Transovarial transmission (TOT) of Toscana (TOS) and Arbia (ARB) viruses in a laboratory colony of Phlebotomus perniciosus is reported. Toscana and ARB viruses were maintained in P. perniciosus females, initially infected by intrathoracic inoculation, for 2 and 3 consecutive generations respectively. TOT was demonstrated in F1 (75%) and F2 (67%) generation adults for TOS and F1 (47%), F2 (37%), and F3 (34%) generation adults for ARB virus. The progressive decline of virus infection rates in each generation suggests that these agents cannot be maintained indefinitely by TOT.
No infection was observed in F1 progeny after female parents were fed through membranes with either virus. Transovarially infected females were able to transmit TOS virus by bite to a susceptible vertebrate. Venereal infection of P. perniciosus females mated to males transovarially infected with TOS virus was seen.