When a foreign animal disease (FAD) such as avian influenza or Newcastle disease strikes a poultry flock, it is customary for a 10-kilometer control area to be drawn around the infected premises. However, Iowa State Veterinarian Dr. Jeff Kaisand said there are circumstances that would make it wise to go beyond 10 kilometers.
Kaisand offered his recommendations while speaking on July 26 during the webinar, “FAD Control Areas, Secure Poultry Supply and the Permitting Process in Iowa,” hosted by the Iowa Department of Agriculture and Land Stewardship.
Kaisand defines a control area as the combined area that includes the infected zone and the buffer zone. The infected zone is typically drawn within a 3-kilometer radius of the infected farm, while the buffer zone ordinarily goes out an additional 7 kilometers beyond the infected zone. However, he thinks of the 10-kilometer standard as more of a minimum, and not a definite measure.
“The control area can be any size we can draw to adequately control the spread of the disease,” he said.
Circumstances that would warrant having a control zone that stretches more than 10 kilometers from the infected premises, according to Kaisand, include:
Geography and land use
Some land is used differently than others. In cases where rivers run through a control area, or there are heavily wooded areas, the birds attracted to those areas could make the spread of an avian virus more likely, he said.
Density of premises with susceptible species
If there is an area that has a lot of sites with susceptible species, the virus could replicate and spread to other sites very easily, Kaisand said.
Climate
There are certain climates that are more conducive to the spread of a viral disease, and in those climates, a larger control area might be needed.
Disease epidemiology
Animal health professionals should question what the rate of the spread of the disease is, and how easily it could spread. Is it spread by aerosol means? Another question to ask is how much virus does it take to spread to another animal.
Ease of diagnosis
Will veterinarians have a difficult time diagnosing the disease if it spreads? If so, Kaisand said, a larger control area would be appropriate.
Other factors
Other factors that should be considered, according to Kaisand, are the species and ages of the susceptible animals in an area, the people and traffic movements within an area, and the biosecurity efforts already in place in farms in the area.
