Partial Inhibitory Effect of Plistophora culicis on the Sporogonic Cycle of Plasmodium cynomolgi in Anopheles Stephensi

Abstract

DURING some experimental work carried out on the cytology of early oocysts of Plasmodium cynomolgi in Anopheles stephensi an interesting observation was made. Three batches of laboratory-bred Anopheles stephensi were fed on a rhesus monkey (M. 172) infected with P. cynomolgi. Dissections of 4–10 mosquitoes on each subsequent day showed that the first and third batches of these mosquitoes were also infected with a microsporidian (Plistophora culicis). (Such infections have previously been described by Garnham¹ and Canning².) Nearly 50 per cent of the dissected mosquitoes showed a moderate infection of P. culicis in the first batch, a light infection of about 5 per cent in the second batch, and approximately 100 per cent with heavy infections of P. culicis in the third batch. A poor rate of infection by P. cynomolgi was found in the first and third batches of A. stephensi, and this was considered due to the partial inhibitory influence of P. culicis on the development of the oocysts in these mosquitoes. This view was supported by the findings of good oocysts counts in the mosquitoes dissected from batch two in which the P. culicis infections were very light.