Disease transmission

Transmission by co-feeding

Some pathogens, like tick-borne encephalitis (TBE) virus, present in some parts of Asia and Eastern and Central Europe, are transmitted in a particular way, which also depends on the vector’s seasonal dynamics. TBE virus is normally short-lived in its rodent hosts and usually does not develop patent systemic infections. This implies that the transmission to ticks during feeding is far from efficient. The feeding mechanism of ticks is different from that of mosquitoes for instance, in that ticks do not probe for superficial blood veins, instead they make a feeding pool with their chelicerae from which they ingest blood and other fluids that flow to the feeding pool. During feeding ticks also produce pheromones (chemical messenger chemicals) that attract other tick stages of the same tick species towards the same feeding pool. Although most commonly found in Amblyomma spp., it has also been observed in other tick genera. When infected nymphs feed next to non-infected larvae, the infection can be transmitted from the nymphs, via the feeding pool, to the unfed and non-infected larvae. Only when sufficient larvae and nymphs are active in the same season, TBE foci exist (Randolph, 2005).