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PAATGIS&RS

Hosts

Tsetse-borne Trypanosomosis is a disease affecting wildlife, livestock and people in sub-Saharan Africa. Wildlife are the natural hosts of tsetse and may acquire prolonged symptomless infections. Livestock exhibit a range of susceptibility to infection, from refractory to highly vulnerable. With respect to Trypanosomosis, African cattle breeds can be classified into two major categories: humpless trypanotolerant taurine cattle (Bos taurus) and the humped trypanosusceptible zebu cattle (Bos indicus). Significant variations in susceptibility to Trypanosomosis has also been observed within and between different breeds of sheep and goats.

At regional level, remotely sensed eco-climatic surrogates (such as vegetation, temperature, relative humidity and rainfall) and historical maps of the zebu/taurine limit enable to map areas which are suitable for zebu or taurine presence. This can be done by means of logistic regression functions applied in a GIS environment.

At country level, aerial photography and satellite data have been used to map distribution limits and density of the various cattle breeds; in some cases emphasis was placed upon trypanotolerance and crossbreeding; the latter is mainly achieved by introducing zebu bulls into a trypanotolerant and/or crossbred herd. This type of studies takes advantage of surveys carried out in the field, combined with remotely sensed data.

Not only present distribution but also future cattle population growth can be assessed by means of models running in a GIS environment so that both spatial and temporal dimensions are accounted for. Constraints to growth such as natural carrying capacity or Trypanosomosis can be put into the calculation and predictive scenarios can be depicted.

The spatial distribution of production systems is an additional piece of information that can be modelled in a GIS for the comprehension of Trypanosomosis impact and the selection of proper control measures. Husbandry systems may differ in many ways: cattle density, herd size, number of owners, level of integration with crop agriculture and with markets.

Prevalence of trypanotolerant or trypanosusceptible cattle, as well as cross-breeding between the two of them, are also elements of distinction. Clustering a series of spatially referenced socio-economic variables allows to draw predictive maps of the production systems.

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