a1 Department of Histology, University of Liverpool
1. Serial sections were examined of thoraces of a selected strain of Aedes aegypti infected with either Brugia pahangi or subperiodic B. malayi and of wild-caught Mansonia uniformis infected with the latter parasite.
2. A few badly damaged flight muscle fibres are seen in the early stages of infection but many more fibres are destroyed at the time when the mature filarial larvae leave the muscle and enter the haemocoel. In the intervening period, when the larvae are growing within the muscle fibres, only minor damage develops, affecting nuclei and/or mitochondria. The nature of such minor damage and the mechanism of complete muscle breakdown differs in the two species of mosquitoes.
3. It was concluded that the muscle damage was sufficiently severe to explain the significant mortality often observed among experimentally infected mosquitoes at the time when the mature filarial larvae enter the haemocoel.
I am very grateful to Dr W. W. Macdonald, of the Liverpool School of Tropical Medicine, who supplied the Aedes aegypti mosquitoes and who has given invaluable help and advice throughout this study. Mr Cheong Weng Hooi and his colleagues in Kuala Lumpur kindly supplied, and partly processed, the Mansonia uniformis mosquitoes. Miss M. A. Johnson assisted with the care of the A. aegypti colony and Mrs J. Oliver helped with some of the histological work.
(Received April 21 1971)