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.