Trypanosomosis, Its Risk Factors, and Anaemia in Cattle Population of Dale Wabera District of Kellem Wollega Zone, Western Ethiopia

Seasonal prevalence of bovine trypanosomosis and trypanosome species distribution in Jimma Horo district, Oromia regional state, Western Ethiopia

A study was conducted to determine the prevalence of bovine trypanosomosis in rainy (June 2019) and dry (February 2020) seasons in Jimma Horoo district, Kellem Wollega Zone, Oromia Regional State, Ethiopia. A total of 720 blood samples were examined using buffy coat and thin blood smear techniques. The packed cell volume (PCV) of each animal was determined. The overall bovine trypanosomosis prevalence was 4.3% (χ² = 1.25, P = 0.26). The prevalence was 5% (95% CI = 4.1-8.3) and 3.3% (95% CI = 2.7-6.3) in the dry and rainy reasons, respectively (P > 0.05). Trypanosoma congolense, T. vivax and T. b. brucei were detected in (60%), (33.3%) and (6.7%) of infected cattle, respectively. The highest trypanosome prevalence was observed in Burka Gudina (7.6%), and the lowest in Melka Nega village (2.1%). There were significant variations between trypanosome prevalence in relation to body condition scores (χ² = 23.16; P = 0.0.00) of examined cattle. No significant difference (P > 0.05) was observed between seasons, age, and sex categories of cattle. The PCV values of trypanosome infected (22.94%) was significantly lower than non-infected cattle (26.47%) (χ² = 19.60; (P < 0.05). The prevalence of bovine trypanosomosis in Jimma Horo district was low and it can be controlled by treatment of infected cattle using sanative pairs of trypanocidal drugs with additional application of deltamethrin pour-on in the dry season. Further, in view of poor sensitivity of buffy coat technique used the use of molecular techniques should be encouraged.

Glossina pallidipes Density and Trypanosome Infection Rate in Arba Minch Zuria District of Gamo Zone, Southern Ethiopia

Background

African trypanosomosis is a disease of both animals and humans resulting from infection with parasitaemic protozoa of the genus Trypanosoma transmitted mainly by the tsetse flies (Glossina species). The disease has been reported in different parts of the country. However, information on the apparent density and trypanosome infection rates of the vectors is very limited in the Southern part of Ethiopia. Therefore, this study was conducted to estimate the apparent density, infection rate of trypanosomes in Glossina pallidipes, and the trypanosome species involved in Arba Minch Zuria district of Southern Ethiopia.

Methods

A cross-sectional study was conducted from January to June 2018 in two purposely selected kebeles of Arbaminch Zuria district and in the escarpments of Nech Sar National Park of Southern Ethiopia. For entomological survey, a total of 40 standard NGU traps were deployed around the watering and grazing areas. A total of 300 fresh Glossina pallidipes were examined for trypanosome infection using a dissection procedure as described by the FAO Training manual for tsetse control personnel.

Results

The study revealed the presence of only one Glossina species, known as Glossina pallidipes, and biting flies including Stomoxys and Tabanus. A total of 2176 flies were caught of which 1803 (82.86%) belong to Glossina pallidipes and the remaining 373 (17.14%) were biting flies. The overall apparent density of Glossina pallidipes and biting flies in the study area were 15.03 fly/trap/day (F/T/D) and 3.11 F/T/D, respectively. Relatively higher Glossina pallidipes and biting flies, respectively, were caught in a wood-grass land (15.87 F/T/D and 3.69 F/T/D) and riverine forest (15.13 F/T/D and 3.42 F/T/D) than bush land vegetation types (13.87 F/T/D and 1.76 F/T/D). The overall trypanosome infection rate of Glossina pallidipes was 17.67% (53/300). Two trypanosome species, namely, Trypanosoma congolense (66.04%) and Trypanosoma vivax (33.96%), were responsible for Glossina pallidipes infection in the study area. Trypanosome infection rate was significantly higher in female G. pallidipes than in male (OR = 3.39, 95%CI = 1.53‐7.52). Significantly, higher trypanosome infection rate was observed in flies older than 20 days (OR = 2.5, 95%CI = 1.12‐5.56) and in hunger stage 1 flies (OR = 14.24, 95%CI = 4.01‐50.59). Glossina pallidipes infection was significantly higher in and around park grazing areas (OR = 3.41, 95%CI = 1.76‐6.6) and wood-grass land vegetation type (OR = 2.7, 95%CI = 1.2‐6.5).

Conclusion

The current study revealed high apparent density and trypanosome infection in Glossina pallidipes in Arba Minch Zuria district of Southern Ethiopia. So, this study warrants the need for strengthening both vector and parasite control strategies in the study area.

African Animal Trypanosomiasis: A Systematic Review on Prevalence, Risk Factors and Drug Resistance in Sub-Saharan Africa

African animal trypanosomiasis (AAT) a parasitic disease of livestock in sub-Saharan Africa causing tremendous loses. Sub-Saharan continental estimation of mean prevalence in both large and small domestic animals, risk factors, tsetse and non-tsetse prevalence and drug resistance is lacking. A review and meta-analysis was done to better comprehend changes in AAT prevalence and drug resistance. Publish/Perish software was used to search and extract peer-reviewed articles in Google scholar, PubMed and CrossRef. In addition, ResearchGate and African Journals Online (AJOL) were used. Screening and selection of articles from 2000-2021 was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Articles 304 were retrieved; on domestic animals 192, tsetse and non-tsetse vectors 44, risk factors 49 and trypanocidal drug resistance 30. Prevalence varied by, host animals in different countries, diagnostic methods and species of Trypanosoma. Cattle had the highest prevalence with Ethiopia and Nigeria leading, T. congolense (11.80-13.40%) and T. vivax (10.50-18.80%) being detected most. This was followed by camels and pigs. Common diagnostic method used was buffy coat microscopy. However; polymerase chain reaction (PCR), CATT and ELISA had higher detection rates. G. pallidipes caused most infections in Eastern regions while G. palpalis followed by G. mortisans in Western Africa. Eastern Africa reported more non-tsetse biting flies with Stomoxys leading. Common risk factors were, body conditions, breed type, age, sex and seasons. Ethiopia and Nigeria had the highest trypanocidal resistance 30.00-35.00% and highest AAT prevalence. Isometamidium and diminazene showed more resistance with T. congolense being most resistant species 11.00-83.00%.

Study on Bovine Trypanosomiasis and Associated Risk Factors in Benatsemay District, Southern Ethiopia

Trypanosomosis is an endemic livestock disease in Ethiopia that hinders livestock production and productivity, especially in fertile agricultural western and southwestern areas. A cross-sectional questionnaire-based and parasitological studies were conducted from October 2020 to July 2021 in the Benatsemay district, southern Ethiopia to assess the knowledge of livestock owners about trypanosomosis, its prevalence, and host-related risk factors associated with bovine trypanosomosis in the area. According to the questionnaire survey, trypanosomosis was the main bottleneck to cattle in two of the selected study Sites in the Benatsemay district. The parasitological survey revealed that 11.46% (44/384) of the cattle were infected with trypanosomosis. Moreover, Trypanosoma congolense (9.11%) is the leading trypanosome species in the area, followed by T. vivax (31.8%). The adult age group (16.15%), poor-conditioned cattle (22.22%), and black-skinned cattle (34.24%) were significantly associated (P < .05) with trypanosomosis infection in the study area. Furthermore, the mean packed cell volume (PCV) of parasitaemic cattle (22.75%) was significantly (P < .05) lower than that of aparasitaemic cattle (29.23%). Therefore, the present study revealed that the prevalence of bovine trypanosomosis in the study area and participatory vector control and the rational use of trypanocidal drugs should be implemented to control trypanosomosis in the area.

Seasonal Patterns: Bovine Trypanosomosis, Glossina pallidipes Density, and Infection in Rift Valleys of Gamo Zone, Southern Ethiopia

Bovine trypanosomosis is a parasitic disease causing serious economic losses in livestock productivity and agricultural development. The disease has been reported in different parts of Ethiopia. However, seasonal pattern of trypanosomosis, tsetse fly apparent density, and infection are very limited in the southern rift valley of the country, particularly in Gamo Zone. Therefore, the objective of this cross-sectional study design was to estimate seasonal prevalence of bovine trypanosomosis, assessing tsetse fly apparent density and its infection by trypanosomes. For the parasitological study, a total of 600 cattle (300 in each season) were sampled and assayed using the buffy coat technique. A total of 80 standard NGU traps were deployed around the watering and grazing areas for the entomological survey. An overall prevalence of trypanosomosis was 10.17% (61/600), of which 7.33% (22/300) and 13% (39/300) accounted for the dry and wet seasons, respectively. The prevalence of trypanosomosis was significantly higher during the wet season (OR = 2.47; p < 0.05), in black coat color (OR = 7.2, p < 0.05), and poor body-conditioned (OR = 3.15; p < 0.05) animals. Two species of trypanosomes, Trypanosoma congolense, 68.85% (42/61), and Trypanosoma vivax, 31.15% (19/61), were circulating in the area. The mean PCV value in infected animals (22.56 ± 4.61) was significantly lower than in non-infected animals (25.3 ± 4.75). Entomological result indicated that Glossina pallidipes (G. pallidipes) was the only species of tsetse found in the study area. Totally, 3,789 flies were caught of which 81.42% (3,085/3,789) belong to G. pallidipes and 18.58% (704/3,789) were other biting flies. The overall apparent density of G. pallidipes was 12.85 flies/trap/day (FTD). Relatively higher G. pallidipes/trap/day were caught in the wet season (13.64 F/T/D) than in the dry season (12.07F/T/D). Of the flies caught, 342 G. pallidipes were randomly selected and dissected. The overall proportion of G. pallidipes infection was 18.42% (63/342) of which 12.28% (21/171) and 24.56% (42/171) were accounted in the dry and wet seasons, respectively. Infection in G. pallidipes was significantly higher during the wet season (OR = 2.32; p < 0.05) and in park grazing areas (OR = 2.45; p < 0.05). In conclusion, trypanosomosis is the major challenge for cattle productivity in the district. So this study warrants the need for strengthening the vector and parasite control interventions in the area.

Anaemia Associated with Trypanosomes Infections in Cattle of West Gojjam Zone, Northwest Ethiopia

Background

African animal trypanosomosis is a major veterinary problem over a large area of the tsetse belt region of Africa. Anaemia is a cardinal sign of trypanosome infections. The mechanism of anaemia due to trypanosomosis is complex and multifactorial in origin. Packed cell volume (PCV) usually gives an indication of the anaemia and disease status of a trypanosome-infected animal.

Methods

A cross-sectional study was conducted from December 2017 to January 2018 in West Gojjam zone, Northwest Ethiopia, to determine the trypanosome infections rate and the possible correlation between parasitic infection and anaemia using the dark ground buffy coat technique, Giemsa-stained thin blood smear, and PCV reading on a haematocrit reader.

Results

The overall trypanosomosis prevalence was 7.81%, 95% CI = 7.45–8.17. Trypanosoma congolense (4.25%) and T. vivax (3.56%) were the trypanosomes species identified in the studied area. PCV for all sampled cattle was analysed to estimate the degree of anaemia. From the total examined animals (N = 730), 356 (48.77%) were anaemic and 374 (51.23%) were nonanaemic. The mean PCV of parasitemic cattle was significantly lower (21.09%, 95% CI = 20.13–22.05) than that of aparasitemic ones (25.96%, 95% CI = 25.68–26.24). There was a positive association between trypanosome infection and anaemia. Although both trypanosome species are significantly associated with a decreased herd mean PCV (<24), the mean PCV of cattle infected with T. congolense (19.45%) was lower than that of infected with T. vivax (23.04%). The herd mean PCV was not significantly associated to locations, age, and sex of the studied animals.

Conclusions

The study confirms that the prevalence of trypanosomes infections and herd mean PCV has a significant association. The mean herd PCV can be a useful cheap tool to screen for possible trypanosome infection. However, there were cattle positive for trypanosomes having mean PCV within the reference interval and negative animals with anaemia. Furthermore, PCV reading should be confirmed by other diagnostic techniques to accurately conclude that trypanosomosis is the only cause of anaemia.

Genital lesions in cows naturally infected with trypanosomes in Abuja, Nigeria

Background and Aim:

Different species of trypanosomes have been reported to cause varying degrees of reproductive disorders in pregnant and non-pregnant animals under experimental infections. Information on reproductive disorders and losses in animals naturally infected with trypanosome species are few. This study was carried out to assess the abnormalities in the genital organs (ovaries, oviduct, uterus, cervix, and vagina) of female cattle naturally infected with trypanosomes in and around Abuja, Nigeria.

Materials and Methods:

Cows showing signs such as emaciation, weakness, or anemia were selected and examined at Gwagwalada and Karu abattoirs, respectively. Venous blood samples were taken from 108 of such animals and screened using standard trypanosome detection methods. The genital organs were also collected and inspected for gross and histopathological lesions in the laboratory.

Results:

Six (5.55%) out of the 108 animals were positive for trypanosomes; 4 (66.7%) were infected with Trypanosomavivax and 2 (33.3%) were infected with Trypanosoma congolense. The mean packed cell volume of the infected animals was 22.83%. Grossly, congestion and ecchymotic hemorrhages were observed in the endometrium, myometrium, and cervical submucosa. Mucometra, hydrometra, and pyometra were also seen in the uterus. Histologically, necrosis of the epithelium and endometrial glands accompanied by mononuclear cellular infiltration was observed in the uterus. There was also sloughing of the endometrial epithelium, vascular congestion, and hypertrophy of serosa of the uterus. There was atropy of the granulosa cells, increased numbers of degenerating tertiary follicles, and absence of corpora lutea in the ovary. No gross or histopathological lesions were observed in the fallopian tube and vagina.

Conclusion:

The lesions observed were restricted to the uterus and ovary of the animals and were less severe when compared to lesions observed under experimental conditions as reported by previous authors.

Prevalence and associated risk factors of bovine trypanosomosis in tsetse suppression and non-suppression areas of South Omo Zone, Southwestern Ethiopia

A cross-sectional study aimed to elucidate the prevalence of bovine trypanosomosis and its potential risk factors was conducted in tsetse suppression and non-suppression areas of South Omo Zone, Southern Ethiopia from November 2018- May 2019. A total of 1284 blood samples from local zebu cattle (642 each in dry and wet season) were examined by using buffy coat technique and thin blood smear method. The overall prevalence was 11.05 % with 14.33 % in dry and 7.78 % in wet season. According to multiple logistic regression analysis of tsetse suppression areas, higher prevalence in female than male (OR = 0.48, 95 % CI: 0.27, 0.83), in poor (OR = 3.25, 95 % CI: 1.26, 11.09) and medium (OR = 2.07, 95 % CI: 0.74, 7.37) than good body conditioned animals was recorded. Moreover, tethered animals (OR = 2.07, 95 % CI: 1.06, 3.92) were more likely to be infected than communal grazers and also higher prevalence in dry season than wet season (OR = 0.52, 95 % CI: 0.30, 0.87). Similarly, in tsetse non-suppression areas, higher prevalence in female than male (OR = 0.48, 95 % CI: 0.27, 0.85) and in wet season (OR = 0.41, 95 % CI: 0.23, 0.7) than dry season was recorded. Trypanosoma congolense and Trypanosoma vivax were found in cattle with the former more prevalent in both areas. Overall pooled mean packed cell volume (PCV) of parasitaemic animals (23.57 ± 3.13) was significantly lower than aparasitaemic animals (27.80 ± 4.95). Similarly, parasitaemic animals from tsetse suppression areas and tsetse non-suppression areas had significantly lower mean PCV than their aparasitaemic counterparts. Mean PCV of T. congolense (23.59 ± 3.22) infected animals was not different (P > 0.05) from T. vivax infected animals (23.26 ± 3.31). It was also indicated that the probability of anaemic animals to be parasitaemic was significantly higher (P < 0.05) than non-anaemic animals in both areas. In conclusion, the prevalence of trypanosomosis revealed its endemicity which bottlenecked the livestock production and productivity in the study area despite of tsetse suppression activities. Therefore, integrated parasite and vector control approach should be undertaken to curve the disease.

Serological examination of trypanosomes infestation in cattle reared in Keffi, Nasarawa State, Nigeria

Background & objectives

Cattle population is relatively dense in Nasarawa State (Nigeria) particularly in Keffi and its environs, where there are more Hausa/Fulani settlers whose main occupation is farming and herding. Unfortunately, the area is purportedly described as a "horde of tsetse fly species" which transmits trypanosomes that cause severe disease in humans, livestock and wildlife species. This study was targeted at examining trypanosome species prevalent among cattle breeds reared in Keffi metropolis.

Methods

A total of 110 cattle, purely based on availability were screened within five working days for trypanosomes infestation using haematocrit centrifugation technique and buffy coat technique. The breeds of cattle examined included White Fulani (64), Sokoto Gudali (26), N'dama (16) and Muturu (4); reared in Jarmai, Gauta and Keffi North districts of Keffi Local Government Area, Nasarawa State, Nigeria. Data collected were analysed using simple descriptive statistics.

Results

It was observed that 18 (16.4%) out of 110 cattle screened were infested with 5 (4.55%) Trypanosoma con- golense and 13 (11.82%) T. vivax. The T. congolense positive cases were 4 (3.64%) in White Fulani and 1(0.91%) in Sokoto Gudali breeds whereas, T. vivax occurrence was 9 (8.18%) in White Fulani breed and 4 (3.64%) in Sokoto Gudali breed. The N'dama and Muturu breeds were absolutely not infested and no mixed infestation was recorded in any of the breeds.

Interpretation & conclusion

Trypanosoma vivax and T. congolense are the predominant trypanosome species in the study area affecting mainly Sokoto Gudali and White Fulani breeds. Since, N'dama and Muturu breeds were observed to be trypano-tolerant; intensive breeding strategy, strain upgrading mechanisms and genetic modifications could be adopted to ensure other cattles' survival and prevent disease transmission in the area and beyond.

A meta-analysis of the prevalence of bovine trypanosomiasis in some African countries from 2000 to 2018

Bovine trypanosomiasis is a disease of cattle. In sub-Saharan Africa, the disease mean prevalence estimates are unknown in most endemic countries. We therefore performed a meta-analysis with the aim of estimating national mean prevalence of bovine trypanosomiasis in endemic countries across sub-Saharan Africa. Relevant articles reporting bovine trypanosomiasis prevalence were retrieved through systematic literature search and scanning of articles reference-lists. Eligibility criteria included that articles reported sample size, prevalence, and diagnostic technique adopted. Overall, data from 180 eligible articles from 19 countries satisfied the inclusion criteria. Meta-analysis of prevalence data based on the random-effects model resulted in an overall mean prevalence of 15.10% (95% CI: 13.22-17.08). National prevalence estimates were generally high except those of Benin and Senegal where estimates ranked below 10.00%. Significant heterogeneity (I² = 98.75%. p = <0.0001) was noted between studies, and univariate meta-regression analysis identified choice of diagnostic method being major contributor to observed heterogeneity (R² = 36.37%); while country of study (R² = 9.57%) and sample size (R² = 3.47%) had marginal effect on heterogeneity. In spite of past and ongoing control activities, bovine trypanosomiasis remains highly prevalent in most endemic sub-Saharan African countries. Nevertheless, dearth of epidemiological data in some countries and the use of less sensitive diagnostic tools limit reliable estimation of the disease prevalence. Therefore, there is the need to intensify efforts in aspects of surveillance and increased application of molecular diagnostic tool(s) across endemic locations as this would raise the chances of achieving a near-accurate estimate of the disease prevalence which is the first step to attempting eradication.

Occurrence of trypanosome infections in cattle in relation to season, livestock movement and management practices of Maasai pastoralists in Northern Tanzania

African animal trypanosomosis (AAT) is a parasitic disease considered to be one of the greatest constraints to cattle production in Tanzania. There is insufficient information on seasonal occurrence of AAT and management practices in Monduli District of the Maasai Steppe ecosystem to guide and prioritize AAT control programs. A cross-sectional survey was undertaken in 10 randomly selected villages of Monduli District. Information on seasonal animal movements, including wildlife interaction, and AAT management practices was gathered using a standardized questionnaire with 130 pastoralists. Blood samples were collected from a total of 960 cattle, in wet and dry seasons. An entomological survey was also undertaken in the dry season. Polymerase chain reaction targeting the internal transcribed spacer 1 (ITS1) was used for parasite identification in cattle blood and in tsetse flies. The overall apparent prevalence of AAT in cattle was 5.8% (95% CI of 4.1-8.3) and 4.2% (95% CI of 2.7-6.3) during wet and dry reasons, respectively. Trypanosoma vivax was the most common species identified in cattle. All tsetse flies (n = 426) collected were trapped in Esilalei village which is in close proximity to Lake Manyara National Park. Tsetse fly infection status was determined to be 7.0%; (CI 95% of 4.9-9.8%) with nearly 50% of infections due to T. congolense. All 130 cattle owners reported that they could easily recognize AAT and the majority (75%) identified the most prominent clinical signs. Nearly all owners (98.5%) identified that tsetse flies were responsible for AAT transmission. All cattle owners (100%) reported the use of trypanocides for AAT treatment, while 2.3% reported to also use herbal medicine. The trypanocides, Novidium® and Berenil®, were the most frequently reported commercial drugs and were used by 42% of cattle owners. Vector control by hand spraying was reported by the majority (90.8%) of cattle owners, while dipping and deployment of insecticide-impregnated targets were reported by few cattle owners (16.2% and 5.4%, respectively). The majority of cattle owners (83.1%) reported to move cattle away from home villages during the dry season with many migrating to areas in close proximity to wildlife parks. This study confirms the presence of circulating pathogenic trypanosomes in tsetse flies which continue to pose a threat to Maasai cattle. The seasonal movement of cattle during the dry season was associated with more clinical cases of cattle trypanosomosis. This study demonstrates the need to strengthen surveillance and control strategies for AAT.

Bovine trypanosomosis: changes in parasitemia and packed cell volume in dry and wet seasons at Gidami District, Oromia Regional State, western Ethiopia

BACKGROUND

Animal trypanosomosis is one of the major disease problems affecting agricultural productivity in Ethiopia. The impact of the disease is believed to vary with season and agro-ecologies in line with fly vector distribution. A cross-sectional study on bovine trypanosomosis was conducted from November 2015 to June 2016, in seven selected villages of Gidami district, Oromia Regional State, western Ethiopia. A total of 930 blood samples were collected and subjected to parasitological and hematological analysis.

RESULT

The overall prevalence of bovine trypanosomosis was 14.1%. The seasonal prevalence shows 9.06% in early dry and 18.4% in early rainy seasons. Three trypanosome species, Trypanosoma congolense, Trypanosoma vivax and Trypanosoma brucei were identified in the examined animals. T. congolense followed by T. vivax were the predominant species (respectively 59.0 and 35.9% in early dry season and 62.0 and 22.8% in early rainy season). The prevalence of T. vivax remained similar in both early dry and early rainy seasons in both lowland and midland agroecologies whereas T. congolense was more dominant in the lowland area in both seasons compared to mid land study sites. The disease was more prevalent in lowland (23.9%) compared to midland (11.1%) during early rainy season (P < 0.001) whereas no significant difference was observed between the two agroecologies during early dry season (P = 0.165). Packed cell volume (PCV) was much lower in parasitemic animals than in aparasitemic cattle whereas the mean PCV value for parasitemic animals (20.36%; 95% CI 19.56 to 21.16) in early dry season was similar to values in early rainy season (20.46%, 95% CI 18.84 to 21.08%). A similar situation was noticed for animals in both low land and mid land study sites.

CONCLUSION

Overall, the detection of trypanosomes in blood was significantly affected by agro-ecology, season and body condition of the animals. Special emphasis should be given to integrated trypanosomosis management in early rainy months where fly population is believed to start increasing.

Prevalence of bovine trypanosomosis in Ethiopia: a meta-analysis

BACKGROUND

Trypanosomosis is a haemoprotozoan disease, mostly transmitted by the tsetse fly (Glossina spp.), it causes severe disease in humans and animals in Sub-Saharan Africa (SSA). The disease results in loss of livestock and agricultural productivity with severe socio-economic impacts. In Ethiopia, bovine trypanosomosis is widely distributed in western and south-western parts of the country. It is estimated that some 10 to 14 million heads of cattle in Ethiopia are exposed to the risk of trypanosomosis.

METHODS

This study describes the prevalence of bovine trypanosomosis in Ethiopia through a meta-analysis. A comprehensive search was conducted on PubMed and non-PubMed indexed articles were also incorporated based on expert suggestion. Eligible studies were selected by using inclusion and exclusion criteria. Pooled prevalence was estimated by random effect model. Publication bias and the variation in prevalence estimates attributed to heterogeneity were also assessed.

RESULTS

Twenty-four studies with relevant prevalence data were identified and included in the analysis. The apparent prevalence of bovine trypanosomosis varied from 1.38 to 17.15 %. The pooled estimate of bovine trypanosomosis prevalence across studies for the entire period was 8.12 % (95 % CI: 6.88; 9.35), ranging from 10.27 % (95 % CI: 7.34; 13.20) in the late 1990s and early 2000s, to 6.81 % (95 % CI: 5.00; 8.62) after 2010. Sub-analysis by region revealed wide variations in prevalence. The highest estimated regional prevalence was 13.30 % (95 % CI: 7.73; 18.88) in Benishangul Gumuz Regional state. A high degree of heterogeneity was observed in most pooled estimates and even after sub-group analysis. The visual inspection of the funnel plot and the Egger's regression asymmetry coefficient [b = 2.18] (95 % CI = -1.09, 5.46; p > 0.05) did not suggest the presence of publication bias. T. congolense and T. vivax were reported to be the predominant causative agents. From the total positive animals, 45.5 and 44.3 % of the infections are accounted to T. congolense and T. vivax, respectively.

CONCLUSIONS

The meta-analysis showed a significant reduction in prevalence of bovine trypanosomosis in recent years, but the reduction is not to the lowest necessary level. Since T. vivax is reported to be one of the most important trypanosome species involved, efforts should also be made to control the mechanical transmission by biting flies.