Seroprev alence and Isolation of Toxoplasma Gondii From Sheep and Goats in Central Ethiopia
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Date
2012-06
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Addis Ababa University
Abstract
A cross-sectional study was conducted in Central Ethiopia from September, 2011 to May,
20 12 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 Tgondii antibodies by MAT. Hearts of those seropositive
sheep and goats (n=54) were bioassayed in mice. Sera and brain of mice were examined for
Tgondii JgG 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'aLiben
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%) of23 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 Tgondii 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=O.OOO) districts
than Fentale district, from hearts of female animals (IRR = 2.1 , 95% CI: 1.36, 3.22;
P=O.OOI) 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=O.OOO) than sheep hearts and from MAT positive mice (IRR = 1.9, 95% CI: 1.32,
2.82; P=O.OOI) than MAT there was a significant agreement (Kappa=O.735, P=O.OOO) 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. A further study to characterize the genotypes of isolated strains is in progress.
Keywords: Bioassay, MAT, Tissue cysts, Sheep, Goat, Toxoplasma Gondii
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Keywords
: Bioassay, MAT, Tissue cysts, Sheep, Goat, Toxoplasma Gondii