Effect of exogenous chitinase in Anopheles aquasalis infected with Plasmodium vivax

Background: The peritrophic matrix (PM) is a chitin fibrous structure produced by secretion of midgut epithelial cells of insects and it is an important protective barrier against pathogens. Substances as chitinases interfere with the PM formation and thickness affecting the life cycle of pathogens in their vectors. The goal of this study is to understand the role of exogenous chitinase in the formation of PM in the vector Anopheles aquasalis infected with Plasmodium vivax. Material and Methods: Anopheles aquasalis females 3-4 days old were experimentally oral fed with blood P. vivax patients containing two to three crosses of parasites (CEPS: 686.297). The control group (a) was fed with only blood of P. vivax patients. The experimental treated-groups were fed with: (b) infected blood mixed with chitinase (1U/ml), while the other (c) has received infected blood added trypsin inhibitor (1 mg/ml). The midguts were dissected 9 days after the infective bloodmeal and the the infection verified. Additionally, blood fed mosquitoes were dissected at 24 hours post infection and their midguts fixed for light, scanning and transmission microscopies. Results and conclusion: The morphology showed that chitinase-treated mosquitoes present absence or delicate PM and scattered bolus in direct contact with the midgut epithelium. The control, chitinase and trypsin inhibitor treated mosquitoes showed averages of infection rates of 64,9±8, 44,1±20 and 54,2±9, median of oocyst numbers per gut 9, 1 and 5 and amplitude of infection varying from 0-104, 0-24 and 0-193, respectively. The comparative analysis of the medians and the infection rates were statistical distinct when the groups were compared with that which received chitinase. In the A. aquasalis the absence of the PM induced by chitinase treatment interfere significantly in reduction of oocysts. It appears that in A. aquasalis the PM can moderate the exporure of Plasmodium vivax the activity of proteolytic enzymes in the midgut and thus ensure the infection.