Seroepidemiological Study of Bovine Brucellosis in Tigray Region,Northern Ethiopia
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Date
2005-06
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Addis Ababa Universty
Abstract
A cross-sectional epidemiological study was carried out ftom September 2004 to March 2005 to detemline the scroprevalence of bovine brucellosis in the intensive and extensive cattle production systems of Tigray Region, to identify the risk factors that contribute to the occurrence of brucellosis and assess the public health significance of the disease.The study populations were compnised of indigenous and crossbred cattle in the Region andsamples were selected by two-stage cluster sampling . Serum samples collected from 1,951cattle above six months of age, of which 1.135 from the intensive farms and 816 from the extensively managed herds were screened for Brucella antibodies by the Rose Bengal PlateTest (REPT) and the reactor sera were further tested by the Complement Fixation Test(CFT).Moreover, information was gathered on age. sex . herd size. managemenl. and agro-ecology ofeach sampled animal to determine the risk factors for brucellosisseropositivity. Likewise.data on farm or herd-leveI risk factors and other farm characteristics were obtained using a questionnaire survey. which was administered in person to 112 intensive farms and membersof animal owners in the 26 extensive herds. Furthermore. in order to asses sthe zoonotic imporlance of the disease. 185 human serum samples were also screened for brucellosis.In this study. the overall seroprcvalence of Brucella antibodies in cattle was 1.49% However individual animal seroprevalence was found to vary from 0. 26% in the intenS sive farms to3.19% in animals reared under the extensive management system statisticall significantdifference was observed in seroprevalence values between the intensive and extensive management systems (p<0_05) The overall herd-level prev'alence varied from 2.68 %in the intensive farms to 42.31 % in the extensively managed herds whereas withm-herd prevalence differed from 0% - 33% m the inlcnsivc farms to 0% - 11% in the extensive herds based on CFT However. no antibodies agalilst
Brucella were detected in the human sera.The results of univariate logistic regression analysis revealed that age. herd size and parity number of animals had no statistically sigificant effect on individual animal seropositivity to brucellosis in the intensive management system. However. in the extensive management system. seropositivity to brucellosis was significantly higher in animals kept under the transhumancc management sub-system (p<0.001).The results also indicated that there was a statistically significant increase in seroprevalence tobrucellosis with increasing age (p<0.01) but not parity (1'>0.05). Significant increment of seropositivity was also observed as herd size increases from small to medium (p<0.05) and then to large sizes (p<0.001). In addition, a significantly higher seroprevalence was found in animals in the lowland than those in the highland agro-climatic zones. Nevertheless, in themultivariate logistic regression analysis. systemic factor (OR = 10.6%,95% CI = 2.3 - 49.3.p<0.01) and age (OR = 4.2, 95% CI = 2.3 - 49.3. p<0.01) were identified as the major risk factor for individual animal seroprevalence in the extensive management system.Transhumance management sub-system was also significantly associated with increased herd seroprevalence (p<0.01) but not herd size (p>0.05) in the extensive manage ment system.Furthemore, there was a statistically significant association between seropositivity tobrucellosis and history of previous abortions (Fisher's exact p<.0001) and stillbirths (Fisher's exact p<0.05) in the extensive herds but only of abortion ( Fisher's exact p<0.01) in the intensive farms.The results of this study showed that brucellosis is an endemic and widely distnbuted diseasein Tigray Region with relatively high seroprevalence in the extensive than the intensivelymanaged cattle.
The implementations of better management practices arerecommended toprevent further spread of the disease.
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Keywords
Bovine. brucellosis. seroepidcnllology,