Farm animals and poultry can carry a range of diseases, some of which can be passed onto humans. These diseases are known as ‘zoonoses’. Transmission may result from direct contact with diseased birds, contaminated feaces, or through consumption of contaminated farm produce. There fore, the consistent practice of proper animal care, good farmer hygiene and sanitation will minimize the occurrence of transmission of diseases from the animals to humans. Some diseases that might be transmitted from poultry to human are :
Avian influenza (AI)
Avian influenza viruses are very contagious among birds and some of these viruses can sicken and even kill certain domesticated bird species including chickens, ducks, and turkeys. Infected birds can shed avian influenza A viruses in their saliva, nasal secretions, and faeces. The primary risk factor for human infection has been direct contact with live or dead infected poultry, but a few cases have resulted from consumption of uncooked poultry products. The signs and symptoms in humans have ranged from conjunctivitis to influenza-like illness to lower respiratory disease.
A potential future threat to public safety comes from the ability of AI viruses to exchange genetic material with human or other animal influenza viruses. This could create a new virus that humans have little or no immunity to that can spread easily between people. Good farming practices are essential to reduce the risk of illness and to prevent them spreading during an outbreak.
Salmonellae bacteria are capable of causing enteritis and septicaemia in birds. Infected animals may produce meat, milk or eggs containing Salmonella. Feed contamination with Salmonella is known to be a source of infection for poultry. Therefore, it is recommended to monitor the Salmonella status of poultry feed, and if found positive to take corrective measures. The use of heat-treated feeds or feeds subjected to other bacteriostatic or bactericidal treatment is recommended (e.g. organic acids). Vaccination can be used as part of an overall Salmonella control programme.
Salmonellosis in humans is caused by the ingestion of food contaminated with Salmonella typhimurium in poultry meat and Salmonella enteitidis in eggs. It is one of the most significant causes of food poisoning in humans. Proper cooking kills Salmonella bacteria in meat and eggs.
Campylobacter bacteria tend to multiply in large numbers in the hindgut of chickens, mainly in the ceca. Insects and rodents promote transfer of the Campylobacter infection from the general environment into the poultry buildings. The antibiotic treatment, phage therapy, competitive exclusion and vaccination have been adapted at the farm level to reduce colonization of Campylobacter in poultry gut. It is a main cause of enteritis in humans. Effective sanitation of drinking water, sourcing of water from high quality supplies, avoidance of contact with pets and other species, good hygienic practices by poultry handlers. All poultry should be cooked to reach a minimum internal temperature of 165°F to prevent infection through infected meat.
E-coli is present in a wide range of animals, from poultry to cattle. E. coli is an opportunistic pathogen that can produce a variety of symptoms in commercial poultry. E. coli is present in the birds and the poultry house environment and infects birds. However, if growers provide birds with proper house environment, ensure that they have easy access to feed and water as well as limit exposure to pathogens, E. coli infections can be limited or eliminated. Infection to humans is caused by eating contaminated food or contact with faeces. Good personal hygiene is essential in prevention of the disease.
It is closely related to the human and bovine tuberculosis bacteria. In humans, M. avium infections can cause local wound infections with swelling of regional lymph nodes. Transmission occurs primarily through aerosolization and inhalation of the agent in dried bird droppings and contaminated soil. The infection is most severe in immunocompromised individuals. The generally accepted methods for controlling avian tuberculosis in poultry include identification and eradication of infected birds using intradermal tuberculin testing, replacement of contaminated housing and equipment, and isolation of new stock from the contaminated environment by rearing and maintaining new stock on wire or concrete floors . Avoiding overcrowding and other stressors, and ensuring that the birds are fed a nutritionally complete and balanced diet are also important in minimising the incidence and impact of this disease.
Caused by avian paramyxovirus. The best protection against the disease in birds is vaccination. Clinical signs in humans include conjunctivitis and possibly mild flu like symptoms. Infections are usually self-limiting with supportive care.
Here is a checklist to decrease human health risks:
- Wear respiratory protection when appropriate.
- Wear gloves when handling birds, animal tissues, body fluids and waste and wash hands after contact.
- Wear dedicated protective clothing such as a lab coat or coveralls when handling birds. Launder the soiled clothing separate from your personal clothes and preferably at the animal facility.
- Keep animal areas clean and disinfect equipment after using it on animals or in animal areas.
Dr. Rajani Rajesh, BVSc & AH
Veterinary Consultant and Surgeon
Kingdom of Bahrain