# 2306
Taking great pains to explain that `low path' H5N1 is different from highly pathogenic H5N1 (and it is), this article on Voxy.co.nz gently informs the reader that a surveillance program in New Zealand had detected two wild bird samples with the low path virus.
First the article (hat tip to Sally on Flutrackers), then some discussion of `low path' vs. `high path'.
Low Pathogenic Virus No Cause For Concern
17 September 2008 - A surveillance programme researching the presence of avian influenza in New Zealand has found low pathogenic (LPAI) H5N1 virus in two samples taken from mallard ducks. Tests indicate that the virus is closely related to viruses found in the past and has been here for some time.
LPAI H5N1 is different to 'bird flu', which is the high pathogenic (HPAI) form of the virus. The samples were taken from healthy birds and there have been no reported bird deaths or disease in the area since the samples were collected, says Team Manager, Animal Response, Dr Andre van Halderen.
"This confirms what we already know - that strains of non disease causing avian influenza viruses are present in our wild bird populations and when we increase surveillance we will find evidence of virus elsewhere. The finding of low pathogenic H5N1 is not unexpected."
Sampling of healthy wild birds took place at seven locations across New Zealand in February this year, as part of MAFBNZ's ongoing avian influenza surveillance programme. A total of 1241 samples were collected from mostly mallard ducks and some migratory bird species in Paparoa, the mouth of Kaituna River, Lake Aniwhenua, Reparoa, Napier, Temuka and Invercargill.
"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, Dr van Halderen said."
Avian influenza viruses are naturally present in many species of wild birds, especially water fowl (ducks and geese) and shorebirds. Strains of avian influenza are categorised as highly pathogenic (HPAI) or low pathogenic (LPAI) on the basis of their ability to produce disease in poultry. HPAI causes severe disease that spreads quickly, causing sudden death in birds. LPAI viruses, depending on the strain, may cause mild or no clinical disease in birds. Most avian influenza viruses are harmless to humans.
Pathogenicity refers to the ability of a virus to cause illness. Low path viruses do not, as a general rule, cause detectable symptoms in its host.
It is not unusual when doing surveillance of healthy appearing birds to find a variety of low path avian flu viruses. Birds, after all, are the primary host of flu viruses.
Low Path Avian Influenza (LPAI), including LPAI H5N1, has been detected numerous times around the world in otherwise healthy appearing birds.
Low path H5N1 is not, however, quite as benign as the article above makes it sound.
In wild birds, and in low concentration (which with just 2 positive samples, this appears to be) these viruses appear to be pretty stable.
Low path tends to remain low path. At least that's the assumption. Our knowledge base is somewhat limited.
But when introduced into domestic livestock, such as ducks, chickens, or turkeys, low pathogenic H5N1 has a potential of mutating into highly pathogenic form of the H5N1 virus.
Even remaining LPAI, the economic impact of an outbreak can be enormous.
- Last year a turkey farm in Virginia detected low path H5N1 in their flock, and tens of thousands of turkeys were culled. Details of this outbreak are available from CIDRAP News.
- In 2002, LPAI H7N2 affected 197 farms in the Shenandoah Valley, and 4.7 million birds were destroyed at a cost of $130 million dollars.
The OIE takes LPAI seriously, and it is now a reportable disease. This from AVIAN INFLUENZA Low Pathogenic H5N1 vs. Highly Pathogenic H5N1 (UPDATE July 23, 2007) (reparagraphed for readability).
LPAI H5N1 ("North American" H5N1)
LPAI, or "low path" AI, commonly occurs in wild birds. In most cases, it causes minor sickness or no noticeable signs of disease. It is rarely fatal in birds.
LPAI strains are not a human health concern. This includes LPAI H5N1.
Evidence of LPAI H5N1 has been found in wild birds in the United States in recent years and is not closely related to the more severe HPAI H5N1 circulating overseas.
<snip list of outbreaks>
In the past, there was no requirement for reporting or tracking LPAI H5 or H7 detections in wild birds so states and universities tested wild bird samples independently of USDA. Because of this, the above list of previous detections might not be all inclusive of past LPAI H5N1 detections.
However, the World Organization for Animal Health (OIE) recently changed its requirement of reporting detections of avian influenza.
Effective in 2006, all confirmed LPAI H5 and H7 AI subtypes must be reported to the OIE because of their potential to mutate into highly pathogenic strains.
Therefore, USDA now tracks these detections in wild birds, backyard flocks, commercial flocks and live bird markets.
Bottom line?
LPAI, even LPAI H5N1, can be found in wild birds almost anywhere in the world. It is probably more prevalent that we know.
The news that New Zealand has detected two wild birds with this virus isn't startling, nor should it unduly worry the public.
On rare occasions LPAI viruses can be introduced into commercial flocks. And when that happens, there is at least the possibility of it mutating into a highly pathogenic form.
And that, of course, would constitute a serious turn of events.
Hence the monitoring, and reporting of the disease.
