The major constraint studied to cattle production in the study areas was trypanosomosis. The parasitological assessment revealed a prevalence of 5.47% with T.congolense and T.vivax being identified species which was relatively lower than previous reports of 8.6%, in Dembecha by [7] and 10.1% from Awi zone [17]. A slight decrease result in this study area might be related to the unending parasite and vector control program practiced by national tsetse and trypanosomosis investigation and control centre (NTTICC). The project apply 1% deltamethrin pour-on and spot-on at half yearly interval on the forest areas and bush lands where high numbers of flies are believed to exist, odor baited, impregnated targets, traps and prophylactic treatments with trypanocidal drugs as tsetse fly control methods. The second reason may be related to expansion of agricultural activities along with increased human population causing destruction of tsetse habitats (forests) which significantly reduced the prevalence of disease in the study area[15]. Conversely, the present study is differing from studies conducted by [18], who record higher prevalence of 20.9% and [14] 23.36%. The variation could be associated with accuracy of the type of test used and short rainy season after sampling increases the prevalence as the density of vectors is high during this period.
Majority of the infection was due T. Congolese species as compared to T.vivax which indicates that transmission was mainly by tsetse flies than biting flies because entomological examination had also showed that tsetse flies catch was higher than biting flies. Similar finding of previous reports [19], 63.4% in selected sites of southern region and [20], 54.3% in West Gojjam was recorded. The increased proportion of infection with T. congolense might be due to that major biological vectors are more efficient transmitters of T. congolense than T. vivax in East Africa [7] and this area is sited in ecology of tsetse fly of Ethiopia which determines the level of their contact with the host and infection.
In this study slight higher infection rates were observed in male than females, but the difference was not significant. This result is comparable to the finding of several researchers such as [21] [22] [19]. The possible reason for slight higher infection rates could be as the information obtained from the questionnaire survey male animals were used for draught purpose and hence travel extended distance in the area where higher challenge of tsetse is present.
Age was one of the risk factors to be assessed and relatively lower infectivity rate was found in animals with age category between 1 and 2 years (young) in as compared to 3–5 years and above 5 years (adult) in the study area without any statistically significant variation. Similar results were reported by[23] [20] [18] [24] [25]. This might be linked to the reality that older animals move long distance for foraging, watering and plough as well as gathering crops in tsetse challenge areas[26]. The reason for this finding might be related in the area suckling calves stayed at home until they were weaned off and they are also naturally protected to some extent by maternal antibodies. Moreover, tsetse’s feeding behavioral choice for older animals because they are engrossed significantly more by odor of large animals and animals that showed less defensive behavior [25].
Animals with black and related coat color were found to be highly infected than red with related and white with related coat and there was significant difference in their prevalence. Tsetse flies have special color selection and decrease in the order of blue > red > green > yellow and Black is approximately as attractive as blue but, notably, tsetse land on black in preference to any other color. There for blue color is used to attract tsetse to an object and black to get them to land on it [27]. As a result traps are prepared blue on the outside and black on the inside to increase the proportion of tsetse that land on the trap area.
The prevalence in animals with poor body condition were significantly higher (P = 0.02) as compared to with good and medium body condition. This result differs with previous report from different parts of Ethiopia [20] [24] [7]. The chronic characteristic of the disease causes a progressive loss of condition, weight loss and tiredness. Conversely, non–infected animals with good body condition have well developed immune status than those non–infected cattle with poor body condition [28].
All of the infected animals were found to be anaemic (PCV < 24%) compared to non-infected animals (25.88%), and the difference was significant (p = 0.00). Similar finding was reported by [17], 21.1% and 26.0% at Awi zone, Northwest Ethiopia and [29], 20.6% and 25.0% at Asosa district of Benishangul Gumuz, Western Ethiopia for parasitemic and aparsitemic cattle, respectively. Here, trypanosomosis may be involved in negatively lowering the PCV value of infected animals. But low PCV value may not exclusively be due to trypanosomosis; but may be due to the poor detection nature of the test used [30] or late recovery of anemic situations after recent treatment with trypanocidal drugs or may be due to the pooled effect of malnutrition and hematophagus helminth infection [31].
The risk of trypanosomosis is also predisposed by apparent density and types of vectors existing in the area. The investigation shows the presence of two Glossina species (Glossina morsitans and Glossina tachnoides) and two genera of biting flies (Stomoxy and Tabanus). Similarly G. pallidipes, G. morsitans, G. fuscipes and G. tachinoides by[32] in Birbir valley, Baro Akobo river system, western Ethiopia and G. Morsitans species of tsetse in Dembecha and Jabitehenan[29].
2.4% f/t/d was the apparent density of total flies caught and apparent density of glossina, stomoxy and tabanus were 1.43f/t/d, 0.47f/t/d and 0.5 f/t/d respectively. Closer results for tsetse, stomoxy and tabanus were reported by [33], 1.45, 0.35 and 0.23 respectively from East Wollega zone, Ethiopia and 2.83 for tsetse flies by [34] from Bench Maji zone, southwest Ethiopia. However, these results were lower than findings of [22] 14.97 f/t/d in Arbaminch, Ethiopia), [10] 16 f/t/d in tana beles valley and [35] 10.68f/t/d in upper Didessa valley. The relatively lower level of tsetse density may be due to differences in season, density of vegetation cover, the interventions practices undertaken by NTTICC and the expansion of settlements and farmlands in the area due to deforestation that limits the tsetse and other flies habitats.
As seasonal comparison relatively lower apparent density of fly was observed in the dry season and very high during the rainy seasons with statistical significant difference. This could suggest that there is a complete raise in the number of tsetse flies due to encouraging ecological situation [36].
The diverse habitats of flora were looked up during the fly investigation period and there was a deviation in proportional allocation of tsetse flies in four vegetation types. Typical territory of savanna grass land was preferred by G. m. submorsitans and G. tachinoides which prefer along the tributary side. Moderately elevated flies were assessed during the wet/rainy/ period in all flora types and the riverine vegetation type is dominated by the vectors than others. This was also reported by[32] [37].
Earlier works on the habitats of flies by [38] [39] [7] had recognized the tsetse ecological elevation at 1600 m.a.s l, and afterward elevation reaches to 2000 m.a.s.l by [40], while in this assessment the upper limit for Glossina species was 1800 m.a.s.l. and for other biting flies above 2000 m.a.s.l. In this survey the majority of the tsetses were dominated in the lowland area so that the apparent density decline as elevation increases (P < .05). This indicated that typical weather, which is largely reliant on elevation, has a pressure on tsetse population.
The monoconical trap has significantly better trapping capacity than the biconical trap in all the flies’ species (P < 0.05). Parallel report of this finding is point out by [32] [33] that biconical trap was not efficient in collection of G. Morsitans. Here, the reason was that biconical trap was immovable as compared to monoconical trap.
From the questionnaire survey all the interviewed ones reared diverse species of animals managed under extensive husbandry system which depends on natural grazing and communal management system. Eighty seven percent of them reports that trypanosomosis is the first obstacle to agricultural activities and animal production. Parallel result have already reported by different researchers like; [41] in Tselemt woreda of Tigray, where (95.7% response rate); [16] in Guraferda and Gimbo districts in the Baro Akobo and Gojeb River basins, where (95.2% response rate); [34] in Bure and Womberma Districts of West Gojjam Zone (91% response rate); [42] in selected districts of BG region (60% response rate) indicated that; trypanosomosis was the major disease of bovine.
All interviewed ones agreed that the reappearance of the disease rise during raining season. This may be due to the favorable condition during this season for emerging of tsetse flies pupas, which buried under the ground during the dry season of the year [36][32].
Most farmers could identify common symptoms that are used as diagnostic tool for trypanosomosis suspected cases like rough hair coat, emaciation, Reduced feed intake, coughing, lacrimation and abortion. Such types of result reported by [43] [19].
Most (80%) interviewed have brief concepts on commonly used trypanosomosis control methods even they didn’t know difference between chemotherapeutic and prophylactic drugs used for trypanomosis. Also problems like inappropriate treatment or extended intervals between treatments and under-dosage have been their gaps. So they bought any trypanomosis drug give for their animals. Ten percent of them complained they use herbal medicine like (Eucalyptus, Onion, Dodracantum) remedies mixed with ordinary saline (Nacl), were used together and drench to adult cattle suspected to be infected and restricts their animal movement towards tsetse habitats even they have good concepts on modern drugs which are costive for them. The rest respondents have no any perception on control methods. Similar results were in accord with survey reports from other tsetse infested regions of Ethiopia [28] [16] [44].