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Salmonella bacteria cause the foodborne illness salmonellosis. Named after Daniel E. Salmon, a veterinarian who spent his career studying animal diseases for the U.S. Department of Agriculture, Salmonella bacteria have been known to cause illness for over 130 years.
Salmonellosis in People
The Centers for Disease Control and Prevention (CDC) estimates that each year in the U.S., about 1 million people get sick from salmonellosis, with 19,000 hospitalizations and 380 deaths. People commonly get infected with Salmonella by eating contaminated food, such as:
- Raw or undercooked meat and poultry products;
- Raw or undercooked eggs and egg products;
- Raw or unpasteurized milk and other dairy products; and
- Raw fruits and vegetables.
People can also become infected with Salmonella by handling contaminated food, such as contaminated pet food, or touching contaminated surfaces and utensils and then accidentally transferring the bacteria from their hands to their mouths.
Symptoms start within 12 hours to 3 days after a person ingests Salmonella. Symptoms of salmonellosis in people include:
- Diarrhea (which may be bloody);
- Vomiting; and
- Stomach pain.
Most people recover from salmonellosis in 4 to 7 days without treatment. Children under 5, pregnant women, the elderly, and people with weakened immune systems (such as those with cancer or other diseases) have a higher risk of getting salmonellosis and may develop more severe symptoms.
Animals, especially cattle, chickens, rodents, reptiles, and amphibians, can naturally carry Salmonella in their intestines and show no signs of illness. People can get salmonellosis from handling these animals or touching contaminated items in the animals’ habitats and then accidentally transferring the bacteria from their hands to their mouths.
Salmonellosis in Dogs and Cats
Salmonellosis is uncommon in dogs and cats. When the disease is seen in an adult dog or cat, the animal typically has another infection or debilitating condition at the same time. Puppies and kittens can get the disease if they ingest a large number of the bacteria. Signs of salmonellosis in dogs and cats include:
- Diarrhea (which may be bloody);
- Loss of appetite; and
- Decreased activity level.
In a study published in May 2017, almost 3,000 stool samples from dogs and cats were collected across the country between January 2012 and April 2014. Eleven laboratories then tested the samples for Salmonella. At the time of the stool collection, some animals were having diarrhea and some were not. Less than 1% (3/542) of cats and 2.5% (60/2,422) of dogs were positive for Salmonella. The study suggests that the prevalence of Salmonella-positive dogs and cats in the U.S. is low and continuing to decline. The study also identified a raw pet food diet as a major risk factor for Salmonella infection.
See the Merck Veterinary Manual, Overview of Salmonellosis.
Salmonellosis in Horses
Salmonellosis is a common cause of diarrhea in adult horses. Horses can become infected with Salmonella by coming into contact with the bacteria in a contaminated environment, eating contaminated feed, or drinking contaminated water. Horses can also become infected by direct contact with animals that are actively shedding the bacteria in their stool.
Stress appears to play an important role in salmonellosis in horses. Often, a horse sick with salmonellosis has recently:
- Had surgery;
- Been hospitalized;
- Been transported;
- Had a change in feed;
- Had another disease, particularly colic; or
- Been treated with antibiotics.
There are three forms of salmonellosis in adult horses:
- Carrier—horses appear healthy but intermittently shed Salmonella in small numbers in their stool. Carrier horses can spread the bacteria to other horses by direct contact or by contaminating the environment or feed and water sources. If stressed, carrier horses may show signs of salmonellosis.
- Mild—horses have a decreased activity level, fever, loss of appetite, and soft but not watery stool. Signs may last 4 to 5 days and usually go away on their own. After recovery, horses may continue to shed Salmonella in their stool for days to months.
- Sudden and severe—horses have a severely decreased activity level, fever, and loss of appetite. These signs come on suddenly. Diarrhea develops 6 to 24 hours after the fever. The diarrhea is fluid and foul smelling, and horses can become dehydrated quickly. There may be signs of stomach pain, straining, or severe colic. Horses may develop a blood infection and clotting problems. The disease progresses quickly, and if untreated, this form of salmonellosis is often fatal.
Salmonellosis can occur in newborn foals, causing a blood infection followed by diarrhea.
See the Merck Veterinary Manual, Salmonellosis in Horses.
Resources for You
- Centers for Disease Control and Prevention
- U.S. Department of Agriculture