Biological aspects in the transmission of Brugia malayi by Aedes aegypti in the laboratory.

Abstract

Biological factors influencing the efficiency of the Liverpool strain of Aedes aegypti (L.) as a vector for sub-periodic Brugia malayi (Brug) were investigated. The mean weights of blood meal in 3 groups of A. aegypti fed on cats with B. malayi were 3.2, 3.3 and 4.0 mg. A. aegypti took in more microfilariae than expected when fed on cats with sub-periodic B. malayi and 1/10 took in less than expected. Microfilariae of B. malayi penetrated the stomach wall of A. aegypti , entered the haemocoele, then penetrated the thoracic tissue. Microfilariae were found in the thoracic muscles within 10 min of ingestion of blood meal with migration continuing for 10 hrs, although most of the microfilariae migrated within the 1st hr. Blood clotting started within 20–30 min after ingestion of blood meal, thus inhibiting the movement of microfilariae. The figures on the migratory rate of the microfilariae when plotted on a logarithmic time scale showed 2 symmetrical curves indicating an inherent pattern difference in the rate of migration. The meaning of these 2 can only be surmised presently. Development of larvae of B. malayi in A. aegypti was similar to that described by earlier workers in Anopheles sinensis Wiedemann and Mansonia dives (Schiner). In individual refractory A. aegypti , all the larvae perished after 48 hrs of development while in individual susceptible mosquitoes, a few survived to complete development of the infective stage. There was an increase in the number of infective mosquitoes when fed on cats with higher densities of microfilariae, although no proportional increase in the number of larvae were found per mosquito. Survival was reduced among the mosquitoes during the first 48 hrs after the infective blood meal when fed on cats with microfilaria densities of 5.0 per cmm and above. The results of preliminary experiments on the age of the mosquito and its ability to support development of the parasite were inconclusive.