Prevalence and intensity of gastro-intestinal helminths in horses in the Sudano-Guinean climatic zone of Cameroon.

BACKGROUND: It is important to understand the biology and health impact of parasites affecting horses in the Western highlands of Cameroon. AIM: to evaluate the prevalence and intensity of infection of gastrointestinal helminths in these animals.
MATERIALS AND METHODS: A total of 894 horses (367 males and 527 females), and aged ≤1 to ≥7 years old were examined. A parasitological investigation of faeces was carried out using two techniques: concentration method of Full Born Willis (flotation in saturated solution of sodium chloride) and Mc Master Technique. RESULTS AND
CONCLUSIONS: From the results the overall prevalence was 100%. Nine species of nematode (Parascaris equorum, Oxyuris equi, Habronema sp., Strongyloides westeri, Dictyocaulus arnfieldi, Trichostrongylus axei, Cyathostome sp., Triodontophorus sp., Strongylus sp.) were identified with the prevalence of 18.48%, 16.94%, 2.99%, 6.05%, 5.22%, 7.75%, 12.49%, 1.09%, and 22.26%, respectively, and one species of cestode (Anoplocephala magna) with a prevalence of 6.73%. Strongylus sp. had the highest mean intensity of infection (1270±942) in female horses. Poly-parasitic infections (92.28%) were more common than mono-parasitic infections (7.72%).

INTRODUCTION

Horses and humans interact in many ways including a wide variety of sports competition, police work, agriculture, entertainment and warfare. The transport of horses across national boundaries for shows and performance competitions make the issue of worm control and containment of resistant strains a matter of global importance.[1] Many products are derived from horses including meat, milk, hair, bones, blood, hooves, and pharmaceuticals. For this reason, this industry deserves the attention of the general public and the government. This new situation requires more information about the sanitary status of these animals and the appropriate measures for ensuring that the horses are in an adequate fitness condition. Among the diseases affecting horses, helminth infections are much extended.[2] These parasites continue to be a significant threat to the health of horses. The nature or extent of damage varies with the parasites.[3] They cause loss of nutrients, blood and serious economic losses. In Kenya, for example, the economic loss to the agricultural sector due to Haemonchus contortus parasite of small ruminants was estimated at US$ 26 million per year.[4] The control of nematodes in horses has been challenging for some years and there is general recognition that improvements should be made to commonly used worm control programmes. These improvements should be based on scientific knowledge of the parasites, appropriate diagnostic techniques and should take into account the presence or potential selection for resistance to available anthelmintics.[1] Horses of all ages are affected without sex or breed susceptibility.[5] There is, therefore, a need to understand the current status of the prevalence and intensity of infection of helminths in horses in the Western highlands of Cameroon, in order to establish a control program to improve their productivity.

STUDY SITE AND METHODS

Period and study site

This study was carried out from March to November 2009 on horses coming from six localities (Fongo-Tongo, Fokoue, Dschang), Western Region and also from Banso, Fundong and Acha in the Northwest Region of Cameroon. Its coordinates lie between latitude 5°N and 10°E. The temperature varies between 15.4°C and 25°C, the relative humidity (RH) ranges from 64.3% and 97% and the annual rainfall ranges from 6.2 mm in January to 320.2 mm in August. The soil is mostly lateritic, feralitic and volcanic in some areas and the climate is the Sudano-Guinean type (Office de Tourisme de Dschang, 2009). As concern the North West Region, it lies between latitude 6°N and longitude 10°E. The temperature varies between 20°C and 22°C, while the annual rainfall varies between 1780 and 2290 mm. The soil type is humic and ferralitic. It has a relative humidity of 82.7%. In these areas two season are predominant; a long rainy season from mid-March to mid-November, and a short dry season from mid-November to mid-March.

METHODS

Collection of faecal samples

Fresh faeces were collected with gloved hands, placed in plastic bags and labeled with the age and sex of the animals, date, time and month of collection. The specimens obtained from horses were immediately transported in ice bag to the Laboratory of Animal Health of the University of Dschang. Faeces were analyzed immediately or within 48 hours after being stored in the refrigerator at +4°C. For each specimen, a systematic macroscopic analysis was done to register the consistency of the faecal material, element present in the faeces such as mucus, blood and eventually worms (Taenia segment, adults of round worms) were also registered as outlined. Faeces were then analysed by the flotation technique using the saturated salt solution as described.[67] The Mc Master technique was performed to evaluate the parasitic load. Identification of the different parasitic stages was done using the morphological characteristic such as, the form, the length, the nature of the egg shell and the identification key. In addition, parasite stages were measured using an ocular micrometer.

Statistical analysis

The Chi-square and analysis of variance (ANOVA) one way tests respectively were used to compare the prevalence and the mean intensity of infections of different gastrointestinal helminths with respect to each locality, age and sex of animal at the P<0.05 significance level.

RESULTS

Eight hundred seventeen horses came from the Northwest and 77 from the West Region with a parasitic prevalence of 91.39% and 8.61% respectively. Nine species of nematodes (Parascaris equorum, Oxyuris equi, Habronema sp., Strongyloides westeri, Dictyocaulus arnfieldi, Trichostrongylus axei, Cyathostome sp., Triodontophorus sp., Strongylus sp. and one species of cestode (Anoplocephala magna) were identified in all six localities [Figure 1]. Independent of locality Strongylus sp. (21.6%) had the highest prevalence, followed by P. equorum (18.8%), O. equi (15.2%), Cyathostome sp. (12.6%), T. axei (10.6%), A. magna (6.3%), D. arnfieldi (5.3%), S. westeri (4.9%), Habronema sp. (2.8%), and Triodontophorus sp. (2%). P. equorum had its highest prevalence in horses coming from Fongo-Tongo and Fundong (20.9%). The same finding was observed in horses coming from Acha (18%), Banso (17.9%), Dschang (17.6%) and Fokoue (17.4%).The prevalence of O. equi was highest in horses coming from Acha (21.2%), followed by those coming from Banso (19.6%), Fundong (16.5%) while, horses coming from Fongo-Tongo (12.3%), Dschang (11.6%), and Fokoue (9.9%) were similarly infected by the same parasite. From this study, we noticed that some parasites prefer horses of a particular age. For example, P. equorum was most prevalent (26.21%) in 1 and 2 years old horses compared to the other ages [Figure 2] while Strongylus sp. (35.4%) were mostly found in horses of the age greater or equal to 7 years old. In contrast, A. magna was absent in animals of this age. In both sexes of horses [Figure 3], Strongylus sp. (20.5%) had the highest prevalence, followed by O. equi (19.0%), P. equorum (18.5%), Cyathostome sp. (12.5%), D. arnfieldi (6.4%), A. magna (6.4%), S. westeri (5.4%), T. axei (5%), Habronema sp. (4.7%) and Triodontophorus sp. (1.5%) [Figure 3]. P. equorum (19.7%), O. equi (19%), S. westeri (6.5%) and the cestode A. magna (7.6%) seem to have some preference for female horses. The tendency is reversed for Cyathostome sp. (13.7%), D. arnfieldi (7.5%), T. axei (7.0%) and Habronema sp. (5.9%). From this study, four types of parasitic associations were identified Figure 4. Quadruple infection (38.37%) was more frequent and involved P. equorum + O. equi + Strongylus sp. + A. magna (19.53%) in one hand, P. equorum + O. equi + Strongylus sp. + Cyathostoma sp. with similar prevalence on the other hand. This was followed by triple infection (32.88%) P. equorum + O. equi + Strongylus sp., double infection (21.03%) with D. arnfieldi + T. axei (21.82%), P. equorum + Strongylus sp. (11.17%), Cyathostoma sp. + Strongylus sp. (10.64%) and single infections (7.72%) with Strongylus sp. (65.21%), T. axei (14.49%), Cyathostoma sp. (8.7%), Habronema (5.8%), S. westeri (1.45%), D. arnfieldi (1.45%), P. equorum (1.45%) and O. equi (1.45%). The intensity of infection of helminths varies with the different ages of the animals [Figure 5] and the highest intensity was observed with Strongylus sp. (1846±1257) in horses with age equal or greater than 7 years.

Figure 1

Prevalence of gastrointestinal helminths of horses per locality

Figure 2

Agewise prevalence of gastrointestinal helminths in horses

Figure 3

Prevalence of gastrointestinal helminths in male and female horses

Figure 4

Types of parasitic association

Figure 5

Agewise intensity of infection (EPG)

DISCUSSION

Nine and 1 species of Nematodes and Cestode were identified respectively following the methodology used, even though other parasites may have been present. Horses (100%) were infested with all type of parasites. Strongylus sp. was the most prevalent parasite in all localities, sexes, and age groups. This finding corroborates the one as[89] in New Zealand and Turkey, respectively. They observed that, Strongyles are the threat of horses. The difference in species and number of parasites obtained in this study can be due to the fact that, horses are graze permanently on free-range exposing them to frequent infections. In addition, to the degree of domestication, some breeders don’t follow the rules of livestock rearing which include good feeding, hygiene and prophylaxis. Some parasites identify in this work are equally found in ruminants, even though the majority of gastrointestinal helminths of horses are host-specific.[10] Part of this study shows that some parasite prefers female horses. This may be due to the production of some hormones. It was equally observed that the intensity of infection of these horses with respect to locality was generally moderate. The high prevalence and intensity of Strongylus sp. shows that there is a risk of infection with this parasite if young and old horses graze together in the same pasture. That is why in mono and poly-parasitic infections, Strongylus sp. had the highest prevalence. Mono-parasitic infection is relatively rare in horses, may be because they are large mammals with a large digestive tube. Poly-parasitic infection is favored by mutual and auto infections. These associations of parasites indicate that they are non-destructive to each other and are not competing amongst themselves. The effects of the presence of worms are not usually spectacular. However, they do cause decreased work efficiency, poor utilization of food, colic, and occasionally death due to blood clots. Some adult worms produce toxins that destroy red blood cells, leading to unthrifty anemic condition.[11] Immature worms migrate through body tissues, creating room for bacteria and fungi to enter, causing other serious diseases.[10]

CONCLUSION

The prevalence and intensity of infection of helminths is influenced by the origin, age, and sex of animals. As concerns the associations of gastrointestinal helminths, quadruple infection was more prevalent (P≤ 0.05) compared to triple, double or single infection. Keeping the above information in view, we suggested to horse breeders that they should regularly contact veterinarians for prophylactic and curative treatment of their animals and also, pasture management should be strictly respected.