The value of vector-based estimates of malaria transmission

Estimating malaria transmission in the human is fraught with problems of reconciling clinical illness with parasitological status. It follows that there is a role for entomological assessments as an independent outcome variable and as a process indicator. Advances in DNA technology have expanded our capacity to identify vectors rapidly, while immunoassays allow the inoculation rate to be measured simultaneously in a number of villages with a precision 3-fold greater than measurements of vectorial capacity. The rapid specific identification of parasites in vectors has been utilized to estimate survivorship in mosquitoes per extrinsic incubation period (EIP), circumventing the need for estimates of survivorship per feeding cycle, lengths of feeding cycles or the length of the EIP. While lack of accuracy does not universally preclude the utility of estimates of the components of vectorial capacity in serving as relative estimates of transmission, particularly as process indicators, more accurate estimates of these parameters, particularly for density-dependent variables, may diminish the associated bias in their measurement. When this is accomplished, we will come closer to obtaining true rather than relative estimates of transmission.