Salivary glands from Anopheles gambiae s.l. collected in Burkina Faso, West Africa, were analyzed by both microscopic examination and immunoradiometric assay to determine the Plasmodium falciparum sporozoite rates. Using the same mosquito samples, the immunoassay revealed positive salivary glands with low sporozoite loads, which were frequently missed by microscopy. A closer agreement between both techniques was found using salivary glands with high sporozoite loads.
We also found a number of mosquitoes with uninfected salivary glands which harbored the circumsporozoite antigen in their thoraces. In a particular village these mosquitoes represented 43.5% of all sporozoite antigen carrying specimens.