Experimental infection of Hyalomma marginatum ticks with West Nile virus.

To define the possible role of Hyalomma marginatum ticks in the transmission of West Nile virus (WNV) in Portugal an experimental infection was established. Ticks were fed on viremic rabbits previously infected with WNV. In different developmental stage of H. marginatum virus isolation and detection of viral antigen and viral RNA were attempted. The oral infection rates were 3%, 33% and 75% for engorged larvae, nymphs and females after oviposition, respectively. Transstadial transmission rates for nymphs exposed to virus as larvae, for adults exposed as larvae, and for adults exposed as nymphs were 33%, 11% and 46%, respectively. No evidence of transovarial transmission was obtained. Ticks in the stages of nymphs and adults were able to transmit the infection to uninfected hosts. This study demonstrated that H. marginatum could be involved in the natural circulation of WNV in Portugal.