Paralysis of cattle by Ixodes holocyclus Neumann

Abstract

The number of engorging female Ixodes holocyclus needed to induce paralysis in young cattle was investigated.

One or two females were insufficient to paralyse 2–3-week-old unexposed calves but 10 caused paralysis. Older unexposed calves weighing 80-160 kg were not paralysed by up to nine females whereas 20 caused paralysis. Nine out of 10 calves which were paralysed subsequently died.

Calves which survived were infested with at least 25 females, a number sufficient to paralyse an unexposed calf. Only two of 11 infestations caused paralysis and no calves died. Tick development was significantly inhibited on these calves and this may partly account for the protection from paralysis.