Brugia pahangi: Exsheathment and Midgut Penetration in Aedes aegypti

Abstract

Exsheathment and midgut penetration by microfilariae (mff) of B. pahangi were studied in intact A. Aaegypti (black-eyed Liverpool strain) and in isolated midguts maintained in vitro in Aedes saline. Penetration of the midgut occurred within 150 min postingestion (PI) of an infective blood meal, with the majority (60%) migrating out from 61-105 min. Penetration occurred anywhere on the midgut, and mff were capable of penetrating the foregut, hindgut and Malpighian tubules. Approximately 60% of the mff ingested migrated out of the midgut in the mosquitoes examined. Exsheathment of mff rarely occurred within the midgut. Nearly 97% of 894 mff examined from the midgut after 5-150 min. PI were sheathed, and approximately 75% of 288 mff retained their sheaths after midgut penetration. The sheath is likely weakened or broken at the anterior end of mff during midgut penetration, and they completely free themselves of the sheath in the hemocoel. Results from inoculation experiments indicate that mff are capable of exsheathing in the hemocoel without midgut exposure, and that occasionally they can develop within the microfilarial sheath.