Prevalence and intensity of soil-transmitted helminths infection among individuals in model and non-model households, South West Ethiopia: A comparative cross-sectional community based study.

Soil-transmitted helminths (STH) is a term used to refer to infections caused by intestinal worms mainly due to A. lumbricoides, T. trichiura, and hookworm species which are transmitted through contaminated soil. This study was conducted to assess the prevalence and intensity of STHs infection among individual members living within the selected household heads (HHs) certified either as a model HHs or non-model HHs based on the implementation level of a training program known as the Health Extension Program (HEP). A community-based comparative cross-sectional study was conducted from April to June 2018 at Seka Chekorsa Woreda, Jimma zone. Model and non-model HHs were selected systematically from each of the randomly selected district villages employing a multistage sampling technique. Sociodemographic and risk factors data associated with STHs infections were collected using a pre-tested structured questionnaire. Parasitological stool sample microscopic examination was done using saline wet mount and Kato Katz thick smear technique. Data analysis was performed using SPSS software version 20 for descriptive statistics, comparison, and logistic regression at a p-value < 0.05 for statistical significance. Overall, 612 individuals were recruited in the study from 120 randomly selected HHs. The prevalence of STHs infections was found to be 32.4%. A total of 45 (14.7%) model and 153 (50.0%) non-model individual participants were positive for at least one species of STHs showing a significant difference between individuals in model and non-model HHs (AOR: 6.543, 95% CI; 4.36-9.82, P<0.001). The dominant STHs were T. trichiura (21.6%) followed by A. lumbricoides (6.4%) and hookworms (2.3%). The intensity of T. trichiura and A. lumbricoides infection have shown a significant difference (p<0.05) while hookworm species infection was not significantly different (p>0.05) for the individuals in the HHs groups. On the other hand, the households training status, age of participants, and latrine use pattern were found significant predictors of STHs infection prevalence in the multivariate analysis (P<0.05). Therefore, the prevalence and intensity of STHs infection was higher among individuals living in a non-model HHs than model HHs.

Introduction

Soil-transmitted helminths (STHs) infection due to A. lumbricoides, T. trichiura, and hookworm species are the most common parasitic infections worldwide but occur in the greatest numbers in Sub-Saharan Africa, East Asia, China, India, and South America [1,2]. About 2 billion people are infected with one or more STHs species. More than 4 billion people are at risk of infection, 135,000 people die a year and 4.94 million years lived with disability attributable due to STHs. Globally, about 819, 439, and 465 million people were infected with A. lumbricoides, hookworm species, and T. trichiura, respectively. Over 450 million, mostly children suffer from significant morbidity; 44 million pregnant women suffer clinical effects from hookworm-associated anemia and also a severe impact on the elders [3,4].

STHs are found most prevalently throughout the tropics and subtropics wherever hygiene is poor, safe water and sanitation facilities are lacking and health services are insufficient. They are transmitted via ingestion or skin penetration of the infective stages [5,6]. Their effects on health include anemia delays in physical growth and cognition, decreased stamina and work output, and complications during pregnancy [7]. Morbidity is related to the number of worms harbored. People with light infections usually have no symptoms while heavier infections can cause a range of symptoms including diarrhea, abdominal pain, malaise and weakness, intestinal blood losses, loss of appetite, reduction of nutritional intake, and physical fitness [8,9].

STHs infections are often overdispersed in endemic communities, such that most individuals harbor just a few worms in their intestines while a few hosts harbor disproportionately large worm burdens. There is also evidence of familial and household aggregation of infection [3,10]. Control of STHs can be achieved by the targeted use of chemotherapy and improvement of sanitation, drinking water, use of pit latrines instead of open defecation, and good hygiene practices. World Health Organisation (WHO) recommends mass drug administration with Albendazole 400mg and Mebendazole 500mg to all people at risk of infection living in endemic areas disregard of diagnosis [11,12].

Additionally, an effective, targeted and simple type of health education is recommended as a first option to create an enabling environment for other strategies to thrive, especially in underprivileged communities. Thus, participation of the community represents one of the cardinal tools of disease control programs as improvements in awareness and understanding can greatly increase the realization and sustainability of long-term STHs control strategies. However, the success of control initiatives involving the community depends on the level of the communities’ uptake of the program, which is linked to the understanding of the community’s knowledge, practices, and perceptions of the disease found to be instrumental in designing and implementing effective community-based programs [13-15].

As a community involving health intervention, the Health Extension Program (HEP) launched by the Ethiopian Federal Ministry of Health in 2003 includes 16 essential health packages categorized under four major program areas. These are hygiene and environmental sanitation; disease prevention and control; family health services; and health education and communication. Those HHs that are trained and successfully implement at least 75% of these training packages become certified model HHs and their health status is also assumed to be superior to non-model HHs [16-18]. Taking the training packages concept into account, there is insufficient empirical evidence to support whether the implementation of the HEP in Ethiopia brought an impact on the prevalence of sanitation and hygiene-related infections such as STHs. Therefore, the objective of this study is to assess the prevalence & intensity of STHs infection among individuals in HEP model & non-model HHs.

Methods and materials

Study area

This study was conducted in Seka Chekorsa woreda, which is found in the Jimma zone of Oromia regional state, southwest Ethiopia. It is located 366 km away from the capital city Addis Ababa and 20 km away from Jimma town. It is bounded by Gomma and Manna woreda in the north, Gera woreda in the south, Dedo woreda and Jimma Town in the East, and Shabe Sombo woreda in the west. This woreda covers an estimated area of 455km2 and has 36 districts (34 rural and 02 urban; of which 29 districts are models while 07 are non-models), has 01 Hospital, 09 Health centers, 35 Health posts, and 84 health extension workers.

The altitude of this woreda ranges from 1580 to 2560 meters above sea level and rainfall ranges from 1,200 to 2,800 mm. The minimum and maximum daily temperatures of the area are 12.6°C and 29.1°C, respectively. Perennial rivers include the Abono, Anja, Gulufa, and Meti. A survey of the land in this woreda shows that 45.3% is cultivable (44.9% was under annual crops), 6.1% pasture, 25.8% forest, and the remaining 22.8% are considered swampy, degraded, or otherwise unusable. Khat, peppers, fruits & teff are important cash crops including Coffee plantations with over 50 km2 area [19]. The 2007 national census reported the total population for this woreda is 208,096, of whom 104,758 were men and 103,338 were women; 7,029 (3.38%) of its population were urban dwellers and around 90% of the residents are farmers.

Study design and period

A community-based comparative cross-sectional study was conducted from April to June 2018.

Source and study population

All HHs selected from the districts in Seka Chekorsa woreda were the source population. Whereas, all individual members in HHs permanently living in the study area at least for 6 months, aged greater than two years, who were voluntary to provide consent to participate in the survey, could provide stool samples and did not take anti-helminthic treatment for 28 days before data collection were included in the study.

Sample size and sampling technique

The total sample size for this study was calculated by Epi-Info Version 7 statistical software (Stat calc) using the double population proportion formula to detect the difference between individuals among model and non-model HHs of 26.05% and 52.1% [20], respectively. With a confidence level of 95%, considered a power of 80%, 1:1 ratio, OR of 2 or with an assumption of 50% reduction, non-response of 10%, and design effect of 2. Therefore, the final sample size was 612 (306 model and 306 non-model individual members living within the HHs).

A multistage sampling technique was applied to select individuals living in the HHs from the villages found in the districts of Seka Chekorsa woreda. In the first stage, from the total of 36 districts in the woreda that were categorized as either model (n = 29) or non-model (n = 7), 04 districts were randomly selected (Buyo Kechema and Kusaro from model districts and Andode Alaga and Meti from the non-model districts). In the second stage, all villages (n = 3) (locally referred to as “zones”) within each of the selected districts were selected. Finally, considering the mean family size of the Jimma zone which is 5.1±1.8, and a total sample size of 612 individual members, 120 HHs were enrolled with systematic sampling. Calculated HHs number was allocated proportionally according to the HHs size within each village (Fig 1).

Fig 1

Diagrammatic representation of the multi-stage sampling technique used to select individuals in model and non-model HHs.

Key: HHs-Household heads.

Study variables

The STHs infection and intensity were the dependent variables while the household training status (HH) (model or non-model), Socio-demographic, Socio-economic characteristics, Personal hygiene, environmental sanitation, waste disposal, and awareness about STHS infections related questions were our independent study variables.

Data collection

Sociodemographic characteristics and risk factors that predispose to STH infection were collected using pre-tested structured questionnaires. Trained data collectors administered the questionnaires that are prepared in English and translated into Afan Oromo language.

Stool sample collection and processing

All individuals were provided labeled stool cups and instructed to bring sufficient stool samples. All specimens were checked for their label and quantity. Direct saline wet mount stool examination technique was performed by emulsifying a small portion of stool sample with normal saline for the microscopic examination using light microscopy at the nearby health post/health center located in each district immediately. Then, aliquots of each specimen were transported to the medical parasitology teaching laboratory of the school of medical laboratory sciences, Jimma University using the cold box for the same-day preparation of the Kato-Katz thick smear technique.

Screening of STHs eggs was based on a 41.7 mg Kato Katz template to determine the parasite’s egg per gram in the stool (EPG) by calculating the number of eggs counted multiplied by 24 [21]. Infection intensity was then categorized as light, moderate, and heavy infection for common STHs infections following the WHO standard procedure [22]. Experienced laboratory technologists performed the laboratory procedures according to the standard operating procedures. Stool samples were randomly selected for quality control and examined by a third person who was blinded to the previous test results.

Data analysis and interpretation

Questionnaires were checked for completeness, data were entered into MS excel, cleaned, and imported to SPSS version 20 for statistical analysis. Descriptive analysis including frequency, mean, and percentage was used to summarize the demographic characteristics of the study participants. The Chi-square test was calculated to observe associations of variables. The geometric mean intensity of the parasite EPG of stool was calculated for all infected and non-infected individuals by incorporating zero counts during the analysis adjusted by adding one to each datasets and removing from the algorithmic results. Independent samples t-test was used to compare the mean difference in intensity of STHs infection between the two households. Bivariable analysis was computed to see the association of each independent variable with the dependent variable. Candidate variables for multivariable analysis were selected when the P-value was less than 0.25 in bivariate analysis. In all comparisons, a P-value of <0.05 was considered statistically significant.

Ethical statement

Ethical clearance and letter of permission were obtained from the Institutional Review Board of Jimma University (IRB letter number, IHRPG/281/2018) and Official permission was sought from Health offices. Written informed consent to participate in the study was obtained from all the adults and assent was sought from all participating children before conducting an interview or collecting a stool sample. Confidentiality of their information was maintained and participants who become positive for any intestinal parasites were linked to the health institutions to be treated according to the Ethiopian drug administration guideline [23].

Results

Socio-demographic, economic characteristics, and hygiene conditions

Overall, a total of 612 individuals were included in the study from the total of 120 HHs visited during the study period. About half, 308 (50.33%) of the study participants were males and most of the study participants 199 (32.52%) were in the age group of 5–14 years, followed by 15–24 years 104 (16.99%). The mean age of study participants was 22.35 ±16.72 years in the range of 2–70 years. There were no significant differences between individual participants in model and non-model HHs in terms of gender (X2 = 0.654, p = 0.419) and age (Χ2 = 0.426, p = 0.514). The mean age for HHs was 40.83±12.041 with the mean family size of 5.16±1.914. The majority of HHs were able to read and write 84 (70%) and farmers 81 (67.5%). Most of the HHs, 54 (45%) of them earn an annual income of 1000–3000 birr and live in earthen mud-plastered houses 112 (93.3%). Annual family income showed significant differences between model and non-model HHs (p < 0.05) (Table 1).

Table 1

Socio-demographic, socio-economic and hygiene conditions among individuals in model & non-model HHs, Seka Chekorsa woreda, Jimma, Southwest Ethiopia.

Variables	Model (n = 306) No (%)	Non-model (n = 306) No (%)	Χ 2	p-value
Gender
Male	149 (48.7)	159 (52.0)	0.654	0.419
Female	157 (51.3)	147 (48.0)
Age
<15	137 (44.8)	129 (42.2)	0.426	0.514
≥15	169 (55.2)	177 (57.8)
Family size (n = 120)
<5	24 (40.0)	24 (40.0)	0.00	1.00
≥5	36 (60.0)	36 (60.0)
Educational status (n = 120)
Unable to read and write	16 (26.7)	20 (33.3)	0.635	0.426
Able to read and write	44 (73.3)	40 (66.7)
Occupation (n = 120)
Farmer	44 (73.3)	37 (61.7)	5.236	0.155
Housewife	15 (25.0)	19 (31.7)
Merchant	0 (0.0)	3 (5.0)
Daily laborer	1 (1.7)	1 (1.7)
Family income (n = 120)
<1000	8 (13.3)	13 (21.7)	15.731	0.001*
1000–3000	19 (31.7)	35 (58.3)
>3000	33 (55.0)	12 (20.0)
Mud-plastered (n = 120)
Mud-plastered, earthen	54 (90.0)	58 (96.7)	2.236	0.135
Stone walls with cement	6 (10.0)	2 (3.3)
Latrine availability (n = 120)
Yes	59 (98.3)	59 (98.3)	0.000	1.000
No	1 (1.7)	1 (1.7)
Latrine lid covered (n = 120)
Yes	50 (83.3)	26 (43.3)	20.670	<0.001*
No	10 (16.7)	34 (56.7)
Hand washing facility (n = 120)
Yes	51 (85.0)	31 (51.7)	15.404	<0.001*
No	9 (15.0)	29 (48.3)
Water source (n = 120)
Pipe	11 (18.3)	0(0.0)	12.110	0.001*
Spring	49 (81.7)	60 (100.0)
Waste disposal (n = 120)
Pit	42 (70.0)	22 (36.7)	13.393	<0.001*
Open field	18 (30.0)	38 (63.3)
Shoe wearing
Yes	279 (91.2)	288 (94.1)	1.943	0.163
No	27 (8.8)	18 (5.9)
Nail hygiene cleanness
Yes	297 (97.1)	288 (94.1)	3.138	0.076
No	9 (2.9)	18 (5.9)

Key

*- statistically significant at p-value < 0.05, n- sample size, No.- Number, X2-chi-square.

Latrine availability to the study participants accounts for (98.3%) of out which (63.3%) of the latrines had a lid cover and about (68.3%) with handwashing facilities near the latrines. The majority of them use spring water (90.8%) as a source of drinking water and then piped water (9.2%). The use of pit waste disposal accounts (53.3%) while in the open field was (46.7%). Whereas, an individual’s shoe-wearing status and nail hygiene cleanness account for (92.65%) and (95.59%), respectively. A total of 78 (65%) HHs heard and knew about STHs locally named ‘Raammoo garaa’ explaining the most associated symptoms are abdominal pain (30%) and diarrhea (28.3%). The contaminated hand was perceived as the most common mode of transmission (49.17%) and deworming was a preventive measure among 41.67% of HHs (Table 1).

Availability of latrine lid cover, hand washing facilities near the latrine, source of water, and waste disposal system has shown a significant difference (P<0.05) between model and non-model HHs. Similarly, HHs’ awareness on source of STHs infection, mode of transmission, and prevention including signs and symptoms showed a statistically significant difference among the two groups of HHs (P<0.05) (Table 1).

Prevalence of soil-transmitted helminths

The prevalence of STHs infection among the study participants who provided a stool sample was 198 (32.35%), out of which 45(14.71%) were among model and 153(50.0%) in non-model HHs, respectively. Whereas, the overall prevalence of intestinal parasitic infections was 212(34.64%), 50(16.34%) among model and 162(52.94%) non-model, respectively. There was a statistically significant difference in the prevalence of STHs (OR = 5.8, 95% CI; 3.936–8.547, P<0.001) and overall intestinal parasites (OR = 5.76, 95% CI; 3.95–8.399, P<0.001) between model and non-model individual members in the HHs.

STHs parasites identified among the study participants were namely T. trichiura 132 (21.57%), A. lumbricoides 39 (6.37%), and hookworm species 14 (2.29%) in a single infection. Whereas mixed infections were found as double STHs in 8 (1.31%), triple STHs in 1 (0.16%), and STHs mixed with other intestinal parasite species in 5 (0.82%) (Fig 2). The difference in the prevalence of A. lumbricoides and T. trichiura was found statistically significant between model & non-model participants (P<0.001). Regarding the mixed infection status, 43(14.1%), 1(0.33%), and 1(0.33%) model individual members in the HHs had single, double, and triple STHs infections while 146(47.71%) and 7(2.29%) non-model individual members in the HHs had a single and double STHs infections, respectively. The status of mixed STHs infection was also statistically significant with the status of HHs (P<0.001). The other intestinal parasites detected in stool samples were E. vermicularis 7 (1.14%), Taenia species 2 (0.33%), and trophozoite of E. histolytica / E. dispar 4 (0.65%).

Fig 2

Prevalence of STHs and mixed parasitic infections among individual participants of model and non-model HHs, Seka Chekorsa woreda, Southwest Ethiopia.

Key: IP: Intestinal parasites, others: (E. vermicularis, E. histolytica /dispar, and Taenia species), mixed infection: Multiple infections of STHs parasites or with any of other types of parasites.

The prevalence of STHs infections between male 96(31.17%) and female study participants 102 (33.55%) did not show a significant difference (P>0.05). The prevalence of STHs parasites among the age group >15 years was found at 101(51.01%) which has no significant difference (P>0.05) from the age group of <15 years 97(49.09%). Of the 322(52.61%) individual members in the HHs trained by HEWs on HSEP, 58(18.01%) were infected and from untrained 290(47.39%) individual members in the HHs, 140(48.28%) were infected with STHs showing a significant difference of the STHs infection in training status (P<0.001).

The intensity of soil-transmitted helminths

The intensity of STHs infection was categorized based on the WHO classification thresholds using Kato-Katz thick smear method of parasites egg quantification expressed in eggs per gram (EPG) of stool. The geometric mean intensity of T. trichiura infection in our study was 2.30 (EPG ranging from 0–1,368), A. lumbricoides with 0.61 (EPG ranging from 0–31,840), and hookworm species with 0.13 (EPG ranging from 0–420). There was no statistically significant difference (P>0.05) in the mean intensity of hookworm species infection between model and non-model individual members in the HHs although A. lumbricoides and T. trichiura infection were having significant difference for the two groups (p<0.05) (Table 2).

Table 2

Infection intensity thresholds of STHs with the HH training status of selected districts of Seka Chekorsa woreda, Jimma zone, Southwest Ethiopia.

STHs species	STHs Infection status		HH status		P-value
			Model	Non-model
Trichuris trichiura	Geometric mean (EPG)		0.56	5.99	<0.001*
	Intensity class	Light	28(19.9)	108(76.6)
		Moderate	0(0.0)	05(3.6)
		Heavy	0(0.0)	0(0.0)
Ascaris lumbricoides	Geometric mean (EPG)		0.26	1.06	<0.001*
	Intensity class	Light	12(23.5)	35(68.6)
		Moderate	01(2.0)	03(5.9)
		Heavy	0(0.0)	0(0.0)
Hookworm species	Geometric mean (EPG)		0.10	0.16	0.341
	Intensity class	Light	07(43.8)	09(56.2)
		Moderate	0(0.0)	0(0.0)
		Heavy	0(0.0)	0(0.0)

Key

*- statistically significant at p-value < 0.05.

The mean intensity of T.trichiura and A.lumbricoides was high in the age group of ≤15 years and ≥15 years for hookworm species. Whereas, the mean intensity of A. lumbricoides was higher among male study participants while hookworm species and T. trichiura were high among female participants. However, the mean intensity of STHs infection has no significant difference with the age and gender of the study participants (P>0.05).

Risk factors of soil-transmitted helminths

Logistic regression analysis was performed to observe whether the overall STHs infection was significantly associated with the potential risk factors. Independent variables of P≤0.25 in Binary logistic regression analysis were selected as potential candidates for multiple logistic regression analysis using the backward stepwise method with Hosmer-Lemeshow goodness-of-fit statistics. A p-value <0.05 was considered a risk factor associated with the STHs infection. After adjusting for confounding variables, the present study reported that the distribution of STHs infections varies between individual members in the model and non-model HHs. The finding showed that individuals in the non-model HHs (AOR: 6.543, 95%CI; 4.36–9.82, p<0.001) were significantly 6.5 times more likely infected with STHs than those in model HHs (Table 3).

Table 3

Bivariate and multivariate logistic regression of risk factors of STHs infection among individuals in model and non-model HHs, Seka Chekorsa woreda, Jimma zone, Southwest Ethiopia.

Variables	STHs +ve (n = 198) No (%)	COR (95% CI)	p-value	AOR (95% CI)	p-value
HH status
Model	45 (22.7)	Ref		Ref
Non-model	153 (77.3)	5.80 (3.94–8.55)	<0.001*	6.54 (4.36–9.82)	<0.001a
Gender
Male	96 (48.5)	0.89 (0.64–1.26)	0.529
Female	102 (51.5)	Ref
Age
< 15	97 (49.0)	1.39 (0.99–1.96)	0.057*	1.52 (1.04–2.21)	0.030b
> 15	101 (51.0)	Ref		Ref
Open defecation free (ODF)
Yes	177 (89.4)	Ref		Ref
No	21 (10.6)	1.77 (0.97–3.23)	0.060*	1.23 (0.23–6.53)	0.807
Latrine availability
Yes	190 (96.0)	Ref		Ref
No	8 (4.0)	3.44 (1.11–10.67)	0.032*	3.33 (0.93–11.91)	0.065
Latrine lid covered
Yes	116 (58.6)	Ref		Ref
No	82 (41.4)	1.75 (1.23–2.49)	0.002*	1.07 (0.56–2.04)	0.843
Water source
Pipe	14 (7.1)	Ref
Spring	184 (92.9)	1.41 (0.75–2.65)	0.292
Hand washing facility
Yes	137 (69.2)	Ref		Ref
No	61 (30.8)	1.42 (0.97–2.07)	0.070*	0.76 (0.48–1.18)	0.221
Hand washing habit
Yes	182 (91.9)	Ref		Ref
No	16 (8.1)	1.83 (0.92–3.64)	0.086*	0.69 (0.27–1.80)	0.448
Shoe wearing
Yes	178 (89.9)	Ref		Ref
No	20 (10.1)	1.75 (0.95–3.23)	0.075*	1.89 (0.65–5.53)	0.243
Nail hygiene
No	182 (91.9)	3.22 (1.47–7.08)	0.004*	1.89 (0.77–4.62)	0.164
Clean	16 (8.1)	Ref		Ref
Waste disposal
Open field	115 (58.1)	2.05 (1.45–2.89)	<0.001*	1.23 (0.833–1.82)	0.298
Pit	83 (41.9)	Ref		Ref
Latrine use pattern
Always	178 (89.9)	Ref		Ref
Sometimes	20 (10.1)	1.75 (0.95–3.23)	0.075*	2.85 (1.43–5.69)	0.003b

Key: Ref: Reference category

*: Potential candidates for multivariate analysis p<0.25

a: P<0.001

b: p<0.05 considered as significantly associated with the dependent variable.

Regarding STHs infection with the age of individual members in the HHs, indicates that those individuals aged below 15 years (AOR: 1.515, 95%CI; 1.04–2.21, p = 0.030) were showing a significant finding of 1.5 times more likely infected with STHs infection than individuals aged above 15 years. The other significant finding was the latrine use pattern of individual members in the HHs, those individuals using a latrine sometimes were 2.8 times more likely to be infected with the STHs infection compared to the individuals using a latrine always. Whereas, those individual members of HHs with no shoe wearing and handwashing habits, dirt on a fingernail, not owning a latrine, not having a handwashing facility near a latrine and without a lid, open field defecating, and disposing of waste in the open field were more likely infected with STHs than individual members in the HHs with the constant variables. However, these independent variables were not significantly associated (p>0.05) with the STHs infection in multivariate analysis (Table 3).

Discussion

This study is the first to provide information comparing the difference in the prevalence and intensity of STHs infection among individual members in the model and non-model HHs in Ethiopia. Regardless of the intensive efforts to train HHs with the HEP agendas having possible indirect impact on hygiene related infections, the STH’s overall prevalence in the study area before and after the implementation of the health extension program was unknown. The current study indicates the prevalence of STHs infection among individuals living in model and non-model families in this rural community to be 32.35%. However, there was a significant difference in the prevalence with the HH status with a reduction of prevalence for those trained and certified on health extension packages. The reduction in prevalence may thus related to the behavioral change to seek healthcare service, the improvement in the hygiene and sanitation conditions after the training or else the existing economic status difference of the households that might reduce their exposure to STHs infection.

The finding of STHs prevalence from our study was found lower when compared to studies conducted in Ecuadorian Amazon, Nigeria, and Ethiopia with the prevalence reports of 52.1% [20], 65% [24], 46.9% [25], 84.24% [26] and 67.3% [27]. Whereas, our STHs infection prevalence was slightly higher than a study in Jimma 20.9% [28] and comparable with 32.5% [29] in Cameroon. These differences may be due to the effect of HEWs training on packages, study participant age, the sample size, annual deworming programs, predisposing factors, and differences in the endemicity of parasites in the study areas.

Regarding species-specific report, this study showed a lower prevalence of T. trichiura (21.6%), A. lumbricoides (6.4%), and hookworm (2.3%) as compared to a studies conducted in Ecuadorian Amazon, Nigeria and Ethiopia with prevalence of 38% [24], 41.5 [27] and 31.3% [28] for T. trichiura, 48% [24], 19.5% [25], 37.2% [27], 67.7% [28] and 42% [30] for A. lumbricoides, and 7.6% [25], 28.4% [27], 45% [28] and 47% [30] for hookworm, respectively. However, a relatively lower prevalence of T. trichiura was observed elsewhere with 18.9% [25] and 11% [30]. Even though its species composition and occurrence vary, poly-parasitism is also common in many tropical and sub-tropical regions of the world in which the maximum number of parasite species found in the same host in our study was three, and the prevalence of poly-parasite infection was 2.29%. This result is lower when compared with the studies reporting 8.66% [31], 56.7% [32] and 12.4% [20]. Variations in distribution and occurrence of STHs infections in different localities might be due to environmental, socio-demographic, and socio-economic factors that favor the transmission cycle of the parasites, sample size, egg output variation, and diagnostic technique performed.

The intensity of STHs infection ranges from light to moderate for individuals in model and non-model HHs except light infection intensity for hookworm species in both HHs. The intensity of STHs infection of individuals between the two HHs showed a significant difference for A. lumbricoides and T. trichiura while no significant difference for Hookworm species. This may be associated with the frequent exposure status of individuals among non-model HHs to the source of infection becoming higher. It could be related with the significant difference in their income status, latrine had coverlid and hand washing facility, and waste disposal mechanisms reducing risk factors. In the study done in the Ecuadorian Amazon, most of the individuals were infected with A. lumbricoides with a moderate intensity (51%) which was higher but 4.0% had a heavy intensity of infections. Similarly, most of the individuals infected with T. trichiura had light intensity (91.0%) [24] which is a lower intensity infection than the present study (96.5%). The intensity level difference may be due to frequent exposure status to the source of infection, the difference in treatment-seeking behavior, the difference in awareness of study participants, risk groups with age, and immunological differences.

Moreover, the current study has identified potential risk factors for STHs infection. Accordingly, age, latrine use pattern, and HH status (model or non-model) were found to be significant predictors of STHs infections in our study. Study participants, who are lower than 15 years were 1.5 times more likely to be infected by STHs than those who were greater than 15 years old. This is probably related to lower age groups having more exposure to soil and unhygienic practices. Similarly, individuals who use latrines sometimes were 2.85 more infected than individuals who use latrines always. This may be related to the possibility of open field defecation practice whenever the latrine is not used increasing the contamination with the parasite’s infective stages from the soil. The HH status in our study was found to be the other potential risk factor for STHs infection as individuals in the non-model HHs were 6.5 times more infected than the model HHs. This may be related to the impact of the training package on improving the lifestyle of hygienic practice, awareness of infectious diseases transmission mode, health care service-seeking practices or the existing economic status differences among the HHs.

Among the HEWs training package trained HHs, the majority of the HHs (65%) knew about STHs and heard the information from health extension workers (50%) and health institutions (4.2%). This was slightly higher as compared to participants of Orang Asli in rural Malaysia, (61.4%) of HH’s main source of information was the clinic while the majority of them could not remember the source [13]. The difference with the present study may be due to the level of awareness of health information increased with the efforts made by the health extension workers implementation of training packages.

Conclusion

The prevalence of STHs infection reported among individual members in the model HHs showed a significant reduction and a significant difference in the intensity of infection when compared to non-model HHs. The HH status, age of study subjects, and latrine use pattern were found significant predictors of STHs infection prevalence in the study area. Poor personal-related hygiene and environmental contamination are still public health problems among the individual members in the non-model HHs which can increase frequent exposure. Therefore, the application of health extension programs in communities should be strengthened sustainably in engaging all family members during the provision of HSEPs. Awareness creation on personal hygiene, lifestyle, and environmental sanitation-related infections such as STHs has to be strengthened along with deworming programs considering the adult community members. Such program implementation studies would better be assessed using a cluster randomized controlled trial study design to rule out the impact of a program to justify the outcome in controlled situations.

Limitations

In the absence of baseline data for STH infection status during program implementation by the ministry of health of Ethiopia, we performed an observational study design after fifteen years of program launch to assess the difference in prevalence and intensity of STHs infection among individuals residing within the two groups of households. Besides, our selected households were also certified by the HEWs for fulfilling minimum requirements of the training packages and we cannot guarantee their sustainable implementation of training packages after their certification. We expect the enrolment and certification of the households to be based on ground level measurable indicator parameters regardless of the economic status or lifestyle improvement of the households. Furthermore, our finding was based on a small sample size and having a study design limitation for assessing the risk of exposure to acquiring STHs infection that might affect our results.

24 Feb 2022

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Additional Editor Comments (if provided):

EDITOR’S COMMENTS

Dear Authors, kindly respond adequately to the points raised by the reviewers. There is need for improvement in the language structure. Clear explanations should be given on the study design and selection of study participants.

COMMENTS TO AUTHORS

FIRST REVIEWER:

First of all, I would appreciate and thanks authors for their interest and work to address evidence gaps on neglected tropical diseases.

General comments:

--I would expect specific target groups in the title and I suggest the title to be shaped as “Prevalence and Intensity of Soil-Transmitted Helminths Infection among individuals in Model and Non-Model Households, South West Ethiopia: A Comparative Cross Sectional Community Based Study”

-There is inconsistent use of the word STH and STHs in the manuscript.

- Given the main focus of your study is on STHs, I was wondering about the relevance of including other intestinal parasites in this study since

-How did authors categorize households as model and non-model?

-Lines 153-154, how was the wet mount examination performed (how specimens collected, transported, and where performed?).

-The sampling technique need to be clearly stated. Explanation for inclusion criteria of study participants should be stated y in the study?

-I suggest the word education (literate/illiterate) in your manuscript to be categorized by using other references? From my point of view, I don’t recommend using the word ‘illiterate’.

-The age category is not consistent in the manuscript; please revisit in the results section.

- The entire manuscript should be checked and proofread; there are language uses, typographical errors, and grammatical lapses that can be very distracting.

-To strengthen the paper more, the authors can suggest concrete recommendations on how the gaps in the program can be addressed.

-Authors suggestion concerning others operational research would be very important.

Specific comments:

The abstract should:

-Before stating the evidence gaps exist on the effect of modeling households on prevalence of soil-transmitted helminths among individuals, abstract should high light brief information about soil-transmitted helminths for readers outside the filed?

-Authors should mention the place where the study was done.

Methods:

- It seems that the authors aimed at testing the hypothesis of ‘individuals in non-model would have a higher prevalence of sol-transmitted helminths than individuals in the model households’. And by taking this into consideration, I was wondering how a cross-sectional study can testify this concept? For such kinds of study, I thought cohort study design would a good option to assess the effect of exposure on the outcome.

-How study participants were selected? Further explanation should be stated on how participants are selected to get a representative study population from model and non-model households? Did author consider stratification in the sampling technique.

--The inclusion criteria should be stated in the study population section.

-Did you include children under 15 years old in the study? State if assent was obtained from children in the ethical statement.

-The laboratory technique should be mentioned and explained as part of the data collection procedure.

- Please describe all the variables that you collected data on in the methods section.

-The data analysis procedure was not well stated and presented. The multivariate logistic regression model considered model and non-model households as one variable; by taking this into consideration how would author made a comparative analysis between those groups to draw a conclusion based on the data presented in the study.

-Please mention the ethical approval number if the study was reviewed and approved.

Results, discussion, and conclusions:

-Explain how the results related to the hypothesis presented as the basis of the study.

- The discussion provides a concise explanation of the implications of the findings, particularly in relation to previous related studies and potential future directions for research. Results should not be restated in the discussion section.

-The conclusion should be drawn based on the data presented in the study.

References:

-Please check all references according to the journals’ guidelines.

SECOND REVIEWER:

The title is very interesting and the manuscript technically sound, and the data support the conclusions. The analysis sounds to have significance on the prevention and control of STHs infection. The data underlying the findings in the manuscript fully available. The language that the authors used to write this manuscript is good. So with minor correction it can be considered for publication

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

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Reviewer #1: Yes

Reviewer #2: Partly

**********

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

Reviewer #1: Yes

Reviewer #2: No

**********

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Reviewer #1: Yes

Reviewer #2: Yes

**********

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Reviewer #1: Yes

Reviewer #2: No

**********

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: the title is very interesting and the manuscript technically sound, and the data support the conclusions. the analysis sounds to have significance on the prevention and control of STHs infection. the data underlying the findings in the manuscript fully available. the language that the authors used to write this manuscript is good. so with minor correction it can be considered for publication

Reviewer #2: First of all, I would appreciate and thanks authors for their interest and work to address evidence gaps on neglected tropical diseases.

General comments:

--I would expect specific target groups in the title and I suggest the title to be shaped as “Prevalence and Intensity of Soil-Transmitted Helminths Infection among individuals in Model and Non-Model Households, South West Ethiopia: A Comparative Cross Sectional Community Based Study”

-There is inconsistent use of the word STH and STHs in the manuscript.

- Given the main focus of your study is on STHs, I was wondering about the relevance of including other intestinal parasites in this study since

-How did authors categorize households as model and non-model?

-Lines 153-154, how was the wet mount examination performed (how specimens collected, transported, and where performed?).

-The sampling technique need to be clearly stated. Explanation for inclusion criteria of study participants should be stated y in the study?

-I suggest the word education (literate/illiterate) in your manuscript to be categorized by using other references? From my point of view, I don’t recommend using the word ‘illiterate’.

-The age category is not consistent in the manuscript; please revisit in the results section.

- The entire manuscript should be checked and proofread; there are language uses, typographical errors, and grammatical lapses that can be very distracting.

-To strengthen the paper more, the authors can suggest concrete recommendations on how the gaps in the program can be addressed.

-Authors suggestion concerning others operational research would be very important.

Specific comments:

The abstract should:

-Before stating the evidence gaps exist on the effect of modeling households on prevalence of soil-transmitted helminths among individuals, abstract should high light brief information about soil-transmitted helminths for readers outside the filed?

-Authors should mention the place where the study was done.

Methods:

- It seems that the authors aimed at testing the hypothesis of ‘individuals in non-model would have a higher prevalence of sol-transmitted helminths than individuals in the model households’. And by taking this into consideration, I was wondering how a cross-sectional study can testify this concept? For such kinds of study, I thought cohort study design would a good option to assess the effect of exposure on the outcome.

-How study participants were selected? Further explanation should be stated on how participants are selected to get a representative study population from model and non-model households? Did author consider stratification in the sampling technique.

--The inclusion criteria should be stated in the study population section.

-Did you include children under 15 years old in the study? State if assent was obtained from children in the ethical statement.

-The laboratory technique should be mentioned and explained as part of the data collection procedure.

- Please describe all the variables that you collected data on in the methods section.

-The data analysis procedure was not well stated and presented. The multivariate logistic regression model considered model and non-model households as one variable; by taking this into consideration how would author made a comparative analysis between those groups to draw a conclusion based on the data presented in the study.

-Please mention the ethical approval number if the study was reviewed and approved.

Results, discussion, and conclusions:

-Explain how the results related to the hypothesis presented as the basis of the study.

- The discussion provides a concise explanation of the implications of the findings, particularly in relation to previous related studies and potential future directions for research. Results should not be restated in the discussion section.

-The conclusion should be drawn based on the data presented in the study.

References:

-Please check all references according to the journals’ guidelines.

**********

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Reviewer #1: No

Reviewer #2: No

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Submitted filename: PONE-D-21-35319.docx

Click here for additional data file.

15 Apr 2022

EDITOR’S COMMENTS

Dear Authors, kindly respond adequately to the points raised by the reviewers. There is need for improvement in the language structure. Clear explanations should be given on the selection of study participants, and study design used.

(First of all, we would like to thank the editor handling our manuscript. We also extend our appreciation to the reviewers who provided concrete comments that can help our write-up to progress one step forward. We have accepted and revised the manuscript incorporating the comments given by the reviewers. Our responses to some of the questions are also incorporated in the comment reviewing pane).

COMMENTS TO AUTHORS

FIRST REVIEWER:

First of all, I would appreciate and thanks authors for their interest and work to address evidence gaps on neglected tropical diseases.

(We would like to thank the first reviewer, for the positive and constructive comment appreciating our focus area which tried to show evidence of STH prevalence and intensity difference among communities targeted with a health extension training program package and its impact on one of the NTDs, which is STHs).

General comments:

--I would expect specific target groups in the title and I suggest the title to be shaped as “Prevalence and Intensity of Soil-Transmitted Helminths Infection among individuals in Model and Non-Model Households, South West Ethiopia: A Comparative Cross Sectional Community Based Study”

(We would like to thank the first reviewer, for the positive and constructive comment appreciating our focus area which tried to show evidence of STH prevalence and intensity difference among communities targeted with a health extension training program package and its impact on one of the NTDs, which is STHs).

-There is inconsistent use of the word STH and STHs in the manuscript.

(Thank you, we made a correction).

- Given the main focus of your study is on STHs, I was wondering about the relevance of including other intestinal parasites in this study since

(Sure, our main focus is to show the prevalence of STH among our study subjects. Since we used saline wet mount and Kato Katz techniques, other protozoans and helminths parasites were detected in the stool of the study participants along with the STHs.

However, we have no special interest to display other IP prevalence except to show there were multiple parasite infections as an additional finding. We will remove it from the document if suggested not relevant).

-How did authors categorize households as model and non-model?

(Thanks, we did not categorize the households into model and non-model. This category was already made by the program criteria as model household heads (members) who attended at least 75% of training packages of health service extension programs (HSEPs), implemented at least 75% of the packages, and were eventually certified for fulfilling these requirements by the government. Otherwise, they were labeled as non-model in the program. Thus, we were aware of the status confirmed from their certificates).

-Lines 153-154, how was the wet mount examination performed (how specimens collected, transported, and where performed?).

(Thanks, Each selected Kebele has at least one health post or an additional health center according to the population in the woreda/district, and also we were traveling having microscopy for the saline wet mount exam. This makes it nearby to the households to be examined within 30 minutes. The collected stool specimen in a stool cup was then transported to Jimma university research laboratory in a cold box within 2 hours of collection for the Kato Katz procedure).

-The sampling technique need to be clearly stated. Explanation for inclusion criteria of study participants should be stated y in the study?

(Thank you for the comment, we rewrote the sampling technique including diagrammatic representation, and added eligibility criteria in the study population section).

-I suggest the word education (literate/illiterate) in your manuscript to be categorized by using other references? From my point of view, I don’t recommend using the word ‘illiterate’.

(Thank you, we have changed to read and write for literate and unable to read and write for the illiterate).

-The age category is not consistent in the manuscript; please revisit in the results section.

(Thank you for the comment, we have reviewed the result section. Our study subjects are the HH heads and members of the HH which makes a range from children to adults. We consider the household level question for table 1, based on their exposure to STH intensity in table 2 and risked age group in table 3. However, now we made a correction to remove ambiguity and explained relevant findings in text only).

- The entire manuscript should be checked and proofread; there are language uses, typographical errors, and grammatical lapses that can be very distracting.

(We appreciate the comment, we have rechecked the whole document for the language, typographic, and Grammatik issues and made corrections in the main text).

-To strengthen the paper more, the authors can suggest concrete recommendations on how the gaps in the program can be addressed.

-Authors suggestion concerning others operational research would be very important.

(Thank you, we have included our recommendation with a suggestion for filling gaps and strengthening the program sustainably in the community).

Specific comments:

The abstract should:

-Before stating the evidence gaps exist on the effect of modeling households on prevalence of soil-transmitted helminths among individuals, abstract should high light brief information about soil-transmitted helminths for readers outside the filed?

(Thank you, we have incorporated introductory information on STH in the abstract section).

-Authors should mention the place where the study was done.

(Thank you, we have incorporated the study area in the abstract).

Methods:

- It seems that the authors aimed at testing the hypothesis of ‘individuals in non-model would have a higher prevalence of sol-transmitted helminths than individuals in the model households’. And by taking this into consideration, I was wondering how a cross-sectional study can testify this concept? For such kinds of study, I thought cohort study design would a good option to assess the effect of exposure on the outcome.

(Thank you for the comment, we understand the suggested cohort design could be more powerful to justify the situation. Also, the baseline assessment was not done while the program was implemented in 2003 to at least look at the trend recommending at least baseline assessments to be performed during launching.

We aimed to assess the impact of the program just by looking at the difference in the prevalence, intensity, and risk factors associated among the individuals from model and non-model HHs at the point of time and provide evidence for further research questions as baseline information).

-How study participants were selected? Further explanation should be stated on how participants are selected to get a representative study population from model and non-model households? Did author consider stratification in the sampling technique.

(Thank you, we have incorporated the comment and explained in the main text. We made a selection starting from the Kebele/districts from the purposely selected Seka chekorsa woreda in the Jimma zone. Then villages/zones were included w/c is located in the district. From the villages, HHs were systematically selected. Finally, all eligible individuals within the HHs were surveyed in our study. Terms like woreda, district, and villages are sequential local administrative strata as a subset of the other respectively).

--The inclusion criteria should be stated in the study population section.

(Yes, we have incorporated it in the mentioned section).

-Did you include children under 15 years old in the study? State if assent was obtained from children in the ethical statement.

(Sure, we have included children aged less than 15 years and mentioned now as their assent was taken).

-The laboratory technique should be mentioned and explained as part of the data collection procedure.

(Thank you, we have explained the technique employed for the stool examination. If the detailed procedure of wet mount examination and Kato Katz techniques are requested, we may add additional documents to the supplementary file).

- Please describe all the variables that you collected data on in the methods section.

(Thank you, we have listed the summary of variables included in our study in the methods section).

-The data analysis procedure was not well stated and presented. The multivariate logistic regression model considered model and non-model households as one variable; by taking this into consideration how would author made a comparative analysis between those groups to draw a conclusion based on the data presented in the study.

(Thank you, we made this clear under the data analysis now. Multivariable analysis was made to see the association of household status (either model or non-model) to STHs infection. This is to give evidence of whether the non-model households have more risk of being infected with STHs. But comparisons were made between the two groups using an independent sample t-test).

-Please mention the ethical approval number if the study was reviewed and approved.

(Thank you, we have mentioned the ethical approval number given by the institutional research ethical review board).

Results, discussion, and conclusions:

-Explain how the results related to the hypothesis presented as the basis of the study.

(Thank you, our results aimed to show the individuals in the model or non-model HHs were compared for the difference in prevalence, and intensity of STHs infection. We re-wrote our result section based on the comments which may clear ambiguity now).

- The discussion provides a concise explanation of the implications of the findings, particularly in relation to previous related studies and potential future directions for research. Results should not be restated in the discussion section.

(Thank you, our results aimed to show the individuals in the model or non-model HHs were compared for the difference in prevalence, and intensity of STHs infection. We re-wrote our result section based on the comments which may clear ambiguity now).

-The conclusion should be drawn based on the data presented in the study.

(Thank you, we re-wrote our conclusion based on our result findings).

References:

-Please check all references according to the journals’ guidelines.

(Sure, references were scanned again to fit the guidelines of the journal).

SECOND REVIEWER:

The title is very interesting and the manuscript technically sound, and the data support the conclusions. The analysis sounds to have significance on the prevention and control of STHs infection. The data underlying the findings in the manuscript fully available. The language that the authors used to write this manuscript is good. So with minor correction it can be considered for publication

(Thank you for the second reviewer, we would like to extend our appreciation for the positive and constructive comment. We have updated the write-up based on the provided comments and hope it will be considered for further process of publication).

Submitted filename: Response to reviewers.docx

Click here for additional data file.

17 Jun 2022

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'.

29 Jul 2022

Response to the Reviewers and editor:

We would like to extend our gratitude to the editor and reviewers in charge of evaluating our manuscript for fitting the journals publishing requirements.

• We have checked the references list; however, we have no article retracted from the journals.

• Thank you the third reviewer for finding our manuscript interesting and could have merit to the field, we appreciate.

• We accept the critical and important comment raised on the mean calculation. However, we prefer to use the arithmetic mean calculation for the sake of simplicity and we have made corrections accordingly such as including zero intensity counts in negative individuals to calculate the mean and updating in the text.

• We made also similar corrections in the main text indicating the way data was analyzed for the methods section.

• We have added the limitation of our study under the discussion section separately.

Submitted filename: Response to reviewers.docx

Click here for additional data file.

7 Sep 2022

Submitted filename: Alemu_PONE-D-21-35319R2_Comments.docx

Click here for additional data file.

15 Sep 2022

PONE-D-21-35319R2: Reviewer’s comments

Response:

(We would like to extend our appreciation to the editor handling our manuscripts review process once again)

Summary

The author have revised the manuscript (discussion) and highlighted the lack of baseline data as a major limitation. Thus, the manuscript may be considered for publication. There are a few minor comments below.

Response:

(We are grateful to the reviewers for their critical comments and corrective suggestions in strengthening our manuscript to be considered for publication. We have responded to the recent comments accordingly in this version.

In the previous version, we have tried to respond forwarding our revised version on raised comments related with data analysis and limitation of our study. To remind, we have incorporated the limitation of our study after the conclusion section of the main text in our former communication.

Whereas, it seems that the issue related with the mean calculation remains unsatisfactory. As a result, we have revised our current version incorporating such comments as well. For the calculation of geometric mean, we have included zero counts in the mean calculation after adding one to each datasets and subtracting one from the result of converted logarithmic calculations)

Specific comments

1. It is important to make it clear what the abbreviation HH is referring to because it appears to be interchangeably used to refer to, 1) household heads, and/or 2) households.

Response:

(Thank you for the comment, we have rewritten based on their concept as HH for household, HHs for household heads and also identified separately in the text whenever it refers to the individual members in the HHs accordingly)

2. Line 24-27: Check grammar for the statement reading “This study…(HEP)”

Response:

(Thank you, We made adjustment to the text in response to your suggested comment)

3. Line 37: Insert the word “to be” between the words found and 32.4%.

Response:

(Noted and we have incorporated the comment in the text)

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

29 Sep 2022

Prevalence and Intensity of Soil-Transmitted Helminths Infection among individuals in Model and Non-Model Households, South West Ethiopia: A Comparative Cross-Sectional Community Based Study

PONE-D-21-35319R3

Dear Dr. Alemu,

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.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Reviewer #3: All comments have been addressed

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Reviewer #4: Yes

Reviewer #5: Yes

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6 Oct 2022

PONE-D-21-35319R3

Prevalence and Intensity of Soil-Transmitted Helminths Infection among individuals in Model and Non-Model Households, South West Ethiopia: A Comparative Cross-Sectional Community Based Study.

Dear Dr. Alemu:

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.

If we can help with anything else, please email us at plosone@plos.org.

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Kind regards,

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on behalf of

Dr. Clement Ameh Yaro

Academic Editor

PLOS ONE