The “ban-wagon” over AI serology

The announcement that flocks in Nebraska, South Dakota, and Virginia have yielded antibody to AI during the past two weeks has resulted in the predictable knee-jerk response by importers of poultry products. Termed the “Ban-Wagon” by Toby Moore of USAPEEC, provisions of bilateral agreements are being applied to the detriment of unaffected producers located hundreds of miles from the affected flocks.

We are not dealing with actual outbreaks of AI infection, confirmed by isolation and characterization of virus. The apparent problem which initiates an export embargo, is simply the demonstration of AI antibody as a component of a comprehensive screening program.

There is no evidence in the majority of cases which involve commercial flocks of any obvious clinical disease nor do these flocks yield pathogens at the time of pre-slaughter testing. The presence of antibody indicates either previous exposure to a specific AI strain or alternatively vaccination, which is not practiced in the USA other than for non-H5/H7 strains in Minnesota.  The duration of shedding of virus is generally limited to two weeks although international regulations require a 90 day period after the last flock was depleted before exports from the State or region can be restored. 

Countries which have  to date  imposed export bans on all poultry products from the three “affected” states include Russia, Taiwan, Japan and Cuba. One can justifiably question whether these nations are free of AI infection and whether their veterinary authorities operate comprehensive surveillance programs as in the US.  In addition some countries do not allow transit through the implicated states creating additional burdens on producers and shippers using rail links. The refusal of Taiwan to import cooked products is not justified by scientific reality since AI virus is heat sensitive. Thailand and China export cooked products despite their de facto endemic H5N1 HPAI status.

It is time to review international trade regulations relating to infectious diseases of commercial poultry. The 90-day period following serological reaction to AI in the absence of either viral isolation or the more sensitive and rapid RT-PCR assay for viral RNA is not justified. The exclusion of exports from entire states is based more on geographic and administrative boundaries than on epidemiological realities. Restraints on transit through implicated states are likewise without scientific foundation and should be reviewed and harmonized.

Given the low intensity of structural and operational biosecurity in our major industry segments, it is inevitable that flocks will become exposed to AI. Infection can be introduced by free living avian species or by indirect contact with personnel and fomites. We have an ever present source of H7N2 AI virus in our “live bird” system of growers and wet markets. Many of our contractors and personnel are hunters of wildfowl. Feed mills operate delivery vehicles without adequate facilities for routine decontamination. If the broiler industry cannot control LT it will never suppress vvND or AI with our current procedures and mindset.

We require reevaluation of biosecurity and adherence to more rigid standards if we are to maintain production and exports in the 21^st Century. A concurrent reappraisal of international trade regulations would contribute to more rational decisions without increasing the risks of disseminating disease.