Quick Answers
Pigeons can carry and spread avian influenza viruses, commonly known as bird flu. However, the risk of pigeons transmitting bird flu to humans is low. Pigeons do not typically come into close contact with domestic poultry and are not considered a major carrier of highly pathogenic avian influenza viruses. Proper hygiene when handling pigeons can prevent bird flu transmission.
What is bird flu?
Bird flu, or avian influenza, is a virus that naturally occurs in wild aquatic birds like ducks, geese, and gulls. There are many different strains of avian influenza viruses. Most bird flu viruses do not cause illness in wild birds, but some strains can be highly pathogenic and fatal especially in domestic poultry like chickens, turkeys, and ducks.[1]
The most common strains of bird flu found in pigeons have low pathogenicity and typically cause few clinical signs of illness in infected birds. However, pigeons are susceptible to infection from more dangerous avian influenza strains, including H5N1, a highly pathogenic strain that emerged in the 1990s and has caused outbreaks in poultry and some human infections.[2]
Symptoms of bird flu
Many avian influenza viruses cause no signs of illness in birds. When symptoms do occur, they can include:[3]
– Respiratory signs: nasal discharge, sneezing, coughing
– Reduced activity, trembling, and poor coordination
– Swollen eyes, head, and comb
– Loss of appetite, weight loss, diarrhea
– Sudden death
Highly pathogenic strains like H5N1 cause severe, systemic disease and high mortality rates in poultry. In pigeons infected with milder bird flu strains, symptoms may be transient or nonexistent.
Transmission of bird flu
Wild aquatic birds are a natural reservoir for avian influenza viruses. The viruses are transmitted primarily through the fecal-oral route – contact with virus-contaminated feces, respiratory secretions, or surfaces. Bird flu outbreaks often start when domestic poultry come into contact with infected wild birds.[4]
Once a poultry flock is infected, the virus can be easily spread between birds through direct contact or contaminated objects, like cages, feed, and equipment. Good biosecurity practices are essential to prevent introduction and spread on poultry farms.
Pigeons may contract bird flu while interacting with wild waterfowl, then theoretically spread it to chickens or turkeys. However, significant transmission from pigeons to poultry has not been documented. Pigeons are considered lower risk vectors compared to waterfowl.[5]
Do pigeons carry bird flu viruses?
Yes, pigeons can be infected with and carry avian influenza viruses, including low pathogenic strains commonly found in wild birds. Several scientific studies have isolated avian influenza viruses from pigeons:[6]
– 2008 study in Guangzhou province, China found 24 of 609 pigeon samples tested positive for H9N2 virus.
– 2009 study in Korea tested 800 pigeons and found 8 birds positive for H9N2 virus.
– 2012 study in India found 10 different influenza A subtypes in 52 of 104 racing pigeons, including H9N2.
– 2016 study in Egypt detected influenza A/H5 viruses in 48 of 169 pigeons.
These studies show that pigeons are susceptible to infection with various bird flu strains circulating in wild birds. However, detection of virus alone does not prove that pigeons are a major source of outbreaks in poultry. Their role as transmitters may be limited.
One extensive surveillance study tested over 75,000 wild birds in the USA between 1998-2015 and found no cases of highly pathogenic bird flu in pigeons or doves, while detection rates were much higher in ducks, geese and swans.[7]
Overall, the scientific evidence suggests pigeons may serve as a minor natural reservoir and vector for low pathogenic flu viruses, but likely pose low risk for transmission of highly dangerous strains like H5N1 to poultry.
Geography and bird flu in pigeons
The strains of bird flu found in pigeons varies by region. One extensive global survey of influenza viruses in pigeons reported:[8]
– Australia: No viruses detected
– North America: Mostly low pathogenic viruses like H7N3, H2N9
– Europe: Similar low pathogenic strains
– Asia, Middle East, Africa: Higher rates of H9N2, a low pathogenic virus that can cause outbreaks in poultry
Areas like China and the Middle East with high rates of H9N2 in pigeons also report more poultry outbreaks associated with this strain. The evidence points to regional differences in pigeons’ potential to transmit viruses to domestic flocks. Proximity to waterfowl may influence local bird flu prevalence.
Do pigeons transmit bird flu to chickens and turkeys?
While pigeons can carry avian influenza viruses, there is limited evidence that they directly transmit infections to poultry and cause outbreaks. Several factors likely limit pigeons’ role:
– **Limited contact between pigeons and poultry** – Pigeons are free-living urban birds that don’t typically interact with chickens and turkeys on farms. Physical separation limits disease transmission opportunities.
– **Low pathogenicity of most pigeon viruses** – Most bird flu strains found in pigeons are low pathogenic types like H7N3 and H9N2 that usually cause mild or no disease. These viruses are less likely to spark major outbreaks than highly contagious strains like H5N1.[9]
– **Resistance of poultry** – Chickens and turkeys do not always contract disease when exposed to viruses that are adapted to pigeons. In one study, chickens did not get sick after being inoculated with 13 different pigeon influenza viruses.[10]
– **Lack of documented outbreaks** – There are few reported cases where contact with pigeons triggered a bird flu outbreak in poultry. However, monitoring is often limited, so the risk can’t be ruled out entirely.
For these reasons, pigeons are generally considered a low transmission risk compared to waterfowl like ducks and geese, which more frequently harbor dangerous bird flu strains.
However, pigeons may pose a greater threat in some regions with high H9N2 prevalence, such as China and the Middle East. More research is needed on the geographic differences in pigeons’ bird flu transmission potential.
Biosecurity recommendations
To limit any potential spread from pigeons, experts recommend the following biosecurity practices:
– Prevent contact between pigeons and poultry – Keep pigeons away from poultry housing, feed, and water sources
– Clean feeding and housing areas to prevent virus buildup
– Avoid moving pigeons between lofts or introducing new birds from unknown sources
– Isolate and test any birds showing flu symptoms
– Wash hands after handling pigeons to prevent disease transfer
Can pigeons transmit bird flu to humans?
Pigeons themselves pose little direct risk of transmitting avian influenza to humans. However, handling infected birds or surfaces contaminated with fresh droppings could potentially expose people to bird flu viruses.
No strong evidence exists of people contracting bird flu from casual contact with pigeons in public spaces. But there are theoretical infection risks from close, prolonged handling of sick pigeons or their secretions.
Human cases from pigeons
There have been a small number of isolated cases where people appear to have gotten infected through contact with sick pigeons:
– In 2007, an Iraqi woman died from bird flu after handling an infected backyard pigeon.[11]
– In 2015, a woman in Egypt developed bird flu symptoms after exposure to dead pigeons near her home.[12]
But such cases are very rare considering how widespread pigeons are globally.
Assessing the risks to humans
Any sick bird can shed avian influenza viruses in its saliva, nasal secretions, and feces. Human infection requires direct transfer of virus-laden fluids to the eyes, nose, or mouth.
Casual exposure to healthy pigeons or their droppings in public spaces is very low risk for bird flu. The main factors that could increase risks include:[13]
– **Prolonged, close contact** – This allows a greater viral exposure dose. Pigeon owners or racers who handle their birds daily over years face higher (but still low) risks.
– **Exposure to sick birds** – A bird shedding large amounts of virus has higher potential for disease transfer. But visibly ill pigeons are infrequently encountered in public.
– **Failure of protective hygiene** – Not washing hands sufficiently after touching eyes, nose, or mouth of pigeons could transfer viruses.
Overall, occasional interactions with pigeons pose minimal risks, but it’s always prudent to take precautions and follow good hygiene practices.
Protective measures for people
To further reduce any theoretical risks from pigeons, the CDC recommends:[14]
– Avoid touching eyes, nose or mouth after handling birds. Wash hands thoroughly with soap and water afterwards.
– Use protective clothing like gloves and face masks when handling sick or dead birds.
– Avoid surfaces potentially contaminated with pigeon droppings. Disinfect areas with bleach.
– Cook poultry products to 165°F minimum internal temperature to kill any potential bird flu viruses.
Following basic hygiene practices provides effective protection, even for people regularly exposed to pigeons.
Conclusion
Pigeons are susceptible to numerous avian influenza strains and can carry and transmit them, primarily low pathogenic viruses adapted to birds. However, significant transmission from pigeons to poultry is uncommon. Their capacity to trigger bird flu outbreaks in domestic flocks appears much lower than waterfowl.
There are minimal risks to humans from casual exposure to pigeons in public spaces. But people caring for infected pigeons could potentially contract bird flu with close contact. Following protective hygiene measures greatly reduces risks. Overall, pigeons rank low on the spectrum of bird flu threats to agriculture and human health compared to wild waterfowl reservoirs. But their potential as vectors merits continued surveillance, especially in regions with endemic strains like H9N2.
