The area-wide epidemiology of bovine trypanosomosis and its impact on mixed farming in subhumid West Africa; a case study in Togo.
This paper reports on an area wide study of all major variables determining the expression of trypanosomosis in cattle in the subhumid eco-zone of West Africa, taking Togo as an example. To enable systematic area-wide sampling, the country was divided in 311 grid-squares of 0.125 x 0.125 sides. Cross-sectional surveys were then conducted to generate maps or digital layers on cattle density, herd structure, ownership and breed. These data layers, except for the breed data, were subjected to a cluster analysis in order to define spatial patterns in animal husbandry systems. This analysis revealed two main systems: one is oriented towards integration with crop-agriculture and a second towards investment in cattle. These two systems could be further characterised by incorporating breed data. Zebu cattle and their crossbreeds are more favoured in the second system. The breed distribution map shows the actual situation but also serves to predict the outcome of progressive crossbreeding. An area wide trypanosomosis survey allowed the production of prevalence maps for Trypanosoma congolense, T. vivax and the associated packed cell volume (PCV) values. A simple curvi-linear relationship was established between vector density and disease prevalence. The regression between disease prevalence and PCV for taurine and zebu plus crossbreeds separately, revealed that taurine cattle maintain a comparatively high PCV level particularly in high prevalence scenarios. The relationship between the average herd PCV and cattle density suggests that herd PCV value may provide a mirror for the number of animals not kept because of the prevailing risk. The regression between agricultural intensity and cattle density subsequently in areas with decreasing herd PCV values reveals that the level of integration of cattle in crop production decreases with a decreasing PCV. Thus, despite the presence of taurine animals in Togo, the omnipresence of tsetse in particular Glossina tachinoides, remains a major obstacle to cattle raising and indirectly mixed farming development and intensification. It is argued that only with the present type of wide scale, spatial studies it becomes possible to clarify all the major variables influencing the expression of trypanosomosis. Spatial epidemiological studies at a macro level may form the basis for area wide trypanosomosis control in West Africa.
Hendrickx
G
G
FAO Trypanosomosis Project, Burkina Faso. hendrickx.vangorp@fasonet.bf
Napala
A
A
Dao
B
B
Batawui
K
K
Bastiaensen
P
P
De Deken
R
R
Vermeilen
A
A
Vercruysse
J
J
Slingenbergh
J H
JH
D000383:Agriculture; D000822:Animal Husbandry; D000818:Animals; D001769:Blood / Q000469:parasitology; D002417:Cattle; D016000:Cluster Analysis; D003430:Cross-Sectional Studies; D005260:Female; D006400:Hematocrit / Q000662:veterinary; D008297:Male; D012044:Regression Analysis; D012424:Rural Population; D012621:Seasons; D016036:Seroepidemiologic Studies; D014037:Togo / Q000453:epidemiology; D014348:Trypanosoma congolense / Q000254:growth & development*; D016689:Trypanosoma vivax / Q000254:growth & development*; D014354:Trypanosomiasis, Bovine / Q000453:epidemiology*; D014370:Tsetse Flies / Q000254:growth & development; D014505:Urban Population