasons outlined. How then does the paragraph beginning on line 74 fit? The other objectives?

Lines 63 and 65: in the former line the authors state that identification and registration are mandatory and in the latter that registration isn’t required. I think this may be a language issue but I’m not sure.

Line 67: Is there a relevant reference for the 2016 earthquake data?

And if there are already data about registration rates in Rome, what does this study add to that information? That should be in the introduction as well.

If this manuscript is also about dog population demographics, how does that relate to the dog registry work and the 3rd and 4th objectives? That should succinctly be included in the introduction.

Line 108: please include a few sentences briefly describing the study area so the reader doesn’t have to find and read another paper to learn this.

Line 109-14: I don’t understand what was done here. I realize the authors were trying to estimate sample size, but it seems to be for two different pieces of work (yet this is one study) and two different confidence intervals. Were the authors looking for a sample size to provide a specific level of precision on the estimates? And since the two sample sizes are quite different which one was used? Only the larger one is needed if that was used.

Line 119: This is a convenience sample which the authors argue is “representative” in the companion cat paper. A few sentences explaining how the respondents were selected is needed here. And in the discussion some justification of why this would be considered representative.

Line 151: excluded dogs > 16 years old but only present data in figure 1 at 13 years and up. Please be consistent and give some explanation for the choices.

Line 152: so, all pairwise combinations of the dog characteristics were tested against each other? Why? And what if the expected frequencies were < 5? At least state how many dog characteristics there were and therefore how many tests were done. And what about multiple comparisons with a p-value of 0.05 overall?

Line 153: what exposure variables were used? I’d like to see a list but a reference to a table or appendix would be ok. State how many there were. And that the other two dependent variables were used as independent variables in the other models.

Line 156: the likelihood ratio test tells you which model fits better in comparing models so that you can decide which variables to include. It doesn’t test whether the final model meets the assumptions for logistic regression. That still needs to be evaluated and included here and in the results.

Results: were all continuous data normally distributed so that the mean is a valid measure of the central tendency? Please add to the methods and adjust to a median if needed.

Line 172: I understand using a Bayesian approach for the estimate but if only 58% of dogs were registered in the sample, then how can the overall estimate be so much higher? Seems like there is something missing here.

Line 179: were these the only dog characteristics that were significantly associated? Please provide actual p-values.

Table 1: given that the subsequent tables have descriptive data for each logistic model this table isn’t needed.

Tables 2-4: please add the actual univariable p-value to the variable row. Then the superscript * will not be needed. You could additionally bold the variables that stayed in the multivariable analysis. Were any interactions considered? There was an association between sex and neuter status, was that examined or a new variable created and used as was shown in Table 1? Why weren’t the owner demographics included in the registry and veterinary care models?

The first part of the discussion feels very generic and not really related to this manuscript and study. Please focus on the objectives of the study and how they relate to important other studies and specifically how they can be used in the future. Order the discussion based on the objectives and don’t include a lot of repetition of results or every article and comparison. This should be a thoughtful and critical discussion of what the results add to the knowledge base, what the limitations are and what can be done in the future. I have only included a few comments below.

Line 234 and following seems like it is related to the limitations of this study? That should be its own section later in the discussion with all other pertinent issues.

Line 253: the term poorer human development index is used several times in the manuscript without definition. And the references here are for countries that are considered to be developed except for references 23 and 24 which might be considered to be poorer or developing. Please edit.

Line 279: reference 26 is a tumor registry not a dog identification and registration paper.

Line 292-3: the authors have a very traditional view that if only the owners were more “responsible” things would be better. That is a very judgmental and often inaccurate and unhelpful portrayal of pet owners. There are real barriers in some cases for owners to do what they should. In fact, alternative reasons to those stated in this sentence could be that they didn’t know they were supposed to register the dog, didn’t know how or what to do, hadn’t had time yet to do it, etc. Please edit.

Reviewer #2: Page 4, line 69: “A number of papers have been published on owned dog population estimate”. I think this sentence seems lost and it can be deleted.

Page 5, line 79: “electronic transponder”. Is this a microchip?

Page 5, lines 84-85: Please briefly explain the main purpose of the DR.

Page 6, Questionnaire design section: How the individuals were selected? Did the authors interview the head of the household or any available individual? I also missed the ethic consideration regarding the interviews.

Page 8, lines 161-164: These are interesting results regarding the human population. However, a demographic description of your human population is missing, and it would add more value to your manuscript. Also, I think authors should provide an additional table for the human demographics.

Page 16, Discussion: I would not write the discussion in topics. Its preferable to be a flowing text as in the background.

The main conclusion and limitations of the study are missing.

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23 Jul 2020

Dear reviewers,

thank you for your comments, which greatly improve the manuscript.

We have followed your instructions in revising the manuscript and put the comments in tables submitted as separate file to facilitate the revision process. One comment regarding the subsections of a reviewer is in conflict with revisions requested by the other one. We apologize but we can not accept both requests.

We also add in the manuscript and in the revision process in PlosONE website, the data availability and the details on interviews as requested by a reviewer.

We hope that, after the performed changes, the article meets the target and the requirements of PLoS ONE.

Sincerely

Andrea Carvelli

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

15 Sep 2020

PONE-D-20-13213R1

Size, demography, ownership profiles and identification rate of the owned dog population in central Italy

PLOS ONE

Dear Dr. Carvelli,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

Many thanks for re-submitting your manuscript to PLOS One

It was reviewed by experts in the field, and they have requested some changes be made prior to acceptance.

If you could make these changes and write a response to reviewers, that will greatly expedite revision upon resubmission

I wish you the best of luck with your changes

Hope you are keeping safe and well in these difficult times

Thanks

Simon

==============================

Please submit your revised manuscript by Oct 30 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Simon Clegg, PhD

Academic Editor

PLOS ONE

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #3: (No Response)

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: (No Response)

Reviewer #3: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The manuscript is understandable with the revisions including the English language edits, but still in need of some editing for English as well as to reduce repetition and make the manuscript more concise, clear and focused. I have therefore not commented line by line, only where I noted obvious needs for editing. Having someone who has written many scientific articles in English language journals review and edit the manuscript would be very helpful!

The Introduction is still too long and a bit repetitive. It moves from national data to Italian registration to international need for data to ownership data in other countries. Please review some recent Plos One articles to see examples of the construction of the introduction. The previous cat focused paper is also an example where the introduction was more focused but don’t use the same sentences--any exact repetition is plagiarism. See as an example Mustiana 2015 in Plos One. Order the topics from most general (international) to most specific (Italy/Rome).

Line 88: note that any fee even a small one, for someone who is very poor may be cost prohibitive. This is an assumption that is untested.

Line 140-2: to be able to say that selection bias was limited, you need to state what was done if the selected person refused to participate here and, in the results, indicate how many people refused to participate.

Page 8: age and number of pets were collected as continuous variables. How did the authors determine what categories to create? Based on what? Gender is applied only to humans. In animals, sex is the preferred term.

Lines 167-8: these sentences are not clear. I think, based on the companion cat study, that the authors are indicating that the interviewers framed the present research as a study of general pet health to avoid bias. And that whether the pet was allowed to roam was not asked?

Line 196: relative to the two sample size calculations, the authors apparently only used the sample size which they first reached, the dog ownership one. Why not also the number interviewed? That needs to be in the manuscript.

Line 209: were the ages normally distributed? Fig 1 would suggest they are NOT normally distributed and therefore the median would be a more correct option.

Table 1 does not appear to add information to that of Table 2. I would either delete or put into the supplement. Alternatively, one column of totals could be added to table 2.

Table 2 only has 312 dogs. What happened to the other 3?

Authors response to L152: does not address my question about multiple comparisons for the chi-square tests for multicollinearity. And the first sentence added is about the chi-square test between outcome and independent variables, not about multicollinearity. Were any variables excluded from any model due to statistical associations with each other? Appears they were not based on a later comment. That needs to be in the results section.

Authors response to L156: in fact, dogs living in the same household are likely not independent which is one of the assumptions for Logistic regression. Please consult with someone who can assist with the statistical analysis.

Authors response to Tables: I’m asking about statistical interactions in the final multivariable models, not multicollinearity. Please add these to the analysis. And because the dogs are clustered or matched within households, households my need to be added to the analysis. That would also allow owner characteristics to be included. There are statistical methods to address this. And if there is a compelling reason to ignore the clustering within households, the authors must include that.

I could make the argument that since the person who answered the survey wasn’t selected as someone who made the decisions for household about the dogs that their characteristics would be unlikely to be related to I&R. That should be included in the discussion as another limitation and may explain why a few HH level variables were significant, but the individual ones were not.

Table 3: please add something to the title about this including the results of 203 owners who were surveyed in x years. And add the 312 dogs to the existing description. Add a bit more to the title, similarly, for Tables 2 and 4.

Lines 271-7: please do not repeat verbatim the section from the cat paper. And there were a number of people selected who refused to participate, no? Please include that in the results. Then adjust this statement and add to the limitations section. This influences non-response and selection biases. Measurement bias wasn’t addressed by the source of participants, only by 1. The training of the interviewers and data entry staff, 2. The validity and reliability of the survey, 3. The way the survey was presented to the respondents, etc. Please be much more careful in the discussion about this and other types of bias and how they were minimized (and if not, how they were likely to influence the results).

Human development index appears in the abstract without any definition or description. Line 292: And isn’t described here either only referenced. Please briefly indicate what indices are included. The next sentence mentions other indices, but none are discussion, unless the dogs per/km2 is the next index—in which case it is about indices to report dog data not potential predictors? Please clarify.

What is the major point of the paragraph starting on line 289? The paragraph ranges through human development index, density in Rome and other countries, and dog and cat ownership.

Line 324: I’m not clear how the homogeneity of the I&R in age (which is quite interesting!) is related to the need for action?

Line 331: Isn’t responsible pet ownership promoted everywhere already? Has it been shown to have an impact on I&R? If there aren’t data to support these strategies, then the authors should at least say how they think these will promote I&R and who and how they should be performed.

Line 343-4: these references are only in a handful of countries and don’t include the US or Canada. Please rephrase.

Line 341: is this about males or neutering in general? The paragraph includes both sexes, but the previous sentences focus on males (I believe).

Line 362: I believe that the authors are saying that if puppies are being imported illegally then they are likely not going to be I&R?

Paragraph starting on line 366 tile 389: There is good information here, but it is long and repetitive. Please edit to be shorter.

Line 406-407: “also more likely to own a cat” than what? This sentence is incomplete.

Lines 409-11: these sentences seem to be saying that: this study was unable to find predictors to confidently predict dog ownership in this or other parts of Italy.

Reviewer #3: This is a nice paper, which has some interesting results from Italy. The science itself seems generally sound, and will be of interest to readers. However, it needs a bit of grammatical reworking, and I have tried to do this below as I am guessing that their first language isn’t English. The changes below don’t need a response writing to them, but hope they help.

Line 19- predictors in the animal population is essential (add in word)

Line 38- The percentage of neutered dogs were higher in females (55%) than in males (8%). (reword)

Line 43/44- including promoting responsible dog ownership, (reword)

Line 57- change human to humans

Line 58- Therefore, the knowledge of the animal population in terms of size (add in word)

Line 62- the lack of information in the pet population is a constant (add in word)

Line 66- owned dog population estimates (make plural, and add in references)

Line 73- please define DRs

Line 75- Nevertheless, while identification is performed on an individual basis, (add in word)

Line 76- change country to countries

Line 78- To date, reliable data on the dog population (add in word)

Line 84- or manage data of both the (add in word)

Line 86- organised toward the general population (add in word)

Line 88- can you please put in the cost of this registration? It may be prohibitive to poor people not to register

Line 90- stakeholders think that the only purpose of the DR is the (add in word)

Line 94- remove high

Line 95- remove the

Line 105- remove an

Line 106- its consequences, such as human and animal injuries (make plural and add in comma)

Line 109- useful for the private sector (add in word)

Line 112- add in comma after evaluated

Line 125- owned dog population, and to identify the human factors…. (change final comma to and)

Line 140- what happened if a person refused to participate? Also, if this was done in 2013- how it is linked to what is relevant now?

Line 141- selecting one in every four people amongst (reword)

Line 147-149- I struggled to follow this, please reword it

Line 155- was asked whether they resided (add in word)

Line 172- estimate the size of the canine population (add in word)

Line 173- comma after ‘investigation (9), ‘

Line 174- remove as prior

Line 74- comma after registered

Line 204- 362,277 dogs were registered in the DR (reword)

Line 210- The age distribution of the dog population showed a moderately different shape for gender (reword)

Line 212- fed mixed food- delete by

Line 216- dogs are usually referred to as gender rather than sex- please change throughout

Table 1 and 2 seem very similar- maybe consider deleting one

Line 234- commonly fed commercial or mixed food (reword)

Line 236- univariable analysis, while multivariable model (add in comma)

Line 258- leishmaniosis- typo- leishmaniasis

Line 260- human bite) and the impact (add in word)

Line 262- demography of the canine (add in word)

Line 290- The percentage of respondents having (make plural)

Line 292- what is the human development index? It would be nice to know what this is and what it means

Line 302- The wide base of the pyramid (add in word)

Line 304- almost identical to that reported worldwide (reword)

Line 305- delete hold

Line 306- replace ‘resulted greater’ with ‘were more common’

Line 310- reword to ‘register new born puppies, owner and address changes’

Line 311- implementing DRs, while no DRs is (add in comma)

Line 315- should be researchers

Line 326- in case an animal becomes lost (reword)

Line 328/9- responsibility of an unwanted litter (add in word)

Line 331- promoting responsible dog ownership (reword)

Line 341- greater than the proportion reported (add in word)

Line 342- reword to – ‘and it is worth noting…’

Line 350- order to reduce the stray dog population (add in word)

Line 360- similar results, while an Irish National (add in comma)

Line 369- commonly performed on an annual basis such as vaccination(add in word)

Line 376- abstain from regularly taking the pet- reword

Line 380- statistically associated with an annual veterinary visit (add in word)

Line 381- Since the cost of veterinary care (add in word)

Line 388- usually on a diet with commercial (add in word)

Line 394/5- identified as a significant factor by (add in word)

Line 396- enough space at their disposal (Add in word)

Line 397- we found that the presence of children (add in word)

Line 407- Cats were popular in the study area… (reword)

Line 408/9 - but different to the results of Murray et al (reword)

Line 410- replace resulted with were

**********

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Reviewer #3: No

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24 Sep 2020

We thank the Editor and the reviewers for their comments, which greatly improve the manuscript.

We have followed your instructions in revising the manuscript and put comments in tables to facilitate the revision process. The file has been uploaded.

Submitted filename: Response to Reviewers R2.docx

Click here for additional data file.

29 Sep 2020

Size, demography, ownership profiles, and identification rate of the owned dog population in central Italy

PONE-D-20-13213R2

Dear Dr. Carvelli,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Simon Clegg, PhD

Academic Editor

PLOS ONE

Additional Editor Comments):

Many thanks for resubmitting your manuscript to PLOS One

I have reviewed the manuscript, and as you have addressed all the comments, I have recommended your manuscript for publication.

You should hear from the Editorial Office soon

It was a pleasure working with you, and I wish you all the best for your future research

Hope you are keeping safe and well in these difficult times

Thanks

Simon

Reviewers' comments:

6 Oct 2020

PONE-D-20-13213R2

Size, demography, ownership profiles, and identification rate of the owned dog population in central Italy

Dear Dr. Carvelli:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

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