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Research Suggests Link Between Factory Farms and Spread of Disease


This spring, an outbreak of avian flu among chickens in the Midwest killed about 47 million birds and drove up the price of eggs across the country, causing them to nearly double.

The germs responsible, called the Highly Pathogenic Avian Influenza A viruses (H5N2, H5N8, and H5N1), are believed to have come from Asia and are spread by migrating ducks and geese. Wildfowl carry the viruses but don't get sick from them, and neither do people – so far.  But chickens and turkeys confined in commercial poultry houses are rapidly wiped out by the disease.

The Maryland Department of Agriculture is predicting that the avian flu will likely hit the state’s Eastern Shore this fall as ducks migrate from the upper Midwest and Canada. The disease could threaten Maryland’s billion-dollar-a-year poultry industry.

“The Maryland Secretary of Agriculture has ordered increased testing for poultry that is coming into the state, and hatching eggs,” said Dr. Michael W. Radebaugh, state veterinarian for the Maryland Department of Agriculture.  “I’ve set out an order, as of Aug. 25, that poultry fairs and shows will be cancelled, because there is a chance there that birds could be intermingled with waterfowl as they come down this fall.”

Among other precautions to prevent spread of the disease, the state is advising chicken farmers to wash their boots and change clothes before entering their poultry houses if they might have stepped in duck or goose droppings. Bird waste may be how the disease is spread.

Bob Martin, food system policy director at the Johns Hopkins Bloomberg School of Public Health’s Center for a Livable Future, said that the problem of disease outbreaks is much broader than just bird waste, and may require a systemic change in how farm animals are kept.

Martin said that diseases spread more rapidly because of the modern meat industry’s method of growing thousands of chickens, turkeys, pigs and other animals close together in huge windowless metal buildings called Concentrated Animal Feeding Operations or CAFOs. The animals must stand in their own waste, and are fed antibiotics to promote their rapid growth -- and this accelerates the spread of antibiotic resistant bacteria.

 “There has been a biosecurity breakdown,” Martin said.  “And these (CAFO) systems are a real problem – the way these animals are packed in together in a warm environment, especially in a cage environment where you get five or six laying hens in a very small confined cage, and there might be 200,000 of them in a barn. It’s just perfect for the generation of a novel virus, or the expansion and rapid explosion of an existing avian flu virus.”

Martin said that bird flu outbreaks – which also popped up in 2004 and 1983 – rarely spread to humans. However,  bird viruses can spread to hogs, which are more biologically similar to people.  And from pigs, viruses have spread and caused deadly disease among humans.

“There was an outbreak of swine flu in 2009 that they’ve traced to a large hog CAFO in southern Mexico,” Martin said. “And the virus spread – actually jumped into the community –where the workers lived. But the virus was actually traced back through DNA gene sequencing, and had been present in some of the breeder animals in North Carolina owned by the same company.” 

This suggests that modern CAFOs do present a threat to human health.  In 2013, Hopkins researchers looked at Pennsylvania communities where CAFO operators sprayed hog waste in farm fields, and found that people who live near these farms are about three times more likely to contract MRSA (Methicillin-resistant Staphylococcus aureus) bacteria infections than the general population.

What’s the answer?   The U.S. government expects to spend hundreds of millions of dollars this year compensating poultry farmers for the death of their animals to disease.

This taxpayer money should be used to help farmers transition to healthier ways of growing livestock.  To reduce the spread of disease, the animals should be raised in lower densities, outside, with sunlight and fresh air -- and without antibiotics.

Tom Pelton, a national award-winning environmental journalist, has hosted "The Environment in Focus" since 2007. He also works as director of communications for the Environmental Integrity Project, a non-profit organization dedicated to holding polluters and governments accountable to protect public health. From 1997 until 2008, he was a journalist for The Baltimore Sun, where he was twice named one of the best environmental reporters in America by the Society of Environmental Journalists.