Non-viraemic transmission of Thogoto virus: vector efficiency of Rhipicephalus appendiculatus and Amblyomma variegatum

Abstract
Previous studies have demonstrated that Thogoto virus is transmitted from infected to uninfected ticks when co-feeding on uninfected guinea-pigs, even though the guinea-pigs do not develop a detectable viraemia. Furthermore, tick to tick transmission is potentiated by factors associated with the salivary glands of ticks (saliva activated transmission). The vector efficiency of 2 ixodid tick species, Rhipicephalus appendiculatus and Amblyomma variegatum, for Thogoto virus was assessed using this model. The number of uninfected recipient ticks that acquired Thogoto virus when co-feeding with virus-infected ticks (donors) on uninfected guinea-pigs was determined. When nymphs of either tick species were employed as donors, there was no significant difference in the number of infected recipient nymphs. In contrast, a significant difference in the vector efficiency of adults ticks was observed: 77.0% of recipient ticks which co-fed with R. appendiculatus donor adults acquired Thogoto virus compared to 44.7% of recipient ticks which co-fed with A. variegatum donors. No significant difference in susceptibility to Thogoto virus infection was observed between recipient ticks of the 2 species. Thus, adults of R. appendiculatus are more efficient than A. variegatum in mediating non-viraemic transmission.