Vector capacity of Rhipicephalus appendiculatus and Amblyomma variegatum for Thogoto and Dhori viruses

Experimental studies were undertaken to ascertain the vector potential of Rhipicephalus appendiculatus Neumann and Amblyomma variegatum Fabricius for Thogoto (THO) and Dhori (DHO) viruses, candidate members of the Orthomyxoviridae. In the first set of experiments, ticks were infected orally by feeding on viraemic hamsters. THO virus replicated in R. appendiculatus and A. variegatum, persisted trans-stadially in both tick species, and was transmitted to susceptible hosts during feeding. In contrast, both R. appendiculatus and A. variegatum were refractory to per os infection by DHO virus. In the second set of experiments, engorged R. appendiculatus and A. variegatum nymphs were parenterally inoculated with DHO virus. The virus persisted trans-stadially in both tick species and was transmitted by bite to susceptible hosts. These results indicate that the midgut acts as a barrier to per os infection of R. appendiculatus and A. variegatum by DHO virus. However, when this barrier is bypassed, i.e. by parenteral inoculation, both R. appendiculatus and A. variegatum can serve as efficient vectors of DHO virus.