In the U.S. new strains of avian flu that are highly infectious among birds have been found on commercial turkey farms in many states, as The Wall Street Journal has reported. An initial outbreak of H5N8 detected in a Californian turkey flock in January has mixed with North American avian flu strains to generate two new strains, including H5N2, which has been detected along the Pacific bird migration route in Washington, Idaho, and Oregon.
In addition, the U.S. Department of Agriculture has announced that H5N2 had been detected in Minnesota, the first instance of the disease in the Mississippi bird migration route. The virus has spread further to commercial turkey farms in Missouri and Arkansas, including to suppliers of Butterball turkeys.
In an editorial, published online at chick-site.com – March 25, 2015, Dr. Simon M. Shane questions the role of field researchers in transmitting infections from wildlife reservoirs to commercial farms. A March 13th article published by Reuters authored by Tom Polansek highlights questions by wildlife biologists as to the status of migratory waterfowl as reservoirs of H5N2 Avian Influenza which has been isolated from turkey farms in Minnesota, Missouri and Arkansas.
It is an irrefutable fact that identical strains of the pathogen have been isolated from affected turkey farms and from waterfowl. The weight of molecular evidence extending back to 2012 indicates the role of migratory birds in the process of genetic reassortment and dissemination from Asia along the Pacific Flyway.
Dr. Brian McCluskey, Lead Epidemiologist for the USDA-Animal and Plant Health Inspection Service stated “we are pointing right now to ducks as the problem.” Exhaustive assays using advanced analytical techniques including gene sequencing have indicated that the H5N2 virus is carried by waterfowl along the Mississippi Flyway and now more recently the Central Flyway, northward from the Gulf of Mexico.
Dr. Hon Ip a Microbiologist for the National Wildlife Health Center questions the conclusions of the epidemiologists stating “when you are talking about where I would put my money I would say that North to South movement (of infection-Ed.) in the beginning of March totally does not make sense.” The fact that the sequence of infections as confirmed was from North to South, ie. the first case from Minnesota (March 4th) then Missouri (March 9th and 10th) followed by Arkansas (March 11th) all within a short period does not preclude that birds migrating Northwards are transmitting the disease.
Epidemiologic investigations take into account both spatial (location) and temporal (time sequence) factors. It is possible that different groups of ducks, whether by species or age cohort are transmitting virus intra-flock or excreting virus at different rates. Given the small number of outbreaks reported, it is not possible to draw any conclusions such as those expressed by Dr. Ip.
Lou Comicelli, Wildlife Research Manager for the Minnesota Division of Fish and Wildlife stated “it is extraordinary unlikely that avian influenza in a turkey flock in Minnesota has anything to do with wild birds.” This statement is totally unsubstantiated and in fact is contradicted by established scientific investigations. These involved studies on the patterns of seroconversion following infection of range-housed turkeys and sentinels in Minnesota. Strains of avian influenza of low pathogenicity were common to turkeys and waterfowl and antibodies in turkeys were detected concurrently with the appearance of migratory species.
Apparently after the diagnosis of AI in Minnesota turkey flocks was confirmed on March 4th, wildlife officials scouted a 15 mile radius around the farm using an aircraft. Apparently they observed 100 ducks and 18 swans that they concluded were non-migratory “resident birds”. Wildlife biologists in Arkansas also doubt the role of migratory birds because the area where the first case was detected in the state “does not attract many wild birds and waterfowl.”
It is incontrovertible that migratory waterfowl are the reservoirs of H5N2 in the current series of outbreaks involving backyard farms and the few commercial turkey units where the disease has been diagnosed. Obviously defects in biosecurity have allowed the virus to be introduced on to those farms. Possible routes include supplying contaminated, non-chlorinated water from open sources to poultry flocks or failure to implement appropriate personal biosecurity. In this respect workers or contractors hunting or those coming in contact with fecal material voided by waterfowl could have been responsible.
Naturally wildlife biologists are in a state of denial since they are directly and indirectly funded by hunting even though they claim that they are conservationists. Any factor which interferes with their status quo represents a risk to their “field research” and wildlife “management”.
We are now in a new era of avian influenza. No longer is our risk represented by a worker traveling North from Mexico or Guatemala. The paradigm shift requires an understanding of the factors associated with infection and persistence of shedding in migratory waterfowl and the factors linking these reservoir populations with commercial poultry. Cooperation and mutual understanding between wildlife biologist and avian epidemiologists will be necessary to establish appropriate policies relating to commercial poultry production and the recreational exploitation of waterfowl. Denial of scientific fact and an inability to comprehend basic epidemiologic principles coupled with disharmony will detract from productive solutions.