Evaluation of Vector Competence of Ixodes Ticks for Kemerovo Virus

Abstract

Tick-borne viruses are responsible for various symptoms in humans and animals, ranging from simple fever to neurological disorders or haemorrhagic fevers. The Kemerovo virus (KEMV) is a tick-borne orbivirus, and it has been suspected to be responsible for human encephalitis cases in Russia and central Europe. It has been isolated from Ixodes persulcatus and Ixodes ricinus ticks. In a previous study, we assessed the vector competence of I. ricinus larvae from Slovakia for KEMV, using an artificial feeding system. In the current study, we used the same system to infect different tick population/species, including I. ricinus larvae from France and nymphs from Slovakia, and I. persulcatus larvae from Russia. We successfully confirmed the first two criteria of vector competence, namely, virus acquisition and trans-stadial transmission, for both tick species that we tested. The estimated infection rates of engorged and moulted ticks suggest specificities between viral strains and tick species/developmental stages.

Keywords: Kemerovo virus; tick-borne orbivirus; ticks; vector competence.

Figure 1

Real-time RT-PCR detection of KEMV genome segment 2 in individual Ixodes persulcatus tick homogenates. Ticks were fed on KEMV-spiked blood: engorged larvae (EL) and nymphs (N: resulting from moulted larvae). Mean Ct values for each group were statistically assessed using the Kruskal–Wallis test (alpha = 5%, *: p-value < 0.001). The lower quartile (Q1) and the upper quartile (Q3) are designated by the lower and upper lines in the graph, respectively. The darker line in the box plot designates the median.