Seroprevalence of bovine brucellosis and associated risk factors in and around Alage district, Ethiopia.

Brucellosis is a zoonotic disease with economic and public health impact, particularly for human and animal populations within developing countries that relay on livestock production. A cross sectional study was conducted between October 2013 and March 2014 in and around Alage district to determine the seroprevalence of bovine brucellosis and associated risk factors. A total of 804 sera samples; 421 from cattle managed under extensive production system and 383 from cattle managed under intensive production system were collected. Multistage cluster sampling method was employed to sample unvaccinated cattle above 6 months of age. Rose Bengal Plate Test and c-ELISA were used in serial for detection of antibodies against Brucella species. The overall seroprevalence was 2.4 %, and herd level seroprevalence was 45.9 %. A prevalence of 3.3 and 1.3 % was recorded in the extensive and intensive farms respectively. Among the three sites, seropositivity of 3.4 % in Naka, 3.3 % in Negelewudisha and 1.3 % in Alage were recorded. Risk factors such as age, sex, number of service per conception, calving interval and reproductive status were associated with serostatus of brucellosis. Taken as a whole, cattle in both intensive and extensive production systems are endemically infected by brucellosis at low level in the study areas. This warrants the need of integrated intervention strategies to minimize the spread of the disease in animals and reduce the risk of transmission to humans.

Spatial distribution of Glossina sp. and Trypanosoma sp. in south-western Ethiopia.

BACKGROUND: Accurate information on the distribution of the tsetse fly is of paramount importance to better control animal trypanosomosis. Entomological and parasitological surveys were conducted in the tsetse belt of south-western Ethiopia to describe the prevalence of trypanosomosis (PoT), the abundance of tsetse flies (AT) and to evaluate the association with potential risk factors. METHODS: The study was conducted between 2009 and 2012. The parasitological survey data were analysed by a random effects logistic regression model, whereas the entomological survey data were analysed by a Poisson regression model. The percentage of animals with trypanosomosis was regressed on the tsetse fly count using a random effects logistic regression model. RESULTS: The following six risk factors were evaluated for PoT (i) altitude: significant and inverse correlation with trypanosomosis, (ii) annual variation of PoT: no significant difference between years, (iii) regional state: compared to Benishangul-Gumuz (18.0%), the three remaining regional states showed significantly lower PoT, (iv) river system: the PoT differed significantly between the river systems, (iv) sex: male animals (11.0%) were more affected than females (9.0%), and finally (vi) age at sampling: no difference between the considered classes. Observed trypanosome species were T. congolense (76.0%), T. vivax (18.1%), T. b. brucei (3.6%), and mixed T. congolense/vivax (2.4%). The first four risk factors listed above were also evaluated for AT, and all have a significant effect on AT. In the multivariable model only altitude was retained with AT decreasing with increasing altitude. Four different Glossina species were identified i.e. G. tachinoides (52.0%), G. pallidipes (26.0%), G.morsitans submorsitans (15.0%) and G. fuscipes fuscipes (7.0 %). Significant differences in catches/trap/day between districts were observed for each species. No association could be found between the tsetse fly counts and trypanosomosis prevalence. CONCLUSIONS: Trypanosomosis remains a constraint to livestock production in south-western Ethiopia. Four Glossina and three Trypanosoma species were observed. Altitude had a significant impact on AT and PoT. PoT is not associated with AT, which could be explained by the importance of mechanical transmission. This needs to be investigated further as it might jeopardize control strategies that target the tsetse fly population.

Majority of T. gondii seropositive chickens (Gallus domesticus) in Central Ethiopia carries the infective parasite.

BACKGROUND: The prevalence of Toxoplasma gondii in free range chickens is a good indicator of the prevalence of T. gondii oocysts in the environment. The aim of this study was to isolate T. gondii parasites from heart and brain of seropositive free range (FR) chickens. FINDINGS: Isolation of T. gondii from pooled heart and brain of 41 direct agglutination test (DAT) positive (≥1:40) free range chickens (Gallus domesticus) was carried out by bioassay in mice. T. gondii specific antibodies in mice were assayed by DAT and microscopy was employed for detection and enumeration of brain tissue cysts. Overall, bioassay was positive in 29 (70.7%) chicken samples. T. gondii tissue cysts were isolated from 59% (24/41) of bioassayed chickens: from 2 of 7 chickens with a titer of 1: ≤ 60, 2 of 5 with titer 1: 180, 6 of 8 with titer 1: 540, 10 of 15 with titer 1: 1620, 1 of 2 with titer 1: 6000, 2 of 3 with titer 1:18000, 1 of 1 with titer 1:54000. None of the isolates was pathogenic for mice. Tissue cysts were detected from 61% of seropositive mice (DAT ≥ 1:40). Generally, tissue cyst counts per brain of mouse were low (mean: 132.7 ± 84.4; range: 47-352). CONCLUSIONS: Majority of T. gondii seropositive chickens (Gallus domesticus) in Central. Ethiopia carries the infective parasite. Tissues from the free range chicken might be a source infection for animals and humans.

Serological responses and biomarker evaluation in mice and pigs exposed to tsetse fly bites.

BACKGROUND: Tsetse flies are obligate blood-feeding insects that transmit African trypanosomes responsible for human sleeping sickness and nagana in livestock. The tsetse salivary proteome contains a highly immunogenic family of the endonuclease-like Tsal proteins. In this study, a recombinant version of Tsal1 (rTsal1) was evaluated in an indirect ELISA to quantify the contact with total Glossina morsitans morsitans saliva, and thus the tsetse fly bite exposure. METHODOLOGY/PRINCIPAL FINDINGS: Mice and pigs were experimentally exposed to different G. m. morsitans exposure regimens, followed by a long-term follow-up of the specific antibody responses against total tsetse fly saliva and rTsal1. In mice, a single tsetse fly bite was sufficient to induce detectable IgG antibody responses with an estimated half-life of 36-40 days. Specific antibody responses could be detected for more than a year after initial exposure, and a single bite was sufficient to boost anti-saliva immunity. Also, plasmas collected from tsetse-exposed pigs displayed increased anti-rTsal1 and anti-saliva IgG levels that correlated with the exposure intensity. A strong correlation between the detection of anti-rTsal1 and anti-saliva responses was recorded. The ELISA test performance and intra-laboratory repeatability was adequate in the two tested animal models. Cross-reactivity of the mouse IgGs induced by exposure to different Glossina species (G. m. morsitans, G. pallidipes, G. palpalis gambiensis and G. fuscipes) and other hematophagous insects (Stomoxys calcitrans and Tabanus yao) was evaluated. CONCLUSION: This study illustrates the potential use of rTsal1 from G. m. morsitans as a sensitive biomarker of exposure to a broad range of Glossina species. We propose that the detection of anti-rTsal1 IgGs could be a promising serological indicator of tsetse fly presence that will be a valuable tool to monitor the impact of tsetse control efforts on the African continent.

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

Cross-sectional study was conducted in Dale Wabera district of Kellem Wollega zone, Western Ethiopia, to determine the prevalence of bovine trypanosomosis and to evaluate association of bovine trypanosomosis to anaemia. Blood samples collected from 384 randomly selected cattle were subjected to parasitological and haematological analysis. For the parasitological survey, blood samples were examined using a buffy coat technique. The packed cell volume (PCV) value of each animal was also measured using hematocrit reader. The overall prevalence of trypanosomosis was 2.86%. The most common trypanosome species identified were Trypanosoma congolense (63.64%) followed by T. vivax (27.27%) and T. brucei (9%). The prevalence showed no significant difference in susceptibility between sex categories, age groups, and different body conditioned animals. The overall anaemia prevalence in the area was 19.27%. The anaemia prevalence was significantly higher in trypanosome positive cattle (54.54%) than in noninfected animals (18.23%) (P < 0.05). The mean PCV value of the infected animals was lower (22.36% ± 7.39%) compared to noninfected animals (27.86 ± 5.38%). There was statistically significant difference (P < 0.05) in the PCV values of infected and noninfected animals. In conclusion, this study confirmed that trypanosomosis poses a threat to cattle production in the area and also contributed to the occurrence of anaemia.

Molecular detection of piroplasms in ixodid ticks infesting cattle and sheep in western Oromia, Ethiopia.

In Ethiopia, ticks and tick-borne diseases are widely distributed and contribute to important economic losses. Several studies investigated the prevalence and species composition of ticks infesting ruminants; however, data on tick-borne pathogens are still scarce. During the study period from October 2010 to April 2011, a total of 1,246 adult ticks and 264 nymphs were collected from 267 cattle and 45 sheep in Bako District, western Oromia, Ethiopia. The study showed infestation of 228/267 (85.4 %) cattle and 35/45 (77.8 %) sheep with adult ticks. Overall, eight tick species, belonging to three genera (Amblyomma, Rhipicephalus, Hyalomma), were identified and Amblyomma cohaerens (n = 577), Rhipicephalus evertsi evertsi (n = 290), Rhipicephalus (Boophilus) decoloratus (n = 287), and Amblyomma variegatum (n = 85) were the more prevalent species. A statistically significant host preference in A. cohaerens for cattle and R. evertsi evertsi for sheep was noticed. Molecular detection of piroplasms, performed only for adult ticks of two species of the genus Rhipicephalus (R. evertsi evertsi and R. decoloratus), revealed an overall prevalence of 4 % (8/202) Theileria buffeli/sergenti/orientalis, 0.5 % (1/202) Theileria velifera, and 2 % (4/202) Theileria ovis. The study showed that tick infestation prevalence is considerably high in both cattle and sheep of the area, but with a low intensity of tick burden and a moderate circulation of mildly pathogenic piroplasm species.