AVMA 2017: Protecting Backyard Poultry Owners Against Zoonoses
Nicola M. Parry, BVSc, MRCVS, MSc, DACVP, ELS
The increasing number of chicken owners in the United States has heightened the risk of bacterial zoonoses and foodborne illnesses. Educating clients is the key to prevention.
To prevent zoonotic diseases from poultry, remember what your mother taught you, advises Richard M. (“Mick”) Fulton, DVM, PhD, DACPV, professor of pathobiology and diagnostic investigation at Michigan State University College of Veterinary Medicine in East Lansing: “Wash your hands before you eat; don’t put your fingers in your eyes, nose, or mouth; and don’t eat poultry that is undercooked.”
Most people become infected with poultry-related zoonoses via contamination of mucous membranes or by eating undercooked meat, Dr. Fulton said at the 2017 American Veterinary Medical Association Convention in Indianapolis, Indiana. He discussed problems associated with the growing number of backyard chickens.
More Backyard Birds Mean Greater Salmonella Risk
Raising backyard chickens has become more popular in the United States over the past 10 years because many municipal ordinances now allow property owners to keep a small number of hens (typically, fewer than 10) for egg production. “This has led to a large demand for small batches of chickens and an explosion of business for small hatcheries,” Dr. Fulton said.
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However, he emphasized that most owners of backyard chickens have limited experience managing them, and they tend to treat these animals as household pets. This behavior increases the risk of transmitting diseases from the birds to humans, he said.
Although multiple zoonotic pathogens pose a risk to clients who keep backyard chickens, Dr. Fulton emphasized that most infections in humans from poultry are related to Salmonella and Campylobacter species. He shared tips on how veterinarians can educate their clients to reduce the spread of these infections.
Risk of Foodborne Illness From Salmonella and Camplyobacter
Salmonella can infect humans who come in contact with poultry or eat improperly cooked eggs or egg products, Dr. Fulton said. Many cases of foodborne infection in people are due to Salmonella ser Enteritidis, he added. Although this bacterium causes only mild perioophoritis in chickens, it causes foodborne illness in humans. Most S Enteritidis infections in humans are associated with consuming undercooked food made with eggs, including bread pudding, Caesar salad, and custom-made mayonnaise, Dr. Fulton said.
He noted that recent Salmonella outbreaks in humans have also been associated with people having close contact with baby poultry. The most common species involved in those outbreaks have been Salmonella Montevideo, Salmonella Infantis, Salmonella Typhimurium, Salmonella Hadar, and Salmonella Braenderup, he said.
Dr. Fulton discussed results from a study of live poultry—associated salmonellosis reported by the Centers for Disease Control and Prevention (CDC).1 The data highlighted 53 disease outbreaks from 1994 to 2010 that involved 2630 human illnesses, 387 hospitalizations, and 5 deaths; 31% of cases occurred in children 5 years or younger, while 42% occurred in children younger than 10. Most cases (71%) were associated with exposure to baby poultry—including snuggling with and kissing baby birds. And even though 58% of the people involved indicated awareness of the risk of acquiring Salmonella infection from contact with poultry, 46% reported keeping birds in their house.
This study also showed an increasing number of Salmonella outbreaks from 2003 through 2013.1 Until relatively recently, some small hatcheries were one source of infection in people, Dr. Fulton noted, because these businesses were relatively unaware of the Salmonella control programs implemented by commercial poultry producers. Great efforts have since been made by small hatcheries to control this situation.
Campylobacter infection, a foodborne illness, typically arises in people who eat poultry that is not cooked properly, Dr. Fulton said.
Tips for Protecting Clients Against Infection
Mick Fulton, DVM, PhD, DACPV, (second from right), teaches necropsy techniques to Afghan veterinary students in Kabul.
To help control Salmonella and Campylobacter infections, veterinarians should share these key points with clients who own backyard chickens, Dr. Fulton said.
Protecting Against Salmonella Infection
In the Home
Veterinarians should warn clients that even baby poultry harbor Salmonella organisms. Clients should not keep these animals inside the home, especially where food is prepared or eaten, or cuddle or kiss them. Children should be supervised when handling baby poultry, and everyone should wash their hands after handling the birds.
Rodent and Fly Control
Because the presence of rodents in the flock environment increases the odds of S Enteritidis infection, Dr. Fulton stressed the importance of rodent control in and around the poultry house.
“Up to 1 million S Enteritidis bacteria are excreted in 1 mouse pellet,” he noted, adding that birds like to peck at anything unusual. Clients should repair holes in poultry houses and ensure that windows and doors are screened properly. His rule of thumb: If an animal can fit its head inside a hole, it can squeeze its whole body inside the building. Clients should place bait stations every 25 feet around the outside perimeter of the building, rotating between anticoagulant and non-anticoagulant types of bait about every 3 months to prevent rodent populations from becoming resistant to any 1 type. Grass and weeds surrounding poultry houses should be less than 3 inches high to prevent rodents from hiding close to the buildings, he said. Finally, clients should avoid piling trash within 100 feet of the poultry building.
Dr. Fulton advised against using cats for rodent control because cats carry fleas and other infectious organisms that pose a risk to chickens, including Toxoplasma gondii and Pasteurella multocida, the latter of which can cause fowl cholera in the birds.
Clients should control flies, which transmit diseases, in the poultry house. In particular, they should control litter and keep manure moisture levels below 30% to prevent fly development, said Dr. Fulton.
In the Poultry House
Clients also can take measures inside the poultry house to control exposure of chickens to S Enteritidis. Stored feed should be covered to keep out rodents and other forms of wildlife so they can’t defecate in the feed. This will also prevent cats from using feed as a litter box.
Proper Egg Handling
Clients can also take steps during egg handling to reduce their risk of exposure to Salmonella, according to Dr. Fulton. They should provide a nest in which the hens can lay eggs, and they should collect the eggs at least once daily. After the eggs have been laid—usually before noon, he said—the nests should be closed off to prevent the birds from defecating in them and contaminating the eggs.
Eggs should be washed carefully with soap and water that is warmer than the eggs. Using cooler water will cause the air cell inside the egg to contract, sucking bacteria through the shell and contaminating the egg, Dr. Fulton said. Warmer water causes the air cell to expand, preventing this bacterial contamination. The clean eggs should be refrigerated until needed. Eggs should be cooked until the whites and yolks are firm, said Dr. Fulton, and dishes such as casseroles that contain eggs should be cooked to a temperature of 160°F.
Protecting Against Campylobacter Infection
Clients can substantially reduce their risk of infection with Campylobacter species by taking careful measures to reduce cross-contamination when preparing foods, Dr. Fulton said. For example, any fruits, vegetables, and other foods that won’t be cooked should be cut before raw meat is cut. After cutting the meat, clients should carefully clean anything that came in contact with it, including kitchen surfaces, cutting boards, and knives. Importantly, clients should wash their hands with soap and water. Dr. Fulton also emphasized that poultry should be cooked to 165°F.
Dr. Fulton stressed this message in particular to help protect clients with backyard poultry against these zoonotic infections: “Your mom was right—always wash your hands.”
- Basler C. Nguyen TA, Anderson TC, Hancock T, Behravesh CB. Outbreaks of human Salmonella infections associated with live poultry, United States. 1990-2014. Emerg Infect Dis. 2016;22(10):1705-1711. doi: 10.3201/eid2210.150765.