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Recognizing and preventing infectious diseases in chickens


Veterinary professionals can educate clients about common zoonoses seen in urban poultry farming

Many homeowners are now keeping flocks of poultry on their property. Acknowledging public interest in this type of urban farming, Janice O’Brien, DVM, MPh, DACVPM, a One Health practitioner, highlighted zoonotic diseases associated with “backyard chickens” in her recent lectures at the Fetch dvm360® veterinary conferences in Kansas City, Missouri, and Atlantic City, New Jersey.1,2

antonivano / stock.adobe.com

antonivano / stock.adobe.com

Investigators have found that the presence of animals in a household environment is a risk factor for zoonotic disease through associated fecal contamination and more frequent interaction with humans. Studies have found that contact with poultry and other food-producing animals increases the risk of diarrhea in children. Additionally, studies have revealed a link between chicken ownership and transmission of Campylobacter spp and Salmonella spp, according to the National Institutes of Health.3 O’Brien discussed these, and other zoonotic diseases associated with poultry, including E coli O157:H7 and avian influenza, during her lectures.1,2


Salmonella spp, which causes the disease, is transmitted through contaminated feed and water as well as direct contact with infected animals and feces.4 Animals may show signs of infection with fever and diarrhea. “Animals, just like people, can be asymptomatic,” said O’Brien.1

Humans infected with Salmonella spp can show gastrointestinal signs of infection such as diarrhea, abdominal pain, nausea, vomiting, and dehydration; as well as flu-like symptoms that may include fever, muscle pain, and malaise.4 Salmonellosis outbreaks in humans can be fatal in infants, according to O’Brien.1,2


Campylobacter spp is transmitted by ingesting contaminated meat, soil and water, or feces; and by direct contact with infected animals.4 O’Brien noted that it has been found in commercially processed chicken livers. “The liver can contain bacteria on the inside and is one of these things that chefs like to undercook,” she said.1

Animals with campylobacteriosis can exhibit diarrhea, anorexia, or vomiting; or may be asymptomatic. The disease can also cause fatal enteritis in new chicks. In humans, this disease can result in abdominal cramps, fever, and diarrhea, and the disease can trigger Guillain-Barre syndrome.1,2,4

E coli O157:H7

Humans can become ill with E coli 0157:H7—a Shiga-toxin-producing bacteria—from contact with an infected animal or by ingesting contaminated poultry products that are raw or undercooked. E coli 0157:H7 can also be transmitted between humans via fecal shedding, which accounts for approximately 11% of infections.5 Runoff water from farms as well as flies can also spread E coli to plants and animals.1,2

Infected humans typically experience bloody diarrhea with abdominal cramping and vomiting and may develop hemolytic uremic syndrome. E coli is a reportable disease, O’Brien noted.1

Avian influenza

Transmittable through inhalation of or direct contact with respiratory secretions, avian influenza is fatal in poultry and a reportable disease. Clinical signs in animals include anorexia, neurologic and respiratory disease, edema of comb and wattle with cyanosis, and hemorrhage.1,2,4

Although avian influenza does affect humans, O’Brien said the disease is currently not easily transmittable between animals and people. “What it usually does is infect the caretaker, but it typically doesn’t spread to other people,” she said.1

O’Brien said if there are a lot of sudden deaths in a backyard poultry flock, the carcasses should not be touched. Instead, health officials should be immediately contacted.1

Preventing disease transmission

Disease transmission isn’t only about the agent, said O’Brien. She explained that human factors and animal factors as well as hygiene and husbandry practices all play a role in transmitting zoonotic diseases.2

Individuals who are younger than age 5 years or older than 65 years, and pregnant women, are at higher risk of receiving a zoonotic disease from their pets. However, signs that a client may be at higher risk are not always obvious.2 “There are a lot of people out there with immunocompromised conditions; anything from rheumatoid arthritis to diabetes to somebody who might be on short-term steroids…The biggest thing about these conditions is that most of them are invisible to us,” she said.

Proper hand washing, wearing personal protection equipment such as face masks and gloves, and washing fruits and vegetables can all help reduce the risk of disease transmission from animals to humans. Additionally, poultry and eggs for consumption should be thoroughly cooked and properly refrigerated, and kitchen surfaces kept clean.1,2,4

It is recommended that individuals avoid sick and wild birds, as well as eating and drinking around animals. An annual influenza vaccine may help humans avoid getting infected with avian influenza.4


O’Brien noted that many urban flock owners are increasingly seeking the advice of small animal veterinarians for health and production issues with their chickens rather than veterinarians who specialize in poultry or food animals. She recommended that veterinary professionals speak openly with clients about their animals and convey the potential zoonoses risks of each species. She added that it is important to recognize the clinical signs of zoonotic infections in animals as well as symptoms of these diseases in humans.2


  1. O’Brien J. Dogs, cats, and chickens, oh my! Zoonoses in companion animal practice. Presented at: Fetch dvm360 conference; October 9-11, 2023. Atlantic City, NJ.
  2. O’Brien J. Dogs, cats, and chickens, oh my! Zoonoses in companion animal practice. Presented at: Fetch dvm360 conference; August 25-27, 2023. Kansas City, MO.
  3. Lowenstein C, Waters WF, Roess A, et al. Animal husbandry practices and perceptions of zoonotic infectious disease risks among livestock keepers in a rural parish of Quito, Ecuador. Am J Trop Med Hyg. 2016;95(6):1450-1458. doi:10.4269/ajtmh.16-0485
  4. The Center for Food Security and Public Health. Zoonotic diseases of poultry. Iowa State University College of Veterinary Medicine. January 2021. Accessed September 22, 2023. https://www.cfsph.iastate.edu/Assets/zoonotic-diseases-of-poultry-table.pdf
  5. Ameer MA, Wasey A, Salen P. Escherichia coli (e Coli 0157 H7). StatPearls. Updated August 8, 2023. Accessed October 11, 2023. https://www.ncbi.nlm.nih.gov/books/NBK507845
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