1.     Introduction

 Trypanosomiasis is a disease caused by several species of protozoan parasites (Trypanosomes) found in the blood and other tissues of vertebrates including livestock, wildlife and people. It is a major impediment to livestock farming in sub-Saharan Africa and limits the full potential of agricultural development in the 36 countries where it is endemic [1]. The tsetse infested area covers one-third of the land area in eastern and southern Africa. In Africa, the overall loss (in both direct and indirect) is estimated as 500 billion dollars a year in term of mortality, abortion, reduced fertility, milk meat production, and ability to work as traction animals [2].

 In Ethiopia, tsetse infested area estimated around 10,997 hectares from the total of 122,190 hectares. The tsetse flies are confined to the southern, southwestern and north-western region where the primary vectors exist along the great rivers basin of Abay, Omo, Gibe and Baro. The fly has infested an estimated 130,000-200,000 square kilometers of fertile land in the country. In generally, in Ethiopia 20,000 heads of cattle die in every year and 14 million heads of bovine at risk contracting Trypanosomiasis at any time [3].

 There are six pathogenic species of trypanosomes which are discovered in Ethiopia, namely Trypanosoma vivax, T. congolense, T. brucei, T. evansi, T. equiperdum, and T. rhodesiense. But the most important trypanosomes in the country are T. vivax and T. congelense. Both species affect a great number of cattle which are the most important species of the domestic animals in Ethiopia [4].

 The problem of trypanosomiasis was also reported to be very serious in the study area. During a survey carried out by Sodo Regional Veterinary Laboratory, farmersreported that trypanosomiasis is the most important constraint to livestock development in the area. And trypanosomiasis was considered to be an important disease of cattle in different part of the country in reports of [5-10].

 However, studies have not yet been carried out on the epidemiology, prevalence and economic significance of bovine trypanosomiasis in this study site. Therefore, the objectives of the study were to estimate the prevalence of bovine trypanosomiasis in study area, to identify the dominant species of trypanosomes and some associated risk factors and to compute Packed Cell Volume (PCV) in relation to trypanosomiasis.

 2.    Materials and Methods

2.1.  Study Area

 Kindo Didaye district is one of the districts of Wolayita zone in the South Nation Nationalities and Peoples Region of Ethiopia. The administrative center of this district is Halale town. The Kindo Didaye district is located at about 444Km of southwest of Addis Ababa and it has an altitude of 800-1690 meter above sea level. And its total area is estimated to be 16,687 hectare of land. The distribution of rain is bimodal, with short rain from January to April and long rains from June to mid-September. The average annual rainfall is 867 mm, the maximum and minimum daily temperature is 30.20 and 21^ºC respectively. The vegetation is savanna type with scattered bush. The livestock populations that are found in Kindo Didaye district include cattle, sheep, goat, horses, mule, donkey and poultry. Among these animals, cattle are the dominant species raised in the area. The cattle population in the district is estimated to be about 180,374 [11].

2.2.  Study Design

 Cross-sectional type of study was conducted in four randomly selected peasant associations of Kindo Didaye district to estimate the prevalence of bovine trypanosomiasis, to identify the prevailing species of trypanosomes and to assess the host related risk factors of a disease.

2.3.  Study Population

 The study population constitutes zebu cattle which are managed under small holder mixed farming system. Animals were allowed to graze freely during the day time and housed during the night. The age of animals was grouped under less than 1 year, 1-3 year, and greater than 3year of age, the body condition of the animals grouped under good, medium (moderate) and poor based on the method of scoring the body condition of Zebu cattle [12].

 2.4.  Sampling Method and Sample Size Determination

 Two stage cluster sampling technique was followed to select the study animals. First, five peasant associations in Kindo Didaye district and house holders from each selected peasant associations are selected by simple random sampling method and all the cattle herds found in each house holder were selected for sample collection. During data collection age, sex and body condition of the animals were recorded.

 The expected prevalence of 6.3% from [10] report on the prevalence of bovine trypanosomiasis in Kindo Koysha district of Wolayita zone, the boarder district to Kindo Didaye district, were taken to calculate the sample size. The number of animals to be sampled in the study was estimated by the formula described by [13]. 

n= 1.96² x P_exp(1-P_exp)/d²

n=90

Where n is sample size, d is absolute precession and P_exp is expected prevalence

 The 95% confidence interval and 5% precision was used, and the calculated sampling size was 90 but 120 samples were taken to increase the precision.

 2.5.  Parasitologicaland Hematological Examinations Techniques

 2.5.1.         Measuring of Packed Cell Volume (PCV)

 Blood samples were obtained by puncturing the marginal ear vein with a lancet and blood was collected directly into a capillary tube and filled up to ¾ of the tube. The capillary tubes were placed in micro haematocrit centrifuge with sealed end outer most of one side. The tube was loaded symmetrically to ensure good balance. After screwing the rotary cover and closing the centrifuge lid, the specimens were allowed to centrifuge at 12,000 rpm for 5 min. Tubes were then placed in haematometer and the readings were expressed as a percentage of packed red cells to the total volume of whole blood. Animals with PCV < 24% were considered to be anemic [14].

 2.5.2.         Buffy Coat Technique

 To do buffy coat technique, the capillary tube was cutted from 1mm below the layer of buffy coat to include the upper most layers of the red blood cells and the content of the capillary tube was expressed on to slide, homogenized on to a clean glass slide and covered with cover slip. The slide was examined under ×40 objective for the presence of parasite [15].

 2.5.3.         Thin Blood Smear

 A small drop of blood from a microhaematocrit capillary tube to the slide was applied to a clean slide and spread by using another clean slide at an angle of 45º, air dried and fixed for 2 min in methyl alcohol, then immersed in Giemsa stain (1:10 solution) for 30 minute. The excess stain was drained and washed by using distilled water, allowed to dry by standing up right on the rack and examined under the microscope with oil immersion objective lens.

 2.5.4.         Data Management and Analysis 

Raw data of individual animals and examination results were stored in Microsoft Excel spread sheets to create data base and transferred to SPSS version 20 software programs for data analysis. Chi square was used to compare the prevalence of trypanosome infection with different risk factors variables like peasant association, age, sex and body condition, while t-test was utilized to compare the mean PCV of the infected animals and non-infected animals. Significance difference was set at p < 0.05 and 95% confidence level.

3.    Result

 3.1.  Parasitological Results

 Out of the total 120 cattle examined, 7(5.83%) were found positive to trypanosomiasis. The prevalence of trypanosomiasis in selected peasant associations is 5% in Halale, 8.3% in Shella, 5.4% in Zerada and 5.1% in Bosa-bortu areas. But the association between peasant associations and the prevalence of trypanosomiasis is not statistically significant (p>0.005).

 The most prevalent trypanosome species in the study area was T.congolense (57.1%) followed by T. vivax (28.6%) and mixed infection from T.vivax and T.congolense was also recorded in (14.3%) of the tasted animals. The prevalence of trypanosome infection was higher in female (6.6%) than male (5.1%) animals; however, there was no statistically significant (p > 0.05) differences observed between the two sexes.

 A higher infection rate of 9.8% was observed in adult animals (animals above one year and below three years of age) and followed by 5.3% in old animals (above three years) and 0% in young animals with in the study area but the variation was not statistically significant (p > 0.05).

 Cattle infected with trypanosome have poor body condition score than the non-infected animal. There was a statistically significant (p < 0.05) difference among the prevalence of trypanosomes in different body conditions.

 3.2.  Heamatological Resuts

The PCV value ranging from 18 to 34 was found from the observed animals. Out of the observed animals, infected animals had a mean PCV value of 19.43% and non-infected animals had 27.14%, and the overall mean PCV value of the study also resulted in 26.69 %. Statistically significant difference (P < 0.05) in mean PCV was observed between infected and non-infected animals.

4.      Discussion

 The study revealed that the prevalence of bovine trypanosomiasis in the area was 5.83% which was relatively in agreement with the previous finding by [10] at Kindo Koysha district of Wolayita zone (6.3%), but it was much lower than the reports of [16] at Humbo District of Wolayita zone (14.2%), [17] at Keto settlement area of south western part of the country (15%). and [18] at Humbo Larena of Wolayitazone (9.3%) and Konsodistrict (11.5%). The difference between reports might be due to the presence of large study time gap, application of relatively well designed methods of tsetse control and disease treatment, expansion of cultivation in the area which indirectly affects flies distribution, expansion of veterinary clinic, and awareness of people towards the control and treatment of the disease.

 The findings of the infection rate with T. congolense in the present study which is57.1% is in the line with the report of [10] at Kindo Koysha district of Wolayita (58%), [3] report form tsetse infested areas of Ethiopia (58.5%), [19] in selected sites of southern region (63.4%) and [9] in West Gojam (54.3%). The increased proportion of infection with T. congolense in the study area may be due to the major cyclic alvectors of the savannah set seflies, (G.moristans and G.palidpes) which are effective in transmitting T. congolense than T. vivax [20] since the study area is located in the tsetse belt of Ethiopia.

 Infection rate in poor body conditioned animals were significantly higher than good body condition animals (p < 0.05) and was in agreement with [9,21] Although higher infection rate was observed in animals of between 1 up to3 years of age (9.6%) and animals above three years of age (5.3%), in the present study no statistically significant (p > 0.05) association was observed in age. This result is in agreement with the previous results reported by [7,9,21]. This could be due to the fact that all animals graze and used as draft as well as harvesting of crops to the same tsetse challenged areas. Young animals of under 1 years of age are protected from the disease and 0% prevalence was observed. This is may be due to suckling calves do not go out with their dams but graze at homesteads until they are weaned off. Young animals are also naturally protected to some extent by maternal antibodies [22]. This could result in low prevalence of trypanosome in calves.

 The prevalence level also different in different areas but the association is not significant. Similarly, sex has insignificant association (P >0.05) with infection rate as it was also reported by [9].

 The mean PCV value of studied animals was significantly (P<0.05) varying between parasitaemic (19.43%) and a parasitaemic (27.14%) animals. This result was in agreement with the previous results reported by [1]. Anemia is one of the most indicators of trypanosomiasis in cattle (Stephen, 1986). The level of anemia or PCV usually gives a reliable indication of the disease states and reduces performance of infected animals [23,24]. Even though significant difference is found in the study, PCV alone could not be used for diagnostic criteria for trypanosomiasis because there are also other factors causing anemia such as worm infestation and nutritional deficiency [14].

5.   Conclusions and Recommendations

 From this study, it is possible to conclude that trypanosomiasis is an important disease and a potential threat affecting the health and productivity of cattle in the study area. The major species of trypanosomes in the study area were T. congolense followed by T. vivax and mixed infection of the two species. Infection with trypanosomiasis negatively affected PCV and body condition. This indicated that trypanosome infection of cattle cause’s loss of body weight and production

 Based on the finding the following recommendations are forwarded:

·                     Further study on the occurrence of tsetse and trypanosomiasis at different season of the year, at different altitude and different species of animals should be conducted.

·                     Trypanosomiasis control measures which are practiced to all parts of Ethiopia, like reduction of tsetse population and mechanical vectors reduction methods should be applied 

Figure 1: Map of study area Source: (Eyasu and Ahmed, 2013) [10].

Figure 2: Mean PCV value comparison of infected and non-infected animals.

 Table 1: Association of risk factors with prevalence of trypanosomiasis.

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