frican animal trypanasomiasis (AAT) is a parasitic disease that causes serious economic losses in livestock from anemia, loss of condition and emaciation. Many untreated cases are fatal. AAT is found mainly in those regions of Africa where its biological vector (tsetse fly) exists (CFSPH, 2009). Bovine trypanasomosis continued to be the major constraints of livestock production in Sub-Saharan Africa, jeopardizing the lives of 55 million people. The risk of infection in humans as well as in domestic animals has greatly affected social, economical and agricultural development of communities within tsetse infested areas which roughly constitutes more than a third (10 million km 2 ) of Africa between 14 o N and 29 o S of the continent (FAO, 2002).
In Ethiopia, Trypanosomosis is widespread in domestic livestock in the Western, South and Southwestern lowland regions and the associated river systems (i.e. Abay, Ghibe, Omo and Baro/Akobo) (MoA, 1995). In (Afework et al., 1998) and (Tewelde et al., 2001) studies, farmers strongly recognized trypanosomo sis as the primary problem for livestock productivity and agricultural development in the northwestern and western parts of Ethiopia, respectively.
Trypanosomosis in cattle locally referred, as "Gendi" is a serious constraint to livestock production in areas of the north and southwest Ethiopia at an altitude of below 2000 meters above sea level (masl). Currently about 220,000 Km 2 areas of the above mentioned regions are infested with five species of tsetse flies namely Glossina pallidipes, G .morsitans, G. fuscipes, G. tachinoides and G. longipennis (NTTIC, 2004).
Trypanosomosis is mainly restricted to areas in which the vector, tsetse fly (Glossina species) can survive. The disease is also found outside the tsetse belt areas transmitted mechanically by biting flies of the genus Tabanus, Hematopota, Chrysops, and Stomxys.
A number of trypanosome species are important in bovine trypanosomiasis (T. brucei brucei, T. congolense and T. vivax) that differ from those causing the human form of the disease, sleeping sickness (T. b. gambiense, T. b. rhodesiense). Economically the tsetse-transmitted trypanosomes (Trypanosoma congolense, T. vivax, and T. brucei) are most important in cattle with 14 million heads at risk in Ethiopia (Getachew , 2005). In Ethiopia, five species of trypanosomes are recorded and the most important trypanosomes in terms of economic loss in domestic livestock are tsetse transmitted species: T.congolense, T.vivax and T. brucei (Abebe, 2005).
Trypanasomosis control is a long-term fight and therefore requires the involvement of decision makers, researchers and farmers. Until now, the use of trypanocidal drugs to treat or to prevent susceptible livestock against trypanosomosis remains the only control measure for most of the farmers. Very limited trypanocidal compounds are available and they have been used for many years. This long-term use of the same molecules selected drug resistant strains of trypanosomes in many African countries (Geerts et al., 2001).
In order to improve the welfare and security of rural communities, particularly Ethiopia, rapid method for assessing risk and diagnosing urgent problems are needed for the control of animal diseases. Although bovine trypanosomosis is considered an important livestock disease in Guto Gida District of East Wollega Zone, there is no information in the literature about the disease situation in the study area. The present study was, therefore, conducted in the district with objective of determining the prevalence of the disease, identifying the species of Trypanosoma and assessing of risk factors of the disease.
The study was conducted in Guto Gida District of East Wollega Zone, Oromia Regional State, Ethiopia. Guto Gida woreda is located at 331 Km West of Addis Ababa. It is situated at latitude and longitude of 9°5 ? N 36°33? E/9.083°N 36.550°E and at an altitude of 1350-2400 meters above sea level (Masl). The climatic condition of the area was highland (dega) (0.26%), midland (woyna dega) (46.74%) and lowland (bereha) (53%) with the mean annual rainfall range from 1800-2200 mm and average temperature 14-26 0 c. The area receives bimodal rainfalls that were long rainy season (June to September) and short rainy season (March, April and May). The Guto Gida people practice mixed framing system that is crop production and livestock rearing and own large number of livestock. The livestock population in the area includes 86,724 cattle; 8,589 equine; 14,171 sheep; 11,821 goats and 57,695 poultry (CSA, 2009).
The study animals were indigenous zebu cattle of all age group (Bos indicus). Animals were allowed to graze freely during the day and housed at night (extensively managed). The age of animals was determined by dentition (Delahunta and Hable, 1986) and categorized into three age groups. The body condition of animals was also grouped based on criteria described by (Nicholson and Butterworth,1986) but grouped in to two broad group good (G + to M) or poor (M -To P -).
Random and purposive sampling methods were followed to select the study animals and study sites respectively. Since there was no previous study conducted in Guto Gida District to establish the prevalence, the sample size was determined by taking 50% expected prevalence of trypanasomosis using the formula given by (Thrusfield, 1995). n = (1.96) 2 .P exp (1-P exp ) d 2 Where: n = required sample size P exp = expected prevalence = 50% d = desired absolute precision = 5% Hence, the sample size required as per the above formula was 384 heads of cattle.
A cross sectional study was carried out to determine the prevalence of bovine trypanosomosis in five peasant association (Tolera, Eba, Muleta, Gari and Abdeta) of Guto Gida District of East Wollega Zone, Western Ethiopia from October 2013 to March 2014.
A total of 384 blood samples were collected from ear veins of cattle. Samples were collected to heparanized capillary tube. During blood collection the necessary bio-data of each animal was recorded. The Buffy coat technique using phase contrast microscope was used for the detection of trypanosomes in the blood.
Species identification was done by morphological examination of trypanosomes on Giemsa stained thin blood smears prepared from the positive animals and examined under a microscope using the oil immersion 100 × objectives (Murray et al., 1977).
ii. Hematological Examination Blood samples for packed cell volume (PCV) were collected from animals using heparinized capillary tubes. The packed cell volume (PCV) was measured after the heparinized capillary tubes containing blood were centrifuged for 5 min at 12,000 rpm in microhematocrit centrifuge and the results were observed using microhaematocrit reader following the standard procedure described by (Murray et al., 1977).
Data collected were entered into Microsoft Excel spread sheet and descriptive statistics was applied to calculate the prevalence of trypanosomosis using SPSS version 16. ANOVA was used to determine the mean values of PCV and variation in the mean PCV between infected and non-infected animals was determined. The Percentages (%) were used to measure prevalence and chi-square (x 2 ) to measure significance of association among variables considered in this study. In all analysis, confidence level was held at 95% and P < 0.05 was set for significance.
From the total of 384 cattle examined with a Buffy coat technique, 30 were Positive for trypanosomes giving an overall prevalence of 7.81%. The prevalence of bovine trypanosomosis between different peasant associations (PA) was 11.39% in Abdeta, 9.89% in Gari, 6.52% in Muleta, 5.40% in Tolera and 5.31% in Eba with no statistically significant difference (p>0.05) (Table 1).
Trypnosoma congolense, Trypnosoma vivax, and Trypnosoma brucie were the Trypnosoma Species identified by Giemsa stained thin blood smear examination. Among the total of 30 cases of trypanosome infections detected 16(53.33%) of the Volume XIV Issue II Version I Year ( )
2014 G f)infections were due to T. Congolese, 9(30%) were due to T. Vivax and the rest (16.66 %) were due to T. brucie with statistical significance difference (Table 2). Sex wise prevalence of trypanosome infection was slightly higher for female (8.37%) than for male (7.18%) animals (Table 3). However, statistical significant difference (P > 0.05) was not observed between sexes. With respect to body condition score, the prevalence was 2.65%, and 19.67% in good, and poor body condition score, respectively with a significant variation (P < 0.05) between them (Table 3). Age based prevalence was 9.21%, 7.42% and 3.33% for animal > 6 years, 1-6 years and < 1 year of age respectively. Although adult cattle have higher infection rate statistical significant difference (P > 0.05) was not observed between age group (Table 3).
The PCV of individual animals was measured for the assessment of degree of anemia. A mean PCV of 20.23% and 27.98% was found for infected animals and non-infected animals respectively (Table 4). The difference was statistically Significant (P = 0.000).
IV.
The distribution of the most common species of trypanasomes infesting cattle in Ethiopia varies greatly from one area to another. Considering this the present study revealed the overall prevalence of 7.81% in the study area, this prevalence of trypanosomes concord with prevalence of 8.55% of Sasiga and Diga district of East Wellega (Tefese et al., 2012) and 5.85%, in Diga District of Eastern Wollega (Dinsa et al., 2012). The similarity of prevalence between these studies might be due to similarity in altitude. In contrast, the result is low when compared with previous reports, 40% in the Wolyta and Dawero zones of southern Ethiopia (Miruk et al., 2008), (24.7%) in Maokomo special district of Benshangul Gumz regional state (Daud and Molalegn, 2011) and 25.7% in the tsetse-infested zones of the Amhara region of northwestern Ethiopia (Cherenet et al., 2006). The relatively low prevalence of trypanosomosis in this report may be due to the differences in agro ecology, which less favors tsetse flies growth and multiplication. And also prevalence rate of 29% along the escarpment of the Upper Didessa Valley (NTTICC, 1998), 25% in Gawo Dale district of Kelem Wollega zone (NTTICC, 2004) were reported.
The associations of the disease with different peasant associations were also assessed. No significance association was observed between prevalence of the disease among the different peasant associations (Table1). This may be due to the result of uncontrolled animal movements between the areas. The sex wise prevalence of trypanosome infection was 7.18% in male and 8.37% in female.Though prevalence a slightly higher among the females, statistically there was no significant difference. Daya and Abebe, (2008), Tefese et al. (2012) report similar results where they observed no significant difference in trypanosome infection between males and females. Onyiah, (1997) and Quadeer et al. (2008), in separate studies added that no statistically significant difference in the prevalence bovine trypanosomosis between sex groups. Therefore, they have equal chance of coming in contact with the flies and allowed in the same ecology having comparable degree to acquire infection.
T.vivax and T. congolense and T.brucei were the species detected from infected animal with statistically significant difference in the prevalence of trypanosome species (P=0.00) (Table 2). This result agreed with work of (Abebe and Jobre, 1996) who reported an infection rate of 58.5% for T. congolense, 31.2% for T. vivax and 3.5% for T. brucei in Southwest Ethiopia, which is similar with current situation in Guto Gida District. The dominant trypanosomes species in the present study was T. congolense. This agreed with work of Tewelde et al., (2001) and (Afewerk, 1998) who reported a prevalence rate of 17.2% and 21% in Upper Didessa of tsetse infested region and in Metekel district respectively. The dominant species was T. congolense which is similar with the current result in Guto Gida District. Additionally, 71.8% prevalence of T. congolense in the Gawo Dale district was reported (Waktole et al., 2008). The predominance of T. congolense infection in cattle may be due to the high number of serodams of cattle as compared to T. vivax and development of better immune response to T. vivax by the infected animal (Leak et al., 1999). Langridge et al., (1976) also reported, G. pallidipes and G.m. Sub-morsitans are efficient in the transmission of T. congolense than T. vivax in Africa that support the present study in Guto Gida District. In contrast, in areas of East Wollega Zone (Sibu Sire) the respective ratios between T.congolense (36%) and T.vivax (64%) infections were reported (Shimelis and Sisay, 2011), because of the abundance of mechanical vectors also known to be effective transmitters of T. vivax (Desquesnes and Dia, 2004).
The association of the disease with age was also assessed. No significance difference was observed with respect to age. The result agreed with report of (Daud and Molalegne, 2011) in Mao-komo Special District of Benishangul Gumuz Regional State, (Molalegne et al., 2010) in Jabi Tehenan district of West Gojjam Amhara regional state (Tefese et al., 2012) in Sasiga and Diga District of western Oromia region, (Efrem et al., 2013) in Lalo kile District of kelem Wollega. Similar findings were also reported by (Cherenet et al., 2006) and (Habtamu, 2009), in tsetse infested region of Amhara and in the Jawi district of the Amhara region respectively. This can be associated to the fact that adult animals travel long distance for feed and water as well as for drought to tsetse high challenge areas. There is also evidence that T. congolense infection was chronic diseases that increase infection rates with age, (McDermott et al., 2003). According to (Torr et al., 2000), tsetse flies are attracted significantly more by odor of large animals. Rowlands et al., (2001) in Ghibe valley indicated that suckling calves did not go out with their dams but graze at home until weaned off. Additionally young animals are naturally protected to some extent by maternal antibodies (Fimmen et al., 1982). These could be the reason for lower prevalence of trypanosomosis that was observed in calves.
We also tried to assess the relationship of infection with body condition score of sampled animals (Table 3). In this study, there was a significant difference in the prevalence of trypanosomosis between animals with good and poor body conditions. This is in agreement with (Mussa, 2002) and (Molalegne et al., 2010). This may be related to the debilitating nature of the disease (Radostits et al., 2007). However, it would be difficult to conclude either poor body condition predispose to trypanosome infection or trypanosome infection cause loss of body condition based on such Volume XIV Issue II Version I Year ( ) 2014 G be verified by using a longitudinal study designs. The disease itself results in progressive emaciation of the infected animals; nevertheless, non-infected animals under good body condition have well developed immune status that can respond to any foreign protein better than those non-infected cattle with poor body condition which can be immune compromised due to other diseases or malnutrition, since malnutrition and concurrent infections depress the immune responsiveness in some cases (Collins, 1994).
A significant decrease in PCV was observed in the trypanosome infected animals signifying anemia to be one of the important consequence of infection (Table 4). It was in agreement to the work done by Tafese et al., (2012) mean PCV value of infected animals (21.45%) was significantly lower (P < 0.05) than that of noninfected animals (26.6%). Daud and Molalegne, (2011); Molalegne et al. (2010) also reported lower mean PCV value in infected animals than the non-infected animals. Rowlands et al. (2001) in also reported in an increase in PCV value, the proportion of positivity decreases and hence mean PCV was a good indicator for the health status of herds in an endemic area.
V.
Trypanosomosis caused by T. congolense, T. vivax and T.brucei with more prevalence of T. congolense was remains the main constraint to animal production and agricultural development in Guto Gida woreda. This dominance of T.congolense suggest presence of biologically (tsetse fly) transmitted trypanosome and the presence of T. vivax in the area indicated the importance of mechanically transmitted trypanosome in the study area. The observed association between reduction in PCV and body condition with infection showed the impact of the disease on productivity of infected animals. Nevertheless, trypanocidal drugs remain the main control tools used by livestock owners.
VI.
| PA | Number of | Number of | Prevalence | T.congolense | T.vivax | T.brucie | X 2 (P |
| animal | animal | (%) | value | ||||
| examined | positive | ||||||
| Tolera | 74 | 4 | 5.40 | 2(2.70) | 1(1.35) | 1(1.35) | 3.464 |
| (0.44) | |||||||
| Eba | 94 | 5 | 5.31 | 3(3.19) | 1(1.06) | 1(1.06) | |
| Muleta | 46 | 3 | 6.52 | 2(4.34) | 1(2.17) | ||
| Gari | 91 | 9 | 9.89 | 5(5.49) | 3(3.29) | 1(1.09) | |
| Abdeta | 79 | 9 | 11.39 | 4(4.16) | 3(3.78) | 2(1.30) | |
| Total | 384 | 30 | 7.81 | 16(4.17) | 9(2.34) | 5(1.30) |
| Species | Prevalence | X 2 | P-value | |
| (%) | ||||
| T.congolense | 16 | 53.33 | 384 | 0.00 |
| T.vivax | 9 | 30 | ||
| T.brucie | 5 | 16.66 | ||
| Total | 30 | 100 |
| Potential risk factors Nomber of animals | Infected animals | X 2 | P-Value | |
| examined | (prevalence) | |||
| Age | 1.29 | 0.178 | ||
| < 1year | 30 | 1(3.33) | ||
| 1-6year | 202 | 15(7.42) | ||
| > 6year | 152 | 14(9.21) | ||
| sex | 1.92 | 0.405 | ||
| Male | 181 | 13(7.18) | ||
| Female | 203 | 17(8.37) | ||
| Body condition | 34.92 | 0.000 | ||
| Good | 262 | 6(2.65) | ||
| Poor | 122 | 24 (19.67) | ||
| Total | 384 | 30(7.81) | ||
| Year 2014 | ||||
| Volume XIV Issue II Version I | ||||
| D D D D ) | ||||
| ( | ||||
| Animal | Number of animal | Mean PCV (%) | X 2 | p-value |
| Infected | 30 | 21.23 | 110.51 | P=0.001 |
| Non-infected | 354 | 27.98 | ||
| Total | 384 | 27.45 | ||
| © 2014 Global Journals Inc. (US) |
The authors acknowledge Jimma University College of Agriculture and Veterinary Medicine (JUCAVM) for financing the study.
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