Bacterial Zoonotic Diseases of Poultry: A Serious Public Health Hazard
Poultry is a significant pathogen reservoir. A wide range of zoonotic disease concerns exists in poultry. Disease transmission can occur through infected poultry. A consumer demand is for safe and high-quality animal protein. Backyard and small-scale production flocks are becoming more popular, as is public concern about global chicken disease outbreaks. Humans can contract infections from chickens in two ways. One is transmitted by contact with live birds, while the other is transmitted through food, as a result of exposure to or consumption of infected birds meat or egg products.
Poultry keeping is one of the most popular livestock enterprises in India, due to its low capital investment and space requirements. The poultry industry comprises of both smallholder and large scale poultry producers under commercial hybrid or indigenous poultry production system. The birds are reared under intensive production. Indigenous poultry production system is the dominant production system in India, which is concentrated in rural and peri – urban areas such as India and other major towns in the country. Zoonoses are infectious diseases of animals (usually vertebrates) that can be naturally transmitted to humans. Zoonoses can be caused by a range of pathogens such as viruses, bacteria, fungi and parasites; of 1,415 pathogens known to infect humans, 61% are zoonotic. Most birds are asymptomatic carriers of the zoonotic diseases though in young birds, diseases like Newcastle disease and avian influenza manifests with high morbidity and mortalities which approaches 100%. Human transmission occurs through exposure to contaminated avian faecal material, oral and nasal discharges or consuming improper cooked avian meat or eggs. Humans also get infected with wild avian zoonotic diseases like West Nile Virus, avian influenza due to the interaction between carrier host and domestic birds which get infected and act as a source of zoonoses. Other major factor contributing to the transmission of new zoonotic pathogens in human population is the increased contact between humans and wildlife. Birdkeepers (pet bird owners and poultry producers) should be aware that some avian diseases can be transmitted to humans. For most people avian diseases do not pose a serious threat, but bird keepers should be aware of them and seek medical assistance if necessary.
The global demand for poultry products has seen an unprecedented rise, making poultry farming a cornerstone of the agriculture industry. However, this surge in poultry production comes with its own set of challenges, particularly the prevalence of bacterial zoonotic diseases.
As veterinarians with multi-species training, when we hear the word “zoonosis”, we automatically think about dogs with rabies, calves with ringworm, and puppies with roundworms. But what about poultry? What are the zoonotic diseases of poultry? The recent cases of H7N9 avian influenza moving from poultry into people makes us think about chickens and public health. Also, the increasing popularity of “urban chickens”, or backyard poultry, means that many clinics and laboratories may be presented with sick birds and need to advise clients on potential human diseases that could be transmitted from poultry or their products.
Public Health Implications:
- Foodborne Outbreaks:
- Contaminated Products: Consumption of undercooked or contaminated poultry products can lead to widespread foodborne outbreaks.
- Cross-Contamination: Improper handling and processing contribute to the dissemination of pathogens.
- Antimicrobial Resistance:
- Overuse of Antibiotics: Poultry farming’s reliance on antibiotics raises concerns about the development of antibiotic-resistant bacterial strains.
- Human Health Impact: Transfer of resistant bacteria from poultry to humans can compromise the effectiveness of antibiotics.
- Economic Burden:
- Healthcare Costs: Treating zoonotic infections in humans incurs substantial healthcare expenses.
- Productivity Loss: Outbreaks may lead to reduced consumer confidence and economic losses in the poultry industry.
List of Zoonotic disease agents associated with poultry
Viruses:
- Avian influenza
- Newcastle disease
Bacteria (primarily food-borne): Campylobacter · Salmonella · Escherichia coli (colibacillosis) · Clostridium perfringens · Listeria monocytogenes · Staphylococci
Bacteria (other): Chlamydia psittaci (ornithosis, psittacosis) · Erysipelothrix rhusiopathiae · Mycobacterium avium (avian TB) · Pasteurella multocida (respiratory pasteurellosis).
Fungi: Aspergillus species* · Microsporum gallinae (favus, ringworm) · aspergillosis is primarily an environmental infection, but is at least potentially zoonotic and is associated with poultry.
Individual susceptibility and the seriousness of these various microbial infections varies with age, health status, immune status (immunodeficient or immunosuppressed), and whether early therapeutic intervention is sought. The ability of a microorganism to make a person sick varies with the virulence of the organism, the dose to which the person is exposed, as well as route of infection. Chlamydiosis, salmonellosis, arizonosis, and colibacillosis are the most common of these infections. Chlamydiosis, salmonellosis, eastern equine encephalitis and avian tuberculosis may be serious and even lifethreatening.
CHLAMYDIOSIS
Chlamydophila psittaci is a bacterial organism that occurs worldwide and affects more than 100 avian species. The disease is also referred to as parrot fever when it occurs in psittacine birds (psittacine refers to parrot-like birds). It is referred to as ornithosis in other birds. Chlamydiosis is primarily transmitted by the inhalation of contaminated fecal dust and is spread by carrier birds that act as the main reservoir for the disease. The organism is secreted in both the feces and nasal secretions. The carrier state can persist for years. C. psittaci can survive drying, which allows it to be transmitted on contaminated clothing and equipment. It can also be transmitted from bird to bird, from feces to bird, and from bird to human. Human-to-human transmission can occur as well, mainly by exposure to infected saliva. Infection in humans is extremely rare and is often misdiagnosed. Treatment for C. psittaci usually consists of tetracycline or microlides in both humans and birds, although the treatment span may be different. Tetracycline is not recommended for children or pregnant women.
SALMONELLOSIS
Avian salmonellosis is an important cause of clinical disease in avian and a source of food borne disease in human. The etiological agent of fowl typhoid and pullorum disease is Salmonella enterica subspecies enteric, serova Gallinarum. Transmission mostly is through faecal – oral route. Chick maybe infected early by vertical transmission either from infected ovary, oviduct or from infected egg during the passage through the cloacae of infected or carrier birds. Humans get infected by eating raw chicken or egg products which are already infected by salmonella or food and water contaminated with faecal material of infected birds. .Fowl typhoid occur as peracute, acute or chronic form of disease affecting mostly adult avian whereas pullorum disease affects the very young chicken mostly two-three weeks of age and in adult, the disease tends to be chronic. Clinical signs in chicken include anorexia, drop in egg production, increased mortality, reduced fertility and egg hatchability. In humans, salmonella infection causes diarrhoea and destroys epithelium leading to gastro-intestinal ulceration.
LISTERIOSIS
Listeriosis is a disease that causes septicaemia or encephalitis in humans, animals and birds. The causative agent is Listeria monocytogenes. Listeria monocytogenes is a medium sized gram positive rod, non- spore forming and nonacid fast bacteria. Most indigenous chicken are carriers of Listeria monocytogenes. Humans are infected by the bacteria through contact with affected birds, and consumption of their product and unpasteurized milk. Most cases and deaths occur in pregnant women, newborns, the elderly and immunosuppressed adults. In avian, all age group are susceptible but the disease is primarily of the young birds where it causes a septicaemia with focal necrosis in the liver, myocardium, pericarditis and occasionally encephalitis manifested as torticollis in broiler chicken. In human, meningitis is the most common of the three forms of listeriosis.
AVIAN TUBERCULOSIS
Avian tuberculosis is caused by the bacterium Mycobacterium avium. This bacterium is closely related to the bacteria that cause human and bovine tuberculosis. In bird species, M. avium causes a chronic debilitating disease with tubercular nodes. In humans, infection with M. avium will typically cause local wound infections with swelling of lymph nodes in the region of the infection. Infection with this bacterium is extremely rare and is of most risk in severely immunocompromised individuals. Infection in humans is caused by ingestion of food or water that has been contaminated with feces from infected birds (called “shedders”). Most Mycobacterium infections are treatable with antibiotics, but Mycobacterium avium, highly resistant to antibiotics, is the exception. Surgical excision of infected lymph nodes is often necessary to eliminate the infection. Poultry flocks with this disease must be euthanized because no treatment is available Fortunately, M. avium is not found in the commercial poultry industry today, but rare cases are found in small flocks where birds are held for several years.
COLIBACILLOSIS
Colibacillosis is caused by an Escherichia coli infection. Like Salmonella, E. coli are found in the intestinal tract and on the skin of animals and are part of the normal bacterial flora. E. coli strains vary considerably in their ability to cause disease. Many strains are not pathogenic, but some can cause disease. Eating food that has been contaminated with a virulent strain can result in severe illness. In poultry, most E. coli infections are a result of complications and the E. coli are considered opportunistic agents. In poultry, E. coli may cause septicemia, chronic respiratory disease, synovitis, pericarditis, infectious cellulitis, and salpingitis. Humans with E. coli infection usually present with diarrhea and a possible fever. Complications for less common types of E. coli infection include dysentery, shock, and purpura (purple rash). The incubation period is 12 hours to 5 days, although most cases will develop within 12 to 72 hours. Treatment of most cases of E. coli involves treating the diarrhea and dehydration that can occur. More severe cases may require the use of antibiotics or other drugs and hospitalization. Antibiotic resistance is a major problem when treating E. coli infections.
Mitigation Strategies:
- Improved Farm Hygiene:
- Biosecurity Measures: Strict adherence to biosecurity protocols to prevent the introduction and spread of pathogens.
- Sanitation Practices: Regular cleaning and disinfection of poultry farms to minimize bacterial contamination.
- Vaccination Programs:
- Preventive Measures: Implementation of effective vaccination programs to reduce the prevalence of bacterial diseases in poultry.
- Disease Monitoring: Regular monitoring of flocks for early detection and containment of potential outbreaks.
- Regulatory Oversight:
- Stringent Standards: Enforcing and enhancing regulatory standards for poultry production and processing.
- Antibiotic Stewardship: Implementing guidelines to curtail the indiscriminate use of antibiotics in poultry farming.
- Public Awareness:
- Safe Food Handling Education: Educating consumers about safe food handling and the importance of thorough cooking.
- Understanding Risks: Creating awareness about the risks associated with undercooked poultry products.
- Research and Surveillance:
- Pathogen Monitoring: Continuous research and surveillance to understand the prevalence and evolution of zoonotic bacteria.
- One Health Approach: Collaboration between veterinary, public health, and environmental agencies to address the interconnectedness of human and animal health.
DISEASE PREVENTIVE MEASURES
The health of backyard poultry may be improved by implementing basic biosecurity measures, improving hygiene, educating owners about the most common diseases and their clinical signs, regular observation and handling of the birds by the owner, increased use of endo- and ectoparasiticides and increased use of vaccination. Bird-keepers should be aware that they can contract certain illnesses from their birds. The frequency of disease transmission from birds to humans is low, but the very young, the elderly, and those with compromised immune systems should be cautious. Many of these diseases are transmitted by ingestion of food contaminated by faecal matter. Prevention of most of these diseases, therefore, simply involves proper hygiene and sanitation. Wearing a face mask to avoid inhaling bird dust is also recommended. If you have persistent flu-like symptoms when no one else you know is affected, see a doctor and mention that you raise birds. Such symptoms may be indicative of a disease spread from birds to humans.
Bacterial zoonotic diseases in poultry pose a significant public health hazard, necessitating a comprehensive and collaborative approach to mitigate risks. As the global demand for poultry products continues to rise, proactive measures in farm management, regulatory oversight, and public education become paramount. By addressing these challenges head-on and implementing effective strategies, stakeholders in the poultry industry can not only safeguard public health but also ensure the sustainability and resilience of poultry farming in the face of bacterial zoonotic threats.
Although infections in humans are relatively rare; there are substantial zoonotic risks from poultry and poultry products that veterinarians and physicians alike should be aware of and keep in mind in their daily practice. Global outbreaks of poultry disease will likely continue to be headline news and raising small flocks of backyard birds continues to grow in popularity alongside the locavore and slow food movements. Whether presented with a beloved pet chicken or simply questioned about a current event, veterinarians need to be prepared to counsel and educate the public on the myths and realities regarding the risks of poultry zoonoses
Compiled & Shared by- This paper is a compilation of groupwork provided by the
Team, LITD (Livestock Institute of Training & Development)
Image-Courtesy-Google
Reference-On Request
