What Diseases Do Ducks Carry to Humans?

Ducks carry a surprisingly long list of pathogens that can infect people, ranging from well-known threats like avian influenza and Salmonella to less obvious ones like the parasite behind swimmer’s itch. Wild ducks serve as the primary natural reservoir of influenza A viruses, and both wild and domestic ducks harbor bacteria, protozoa, and other organisms that reach humans through direct contact, contaminated water, or undercooked meat.¹ The risks vary depending on whether you keep backyard ducks, work on a duck farm, swim in a lake frequented by waterfowl, or simply eat duck products, and the details matter more than the headlines suggest.

Avian Influenza

This is the disease that draws the most public concern, and for good reason. Wild ducks, especially dabbling species like mallards, are the main reservoir of influenza A viruses. These birds can carry highly pathogenic strains, including H5N1, and spread them across continents during migration without necessarily getting visibly sick themselves. In experimental infections, mallards shed large amounts of virus yet showed no illness or death, which makes them effective long-distance carriers.² Other species like tufted ducks shed virus too but tend to get sick and die, which limits their ability to spread it far.

Transmission from ducks to humans typically happens through close contact with infected birds or their droppings, not through casual encounters at a park pond. Live bird markets, where ducks and other poultry are sold in close quarters, are one well-documented setting where influenza viruses jump from animals to people.³ The virus replicates primarily in cells lining the intestinal tract of ducks, meaning fecal contamination of water and surfaces is a key route. Human infections with avian influenza are still relatively rare, but when they happen the illness can be severe, with H5N1 carrying a high fatality rate among confirmed cases.

The broader worry is reassortment: when an avian influenza virus and a human influenza virus co-infect the same host (often a pig, but potentially a person), they can swap genetic segments and create a new strain with pandemic potential. Both the 1957 and 1968 influenza pandemics are thought to have originated when human-adapted viruses acquired surface proteins from avian influenza strains.⁴ Ducks sit at the center of this cycle as the primary wild reservoir feeding new virus variants into domestic poultry and, occasionally, into the human population.

Salmonella

Salmonella is probably the most common duck-to-human pathogen in everyday life, especially for people who keep backyard poultry or handle duck products in the kitchen. Ducks carry Salmonella in their intestines and shed it in their droppings without looking sick. A review of studies across multiple countries found Salmonella in roughly 20% of live ducks, about 28% of duck meat and parts, and more than 30% of samples from duck-rearing environments.⁵ Those are high numbers, and they explain why duck meat and poultry products in general are considered a leading source of human Salmonella infections.

In the United States, backyard poultry flocks have become much more popular over the past two decades, and outbreaks of Salmonella linked to live poultry have risen in parallel. Between 2015 and 2022, the CDC tracked 88 multistate outbreaks tied to backyard poultry, resulting in nearly 7,900 illnesses. About a quarter of patients were children under five, a group particularly vulnerable to severe dehydration from Salmonella infection.⁶ Duckling exposure specifically was reported by 38% of case-patients in an earlier analysis of outbreaks from 1990 to 2014.⁷

The problem is not just the birds themselves. Salmonella contaminates feathers, bedding, coop surfaces, and anything the birds touch. People get infected by handling ducks, cleaning enclosures, or letting children cuddle ducklings without washing hands afterward. During the COVID-19 pandemic in 2020, when backyard poultry purchases spiked, over 1,700 Salmonella illnesses were linked to contact with privately owned poultry in a single year, a jump from all previous years.⁸

Campylobacter

Campylobacter bacteria are common residents of the duck gut, and they cause one of the most frequent bacterial foodborne illnesses worldwide. The two species that matter most are C. jejuni and C. coli, both of which can cause gastroenteritis in people. Studies have found Campylobacter in about 37% of cloacal swabs from ducks, and the bacteria also show up in the birds’ drinking water, on egg surfaces, and in the soil of their resting areas.⁹

What makes duck-associated Campylobacter particularly concerning is how closely it matches the strains that make people sick. Some studies have found that Campylobacter genotypes from ducks are very similar to human clinical isolates, suggesting direct or indirect transmission from ducks to people.¹⁰ Most human infections come from eating undercooked poultry or cross-contaminating kitchen surfaces, but waterfowl also seed Campylobacter into recreational water bodies, creating another route of exposure for swimmers and others who use those waters.¹¹

Psittacosis

Psittacosis is caused by the bacterium Chlamydia psittaci, and while the name suggests a parrot-specific disease, ducks are a well-documented source of human infections. People catch it by inhaling aerosolized particles from bird urine, feces, or respiratory secretions.¹² In humans, psittacosis typically causes an atypical pneumonia: fever, headache, dry cough, and sometimes severe respiratory distress. It responds well to antibiotics when recognized, but it is often misdiagnosed because clinicians do not think to ask about bird exposure.

Duck farms are a consistent source of outbreaks. In France, five severe cases of psittacosis in duck farm workers were reported in early 2006. Investigation of all duck flocks at the three affected farms found C. psittaci being actively shed from the birds’ cloacas and tracheas, even though the ducks appeared healthy.¹³ This is a recurring theme with duck-carried diseases: the birds often show no symptoms while actively shedding dangerous pathogens.

A study tracking C. psittaci through the entire mule duck breeding process found that environmental contamination, closely correlated with how much the birds were shedding, was the most probable source of worker exposure.¹⁴ The risk is highest during activities that kick up dust: cleaning barns, moving bedding, and processing birds after slaughter.

Swimmer’s Itch

If you have ever waded into a lake and come out with an itchy, red rash of small bumps, ducks may have been indirectly responsible. Swimmer’s itch, known clinically as cercarial dermatitis, is caused by the larvae of parasitic flatworms that use waterfowl, including ducks, as their definitive host. The parasites need both aquatic snails and birds to complete their life cycle. Snails release free-swimming larvae called cercariae into the water, and these larvae are meant to burrow into a duck’s skin. When they accidentally encounter a human instead, they penetrate the skin but cannot develop further, triggering an allergic inflammatory response.¹⁵

The rash is self-limiting and not dangerous, but it can be intensely itchy and unpleasant. It is mostly associated with larvae of the bird schistosome genus Trichobilharzia.¹⁶ Lakes and ponds with large resident duck populations and healthy snail populations are the most common settings, particularly in warm shallow water during summer months. Toweling off immediately after leaving the water can reduce the risk, since cercariae tend to penetrate the skin as water evaporates.

Cryptosporidium and Giardia

Ducks contribute to the spread of two waterborne protozoan parasites that cause gastrointestinal illness in people: Cryptosporidium and Giardia. A study of wild ducks along the Rio Grande River valley found that about half the birds were carrying Cryptosporidium and about 28% were shedding Giardia cysts, sometimes in very high concentrations.¹⁷ A Hungarian study found lower prevalence rates but confirmed that aquatic ducks and geese play a role in spreading human-pathogenic strains of both organisms into the environment.¹⁸

Both parasites cause watery diarrhea, stomach cramps, and nausea. Cryptosporidium is particularly problematic because it is resistant to chlorination at standard levels, meaning it can survive in treated recreational water. People who swim in or accidentally swallow water from duck-frequented lakes and ponds face some level of exposure risk. For immunocompromised individuals, Cryptosporidium can cause prolonged and severe illness.

West Nile Virus

Ducks do not transmit West Nile virus (WNV) directly to people. Instead, they serve as amplifying hosts: mosquitoes bite an infected duck, pick up the virus, and then bite a human. The connection is indirect but real. When WNV hit a commercial waterfowl operation in Wisconsin, the virus was detected by PCR in about 84% of dead birds, and neutralizing antibodies were found in roughly half of a random sample of asymptomatic or recovered birds.¹⁹ That indicates high levels of virus circulation in the flock, meaning any mosquito feeding in the area had a good chance of picking up WNV and potentially passing it to a person.

Most human WNV infections cause no symptoms or a mild fever and body aches, but a small percentage progress to neuroinvasive disease with encephalitis or meningitis, which can be fatal. Areas with large concentrations of waterfowl and active mosquito populations create the conditions for human risk. Mosquito control around duck farms and wetland areas is one of the most practical interventions.

Foodborne Risks from Duck Meat and Eggs

Eating duck carries the same categories of foodborne risk as other poultry, though duck products have received less attention from epidemiologists. Duck meat has been linked to outbreaks of salmonellosis, and contamination with Campylobacter, E. coli, Listeria monocytogenes, and enterococcus has been documented in duck meat samples.²⁰ Contact with young birds, including ducklings, has also been linked to Salmonella outbreaks in settings like nursery schools.

Duck eggs deserve special mention. In many Asian cuisines, duck eggs are eaten salted, preserved, or partially incubated (as balut). The shells can carry Salmonella, and improper handling or incomplete cooking creates a route of infection. The review data cited earlier found Salmonella on about 17.5% of duck egg shells and contents sampled across studies.⁵ Thorough cooking eliminates the risk from both meat and eggs, but cross-contamination in the kitchen is a persistent hazard.

Occupational Hazards for Duck Farm Workers

People who work with ducks daily face a concentrated version of all these risks. Psittacosis is the clearest occupational disease tied to duck farming. In one investigation at an Australian duck farm and processing plant, serological testing showed that 76% of workers had been exposed to C. psittaci, with a strong association between years of employment and likelihood of exposure.²¹ In other words, the longer you work around ducks, the more certain it becomes that you will encounter the pathogen.

Respiratory protection, good ventilation in barns, and minimizing dust during cleaning and processing are the standard recommendations. But compliance is uneven, especially on smaller farms. Avian tuberculosis, caused by Mycobacterium avium, is another occupational concern, particularly for people working in zoological gardens or captive bird facilities where waterbirds are housed. The bacterium can spread from birds to mammals and to their keepers.²²

Antibiotic Resistance Spreading Through Duck Populations

Beyond the diseases themselves, ducks contribute to a subtler but potentially more consequential public health threat: the spread of antibiotic-resistant bacteria. Mallard ducks harbor a range of gut bacteria, including Enterobacteriaceae species, that carry resistance genes against multiple classes of antibiotics including beta-lactams, aminoglycosides, quinolones, and sulfonamides.²³ On duck farms in Bangladesh, more than 40% of C. jejuni isolates and about 32% of C. coli isolates from ducks were multidrug-resistant.⁹

Wild ducks compound the problem by carrying resistant bacteria across borders during migration. A study in Poland found antibiotic-resistant Salmonella in wild mallards and noted that because these birds migrate globally, they could transfer resistance genes from countries with heavy antibiotic use to countries trying to reduce it.²⁴ This matters because even if a resistant bacterium from a duck does not directly cause disease in a person, it can share its resistance genes with bacteria that do.

How Climate and Migration Patterns Affect Risk

The geography of duck-carried diseases is not fixed. Migratory waterfowl carry pathogens between breeding, wintering, and stopover sites where large numbers of birds from different species and flyways converge.²⁵ These mixing events are opportunities for viruses and bacteria to jump between bird populations and, eventually, into human communities.

Climate change is reshaping these dynamics. Many waterfowl species are shifting their ranges northward, spring migration is happening earlier in many populations, and species composition at stopover sites is changing. Extreme weather events can trigger abnormal movements, as was apparently observed in 2006 when mute swans fleeing a cold snap near the Caspian Sea likely spread highly pathogenic H5N1 toward Western Europe.²⁶ All of this means the places where duck-carried pathogens show up are gradually shifting, and the timing of risk periods may change as well. Communities near wetlands, lakes, and agricultural areas that were previously low-risk could find themselves dealing with new exposure patterns as duck populations and their associated microbes redistribute.

Practical Steps for Reducing Your Risk

The diseases are varied, but the prevention strategies overlap considerably. If you keep backyard ducks, wash your hands thoroughly after handling birds, eggs, or anything in their living space. Do not let children kiss or snuggle ducklings, despite the temptation. Keep duck living areas separate from human living spaces and clean enclosures regularly while wearing a dust mask to reduce aerosol exposure. For duck meat and eggs, cooking to proper internal temperatures eliminates bacterial and parasitic risks. Treat raw duck in the kitchen the same way you would treat raw chicken: separate cutting boards, thorough surface cleaning, and no rinsing the raw bird under the faucet where it can spray bacteria onto surrounding surfaces.

For recreational water users, the risks are harder to control but worth knowing about. Avoid swimming in warm, shallow areas of lakes with large duck populations, especially during late summer when snail-borne cercariae peak. Towel off briskly after leaving the water. If you live near wetlands and notice heavy mosquito activity coinciding with waterfowl presence, mosquito repellent and source reduction (eliminating standing water around your property) reduce your West Nile virus exposure. For farm workers and anyone with occupational bird contact, respiratory protection during high-dust activities and regular health monitoring are the practical baseline.