“Ministry of Primary Industries predictive modelling of disease risk has taken into account data about tick activity, herd susceptibility and the known distribution of different theileria strains.
“This indicates that beef and grazier farms in the east coast are likely to be at elevated risk of disease,” Harris said.
Movement of bull beef calves for rearing or dairy heifers for grazing into the east coast presents extra risks.
The risks result from animals harbouring ticks or animals with theileria being introduced to areas where previously it was not present.
The farm effects of the introduction of theileria would depend on how many ticks or infected animals were introduced into a herd where the parasite had not been encountered before and where there was no immunity to it.
Where this number was small for either factor, the effects might not necessarily be seen during this year but might occur in the autumn or spring 2014.
Disease resulted when animals that had not encountered theileria (ikeda) were exposed to it for the first time.
Other factors such as stress through weaning and calving might increase the severity of disease.
“We do not know what all the factors are that result in one farm being severely affected while another similar farm is less affected.
Farmers buying or accepting stock should ask about the health status of the animals and consider treating animals for ticks if they have come from outbreak areas.
Similarly, farmers moving stock off property – for example, to graze – should understand the risk of where they are going.
Ongoing research into theileria indicated young animals were at heightened risk of developing signs of disease at weaning so extra vigilance was required for beef because it was stressed animals that were particularly at risk as were animals in regions with ticks where disease had not previously been reported.
These were the so-called naive animals which, when theileria hit, were the most severely affected.
A ministry survey of 122 affected farms showed the average number of recorded deaths was just below 1%, with a range of zero to 15%.
However, the impacts seen on a few beef farms had been much more severe.
Encouragingly, analysis also indicated the recommended preventative measures and treatment for theileria had been effective.
Farmers concerned about the health of animals should consult a vet without delay. More information: Theileria and anaemia in cattle
