The objective of present study was to determine prevalence and intensity of gastrointestinal nematodes in naturally infected sheep and associated risk factors in and around Hirna, western Hararghe, Ethiopia. 384 faecal samples were examined using egg flotation technique. Out of which 272 (70.83%) were found positive for gastrointestinal nematode infection. Coprological investigation revealed that sampled sheep were infested by a variety of helminth nematodes. Strongyle type were the most frequently (58.59%) recovered nematode eggs followed by Strongyloides (23.44%) and Trichuris species (2.08%). The eggs per gram (EPG) count was determined using McMaster technique which showed that 133 (48.90%) of the sheep were lightly infested, 96 (35.29%) sheep were moderately infested and 43 (15.81%) sheep were heavily infested. There was significant association between the gastrointestinal nematode infection and animals with different body condition scores. Animals with poor body condition had a significantly higher worm egg count (p < 0.05) as compared to sheep in moderate or good body condition. There was no significant difference (p > 0.05) in prevalence between different sex and ages. The present study showed that ovine gastrointestinal nematodes are of the major cause of helminthiasis in the study area. To get clear epidemiological picture detailed study should be conducted to clearly identify parasitic nematodes using faecal culture and postmortem examination in the study area as well as farmers should be educated on the importance of the parasitic diseases, its economic losses and the correct ways to improve animal husbandry system.
In Ethiopia, sheep are the second most important livestock species next to cattle and ranks second in Africa and sixth in the world in sheep population (Gizaw et al., 2007). The frequent droughts and large tsetse infected areas in sub-Saharan Africa requires more small ruminants in order to supplement cattle production (Gizachew et al., 2014). So, sheep population in this region has become adapted to a range of environments from cool alpine climate of the mountains to the hot and arid pastoral areas of the lowlands (Mirkana, 2010). Despite their physiological adaptation and ability to thrive under harsh environmental conditions, the full exploitation of their productivity is hindered in the tropical environment due to a combination of factors such as drought, poor genetic potential of the animals, traditional system of husbandry and presence of numerous diseases (Waruiru et al., 2005).
Gastrointestinal parasitic infections are a world-wide problem for both small- and large-scale farmers, but their impact is greater in sub-Saharan Africa in general and Ethiopia in particular due to the availability of a wide range of agro-ecological factors suitable for diversified hosts and parasite species (Regassa et al., 2006). Helminth infections in small ruminants are among serious problem in the developing countries, particularly in those areas where nutrition and sanitation standards are generally poor. Most parasitic helminthes infect their host via oral route and live either at mucosal surface of the gastrointestinal tract or cross the mucosal barrier on their way to predilection site. The problem is greater in tropical countries with good rain fall (Mulcahy et al., 2004). The epidemiology of gastrointestinal parasites in livestock varies depending on the local climatic condition, such as humidity, temperature, rainfall, vegetation and management practices. These factors largely determine the incidence and severity of various parasitic diseases in a region under consideration (Bekele, 1993). Although the reasons for the occurrence of parasitic diseases are multiple and often interactive, the vast majority occur for one of four basic reasons. These are: i) an increase in the numbers of infective stages, ii) an alteration in host susceptibility, iii) the introduction of susceptible stock and iv) the introduction of infection into a clean environment (Taylor et al., 2007).
In Ethiopia sheep and their products provide direct cash income through the sale of live sheep and hides. Sheep are considered as living bank for their owners and serve as source of immediate cash need and insurance against crop failure especially, where land productivity is low and erratic rainfall, sever erosion, frost and water logging problems are common. Thus, sheep in the small holder farming system provide continuous service to the economic stability and effective operation of the crop production system (Gryseels and Anderson, 1983). Majority of these economic losses are caused by gastrointestinal parasites in a variety of ways: they cause losses through lowered fertility, reduced work capacity, involuntary culling, a reduction in food intake and lower weight gains, treatment costs and mortality in heavily parasitized animals (Ibrahim et al., 2014). Small ruminants under intensive and extensive production systems are extremely susceptible to the effects of wide range of helminth endoparasites. Owing to basic limitations in scope and coverage of most of the studies conducted in Ethiopia, sound helminth control strategy has not yet been established to any of the agro-ecological zones of the country (Abede and Esayas, 2001).Therefore, considering the above said points present study was designed with the objectives of identification of the major GIT nematodes of sheep in Hirna district and determination of prevalence of gastrointestinal nematodes in the study area in relation to different risk factors.
A cross sectional study was conducted from November 2015 to April 2016 on indigenous breeds of sheep reared and managed under semi-intensive and extensive husbandry systems. The animals were grouped into two classes on the basis of age i.e., young (less than one year age) and adults (equal to or greater than one year age) (Kumsa et al., 2011). Similarly, body condition score was classified into three levels i.e., poor, medium and good (Pant et al., 2009).
Systematic random sampling technique was conducted to collect the fecal sample from individual study animals for coprological examination. Age, sex and body condition was considered as risk factors for the occurrence of nematode infections in sheep. Since there was no record of previous prevalence in the study area, the sample size was calculated according to Thrusfield (2005) formula by using 50% expected prevalence with 5% absolute precision at 95% confidence interval.
Where, n= the sample size
Pexp= expect prevalence (0.5)
d=desired absolute precision (usually 5%)
z= required confidence level, (Z=1.96 for 95% confidence interval)
Therefore, by substituting the values of variables in the formula the sample size was determined to be 384, which is used as representative animal on which the study was done to know the prevalence of gastrointestinal nematodes.
Fecal samples were collected directly from the rectum of each animal by using rectal gloves or from freshly passed droppings and were placed in sampling bottles containing 10% formalin and labeled. During sampling, data regarding age, body condition and sex were also recorded for each sampled animal. Finally samples were transported at room temperature to Hirna Veterinary Regional Laboratory for coprological examination.
The collected fecal samples was processed and examined by simple fecal floatation technique for qualitative investigation of types of gastrointestinal nematode eggs by using NaCl (sodium chloride) as floatation solution. The eggs of different parasitic species were identified using keys given by Soulsby (1986). Positive fecal samples were subjected to McMaster egg counting technique and the degree of infection was categorized as light, moderate and severe (heavily) infection according to their egg per gram of faces (EPG) counts. Egg counts from 50-799, 800-1200 and over 1200 eggs per gram of feces were considered as light, moderate and massive infection respectively (Soulsby, 1986; Urquhart et al., 1996).
The prevalence was calculated by dividing the number of animals harboring a given parasite by total number of animals examined. The data was entered and managed in excel worksheet and analysis was conducted using STATA-11(Stata Corp. College Station, Texas, USA). Percentage (%) function was used for measuring prevalence and Chi-square test (χ2) function was used for measuring association between the risk factors as well as prevalence of various parasites where confidence level was held at 95% and P < 0.05 set for significance.
Results and Discussion
Out of total 384 animals examined, 272 animals (70.83%) were found positive for different types of gastrointestinal nematodes. The findings of this study were similar to those of Dilgasa et al., (2015), Lemma and Abera, (2013) and Admasu and Nurlign, (2014), who reported prevalence of 68.4%, 68.1%and 72.16% respectively. The current prevalence was slightly lower, than the previous reports of Bikila et al, (2013) in Gechi District, Southwest Ethiopia, Gizaw (2015) from Kaffa and Bench Maji Zones, Ethiopia, Abebe and Esayas, (2001) from eastern part of Ethiopia and Tefera et al. (2011) in and around Bedelle, who reported the prevalence of 84.3%, 96.7%, 95.6% and 91.3%, for the above mentioned areas respectively. The higher prevalence observed in different parts of Ethiopia could be due to over stocking, poor nutrition (starvation), poor management practice of the animals (lack of sanitation) and frequent exposure to the common grazing lands that have been contaminated. This difference could also be due to the sample size considered, types of techniques utilized and the prevalence varies greatly from region to region, corresponding to ecological and climatic diversity as well as the existing host ranges (Ayele et al., 2014).
Among 384 sheep, 225 sheep (58.59%) were found to be infected with Strongyle type species, 90 sheep (23.44%) were found to be infected with Strongyloides species and 8 sheep (2.08%) were found to be positive for Trichuris species (Table 1). These finding were in consonant with that of Tigist, (2008), Temesgen, (2008), Ragassa et al, (2006) and Lemma and Abera, (2013) who reported 56.6% Strongyle type, 8.2% Strongyloides and 5% Trichuris in Debre Zeit, 66.6% Strongyle type and 3.3% Trichuris species in Bedelle, 70.2% Strongyle type and 4.5% Trichuris species in Western Oromia and 64% Strongyle type and 7.4% Strongyloides and 3.7 Trichuris in Asella, South eastern Ethiopia respectively. This may be related to similarities, in climatic conditions, grazing and/or management system. However contrary to the present study Abebe and Esayas, (2001) reported prevalence of 97.03% Strongyle type, 45.22% Strongyloides and 30.25% Trichuris species in eastern part of Ethiopia and this difference may be related with geographical conditions and climatic changes in the eastern parts of the country. The high prevalence may be due to the suitability of the climatic condition of Hirna district for survival and transmission of the parasites. The prevalence of Strongyloides species in the present study was 23.44 % which is in agreement with the reports of Tefera et al. (2011) from Bedelle and Tigist, (2008) from Debre Zeit, who reported 13.04% and 8.2%, respectively. Prevalence of Trichuris species in the present study was 2.08% and this finding was in route with the work of Tigist (2008), Temesgen, (2008), Ragassa et al. (2006), Lemma and Abera (2013); with prevalence of 5%, 3.3%, 4.5% and 3.7%, respectively. The current finding however was lower as compared to 45.2% from Eastern part of Ethiopia by Abebe and Esayas (2001).
|Parasite Egg Types||Number of Animals Examined||Positive Samples||Prevalence (%)|
|Strongyle type spp||384||225||58.59|
Variation between Body Condition Score, Sex and Age
In this study statistically significant difference in prevalence (P <0.05) between animals with different body conditions was observed and prevalence of 90.41%, 73.0% and 44.59% were recorded for poor, medium and good body conditioned animals respectively (Table 2). In the present study, an animal with poor body condition seems to have higher prevalence of major gastrointestinal nematodes. This higher parasitic infestation in sheep with poor body condition score is consistent with reports of Bisset et al. (1986), Lemma and Abera, (2013) and Yonas and Goa (2017) suggesting that well fed animals develop good immunity that suppresses the fecundity of the parasites. This study also supports the report from Kenya by Kanyari et al. (2009) who reported that animals with good body condition had lower prevalence of gastrointestinal parasites than those with poor body condition.
Table 2: Prevalence of gastrointestinal nematode infection based on age, sex and body condition scores using coprological examination
|Risk Factors||No. of Animals Examined||No. of Positive Samples (%)||χ2||P- value|
The present study showed no statistically significant differences (P > 0.05) in the prevalence of GIT parasites between sex groups (Table 2). This finding was in agreement with the reports of Ragassa et al. (2006), Ghanem et al. (2009) and Yonas and Goa (2017) who reported that sex of animals did not show significant association with the prevalence of GIT parasites. This indicated that male and female sheep have equal chance of infection if they are exposed to the same contaminated common grazing pasture. However, our findings were not in agreement with that of Dagnachew et al. (2011), Bashir et al. (2012) and Lone (2011) who reported higher prevalence of GIT parasites in females than in males and Zvinorova et al. (2016) who reported higher prevalence of GIT parasites in males than in females. It is assumed that sex is a determinant factor influencing prevalence of parasitism and females are more prone to parasitism during pregnancy and peri-parturient period due to stress and decreased immune status (Urquhart et al., 1996).
Age wise observation revealed no significant difference (P > 0.05) in infestation of GIT parasites despite slightly higher infection noticed in younger animals (Table 2). This finding was in consonant with reports from Gechi district of south west Ethiopia, Semi-arid part of Kenya, Gambia and Wolaita Sodo, southern Ethiopia by Bikila et al. (2013), Waruiru et al. (2005), Fritsch et al. (1993) and Yonas and Goa (2017) respectively. They described as GIT parasites affect both ages equally. The present finding were not in agreement with the finding of Regassa et al. (2006), Colditz et al.(1996) and Kanyari et al.(2009), Zvinorova et al. (2016) who reported that young animals are more susceptible to parasitic infections than older ones. The researchers have justified the result as it could be because adult animals may acquire immunity to parasites through frequent challenge and they expel the ingested parasite before establishment of infection. Young animals are susceptible due to immunological immaturity and immunological unresponsiveness (Gizachew et al., 2014). However, in this study the absence of significant difference in parasites infestation between ages of animals could be attributed to the small number of young animals used.
Fecal samples collected from 272 positive animals were subjected to Mc master technique and 48.90%, 35.29% and 15.81% infection was classified as light, moderate and heavy infection of gastrointestinal nematodes (Table 3). The results for relative severity of GIT nematode infestation in studied animals are in accordance with a previous study by Tefera et al. (2011) in and around Bedelle, where 46.56% were lightly, 44.97% were moderately and 8.47% were massively affected. The above finding was also in line with the report of Bikila et al. (2013) from Gechi district of south west Ethiopia with prevalence of 25.5%, 63.8% and 10.7% for light, moderate and massive infestations, respectively.
Table 3: Level of infection based on egg per gram (EPG) count of examined positive animals for GIT nematodes
|Intensity of Infection||Examined No. of Samples (%)||EPG|
|Light||133 (48.90)||50 – 799|
|Moderate||96 (35.29)||800 – 1200|
|Heavy||43 (15.81)||> 1200|
The present study showed that ovine gastrointestinal nematodes are of the major cause of helminthiasis in and around Hirna. It also revealed higher prevalence of infestation with Strongyle type parasites. Age, body condition and sex were considered as the most prominent risk factors associated with gastrointestinal nematode infection. However no significant difference in the prevalence of the parasite due to age and sex was observed except for the body condition score (P < 0.05) in which higher prevalence was recorded in animals with poor body condition.