Prevalence of Major Gastrointestinal Nematode and Degree of Parasite Infestation in Sheep of Bako Agricultural Research Center Community Based Breeding Program Project Small Holder Farms at Horro District- Juniper Publishers

Journal of Dairy & Veterinary Sciences- Juniper Publishers

Helminths are most frequently a problem in young animals reared in permanent animals’ pasture, although cases of severe diseases may occur in adult animals kept in sub urban paddocks and subjected to overcrowding and poor management [28]. Many low to moderate infection are sub clinical although, they may cause reduced weight gain and performance. Young, non-immune animals are most susceptible and manifest clinical disease which may include diarrhea, colic and hypoproteinaemia [29]. Pasture larval levels increase markedly during the summer months when conditions are optimal for rapid development of eggs to L3. There is also increasing evidence that may infective L3 ingested during autumn show a degree hypobioxis under ileum in the large intestinal mucosa until the following spring [28]. Resistance affected adversely by stress and nutritional deficiencies. Moderate infection can be tolerated by a good plane of nutrition and management with in similarly infected but poorly [30].

Factors affecting Epidemiology Nematode Parasites

The development, survival and transmission of the free-living stages of nematode parasites are influenced by micro-climatic factors within the faecal pellets and herbage. These include sunlight, temperature, rainfall, humidity and soil moisture. Under optimal conditions (high humidity and warm temperature), the development process takes 7 to 10 days, but for H. contortus a more rapid translation of eggs to larvae can occur in warm wet conditions. In most African countries, the temperatures are permanently favorable for larval development in the environment. Development of trichostrongylid larvae occurs in a temperature range of approximately 10-36 °C. The optimal humidity requirement for free- living stage development of most species is 85%. Although desiccation is lethal for the free-living stages of parasite worms, the important nematode parasites can survive such conditions either as embroynated eggs or as infective larvae [31].

The seasonal fluctuations in numbers and availability of the infective larval stages are also influenced by the level of contamination of the pasture (Figure 2). The latter is controlled by the biotic potential (fecundity) of the adult parasites in the host, the density of stocking, and the immune status of the host. Although different species of GI nematodes of small ruminants have varying egg-producing capacities, H. contortus is one of the most prolific nematodes. A female H. contortus may produce thousands of eggs each day, and larval numbers on pasture can rapidly increase during the wet seasons [28].

Diagnosis of Nematode Infestation

Clinical diagnosis of GIT nematodes of sheep and goats needs history of the area, history of anti-helminthes treatment, grazing history, age of animal and clinical signs manifested by the disease. But as GIT nematodosis share common clinical manifestations with other diseases laboratory diagnosis is important. The diagnosis of nematode parasites of small ruminants is based on demonstrating the presence of their eggs, or larvae, in faecal samples, or the presence of parasites recovered from the digestive tracts of the animals [32].

The following diagnostic procedures for helminth infections of small ruminants are relevant to African conditions. Faecal examination by means of the modified McMaster technique for the enumeration of worm eggs and larval differentiation by faecal culture methods are the most common routine means for the diagnose helminthosis in small ruminants. The strong lid nematode genera produce eggs that are similar in appearance and cannot be easily discriminated, which means that genus identification cannot accurately be made by faecal examination alone. To identify nematodes in faecal samples, faecal cultures are required to yield L3 larvae, which generally can be differentiated to genus level. Nematodirus, Strongyloides and Trichuris species have eggs that can be differentiated by their distinct morphological features [33].

Laboratory Diagnosis

Although there is much current interest in the use of serology as an aid to the diagnosis of helmenthosis, particularly with introduction of ELISA test, diagnosis GIT parasitic infections still depend mostly on parasitological findings of eggs and/ or parasite in fecal samples [28].

Faecal Examination

Fecal examination for the detection of worm eggs is most common and routine work in GIT nematode diagnosis. Examination of faces for nematode eggs may vary from a simple direct smear to more complex methods involving centrifugation and the use of flotation fluids [34].

Direct Fecal Smear Examination

The presence or absence of worm eggs in fecal sample using direct smear of fresh faces on microscope slide and examination under low power objective microscope is routine procedure. However, this technique is only useful to detect nematode eggs when it exists high concentration in faces. Other disadvantages of direct techniques include difficulty to identify them since the eggs are partially covered by debris materials and quantitative results could not be obtained although it is fast and easy technique [34].

Concentration Techniques

Light infections are not easily detected using direct smear; therefore, concentration technique was developed to overcome the short coming of direct smear. The concentration techniques that are widely used include the use of salt or sugar solution and centrifugal concentration techniques. In both cases the logic behind is to concentrate the nematode eggs in each portion of sample or processed fecal material. In flotation the type of egg recovered is related to specific gravity of solutions; half saturated sodium chloride with specific gravity of 1.125 is capable of floating Trichostrongloids and strong lid eggs while fully saturated sodium chloride with specific gravity of 1.204 is preferred as generalpurpose solution [35].

Egg Counting Technique

The demonstration of a parasitic element in excreta includes: the presence of parasite. However, this information is not always enough. In the case of gastrointestinal strongylosis, the number rather than the presence of parasites is important. A technique called Mac Master. This technique is said to be easily applicable low technology parameter to indicate the level of infestation and degree of worm burden in some instances. The method enables to determine the number of eggs per gram of faces, although it is difficult to relate directly with the burden of parasites in large ruminants, still it is widely used, and best correlation was observed in small ruminants and the method is also used to detect anti helmhentic resistance.

Fecal Culturing

Grazing sheep and goats usually have mixed nematode infections. Only few nematode parasites have characteristic eggs that enables as to differentiate to genus level (Nematodirus spp, Trichuris spp, strongyloides spp,) but those trichostrongyle and strongyles are not easily differentiated, for this reason fecal culturing and larval identification based on the keys available is useful technique.

Treatment

Small holder farmers and pastoralists of Ethiopia practice varying degrees of parasite control in their livestock. These practices range from the use of anthelmintic drugs of varying quality, to the use of traditional medicines [36]. The prophylactic treatment of nematode infection depends basically on the use of anthelmintics [37]. Notable, the availability of safe, broad spectrum anthelmintics has helped to reduce the incidence of a great number of worm diseases (Figure 3). In general, anthelmintic groups are greatly effective against the immature and mature stages of virtually all the important gastrointestinal nematodes as well as many extra intestinal helminth species [38]. The drugs of choice for small ruminants’ nematode infection areIvermectin 0.2mg/kg, oxfendazole 5mg/kg, fenbendazole 5mg/kg, levamisole 2.5mg/kg, albendazole 4-8mg/kg and febantel 5-10mg/kg. These anthelminthic have high activity against mature and immature stage nematode. Antibiotics are also given to prevent secondary bacterial infection [39].

Control and Prevention

Control of endoparasite is the most desirable although internal parasite problem is usually related to management practices that increases exposure. Whereas ongoing preventive management practices minimizes losses caused by parasitic infection. Control of nematode infection in small ruminants may be achieved by pasture management. Animal must be removed from infected ground, placed on dry pasture and supplied with clean drinking water. Draining and resting pasture during dry summer kill many larvae that readily survive cold winter. Their feces should not be used for fertilizing lands on which crops for green feeding are grown, moist grasses should not be given to animals, and adult should not graze together with young stock [39].

Proper Nutrition

The strongest link between nutrition and parasitism has been illustrated between protein intake and resistance to GINs infection. The most dramatic has been the abolishment of the peri parturient egg rises in lambing ewes by providing protein accordingly. Supplementation with phosphorus has been shown to prevent worm establishment [40].

Pasture Management

A safe pasture is one that had no sheep grazed on it for 6 months during cold weather or 3 months during hot/dry weather. Weaning sheep at 2 months of age and rotating them through pastures ahead of the adults will minimize the exposure to large numbers of infective larvae. Pastures should be rotated following any administration anthelmintic to the animals [41]. Nematophagous Fungi: Act as a biological control agent. Nematophagous fungi are micro-fungi which utilize nematode larvae as their main source of nutrients. The fungi are ingested by ruminants pass through the digestive tract and colonize fecal material. Three predaceous fungi have been identified but only one is suitable for including in ruminant diets. Duddingtoniaflagrans has thick-walled spores that can be fed to ruminants and passes safely through to the feces. The spores must be fed daily to maintain the reduction in L3 numbers [42].

Anthelmintic Usage

If possible, anthelmintic use should be restricted to 2 or 3 times per year by combining anthelmintic use with the epidemiology of nematode infection. Regular monthly dosing, as practiced on some farms, cannot be recommended. Use the full dose of an anthelmintic as well as alternate the type of anthelmintic used. The generally accepted view is that anthelmintics should be alternated on an annual basis [43].

Materials and Methods

Description of the study area

The study was conducted in selected peasant associations of Horro district by the help of Bako agricultural research center because it has community-based breeding program project supported by international livestock research institute with objective of improving breeding in horro sheep at two selected sites of the district namely Laku Ingu and Githilo Dole. Which are considered as the origin of horro sheep, presence of large sheep populations, and presence of ear tag for suitable sampling and known history of anthelmentics treatments. There are 135 small holder farmers in the community based breeding program project those have 12-15 sheep on average. Horro district is in Horo Guduru wollega Zone of Oromia regional state at the distance of 328km to west of Addis Ababa. Horro Guduru Wollega zone is located between 09º29´N and 37º26´E, at an altitude of 2,296` m.a.s.l, with a uni-modal rainfall ranging between 1200mm- 1800mm. The rainy season occurs from April to mid-October. Maximum temperature of 23-27 are reached from January to March, and temperature range of 7 °C -15 °C is normal from October to November.

Study Population

The study animals comprised indigenous Horro sheep of randomly selected small holder farms from 135 small extensive farms kept together on communal grazing pasture of the peasant association day time and separately housed at night by individual house holders. Those small farms owned by small holder farmers under community-based breeding program of Bako Agricultural Research Center supported by ILRI at both peasant associations. Single small farm contains an average flock size of 12-15 animals. The study animals will be taken from those selected peasant association’s small holder farmers depending on their total number of animals. A total of 384 sheep were sampled from both site regardless of sex, age, body condition score etc.Animal in each selected districts were grouped into age groups as young (<1year) and adult (>1 year) based on birth register and body conditions (poor, medium and good) as per Kempster.

Study Design

Cross sectional study was conducted to determine prevalence of major gastrointestinal nematode and degree of parasite infestation in sheep of Bako Agricultural Research Center community-based breeding program project small holder farms at Horro district. The study sites were selected purposively whereas farmers and the individual sample animals were selected by simple random sampling method. Depending on numbers of eggs counted, animals were then categorized as lightly, moderately and severely (massively) infected according to their egg per gram of faeces (EPG) counts. Egg counts from 50-799, 800-1200 and over 1200 eggs per gram of faeces were considered as light, moderate and massive infection respectively [28].

Sample Size and Sampling Method

Simple random sampling strategy was followed to collect feces from the individual animals. Those all study sheep were from two purposively selected peasant association of Horro district managed together for the most part and grazed on permanent communal pastures. Due to study animals were under community-based breeding program the proportion of female to male is high. Sample size for fecal collection was determined using the formula given by Thrusfield. Accordingly, using expected prevalence of 50% at 95% confidence intervals and 5% desired absolute precision a sample size of 384 animals were collected because no previous work in district even in those farms. Sample size determined by the following formula.

Where N= Sample size

P= expected value

d= desired absolute precision

Then by taking p=50% and d=5%

N =1.962 x 0.5(1-0.50)/0.05

N=384

Study Methodology

Sample Collection and Laboratory Analysis

An average of 5gm of fecal sample was collected from rectum of each sampled sheep those were not dewormed for at least three months in to a plastic container and clearly labeled corresponding to detailed information recorded and transported for examination. After collection the fecal samples were preserved with 10% of formalin to prevent the egg from hatching during transportation because the study site is far from the laboratory where the samples processed then taken to Bako Agricultural Research Center (BARC) animal health laboratory for coprological investigation. When samples were reached in the laboratory they were immediately stored in the refrigerator (4 °C) until they were processed for further preservation. Floatation techniques were employed to diagnose eggs of nematodes using saturated sodium chloride (40%) as flotation fluid and the slides prepared were examined under microscope (x10). Eggs of the different nematodes were identified on the base of morphological appearance and size of eggs and Macc master egg counting technique was also done for positive samples to categorize the severity of the infestation level. The degree of faecal egg output per gram was determined as described by Hansen & Perry [44] in mixed infection with different GI nematode species.

Data Analysis

Data generated from laboratory investigations will be recorded and coded using Microsoft Excel spreadsheet (Microsoft Corporation) and analyzed using SPSS version 20 statistical software. Descriptive statistics will be used to determine the proportion of diseases based on sex, peasant associations, body condition and age. Chi-square test and the p-value will be used to determine the presence of association among the different variables and the major animal health problems caused by parasites. A calculated two value at the specified degree of freedom(df) greater than the tabulated value of two at that df will be reported as having a significant association and vice versa. A p-value less than 0.05 will be considered as having statistically significant. 95% confidence interval will be used for interpreting the result.

Results

The overall prevalence of gastrointestinal nematodes in sheep during the study period was 36.7% from the positive samples, 64 (16.66%) were positive for strongyle type egg, 30 (7.81%) were positive for Trichuris egg, 29 (7.55%) were positive for strongyloides egg for single infection and gastrointestinal nematodes were appeared as multiple infection in 18 positive animals as Strongyle and Trichuris 10 (2.60%), Strongyle and Strongyloides 6 (1.56%), Trichuris and Strongyloides 2(0.52%) (Tables 1& 2). Most of the samples were found with single infection 123 (87.23%) than multiple infections (12.76%). The prevalence of gastrointestinal nematode parasite was higher in female sheep (37.8%) than male (32.9%) in the study area. Among age groups, higher prevalence (59.29%) was observed in young animals as compared to adult (27.3%) (Table 3).

The prevalence of gastrointestinal nematode was higher in female sheep (37.8%) than male (32.9%). Of the total 384 sheep examined, 127, 188 and 69were categorized as having poor, medium and good body condition scores. Infection prevalence was significantly higher in animal with poor body condition when compared to that of medium and good body condition scores. The overall infection prevalence according to body condition grades, 59.1%, 27.1% and 21.7% with poor, medium and good, respectively (Table 4). The prevalence of gastrointestinal nematode was higher in Githilo Dole (38.459%) than Laku Ingu (34.2%) with almost minimal difference.

Results of Quantitative Fecal Egg Counts

Fecal samples positive for GIT nematodes in this study were subjected to Mc Master egg counting chamber for EPG count to determine the degree of severity of parasitic infestations. The majority of positive study animal had the EPG count of less than 800.The animals positive for nematodes by floatation technique was subjected to McMaster technique and are classified as lightly (57.4%), moderately 34 (24.1%) and severely 26(18.4%) infected with GIT nematodes (Tables 5 & 6).

Discussion

Many studies showed that gastrointestinal nematodes are the leading causes of productivity losses in small ruminant production in Ethiopia [45]. The coprological examination done for this study using simple test tube faecal floatation techniques revealed that an overall gastro-intestinal nematode infection prevalence of 36.7% of sheep originating from this area which were being parasitized at least by one type of gastrointestinal nematodes.

In this study, infections with strongyles were the dominant one among the examined animals. Infections with Strongyloidiasis spp and Tricuris were also identified with limited proportions accordingly. This agrees with several studies conducted so far [46-48]. who reported high proportion of strongyle infection? This might be since ruminants have different level of resistance for different species of parasitic infections and several nematode parasites produce strongyle like egg which only identified on larval stage by fecal culture.

The present study shows no statistically significant differences (P > 0.05) between two sex groups, male (32.9%) and female (37.8%). This finding agrees with report by Assefa & Sissay [49], with gastrointestinal helminths affecting both sex groups equally. This is due to equal exposure of both sexes, and they are from similar agro-ecology. The variation may occur in the intensity of infection due to post-parturient parasite rise in lambed sheep. The absence of association between sexes is inconsistent with previous reports [50,51]. Nevertheless, itis agree with a higher prevalence of helminth infection in female animals. It is assumed that females are more prone to parasitism during pregnancy and per-parturient period due to stress and decreased immune status [28].

In this study, a significant difference was observed in prevalence of nematode infection in relation to body condition score where a higher prevalence of gastrointestinal nematodes parasites was recorded in poor (59%) and moderate (27.1%) body conditioned animals as compared to animals having good (21.7%) body condition. This finding agrees with [52-54]. In addition, [55] indicated that animals with poor condition are highly susceptible to infection and may be clinically affected by worm burdens as compared to well-fed healthy animal. Moreover, Knox et al. [56] observed that a well-fed animal was not in trouble with worms, and usually a poor diet resulted in more helminth infections. The study further revealed that small ruminants with medium and poor body condition score have higher prevalence rate of nematodiasis infection which is consistent with previous reports. This might be due to either well-fed animals have good immunity or parasitic infection leads to poor immunological response to the fecundity of the parasites.

Age wise observation revealed statistically significant difference in infestation of parasites between ages with prevalence of 59.2% in young and 27.3% in adult sheep. This finding disagrees with reports from Gambia and Semi-arid part of Kenya that indicated that GIT helminthes affect both ages equally [57,58]. The present finding agrees with most literatures that young animals are more susceptible to parasite infection than sheep older than 1 year of age. The researchers justified the result that it could be because adult animals may acquire immunity to the parasite through frequent challenge and expel the ingested parasite before they establish infection [59]. The finding also agrees with reports of higher prevalence in young animals in Ethiopia. Age was considered as an important risk factor in GIT helminthiasis [60]. Several authors have documented that adult and old animals develop acquired immunity against helminth infections as they get mature due to repeated exposure [28].

The current study has shown the presence of mixed infection characterized by the presence of two or more nematode parasites in sheep which agrees with the findings of other researchers in the country and elsewhere. These Mixed infections have been suggested to be an important cause of morbidity and loss of production in sheep. Moreover, the presence of interaction and compromization of the immune system of the host by mixed infections described increase in their susceptibility to other diseases or parasites.

In relation to peasant associations the prevalence of GIT nematodes is relatively high in Githilo Dole (38.4%) as compared with Laku Ingu (34.1%). However, the difference in prevalence between the two sites was not statically significant (P>0.05). This also agrees with report by [61-63]. Significant difference was not reported in animals reared in similar geographical areas. In this study, absence of association between location and prevalence in sheep could be due to relative similarity in agro-ecology between study locations, similar deworming strategy by Bako Agricultural Research Center and a relatively similar management systems practiced by farming communities.

Conclusion and Recommendation

The gastrointestinal nematodes of sheep are one of the important parasitic diseases that obviously result in reduced productivity of sheep. Therefore, the high prevalence of nematode infection observed in the study area indicates potential contribution to limiting the productivity and compromised wellbeing of the animals. The infection was found higher in animals with poor body conditions than medium and good body conditioned sheep. Therefore, attention should be given to animals with poor body condition in control of the nematode infections. According to the results of this study, the prevalence of gastrointestinal nematode was found 36.7%.

Generally, gastrointestinal nematodes were prevalent in Horro district and sheep of the study area were infected with diversified gastrointestinal nematodes that can seriously affect the health and productivity of the animals. These parasites affected all age and sex groups prevailing agro-climatic conditions like overstocking of the animals, grazing of young and adult animals together with poorly drained land provide an ideal condition for the transmission of the endoparasites to build up clinical infestation of the host [64]. Furthermore, weak status of animal health services and lack of proper management, crop-livestock mixed farming is highly practiced, and most land is cultivated so that many species of animals including sheep are kept together on communal grazing land which is the source of parasitic infection. They give the first line to draught animals and forced sheep to graze behind on overstocked areas which lead them to graze close to the ground and on fecal materials, causing in the uptake of higher numbers of infective larvae. All in all, the finding suggests that the study area is favorable for the continual maintenance and successive transmission of helminthes parasites to vulnerable hosts [65- 67]. Many animals were sub-clinically infected without attracting understanding of farmers to undertake control measures (Figure 4).

Based on the above conclusions, the following points are forwarded as recommendations:

a. Regular de-worming program using broad spectrum anthelmintic and good management practices should be implemented to minimize pasture contamination with larvae.

b. Further epidemiological study should be conducted in the area including environmental factors like management conditions that helps to design an appropriate control measures.

c. Quantitative method of study should be conducted to determine the parasite load and it is effects on the different body parameters.

d. Detailed study should be conducted to clearly identify nematode parasites using fecal culture and postmortem examination in the study area.

e. Separating the most susceptible young animals from adults, this is a possible source of contamination.

f. Proper screening and monitoring of the sheep should be carried out regularly in the sheep

g. Furthermore, parasitic control and prevention should be implemented in the area. 

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