Cattle and sheep losses of over 50 per cent have sometimes occurred when previously unexposed stock have grazed in infested country. New-born calves are particularly susceptible to tick toxicity.
Often few ticks are found on cattle dying from paralysis and this had led to the belief that small numbers of ticks can kill even adult cattle. The likely explanation is that the engorged ticks have dropped of before the animal became paralysed. Research suggests that ten female ticks are required to paralyse two- to three-week-old calves while older calves are paralysed by 20 ticks, but not by ten ticks.
It has been suggested that to reduce tick paralysis in cattle, the calving time should be in winter rather than spring and cows should be put in "clean" paddocks to calve. Farming practices to maintain enzootic stability should also be considered.
Contributed by R. Brooks. Last updated: January 2008
