The Ministry for Primary Industries believes the impact of the new strain of theileria cattle parasite will lessen now that farmers and veterinarians are better at dealing with it.
Katherine Clift is the manager of response at the Ministry for Primary Industries.
She says the new strain of theileria - known as Ikeda - is now very wide-spread across the middle and upper North Island, on more than 200 farms, and cannot be eradicated.
She says the Ministry's efforts are going into managing its impacts - and that the Ministry expects the severity of the parasite will lessen now that it's being identified more quickly on farms.
Ms Clift says it's unlikely we'll ever know how the ikeda strain got into the country.
She was unable to comment on whether this particular strain of the virus came into the country via Australian cattle.