Bionomics of the Primary Malaria Vector, Anopheles pseudopunctipennis, in the Tapachula Foothill Area of Southern Mexico

Malaria, the more important vector-borne disease in Mexico, is transmitted predominantly by Anopheles pseudopunctipennis in roughly two-thirds of the malarious areas of Mexico. Included in this report are the results of studies to clearly define the relationships of humans to An. pseudopunctipennis mosquitoes in foothill areas near Tapachula, Chiapas, Mexico. Mark-recapture methods were used in studies of the gonotropic cycle. A 3-day cycle was documented for wild-caught, marked and released populations of mixed physiological age. A 4-day cycle was documented for marked and released females that were laboratory-reared. The Human Blood Index HBI, which is the percentage of human blood meals in engorged mosquitoes, was greater than 30 in pooled samples from all study sites. A shift from feeding on humans to feeding on other animals occurred with outdoor host-seeking populations after DDT was sprayed on house walls. Approximately 60 of all nulliparous females required a second blood meal to complete their first gonotrophic cycle. This phenomenon greatly increases the capacity of this vector to acquire and transmit malaria. During the wet season most larvae were collected from largely temporary habitats, such as seepage spring, rainwater pool and pond habitats containing filamentous algae. Coincidentally, the largest numbers of mosquitoes coming to human hosts were in those villages located closest to the river. Transects were employed to quantify the seasonal dynamics of An. pseuilopunctipennis larvae. The primary factor was availability of aquatic habitats with filamentous algae. In hierarchical order, habitat availability is regulated by the quantity and turbulence of water flow in the river. Finally, water flow is regulated by rainfall in the mountain and foothill areas. The finding of the new variant P. vivax PV 247 antigen in wild-caught specimens of An. pseudopuncripennis further extended the geographical range of this Asian strain of P. vivax malaria.