The first ever identification of low pathogenic H5N1 avian influenza in wild birds in New Zealand has just been announced by the MAF Biosecurity Response Team. It essentially dismissed the finding as no danger whatsoever to either poultry or people in this two-island nation deep into the Southern Hemisphere. Are they right to be so laid back and does experience elsewhere indicate insufficient caution being taken?
Two ducks near the South Island city of Invercargill, one at an estuary 2km west of the city of and one at Roslyn Bush, were found to be carrying the virus following a surveillance programme in February 2008 that tested six other sites throughout the country. The findings were confirmed the week beginning September 15, 2008, said a report by Southland Times. Invercargill was the only site with infected wild birds.
A low path virus
MAF Biosecurity animal response team manager Dr. Andre van Halderen said it was the first time H5N1 LPAI (low pathogenic avian influenza) had been recorded in New Zealand. He stressed it should not be mistaken for H5N1 HPAI, the highly pathogenic avian influenza virus that has spread in parts of Asia, Middle East, Europe, and Africa, killing more than 200 people and forcing the destruction of millions of birds. H5N1 HPAI has not been recorded in New Zealand.
"The low pathogenic avian influenza viruses are adapted to waterfowl and shorebirds, which are their natural hosts," said van Halderen. He said nature of this low path virus meant it was impossible it could cross-species jump into humans and mutation was highly unlikely. "There's a negligible risk of it firstly getting into birds [poultry] and because it's low-path it causes very mild or no clinical disease in domestic poultry. It's only through mutation into highly pathogenic strains that you will get strains arising which cause problems," he said according to Southland Times and Stuff.co.nz.
Laid back attitude
This laid back attitude adopted by the New Zealand government appears to be based on the assumption that low path H5 (and H7) subtypes are completely benign. Does this view stack up with experience elsewhere? Unfortunately, the answer is no.
Incidences of low path H5 and H7 avian influenza mutating into high path types during in poultry are not uncommon. Two of the most well established and costly examples involved H7 subtypes in Canada and the Netherlands. During 2004, low path H7N3 mutated into a high path virus strain during an outbreak in British Colombia Canada leading to eventual death and destruction by culling of 20 million birds.
Low path H7N7 mutating into high path virus in the Netherlands a year earlier wrought even more havoc. Over 30 million poultry were culled, around 80 poultry workers contacted the virus showing either conjunctivitis or flu-like symptoms, and many more were found to be carrying H7N7 antibodies. One veterinarian died from the disease and there was strong evidence of human to human transmission.
More recently (2008), an outbreak of high path H7N7 in the County of Oxfordshire in the United Kingdom (UK) is thought to have arisen by mutation from a low path virus resident in the flock. Even more bizarre was progress of low path H7N2 in North Wales and northwest England in 2007. Starting with the purchase of a dozen layer hens from a hobby bird market, it quickly moved into the human population as a low path virus. Though eventually controlled, it infected more humans than birds and achieved some human to human transmission. Most human symptoms were mild although one infected couple in the County of Lancashire told the media how they suffered full blown influenza and were so ill they “thought they were going to die.” Wild birds are thought to have been the original source for all of these outbreaks.
Van Haldren said, "The risk of HPAI 'bird flu' reaching New Zealand is unchanged and remains low. This finding does not affect New Zealand's avian influenza disease-free status, and poultry consumers have no cause for concern." While this is certainly true in theory, the world is extremely sensitive to even a "whiff" of H5 or H7 bird flu, irrespective of whether high or low path.
Reaction from other countries
Governments are quick to ban imports from affected countries in an effort to stay completely free of the virus. This will include countries like the Philippines, one of only several East Asian nations to stay free of H5N1, and Hong Kong and Japan, which although currently H5N1 free, know first-hand the damage caused from previous outbreaks. Even countries where the disease is currently spreading or indeed endemic are quick to pull down the shutters on imports from countries announcing H5 or H7, high path or not.
A recent change in the World Organisation for Animal Health (OIE) official policy suggests this non-government organisation believes there is a real risk from low path H5 and H7 subtypes. In the past, there was no requirement for reporting or tracking LPAI H5 or H7 detections in wild birds, but the OIE then changed its requirement for reporting detections of avian influenza. Since 2006, all confirmed LPAI H5 and H7 subtypes must be reported to the OIE because of their potential to mutate into highly pathogenic strains. For this reason, the U.S. Department for Agriculture (USDA) now tracks these detections in wild birds, backyard flocks, commercial flocks, and live bird markets.
A very recent example of one country reacting to another’s low path H5 or H7 avian influenza was the Republic of the Philippines (RP) confiscating all poultry imports from Denmark. According to a Department of Agriculture (RP) report, Agriculture Secretary Arthur Yap directed quarantine officers and inspectors at all major airports and sea ports in the country to confiscate all incoming shipments of live birds, poultry, and poultry products from Denmark.
The ban was in response to an outbreak (April 29, 2008) of low pathogenic H7N1 at a wild duck farm on Fyn Island in Southern Denmark. The majority (1500) of the 2000 plus birds culled were wild mallard ducks because main business of the farm was breeding birds to re-stock wild bird populations for hunting purposes. The other birds culled were 250 domestic ducks and 300 geese. Though not widely reported, OIE was informed, which is presumably from where the RP authorities learned about this outbreak of disease in Denmark. This was in response to a low path H7 virus which does not carry the same "baggage" as H5N1.
The New Zealand authorities say their tests have indicated that low path H5N1 virus might have been in the country for some time and could even be endemic. The ducks were healthy and were not killed as a result of infection, Dr. Van Halderen said. This should not be taken as a source of comfort because it means they are free to excrete the virus and spread it in the environment. Ducks (wild and domestic) are not called the "silent carrier" or "Trojan Horse" of H5N1 without good reason. The authorities in New Zealand say they expect increased surveillance to show H5N1 LPAI is present elsewhere in the country.
Authorities in neighbouring Australia appear to be taking the finding a lot more seriously, according to a report by Stuff.co.nz, which said Australian poultry owners are being warned to step up their own biosecurity checks in the wake of the discovery. "Australian poultry owners should ensure wild water-birds cannot access poultry feed or water and should limit contact between wild water-birds and poultry," said Biosecurity Queensland's chief veterinary officer Ron Glanville. "This is just a commonsense, precautionary measure."