VECTOR COMPETENCE OF AEDES-ALBOPICTUS AND AEDES-AEGYPTI (DIPTERA, CULICIDAE) TO DENGUE-1 VIRUS ON TAIWAN - DEVELOPMENT OF THE VIRUS IN ORALLY AND PARENTERALLY INFECTED MOSQUITOS

The vector competence in Ae. aegypti (L.) and Ae. albopictus (Skuse) f rom southern Taiwan to the dengue 1 virus was studied to elucidate the distribution of dengue infection during the 1987-1988 outbreak. The b rain of Ae. aegypti was infected as early as 3 d after intrathoracic i noculation. The esophagus and the proboscis (tissues within the labium ) were infected 5 d after inoculation. The salivary gland was highly s usceptible to the virus, but no specific infection site was found. Gan gli, muscles, and diverticula within the thorax were not infected. In the abdominal area, the ventral diverticula, Malpighian tubules, gangl ia, and the dorsal vessel were not infected. However, the entire gut w as susceptible to dengue 1 virus, although it was not infected simulta neously. Only a certain type of midgut epithelial cells was infected b y the virus. The ovarioles, oviducts, and accessory glands frequently were infected. However, the spermathecae were not infected, perhaps be cause of the chitin-rich outer layer. Infections of the testes, vas de ferens, seminal vesicles, and accessory glands of males also were dete cted in this study. The tissues of the proboscis were never infected i n Ae. albopictus but frequently were infected in Ae. aegypti, indicati ng that the virus may escape the salivary gland barrier more efficient ly in Ae. aegypti than in Ae. albopictus. When these mosquitoes were f ed on hanging drops, the salivary gland infection and transmission rat es of Ae. aegypti were always higher than those of Ae. albopictus. On Taiwan, Ae. aegypti appears to be a more competent vector in the trans mission of the dengue 1 virus than Ae. albopictus.