The discovery of bird flu in United States dairy herds raises the stakes on the impact the disease could have in New Zealand, should it spread here.
“It is a real game changer when it turned up in the US cattle population. We have been keeping a very close eye on it and there are concerns for a number of reasons,” said Nigel French, professor of infectious disease epidemiology and public health at Massey University.
“It could affect one of NZ’s major industries, while the rapid rate of the outbreak’s spread is also a concern, and how it has spread across species.”
The impact on infected US herds has been significant, affecting 10% of the cows in herds that often total 20,000-30,000 cows per herd (see accompanying article).
Robust surveillance, strict biosecurity and a good knowledge of symptoms are all vital to try and keep the disease at bay here, French said.
While there is no specific cattle vaccination against bird flu, French said discovery here would probably rapidly accelerate its development.
“It is a disease that has a relatively low level of risk, but high consequence attached to it.”
The Ministry for Primary Industries’ chief veterinary officer, Dr Mary van Andel, said the US situation is the first globally where bird flu has spilled over into cows.
She confirmed US Department of Agriculture assertions that pasteurised milk is safe to consume, and said strong surveillance systems are in place to detect bird flu should it arrive.
“At present, we consider the risk of it arriving here on managed pathways is low, but we continuously reassess the threat of HPAI [highly pathogenic avian influenza] arriving here and monitor international developments.”
The most likely pathway is not via controlled ports and facilities but through wild migratory birds. She confirmed there are two vaccinations against bird flu registered in NZ for emergency use.
“As HPAI has established in wild birds and spread around the world with them, vaccination is having to be reassessed as a tool in the toolbox of disease control.”
Migratory bird expert and Massey University professor Phil Battley said it is possible to paint a potential scenario for cattle infection from birds here.
“We are protected due to our isolation, but only to a point. The fact is it has been detected in the Antarctic, and that it has affected mammals (seals).”
One plausible pathway is through infected pied oystercatchers passing it onto Canterbury dairy cows.
The coastal birds migrate inland to farms down the South Island east coast where they breed from August, often in riverbeds.
