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 and
samples were selected by two-stage cluster sampling . Serum samples collected from 1,951
cattle 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 Plate
Test (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 of
each sampled animal to determine the risk factors for brucellosis seropositivity. 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 members
of animal owners in the 26 extensive herds. Furthermore. in order to
asses
s
the 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 to
3.19% in animals reared under the extensive management system statisticall significant
difference 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 to
brucellosis 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 the
multivariate 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 to
brucellosis 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 disease
in Tigray Region with relatively high seroprevalence in the extensive than the intensively
managed cattle. The implementations of better management practices are recommended to
prevent further spread of the disease.
Description
Keywords
Bovine. brucellosis. seroepidcnllology,