Salmonella is a concerning bacteria that can cause illness in both humans and animals. Some types of birds are more likely to carry Salmonella than others. Understanding which birds may harbor this bacteria can help prevent transmission to other animals and people.
What is Salmonella?
Salmonella is a genus of rod-shaped bacteria that can cause foodborne illness known as salmonellosis. There are over 2,500 different serotypes or strains of Salmonella bacteria. Some strains are host specific, meaning they typically infect only certain types of animals, while others can infect multiple species. Salmonella infection usually results in gastrointestinal symptoms like diarrhea, fever, vomiting, and abdominal cramps within 12-72 hours after infection. Most people recover without treatment, but Salmonella can cause severe illness or death in vulnerable populations like the elderly, infants, or those with compromised immune systems. Antibiotics are only used in severe cases.
Salmonella bacteria are transferred through the fecal-oral route. They can be spread when people eat or drink contaminated food or water, have contact with animal feces, or do not practice good hygiene. Birds can carry Salmonella in their gastrointestinal tract and intermittently or consistently shed the bacteria in their droppings. People may become infected with bird-associated strains of Salmonella through direct contact with live poultry, or by handling raw poultry meat or eggs. Backyard poultry flocks have become increasingly popular, which has led to more human Salmonella outbreaks linked to live poultry contact in recent years.
Which bird species commonly carry Salmonella?
Many different bird species have been known to carry Salmonella strains that can make humans and other animals sick. Some of the bird types most likely to harbor Salmonella include:
Chickens
Chickens are a major reservoir of Salmonella. In commercial poultry flocks, Salmonella rates tend to be high, with up to 90% of chickens infected. Backyard chicken flocks also have significant Salmonella carriage rates. Contact with live chickens or their environments is a well-known source of human salmonellosis outbreaks. Some specific Salmonella serovars commonly found in chickens include S. Enteritidis, S. Heidelberg, S. Kentucky, and S. Typhimurium.
Ducks
Ducks can be infected with several Salmonella serotypes, including some strains typically found in chickens and others more specific to ducks. One study of domestic ducks in small farms in Vietnam found Salmonella carriage rates up to 54%. The most common serotypes were S. Typhimurium and S. Enteritidis. Ducks do not always show symptoms of illness with Salmonella infection. Contact with ducklings has been linked to human Salmonella outbreaks, so they should be handled with caution.
Turkeys
Many Salmonella strains affect turkeys, especially in large commercial flocks where infection rates may exceed 50%. Turkeys do not always appear sick when infected. Commonly detected serotypes include S. Reading, S. Hadar, S. Virchow, and S. Saintpaul. Raw turkey products are considered a significant source of human Salmonella infections. The CDC monitors outbreaks linked to turkey closely and provides guidelines for safe handling and cooking.
Geese
Geese can carry Salmonella just like other poultry species. One study cultured samples from geese and found Salmonella carriage rates around 32%. S. Typhimurium, S. Enteritidis, and S. Virchow were some of the predominant serotypes. There have been foodborne disease outbreaks traced back to contact with live geese or contaminated goose meat and eggs. Safe handling practices are important when raising or preparing geese.
Pigeons
Salmonella has been isolated from pigeons in many regions. Reported carriage rates vary widely from 2-50%. Several serotypes are common in pigeons, including S. Typhimurium, S. Enteritidis, and S. Infantis. Pigeons shed Salmonella in their droppings, which can contaminate surfaces in urban areas. Feeding pigeons and exposure to unsanitary surfaces they frequent increases Salmonella infection risk for the general public.
Songbirds
Songbirds like finches, sparrows, starlings, and swallows can also be infected with Salmonella. However, songbirds are not usually major carriers. Infection rates are generally low, around 1-5% for most species. The most common serotypes found in songbirds include S. Typhimurium, S. Montevideo, and S. Meleagridis. Songbirds are less likely than poultry to transmit Salmonella illness to humans.
Parrots
Parrots sometimes carry Salmonella, with infection rates from 0-15% reported for different parrot species. Several Salmonella outbreaks have been linked to contact with live parrots or parakeets, as well as consuming contaminated bird food. Some serotypes more commonly isolated from parrots include S. Typhimurium, S. Enteritidis, S. Hadar, and S. Infantis. Salmonella can cause actual illness in parrots, so infected birds may show symptoms.
Raptors
Birds of prey like eagles, hawks, falcons, and owls can be infected with Salmonella, likely through consuming infected prey. However, raptors seem to be fairly resistant carriers. One study found Salmonella in only about 2% of tested captive raptors. When they do carry Salmonella, serotypes like S. Typhimurium, S. Enteritidis, and S. Thompson are often detected. Wild raptors are less significant in transmitting Salmonella to people.
Why do birds carry Salmonella?
There are several reasons why Salmonella bacteria are so prevalent in many bird populations:
- Asymptomatic carriers – Birds can pick up Salmonella from the environment and other infected animals. Many birds do not show signs of sickness when infected.
- Fecal shedding – Infected birds shed Salmonella at high levels in their droppings which further contaminates the environment.
- Rodents and insects – Rodents and insects attracted to bird habitats can introduce Salmonella and spread it between flocks.
- Stress – Stress from transport, overcrowding, molting, or poor nutrition may activate Salmonella already present in a bird’s gut.
- Density – Higher density of birds in close quarters facilitates Salmonella transmission.
- Immature immune systems – Baby birds have more immature immune function that is less effective at controlling Salmonella.
Due to the natural biology and living conditions of many bird species, Salmonella often thrives and spreads readily between individual birds and entire flocks. Once established, the bacteria continue to circulate and infect new individuals introduced to the population. This helps explain why Salmonella carriage rates can be so high in types of birds like chickens, ducks, and turkeys. Understanding this cycle of transmission is key for control methods.
Preventing Salmonella in backyard and commercial flocks
Since Salmonella is so common in bird populations, active prevention steps are needed to protect bird health and human safety:
- Keep wild birds, rodents, insects out of bird housing areas
- Disinfect housing between new flocks
- Avoid overcrowding and stress
- Promptly remove sick/dead birds
- Only bring in birds from Salmonella-free flocks
- Vaccinate chicks (some serotypes)
- Give probiotics to help mature immune systems
- Use sanitary processing for commercial flocks
- Follow biosecurity protocols
These measures are especially critical for commercial poultry operations, where Salmonella is a constant concern. But even small backyard flocks benefit from steps to exclude vermin, disinfect, and isolate new birds until Salmonella-free status is confirmed. Proper handling and cooking of raw poultry products, cleaning after handling live birds, and not keeping birds in the house can also help prevent human Salmonella infections.
Conclusion
Salmonella carriage is a common issue in many bird species, especially poultry. Birds can harbor Salmonella without any symptoms and shed bacteria in their droppings that can infect people. Chickens, ducks, turkeys, and geese are among the birds most likely to be infected and spread Salmonella. Songbirds, parrots, and raptors have lower Salmonella rates but may still pose a transmission risk in some circumstances. Understanding which birds carry Salmonella helps inform preventive measures in bird flocks and proper handling to avoid human illness. This includes exclusion of vermin, stress reduction, disinfection, and protective cooking and hygiene practices.
