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Study on the prevalence of bovine trypanosomosis in Assosa district of the BenishanGulgumuz region, west Ethiopia

Shibabaw Bejano, Teshome Kifle1 and Wendimu Bireda

Department of Animal Science, Assosa University, P O Box 18, Assosa, Ethiopia
1 BenishangulGumuz Regional Veterinary Laboratory


A cross-sectional study was conducted in Assosa district to determine prevalence of bovine trypanosomosis and evaluate its severity. The study employed parasitological blood screening of 322 randomly selected cattle. For parasitological identification, blood samples were examined using Buffy coat technique.

In general, from the total blood samples collected, the prevalence of trypanosomosis was 22.1% for  T. congolense, 14.3% mixed T. vivax and T. congolense 4.67%, T. vivax 2.2% and T. brucei 0.9%. The highest and the lowest prevalence were recorded in Kushmengle, 27.8% and Abramo,18.2%, respectively. The trypanosoma infection was slightly higher in males (22.5%)  than females (21.5 %). Age-wise prevalence was 11.7% in animals <22 years,  23.2% in animals of > 2 years. From the total sampled cattle, 51.1% were subjectively rated as having poor, 20.2 % medium and 0% good body condition and prevalences were 51.1%, 20.2% and 0% for poor, medium and good, respectively. The finding of this work revealed that trypanosomosis was an important problem in Assosa district; causing significant economic loss due to its negative impact on the productivity of cattle.

Key words: cattle, species


Livestock in developing countries contribute up to 80 percent of agricultural GDP and about 600 million rural poor people rely on livestock for their livelihoods (reference??). Livestock does not only provide poor people with food, income, traction and fertilizer but also act as catalysts that transform subsistence farming into income-generating enterprise (ILRI 2005). However, the African continent is faced with the challenge of satisfying the increase in demand for livestock products, in particular for milk and meat. This is mainly due to the low level of livestock production, which is caused among many reasons by parasitic, viral, bacterial and fungal livestock diseases. Trypanosomosis is arguably the most important of disease in the tropics (Jahnkeet al1988).

Trypanosomosis is a serious parasitic disease, which occurs in large areas of Africa, Latin America, the Middle East and Asia. It affects most species of domestic livestock, many species of wild animals and human. The most important trypanosomes in terms of economic loss in domestic livestock are the tsetse-transmitted species such as T. congolense, T. vivax and T. brucei(Mulligan 1970). Closely related T. brucei subspecies, T. b. rhodesienseandT. b. gambiense, cause human sleeping sickness. In Africa it was estimated that about 50 million people (Kuzoe 1991) and 48 million cattle (Kristjansonet al 1999) are at risk of contracting trypanosomosis. A study conducted on Africancattle showed that cattle in tsetse-free areas produced 83% more milk and 97% more meat per unit land area than those in tsetse-infested area (Kristjansonet al 1999). At national level, African livestock producers and governments spend at least 30 million USD per year to treat animals exposed to trypanosomosis, administering 25-30 million curative and prophylactic treatments of trypanocidal drugs (Borne 1996).

Trypanosomosis has serious impacts on the individual animal and national development endeavors. On an individual basis, untreated animal or human trypanosomosis will lead, at best, to a chronic debilitating condition and, at worst, to death. Furthermore, animals infected with trypanosomes are reported to have reproductive disorders (Ikedeet al 1988) and it can cause severe losses on production performance in cattle and water buffalo (D'Iterenet al 1998).

Trypanosomosis is vector borne disease transmitted mainly cyclically by tsetse flies, although,-transmission through other biting flies, coitus, and iatrogenic means can occur. The three main groups of tsetse flies for transmission of trypanosomosis are Glossinamorsitans, which favors the open land of the savanna, and Glossinapalpalis, which prefers the shaded habitats immediately adjacent to rivers and lakes and Glossinafusca, which favors the high dense forest areas (Urquhart et al 1996).

Even though thetrypanosomosis is endemic in south western areas of Ethiopia where it presents a significant impact on the agricultural sector, and in line with this ,Assosa district is one of the areas located in south western parts Ethiopia with tsetse infestation and no researches has been conducted estimatingprevalence of bovine trypanosomosis.Therefore, the objectives of this study were to determine the prevalence of bovine trypanosomosis in Assosa district, and to evaluate the severity of the disease in infected cattle.

Materials and methods

Study area

The study was conducted in six peasant associations (Assosa town, Mangle32, Abramo, Kushmengle, Mangle 38 and Baro) in Assosa district. Assosa district locatedin Assosa zone of BenishanguleGumuz Regional State, western Ethiopia comprises a total land area of about 2317 km2. It is located about 660 km from Addis Ababa. The study area shares common boundaries with Bambasidistrict in the south, Menge and Odabildgiludistrict in the East, Homesha and north Sudan in the west. The district is divided in to 74 peasant associations with total human populations of 104,147. The District has an altitude of 1400-1570 meter above sea level, an average temperature of 270c and average annual rainfall of 900-1200 mm. The major agricultural activity in the area is mixed farming system whereby crops are cultivated and different animal species are raised. The total livestock population of the district is estimated at 26,124 cattle, 4,382 sheep, 17,509 goat, 5,930 equines and 34,710 poultry (CSA 2011).

Figure 1. Map of the study area showing relative location of Assosa in BenshangulGumuz Regional State.
Study animals

Cross-sectional type of studywas conducted to determine current prevalence of bovine trypanosomes and its severity from November 2014 to May 2015. The study animals were classified in different body conditions (poor, medium and good) according to Nicholsan and Butterworth (1986), and other factors including ,age group (< 2 years and>2 years), sex and source animals. were assessed to observe the influence of immune status ,stress and tsetseinfested area on the prevalence of trypanosomosis respectively.The study animals were zebu cattle under extensive management system. The animals graze the communally owned pastureland with the same agro-ecology without any supplementary feeding throughout the year.

Study design, sample size determination and sampling methods

The sample size was determined by using 95% level of confidence interval with expected prevalence of 25.4% (Abenet 2011) with desired absolute precision of 5% (Thrusfield 2008). The formula used to calculate the sample size was:

N= (1.96)2Pexp (1-Pexp)/d2

Where, N= required sample size for one strata

Pexp= expected prevalence (in this case 25.46 %)

d= desired absolute precision (in this case 5%),

Therefore; 1.962x0.2546 (1-0.2546)/ (0.05)2 = 322 cattle

Specimen collection and laboratory analysis
Collection of blood sample

A total of 322blood sample were collected from selected six villages of the district by simple random sampling method. Blood samples were collected by ear vein puncture using a sterile lancet into a pair of heparin-ized capillary tubes (75x1.2mm) from each of the randomly selected animals. Each tube was sealed with cry steal seal on one end (Murray 1988) properly handled and transported by ice box to the regional laboratory.

Parasitological examination

Measuring of packed cell volume (PCV) values or being anemic or not for each animals sample in the pre-intervention survey in all six sites were analyzed and marked difference was noticed. Accordingly parasitaemic animals had generally lower mean PCV value than aparasitaemic ones. And in addition to this, about 22.05 %( n=71) of the parasitaemic animals their packed cell volume is below 91.5 % ( n=65) were the normal range (Radostits 2006).

The blood sample was centrifuged at high speed (12,000 revolution per minute) for 5 minutes. Finally the packed cell volume values was read by micro haematocrit reader, which can be adjusted individually for the length of the blood column in each tube, to get a value indication on the presence, absence and degree of anemia (Uilenberg 1998).

Buffy coat examination to demonstrate parasite

After centrifugation, the capillary tube was cut down using diamond pointed pen 1mm below the Buffy coat to include the upper most layers of the red blood cells and 3mm above to include the plasma so that the contents was gently expressed on to a slide, mixed and covered with a cover slip (22 x 22mm). The preparation was then examined under 10x eye piece in combination with a 40x objective microscopes to get optimum view allowing large visual field and sufficient magnification for easy identification of trypanosomes. Morphological features after giemsa staining under 100 x objectives will be used (Murray 1988).

Data Management and analysis

Data on attributes of each animal’s sample (address/site, sex, age and body condition) and the corresponding laboratory data was recorded in Excel spread sheet. The data on Excel was transferred to SPSS version 20 software, where descriptive statistical methods, Chi square testof independence where employed to determine and compare the prevalence between the respective data attributes. The prevalence of bovine trypanosome infection was calculated as the number of parasitological positive animal based onbuffycoat examination method to the total population at risk (Thrusfield 2008).

Results and discussion

Prevalence of trypanosomesinfection

The overall prevalence reported in the present study was 22.05% this is in line with the prevalence 25.46% reported earlier in the districts and neighboring districts (Abenet 2011) while lower than 41.1% recorded in Assosa and around Bambasi by (Shimelis et al2011). This is may be attributed to the changes in ecology of tsetse fly and other biting fly infestation which may be lower during the current study due to the higher intervention practices by sustainable tsetse control program. Trypanosomosiscaused by T.congolense, T.vivax and T.brucie is a major problem of Assasa district and it is widely distributed in vast area of land suitable for livestock extensive husbandry system. The prevalence due to T.congolense was the highest 46 (14.28%) compared to trypanosome infection due to T.vivax 7 (2.2%) and T.brucei 3(0.9%). This may due to the high ratio of T.congolense in the tsetse infested area may ascribe to the more efficient transmission of T.congolense by major cyclical vectors than T.vivax.

Table 1. Distribution of trypanosomes species in the study area

Parasite species

N° of positive animals

Prevalence in %




















Prevalence of trypanosomosis in relation to the peasant association

The highest and the lowest prevalences were recorded in Kushmengle, 15(27.8%) and Abramo, 10(18.2%) respectively (Table 2).  However, there was no significant difference in prevalence of trypanosomosis with respect to peasant association. The absence of statistically significant difference in prevalence among the peasant associations observed in the current study is due to the fact that almost all peasant associations have the same altitude ranging from 1400-1570 meters above sea level. This may provide similar conditions for distribution of tsetse fly population in the area resulting in the cattle to be under similar level of risk for trypanosomosis.

Table 2. Prevalence of trypanosomosis in relation to the peasant association
of Assosa district


N of animals

N of positive



Assosa town


13 (23.2 %)



Mangle 32


11 (21.2 %)



10 (18.2 %)



15 (27.8%)

Mangle 38


13 (22.8 %)



9 (18.7%)




The prevalence of trypanosomosis in relation to sex

Trypanosomosis infection in male was slightly higher than female. During examination 173 male animals and 149 female were examined. Out of examined animals 39 (22.5%) and 32 (21.5 %) were recorded for male and female respectively which are infected by trypanosome parasites but this is not statistical significant . The finding that male and female cattle are under same level risk for trypanosome exposure is in agreement with previous works Habtewold (1993), Terzu (2004) which may indicate the absence of preference of the vector for a particular sex. Although statistically insignificant, higher infection was registered in male compared to females which may be due to that males are more stressed than females because of their use for traction and mating Adane (1995), Getachew (1993).

Table 3. The prevalence of trypanosomosis in relation to sex


N of animals

N of animals

Prevalence in

















Prevalence of trypanosomosis in relation to age

According to the present study, animals examined were divided in different age groups as <2 years and >2 years. Out of the sampled animals 34. 4 (11.7%) were <2 years and 288 67 (23.2%) animals were >2years. From 34(<2 years) examined animals 4 (11.7%) animal were positive and > 2 years out 288 animals were examined, 67 (23.2%) animals were positive for trypanosomosis disease. The difference in prevalence of bovine trypanosomosis due to difference in age of the animals was statistically insignificant.

In addition to these different age groups of cattle examined and the result indicate trypanosome infectionwas higherin adult (>2years) and slightly low in young cattle (<2years). The higher prevalence of trypanosomosis observed in old cattle agrees with the reports Muturi (1999) at merebabaya south Ethiopia.This may be due to the fact that old and young animals had incompetent immune system. The same fact may hold true for the significantly higher prevalence rate recorded in poor conditioned animals in this study whose immune system is already compromised due to poor state of nutrition or other concurrent infection making them more susceptible to trypanosomosis. Previous works by Afewrk (1998) and Haile (1996) also reported similar findings.

Table 4. Prevalence of trypanosomosis in relation to age


N° of animals

N° of animals




≤ 2year






>2 year








Prevalence of trypanosomosis in relation to body condition

From 322 cattle, examined 45, 238 and 39 were rated as having poor, medium and good body condition,respectively. Out of infected animals examined 23(51.1%) were poor, 48(20.2 %) medium and 0(0%) good in their body condition and prevalence was recorded 51.1%, 20.2% and 0% for poor, medium and good body condition which is statistically significant (P < 0.05%) table 5. Similar result was reported by Abenet (2011).

Table 5. Prevalence of trypanosomosis in relation to body condition


N of animals

N of animals
positive %





23 (51.1)





48 (20.2)



0 (0.00)






The authors would like to thank BenishangulGumuz Regional veterinary Laboratory for providing all the necessary facilities. We are also like to thank owners of cattle for delivering of their cattle.


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Received 23 June 2016; Accepted 10 August 2016; Published 1 December 2016

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