Panveld oviposition sites of floodwater Aedes mosquitoes and attempts to detect transovarial transmission of Rift Valley fever virus in South Africa

Floodwater aedine mosquito eggs were recovered from soil samples taken from grassland depressions, called pans, in the Orange Free State Province of South Africa. A sedge, Mariscus congestus (Vahl) C.B.Cl., was a useful indicator of Aedes (Ochlerotatus) juppi McIntosh oviposition areas. No transovarial transmission of virus was demonstrated by Ae.juppi females reared from the eggs and allowed to feed shortly after eclosion on hamsters. No virus was recovered from 557 pools of 5425 adult Ae.juppi that were collected as eggs and reared to the adult stage in the laboratory. Rift Valley fever virus replicated to high titres in experimentally infected Ae.juppi females, but horizontal transmission experiments proved inconclusive.