Overview of Listeria in Dogs
Listeria is a food borne bacterial illness caused by the bacterium Listeria monocytogenes which can infect humans as well as dogs and cats. Listeria is a bacteria found in soil, water, and in some animals, including poultry, cattle, sheep and goats. It can also be found in rabbits, guinea pigs, and other species.
Dogs can be infected with Listeria by the same sources as human exposure, including infected meats and dairy product as well as contaminated dog food. There have been various pet food recalls due to contamination with listeria including the Bravo Pet Food Recall in May 2014.
Dogs fed raw diets are at a higher risk for Listeria infection. The U.S. Food and Drug Administration (FDA) cites a two-year study from October 2010 through July 2012 by the FDA Center for Veterinary Medicine (CVM). In the study, over 1,000 samples of pet food were screened for bacteria that can cause foodborne illnesses. The FDA stated, “The study showed that, compared to other types of pet food tested, raw pet food was more likely to be contaminated with disease-causing bacteria.” The participating laboratories analyzed the raw pet food for harmful bacteria, including Salmonella and Listeria monocytogenes.
Infection with Listeria, commonly called Listeriosis, can cause severe infection in pregnant women, elderly people and humans with suppressed immune systems. Healthy people and dogs are rarely infected.
Many aspects of the disease spread, symptoms, diagnosis, treatment and prevention in humans are the same as those in dogs.
Sources of Listeria
Dogs can be exposed to Listeria from contaminated dog foods as well as eating contaminated garage.
Listeria can be present in raw milk and foods made from raw milk and contaminate a variety of processed meats and dairy products. Unlike many other bacteria, Listeria can grow in refrigerated temperatures and even spread to other foods in the refrigerator which makes it a challenging organism. However, Listeria is killed by pasteurization and cooking.
Common sources of Listeria in dogs include:
- Raw pet food diets
- Contaminated dog food
- Dogs fed table scraps that are contaminated. Sources of human foods associated with Listeria include:
- Raw vegetables (that have been contaminated from the soil from contaminated manure used to fertilize the soil) or deli-prepared salads.
- Infected animal meats such as from deli meats, hot dogs, meat spreads
- Dairy products such as ice cream
- Unpasteurized milk or foods made with unpasteurized milk
- Soft cheeses e.g. Feta, Brie, Camembert, Panela, Queso fresco and other blue-veined cheeses.
- Smoked refrigerated seafood
Can Dogs Spread Listeria to People?
According to the Ontario Veterinary Medical Association, “It is highly unlikely that a dog that has eaten contaminated meat would pass the infection on to humans. A small percentage of healthy pets can shed Listeria in their stool at any time.”
Our research suggests that dog to human contact is unlikely. Most human infections are directly from the list above including contaminated meat and dairy products.
Listeria can be spread by eating the bacteria, direct contact or by inhalation.
Diagnosis of Listeria in Dogs
Blood tests can confirm the diagnosis of Listeria. For dogs with neurologic symptoms, analysis of the cerebrospinal fluid can also be suggestive of infection.
Symptoms of Listeria in Dogs
Symptoms can vary with the individual dog, from no symptoms, very mild flu-like symptoms to severe neurologic symptoms. Not all dogs exposed to listeria will develop symptoms or become ill.
Symptoms may include: Diarrhea, nausea, vomiting, weakness, fever, muscle soreness, lethargy, lack of coordination, and/or a stiff neck. A severe consequence of Listeria is meningitis which is a disease of inflammation of the membranes covering the brain and spinal cord. In addition to the above, infection of pregnant women can cause miscarriage; stillbirth or the baby can be born with a life-threatening infection. The same things are believed to be true of dogs. Listeria has also been shown to cause skin infections in dogs.
How Long Does it Take to Show Symptoms of Listeria
Due to the infrequent diagnosis in dogs, the incubation period of Listeria is unknown. In humans, it can take as little as 2 to 3 days from the time you are exposed to Listeria to show to as long as 2 months (70 days). The same is believed to be true in dogs.
Who’s At Risk For Listeria?
Those at highest risk for Listeria include newborns, pregnant women, elderly and those with underlying health problems or those that are immunosuppressed are at greatest risk. For example, older adults, people receiving medications to prevent organ transplant rejection, and those with weakened immune systems such as those with cancer, those under treatment with chemotherapy, HIV/AIDS, liver disease, kidney disease, diabetes, or alcoholism. Pregnant women can have flu-like signs but can affect the fetus leading to miscarriage, stillbirth or life-long health problems. If you have any symptoms – please contact your physician.
It appears risks of infection in dogs are similar to those in humans. Dogs with underlying diseases, weakened immune systems and senior dogs are at increased risk.
Treatment of Listeria in Dogs
Treatment may vary depending on the severity of the symptoms. Mild symptoms may be treated symptomatically with pain relievers and gastrointestinal protectant medications.
Severe cases may require antibiotics and hospitalization. Common antibiotics used include: Ampicillin, penicillin, amoxicillin, Trimethoprim-sulfamethoxazole, and fluoroquinolones such as baytril or ciprofloxacin. Gentamicin may also be given to patients with impaired immune systems.
Prevention of Listeriosis in Dogs
The following tips help prevent you and your dog from exposure to Listeria infections.
- Wash you hands well in warm soapy water for at least 20 seconds before and after handling food as well as after handling dogs, litter boxes, fecal matter or gardening.
- Use bags or tools to pick up and/or dispose of feces.
- Monitor for pet food and treat recalls that may affect your dog’s food.
- Don’t feed your dog human foods, especially uncooked meats and unpasteurized dairy products.
- Keep your refrigerator at 40 degrees or lower and clean your refrigerator regularly.
- Clean all food preparation surfaces (knives, countertops, and cutting boards) with warm soapy water after handling and preparing uncooked foods. If possible, nonporous boards should be washed in the dishwasher.
- Sanitize your kitchen using teaspoon of unscented bleach to one 1 quart of water. Spray surfaces and allow solution to sit for 10 minutes then wipe down with clean paper towels.
- Regularly laundry dishcloths and dishtowels.
- Do not drink raw unpasteurized milk or eat foods that have unpasteurized milk in them. Do not feed these products to your dogs.
- Thoroughly rice all raw fruits and vegetables under running water. Soil contamination can spread the bacteria.
- Keep uncooked or undercooked meats, poultry, and seafood separate from your other foods including vegetables, fruits, and cooked foods.
- Thoroughly cook raw food from animal sources. This includes meat, poultry, and seafood.
- Consume perishable and ready-to-eat foods as soon as possible.
- In addition to the above, persons or dogs in higher risk groups such as with weakened immune systems should heat hot dogs, cold cuts, and deli meats before eating or feeding them.