Quantification of Plasmodium malariae infection in mosquito vectors

Plasmodium malariae occurs in various tropical regions throughout the world and causes low, yet significant, levels of morbidity in human populations. One means of studying the ecology and frequency of this parasite is by measuring sporozoite loads in the salivary glands of infected mosquitoes. An effective, species-specific test that can be used to detect the presence of sporozoites in mosquitoes is the circumsporozoite ELISA. The aim of the present study was to standardize the circumsporozoite ELISA for P.malariae, by setting quantification parameters using, as antigen, either a synthetic peptide or extracts of whole sporozoites. The standard quantification curves produced indicated that the assay had a lower threshold of sensitivity of 250 sporozoites in a 50-microl sample, equivalent to about 1250 sporozoites in a mosquito.