Microfilarial perforation of the midgut of a mosquito.

To determine whether the midgut envelope of mosquitoes is disrupted by the passage of microfilariae, ultrastructural changes induced by microfilariae of Brugia malayi were observed in midguts of Aedes aegypti mosquitoes. Basal and apical plasma membranes were destroyed, disrupting the full depth of the midgut wall. Ingested ferritin lay against the gut wall, suggesting absence of the peritrophic membrane during penetration. Exsheathment of microfilariae appears to be enhanced by movement against the constricting midgut wall. It was concluded that particles present in the lumen of the gut may be disseminated passively to the hemocoel.