Epidemiology of Bovine Trypanosomosis and its Economic Impact in Tsetse-Infested and Tsetse-Free Areas of Amhara Region, North-West Ethiopi
The epidemiology of bovine trypanosomosis was studied in tsetse-infested and tsetse-free areas of Amhara Regional State, North-West Ethiopia. A multidisciplinary work was undertaken to elucidate the key factors determining the presence of tsetse flies and magnitude of bovine trypanosomosis. Cattl...
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| Format: | Thesis |
| Language: | English |
| Published: |
2004
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| Online Access: | http://psasir.upm.edu.my/id/eprint/23/2/1000548962_t_FPV_2004_10.pdf http://psasir.upm.edu.my/id/eprint/23/ |
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| Summary: | The epidemiology of bovine trypanosomosis was studied in tsetse-infested and tsetse-free
areas of Amhara Regional State, North-West Ethiopia. A multidisciplinary work was
undertaken to elucidate the key factors determining the presence of tsetse flies and
magnitude of bovine trypanosomosis. Cattle were selected from tsetse-infested and
tsetse-free areas for monthly monitoring of trypanosome infection by blood sampling on
glass slides, dried blood spot and buffy coat spot on filter papers. In this study,
parasitological, serological (Ab-ELISA) and PCR methods were used to characterize
trypanosomes infecting the vector and the host.
A total of 795 blood samples from cattle were examined from the tsetse-infested and
tsetse-free areas; 13.5% of wet blood film and 15.6% of thin blood film were found
positive for trypanosomes while PCR detected 18 % trypanosome infections. The
dominant species was T.vivax, followed by T.congolense and T.brucei. T.vivax was
higher in tsetse-free areas, whereas T.congolense was more in tsetse-infested areas,
T.brucei and mixed infection of T.congolense and T.vivax were only present in tsetseinfested
areas. The monthly trypanosome prevalence in tsetse-infested areas varied from
15 to 28% and in tsetse-free areas was 9 to 27%, with December having the highest
prevalence in both study areas. Sera and dried blood spot on filter paper in Ab-ELISA
showed strong correlation, providing for the use of the more convenient dried blood spot.
In the retrospective study 7079 samples and accompanying data were analyzed for 5
consecutive years from the year 1997 till 2001. The prevalence of trypanosome infections
was highest during the early dry season (September to December). Trypanosome
infections were mainly due to T. vivax. Trypanosomosis reduced significantly the average
packed cell volume and the body condition of the host. The monthly prevalence of
infection was correlated with the density of biting flies suggesting their important role in
transmission of trypanosomosis in the tsetse-infested and tsetse-free areas of the Amhara
Region of north-west Ethiopia.
Flies were trapped for 3 days each month in the study period using 4 types of traps
(`Biconical’, `NGU’, `Pyramidal’ and hand net). A total of 5652 tsetse and other biting
flies were captured; 3532 flies from tsetse-infested areas and 2120 flies from tsetse-free
areas. PCR amplification analyses for trypanosome identification were carried out on
3751 flies, with primer sets specific for Trypanosoma (Duttonella) vivax, T.
(Nannomonas) congolense and T. (Trypanozoon) brucei. Of 3751 flies; 699 (18.64%)
were positive in PCR analysis with 132 (12.13 %) from tsetse-free areas and 567 (21.29
%) from tsetse-infested areas. Comparing within the type of flies, out of 1314 tsetse flies
(Glossina morsitans submorsitans and Glossina tachinoides) 366 (27.85 %) were positive
and out of 2437 other biting flies 333 (13.66 %) were found positive (P<0.01). Therefore
PCR can be used to generate baseline data for fly infection.
From the 15 risk factors identified for trypanosome infection, multivariable logistic
regression model produced the final logistic model containing seven variables (biting fly
density, season, transhumance grazing, traction oxen, origin of the herd, area (tsetseinfested
and tsetse-free) and Packed Cell Volume). Their significance was P=0.05 which
showed a significant association with trypanosome infection.
The socio-economic effect of trypanosomosis was evaluated using Participatory Rural
Appraisal (PRA) technique. Selected districts with three different trypanosomosis risk
(high, medium and low) demonstrated much overlap between the farmers’ perception of
the disease (gendi) and bovine trypanosomosis. For example, ‘gendi’ was associated with
chronic weight loss, abortion, calf mortality and decrease milk yield in the high
trypanosomosis risk area compared to the other two areas.
In conclusion, this study reported for the first time the use of PCR based assay on sample
optained from Amhara Region, North West Ethiopia to detect trypanosome from
naturally infected biting flies (dried blood meal residue) and dried buffy coat spot on
filter paper from cattle. The dominant species noted was T.vivax. The epidemiology of
trypanosomosis in cattle is also dependent on other biting flies apart from tsetse flies.
Consequently, the eradication of tsetse flies alone will not necessarily lead to eradication
of trypanosomosis. |
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