SEROPREVALENCE AND ISOLATION OF TOXOPLASMA GONDII FROM SHEEP AND GOATS IN CENTRAL ETHIOPIA
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2012-06
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Abstract
A cross-sectional study was conducted in Central Ethiopia from September, 2011 to May, 2012 to estimate the seroprevalence and risk factors of toxoplasmosis in sheep and goats of Central Ethiopia. Additionally, follow-up experimental study on mice was conducted during the same period in order to: isolate viable T. gondii, enumerate bradyzoites cysts and compare the diagnosis of T. gondii infection by Modified Agglutination Test (MAT) and bioassay. Blood and heart samples (n=357) from sheep and goats originating from Ambo, Ada’a-Liben and Fentale districts were collected from HELEMEX export abattoir, Debre Zeit and sera were examined for T. gondii antibodies by MAT. Hearts of those seropositive sheep and goats (n=54) were bioassayed in mice. Sera and brain of mice were examined for T. gondii IgG antibodies and tissue cysts, respectively. To this effect, the overall seroprevalence of anti-Toxoplasma gondii antibodies in sheep and goats was 20.5% (n=73/357). The present study revealed that seroprevalence was higher in small ruminants of Ambo (Odds ratio [OR] = 2.7, 95% confidence interval [CI]: 1.07, 6.80; 0.036) than Ada’a-Liben district, in sheep (OR=1.7, 95% CI: 1.02, 2.90; P=0.041) than goats and from samples of March (OR=5.4, 95% CI: 1.70, 17.07; P=0.004) than from samples of April. Among the 54 bioassays performed, viable T. gondii was isolated from hearts of 8 (34.78%) of 23 sheep and 13 (41.9%) of 31 goats. Quantification of cysts per brain of mice showed an average of 34.73 tissue cysts with a minimum and maximum of 0 and 554 respectively. Most appreciably, 2 of 21 T. gondii isolates from sheep and goats were mouse-virulent. The final Zero-inflated Poisson regression model of potential predictors of cyst count showed that cyst count was higher from heart samples of Ambo (Incidence risk ratio [IRR]= 1.8, 95% CI: 1.15, 2.69; P=0.009) and Ada’a-Liben (IRR = 3.2, 95% CI: 2.22, 4.76; P=0.000) districts than Fentale district, from hearts of female animals (IRR = 2.1, 95% CI: 1.36, 3.22; P=0.001) than male animals, from hearts of adult sheep and goats (IRR = 1.5, 95% CI: 1.11, 2.08; P=0.009) than young sheep and goats, from hearts of goats (IRR = 1.5, 95% CI: 1.19, 1.78; P=0.000) than sheep hearts and from MAT positive mice (IRR = 1.9, 95% CI: 1.32, 2.82; P=0.001) than MAT negative mice.
VIII
There was a significant agreement (Kappa=0.735, P=0.000) between MAT and microscope examination of cysts for diagnosis of T. gondii infection in mice. In conclusion, the present study confirms the widespread presence of T. gondii antibodies and tissue cysts in sheep and goats in Central Ethiopia. Results of the present study indicate that asymptomatic sheep and goats can harbor mouse-virulent T. gondii which might be hazardous for people who consume raw or undercooked meat. Emphasis should be made on the hazards associated with the consumption of raw meat as ingestion of raw meat could be source of human infection in Ethiopia. This is the first report on isolation of viable T. gondii from sheep and goats in Ethiopia. A further study to characterize the genotypes of isolated strains is in progress.
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Keywords
Bioassay, MAT, Tissue cysts, Sheep, Goat, Toxoplasma gondii