Zoonotic Diseases in Dogs

What is a zoonotic disease?

Zoonotic disease or zoonoses are terms used to describe an infection or disease that can be transmitted from an animal to a human.

Are there many zoonoses?

Altogether, well over 100 diseases can be transmitted from animals to humans, although most are rare in North America. All domestic animals, including dogs, cats, birds, horses, cows, sheep, goats, and rabbits can potentially spread diseases to people, but it rarely occurs. Most of these potential diseases can be avoided if pet owners exercise basic hygiene principles, especially hand washing.

Am I at risk for contracting a zoonotic disease from my dog?

Current evidence supports the fact that pet dogs pose a minimal zoonotic risk to their human companions. Risk may be slightly higher in people with a compromised immune system from disease or medication, such as:

• people with AIDS/HIV
• people on chemotherapy or receiving radiation therapy
• people who are elderly or have chronic diseases
• people with congenital immune deficiencies
• people who have received organ or bone marrow transplants
• people who are pregnant (the fetal immune system is not fully developed, and the pregnant person's immune system is altered during pregnancy)

If you fall into one of these categories, it does not mean you have to give up your pet. It simply means that you should take some precautions, such as monitoring your dog for any signs of illness, washing your hands after extensive handling of your dog, and avoiding direct contact with your dog's feces or urine.

It is important to keep in mind that numerous studies prove the benefits of having a pet far outweigh the risks. Sharing your home with a pet is often just what the doctor ordered.

What are the most common zoonotic diseases of dogs?

The most common zoonotic diseases include the following:

• ringworm
• salmonellosis
• leptospirosis
• campylobacter infection
• giardia infection
• cryptosporidium infection
• roundworms
• hookworms
• tapeworms
• mange
• rabies

What zoonotic diseases are the most likely to cause serious illness in people?

Zoonotic diseases most likely to cause serious illness in people include:

• Rabies, caused by a virus, is almost invariably fatal in humans.
• Certain infectious organisms, such as the bacteria Salmonella and Campylobacter and the protozoan Giardia, can cause severe gastroenteritis.
• Leptospirosis, known as Weil's disease in people, can cause extremely serious liver and kidney disease. It is transmitted through the urine of affected animals. Transmission from dogs to humans is rare, however, as humans usually contract this disease from exposure to water that has been contaminated by the urine of wild animals.
• Roundworms, hookworms, and tapeworms (Echinococcus species) can cause problems due the larval stages in our bodies, but human illness from these causes is rare. Direct handling of infected dog feces containing eggs can potentially cause an infection in a susceptible person. Roundworm and hookworm larvae can cause a condition called larval migrans, where the larvae migrate through various body tissues, causing inflammation. 
• Echinococcus tapeworm infections are becoming more common in areas of Canada and the United States where they had not been recognized before (see handout "Echinococcosis in Dogs" for more information on this disease). Exposure to the eggs of this tapeworm can cause damaging cysts (hydatid cysts) to form in the liver and other parts of the human body. 
• Ringworm, caused by the fungus Microsporum canis, and mange, caused by the mites Sarcoptes, Cheyletiella, and Trombicula, are transmitted relatively easily to people through direct physical contact. These zoonotic skin diseases can cause itchy, scaly skin lesions.

How can I reduce the risk of contracting one of these diseases from my dog?

Simple hygiene and common sense will drastically reduce, if not eliminate, the risk of zoonotic spread of disease from dog to people. Some of the things you can do include:

• Make sure that any sign of illness or disease in your dog is diagnosed and treated promptly by your veterinarian. If your dog is sick, make sure you wash your hands after any contact with him.
• Bathe and groom your dog. This will increase the chance of early detection of any skin lesions.
• Give your dog a broad-spectrum deworming product on a regular basis. The simplest way to do this is to use a monthly heartworm product that includes a dewormer.
• Wear gloves when gardening or working in areas where dogs, cats, or other animals may have urinated or defecated.
• Pick up any feces on your property and stoop and scoop when you take your dog for a walk. Dispose of all waste materials promptly and safely.
• Do not allow your children to contact your pet's feces or your pet to contact your children’s feces.
• Always ensure you wash your hands after handling any animal.
• Provide separate food and water dishes for your dog, and wash and store them separately from your family's dishes.
• Wash pet bedding frequently.
• Use flea and tick control products on a routine basis, preferably ones that also control skin mites.
• If you or anyone in your family is immunosuppressed, ask your veterinarian if any additional precautions need to be taken.

Following these simple precautions ensures you have done everything to reduce risk to you and your family.

Can I transmit disease to my dog?

Transmission of disease can occur from people to dogs. Common examples include certain viral respiratory infections, tuberculosis, ringworm, MRSA bacteria, and fleas. Additionally, gastroenteritis due to Campylobacter and Salmonella infections can be passed from an infected family member to the family dog. Like people, immunosuppressed dogs would be at a greater risk.

While technically not zoonotic diseases spread from dogs, there are a number of vector-borne diseases that can be transmitted to both dogs and humans. Examples include Lyme disease and Babesiosis spread by ticks, and Leishmaniasis spread by sandflies. Ticks, fleas, mosquitos, and flies are all considered potential vectors. Many diseases are regional and tropical climates have higher prevalence, but this can shift over time due to climate change and other factors.