Epidemiological concepts and strategies for parasite control: what changes are likely to occur?

Climate warming and changes in habitat suitability for Boophilus microplus (Acari: Ixodidae) in Central America

Remote sensing on the basis of AVHRR (advanced very high resolution radiometer) satellite imagery was used, together with standard geostatistical methods (cokriging), to estimate the distribution of habitat suitability (HS) for the tick Boophilus microplus (Canestrini) in Central America. Most attention was paid to the expected limits of tick distribution as well as the temperature and vegetation values responsible for different HS zones and their variability within the year. The highest HS extended through wide areas of southeastern United States, much of Mexico, and other countries of Central America. Areas with higher HS had relatively stable temperatures (within 20-25 C) throughout the year, and had a NDVI (normalized derived vegetation index) of around 0.4. These areas need to be targeted to ensure acaricide usage at optimum intervals and to avoid the formation of areas with enzootic instability. A seasonal analysis of the climate trend through the study period (1982-1999) revealed a warming cycle, together with a rise in NDVI index values. The main consequence of this trend is the gradual increase in unsuitability in areas where the tick is already established, with the establishment of new foci in zones currently too cold to support tick populations. The cooling periods of 1-2 yr that were observed between warming cycles may also lead to enzootic instability when warm zones cool to within the suitability range. As the model is remotely sensed, a continuous update of the B. microplus distribution could be performed, assuring maximum efficiency in developing management strategies.