Epidemiology of Bovine Trypanosomosis in Selected Sites of the Newly Established Settlement Areas East Wollega Zone, Western Ethiopia
No Thumbnail Available
Date
2006-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ADDIS ABABA UN IVE RSITY FACULTY OF VETERI NARY MEDICINE
Abstract
A study o n the epide mio logy of bovine trypanosomosis in selected sites of the new ly established
sett le ments of A nger I. Anger II and Ke nar areas was conducted in East Woll cga Zone, Oromiya
Region, Western Ethiopia. T he p urpose of t be study was \0 delemli nc the prevalence of the
disease and associating ri sk factors and est imate the appare nt d ensities and d istributions of tsetse
and other biting n ics. It was also to generate baseli ne data thaI may ass ist in dec ision mak ing for
platU1 ing and implementation of the sett lement pro grammes. Retrospective study and
quest ionnaire survey we re conducted to coll ect backgrou nd descri ptive data and cross-sectio nal
survey to dctennine the preva lence and vector apparent densit ies and d istribut ions in late rainy
and dry seasons in 200S /06. A to tal of 576 callie we re sa mp led and the bufTy coat technique was
applied to diagnose the trypanosome infection and 96 mono· pyramidal t raps to capture the vector
ny. DifTercnces between parameters were tested for signi fi cance at probability levels of 0 .0.5 or
less Results of the retrospective st udy and q uest iOlmaire survey indicated that bovine
trypanos011l0sis is the major constraint to cattle product ion in the seillement areas. The curative
and preventive doses of trypanocidal dmgs are commonly used 10 control the disease. I lo\\,(:\,er.
man} cattle owners have developed the pmctices of selling out their work oxen after each crop
season as the coping mechanism with the d isease risk to rep lace by new animals and generate
additional Income s frolll sa les . The entomological survey showed that only two tsetse species.
Glossina mo"s;rans slIbmorsirons and G. rachilloides were found to exist along with other biting
flies of the tabanid and l1luscid groups. The G. m. submorsirofl.l- was detected at a Illean app·arcnl
density (fly trap. day) of 0.01 and G. tachilloides at 0 .3S. The overall apparent densities
(Oy trap day) were found to be 0.36 (95% CI = 0.22 - 0.50). 1.26 (95~, CI = 0.55 - 1.97) and
41.IS (9S% C I = 28.8 - S3.S) for tsetse, tabanids and muscid flics respectively in the study arl.!as.
The seasonal apparent densities were 0.40 and 0.33 (p> 0.05). 2. 18 and 0.34 (p < O.OS ), 76.0 and
6.29 (p < 0.05) for tsetse, tabanids and musc id fly in late ra iny and dry seasons In corresponding
order. The fly apparent densit ies in different vegetation types were assessed but the dlffer..:n ccs
were not statistically significant (p > O.OS) for all ny kinds. The sex ratio for tsetse fl) was
detennined and fewer proportion of ma le flies detected (21 /58) and (IS/47) du ring late rainy
season and the dry season, respectiV el y. The average age for ma le tsetse fly samp le population
x
was estimated from wing fray analysis and observed to be 19 and 16 days for late rainy season
and dry season , re spectively. The overall prevalence of bovine trypanosomosis was 8.9% (95%
CI = 7 - II %) the seasonal infection ra te being 14 .9% (95% CI = II - 19%) and 2.8% (95% CI =
I - 5%) with stat ist icall y signifi cant difference (p < 0 .001) be tween lat e rainy and the dry seasons
rc specti vely. In all ca scs th e dominant trypanosome species was Tt:)'panosoma congolense
56.8% (95% CI = -n - 71 %) followed by T. V;Va\: 3 1.4 % (95% 1 1 - 470'0) . The prevalence of
trypanosome infection in new ly introduced cattle fro m tset se free arcas was 11.4 % (95% CI = 8 -
16%) whilst in native an im a ls 4.3% (95% Cl = 2 - 6%) with a stat isti cally signi fi cant difference
( p < 0.01) between the two groups. The prevalence by sex was 8.4% (95% C I = 4 - 12 %) in the
fe ma le and 9.1 % (95% CI = 6 - 12 %) in male counterpart. T he in fection ra tes in differcl1l1 age
groups were nil, 8.0% (95% CI = 5 - 12 %) and 10.0% (95% CI = 7 - 13%) in animals of less
than I, I - 4 and nbovc 4 year-o ld , respectively. The differences in infecti on were not stati sti ca ll y
significant (p > 0.05) betwecn scxes and age groups. Analysis of the interaction of the assumed
risk fac to rs indicated season and origin to be the risk fact ors (p < 0.0 I) for trypanosome inf(!ct ion
among the catt le popu lat ion of the sett lement areas. However. sex was not (p > 0.05) while age
was signified to be risky which is largely dctennined by absence or prescnce of exposure to tselse
cha ll enge. The risk of acquiring in fcction was lower in the dry season as comparcd to late rainy
season (OR = 0. 13. 95% CI = 0.06 - 0.28) and 3.36 times higher (OR = 3.36, 95% CI = 1.64 -
6.88) in the new ly introduced than in the native cattle population. The mean PCV values were
27.23% (95 % CI = 26.77 - 27.69%) and 20 .22 % (95% CI = 18 .75 - 21.68%) with statistica ll y
significant difference (p < 0.001) for the non-paraslIaemic and parasitaemic animals respective ly.
The mean PCV ,' aille was negatively correlated (r = -0.35) wnh thc trypanosome prevalence.
Bovine u),panosol11osis is the major constraint in the newly established settlemen t areas.
Introduction of susceptibl e catlle populat ion to tsetse infested settlement areas wou ld resu lt in
heavy lo sses espeCially annna ls coming from tsetse free areas bemg the high fisk group when the
vector challenge is high. Different epid emio log ical c ircumstances appeared to exist that would
maintain the contact between tsetse and the hosl animal. Interiorly tsetse-infcstcd wooded bordcrs
of many rivers and streams that lra\ erse the areas as well as scrap of forcst at the edge of
sett lements to which C. /(IchillOides seems well adapted would sustain theIr constant interactIons.
On the other hand moderately infested peripheries to which C. m. subm orsirolls receded that have
a link with the major tsetse belt const itute a potential risk to the a reas. Furthennorc. the frequent
x,
movement of ani mals coming fro m or c rossing the tsetse·infestcd areas to the major market outlet
in Uke. Kenaf prefecture is the maj or source of infected an imals. The vast potent ial land in th e
settlement areas would on ly be exploited if th c problcm of animal trypanoso l11 os is is resolved
under the present cro p· li vestock farming system . Therefore, communit y based intcgratcd cOIlltro l
option shou ld be promoted with strong surveillance and moni toring act ivit ies
Description
Keywords
Bovine. Origin, Settlement, Seaso n, Trypanoso mo sis, Trypanoso me, Tsetse.