The Green Party's primary industries spokesperson is questioning why the Ministry for Primary Industries didn't try to eradicate a deadly cattle parasite when it was first detected in Northland two years ago.
However, the ministry says eradication would be impossible.
Nearly 500 beef and dairy herds throughout the North Island have now been infected by the parasite, theileria orientalis ikeda, that makes cattle anaemic.
Up to 30 percent of animals in each herd can show symptoms and recent modelling suggests 1900 cattle deaths could be attributable to the parasite.
In some of the worst hit herds about 5 percent of cattle are dying.
Steffan Browning of the Greens believes the Ministry for Primary Industries should have used the National Animal Identification and Tracing Scheme (NAIT) to identify infected stock and farms when the parasite was first detected, with the aim of eradicating it.
"If MPI had used NAIT and other tools available to it straight away they may have been able to get on top of this costly protozoa that's effecting cattle in any area where ticks can survive."
However, the Ministry for Primary Industries says there's no way theileria ikeda could have been stopped once it was in the country.
It says because the cattle tick which spreads the parasite is geographically widespread, has free-living life stages, and is found on other livestock and feral animals there's no way it could be eradicated.
The ministry says any control on cattle would have had a limited impact on the distribution of the parasite.
It predicts herds will build up immunity to theileria ikeda over time.
