AN ELECTRON-MICROSCOPIC STUDY OF RIFT-VALLEY FEVER AND SINDBIS VIRAL-INFECTION IN MOSQUITO SALIVARY-GLANDS (DIPTERA, CULICIDAE)

Aedes aegypti Linnaeus and Culex theileri Theobald were infected by in trathoracic inoculation with Sindbis virus, while Aedes circumluteolus (Theobald) was infected with Rift Valley fever virus. After a lengthy incubation period of 45-63 days, the salivary glands were removed and studied by transmission electron microscopy. No pathological changes or damage was observed. Arrays of Sindbis virus particles were present in both Ae. aegypti and Cn. theileri, associated with distended endop lasmic reticulum but no virions were seen within vacuoles. Virions occ urred freely in the cytoplasm in Cs. theileri but not in Ac. aegypti. In Aedes circumluteolus, arrays of Rift Valley fever virus that accumu lated in the cytoplasm were being released into the salivary duct thro ugh microvilli. The Rift Valley fever virions measured slightly less t han those cultured in mouse brain-tissue. The known degree of vector c apability of each mosquito species is discussed in relation to the ult rastructural observations.