Seroepidemiological Study of Bovine Brucellosis in Tigray Region Northern Ethiopia
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Date
2005-06
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Addis Ababa University Faculty Of Veterinary Medicine
Abstract
A cross-sectional epidemiological study was ca rried oul fTom September 200-t to March 2005
to detemline the scropreva lence ofbovinc brucellosis in the int ensive and extensive cattle
production systems of Tigray Region, to identify the risk facto rs Ihal contribu te to the
occurrence of brucellosis and assess the public health significance of the disease.
The study populations werc compnsed of indigenous and crossbred c<lIlle in the Region and
samples \\' ere selected by twa -stage clu ster s ampling. Serum samples collected from 1,951
cattle above six months of age, of which 1.135 from the intensive famls and 816 from the
extensively managed herds \\cre screened for Brucella antibodies by the Rose Bengal Plate
Test (REPT) and the reactor sera \\ere 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 seroposi ti\'ity. Likewise.
data on fann or herd-lc\-eI rISk factors and other farm characteristics \\ere obtained using a
questionnaire survey. \\ hich \\ as administered in person to 112 intens ive fanns and members
of animal o\\ners In the 26 extensi .... e herds. Furthermore. in order to assc~s the zoonotic
imporlance of the dIsease. 185 human serum samples were also sc reened for brucellosis.
In this stud). the 0\ erall "eroprc\-alence of Brllcella antibodies in cattle \\ a~ I .!9"fO. Ho\\ e\'cr.
indi\'idual aOimal seropre\'alence \\as found to .... ary from 0.26% m Ihe mtenSI\e famls to
3.19°'0 in animals reared under the extensive management system :-,tatlstlcall) signi fi cant
difference \\as observed in seropre\'alence val ues bel\\een the mtensi\·c and extensive
management s:~tems (p<O_051 The o\'erall herd-level pre\'alence vaned from 2.68 ~o in the
intensi\·e farms to ..!2.31% in the c"\tcnsl\ely managed herds \\her("as \\ithm-herd prevalence
differed from 0% - 33% m the inlcnsivc farms to 0% - 11% in the cxtensm;, herds based on
CFT However. no antibodies agalilst Brucella were detected III the human sera
The result:; of UOl\3riate logistic regression analysis re\ealed that agt:. herd Sl/e and pari ty
number of animals had no statistically Slglll ficant effect on individual animal seropositivity to
brucellosis in the Intensive mana:;ement system. Ho\\e\er. m th~ c'\ t~n~l\e management
system. seropositivity to brucellf':>ls \\as slg.lllficantly higher III ammals. kept under the
transhumancc managcmem sUb-s~:>lem than alllmais III the sedentar: sub-system fp<O.OOI)
The result .. also indIcated that there \\as a ~taIl511ca1\) slgmficant increase III seroprcvalence 10
\"Ill
brucellosis with increasing agc (p<O.O I) but not parity (1'>0.05). Significant increment of
seropositivity was al so observed as herd size inc reases from small to medium (p<0.05) and
then to large sizes (p<O.OO I). In addition. a significantly higher seropreva lcnce was found in
animals 111 the lowland than those in the highland agro-climatic zones. Nevertheless, in the
multivariate logistic regression onalysis. systemic factor (OR = 10.6%, 95% CI = 2.3 - 49.3.
p<O.OI) and age (OR = 4 2,95% Cl = 2.3 - 49.3, p<O.OI ) were identified as the major risk
factor for indi\·idual animal seroprcvalence in the extensive management system.
Transhumance management sub-system was also significantly associated with increased herd
scroprevalence (p<O.OI) but not herd size (p>O.05) in the extensive management system.
Furthemlore, there was a statistically signi ficant association between seroposi tiviry to
brucellosis and history of previous abortIons (Fisher"s exact p<O 001) and s till births (Fisher's
exact 1'<0.05) in the extensive herds but only of abort ion (Fisher's exact p<O.OI) in the
intensive farms.
The results of this study :;ho\\cd that brucellosis is an endemic and widely dlstnbutcd disease
in Tigray Region \\ ith relatively high seroprc\'alence in the extensive than tht: intensively
managed callIe. The implememations of better management prac tices are recommended to
prevent further spread oftht: disease.
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Keywords
Bo\ine. brucdlosis. seroeptdenllology. seroprc\"aJencc, Tigray Region. ~orthem EthioPia