Trypsin and aminopeptidase activities in blood-fed females Anopheles dirus (Diptera: Culicidae) of differing susceptibility to Plasmodium yoelii nigeriensis.

Midgut proteolytic enzymes contribute to the success or failure of Plasmodium infection of the mosquito. The present study investigated trypsin and aminopeptidase activities in the midgut of two strains of Anopheles dirus selected for susceptibility and refractoriness to Plasmodium yoelii nigeriensis. At intervals of 6 hours following a bloodmeal, the midguts of fully engorged female mosquitos were dissected, homogenized, and assayed for enzyme activity. No differences trypsin activity (nmole/min) were observed between the two strains throughout the course of blood digestion. By contrast, the aminopeptidase activity measured at 0 to 18 hours post-feeding was the same for the two strains, but at 24, 30 and 36 hours significantly less activity was observed in the refractory females. The results suggest neither trypsin nor aminopeptidase plays a role in the limitation of parasite development.

Comparative susceptibility of two forms of Anopheles sinensis Wiedemann 1828 (Diptera : Culicidae) to infection with Plasmodium falciparum, P. vivax, P. yoelii and the determination of misleading factor for sporozoite identification.

Two karyotypic forms of laboratory-raised Anopheles sinensis, ie Form A (XY1) and Form B (XY2), were experimentally infected with various indigenous strains of Plasmodium falciparum and P. vivax using an artificial membrane feeding technique, and a rodent malaria, P. yoelii, using a direct feeding technic and dissected 7-9 days and 10-15 days after feeding for oocyst and sporozoite rates, respectively. The results revealed that two forms of An. sinensis were refractory vectors for P. falciparum and P. yoelii since 0% of oocyst and sporozoite rates were obtained, but poor vectors for P. vivax since 0.00-85.71% and 0.00-5.88% of oocyst and sporozoite rates were recovered. The sporozoite-like crystal found in the median lobe of the salivary gland of An. sinensis which could be a misleading factor in identification of true sporozoites in the salivary glands is reported for the first time.