Zoonotic Disease: What Can I Catch from My Dog?

What is a zoonotic disease?

While most canine infectious diseases affect only dogs, and most human infectious diseases affect only humans, it is important to be aware that some of these diseases--called zoonotic diseases--can be transmitted between dogs and people. You are much more likely to contract ailments from other humans than you are from your dog. However, simple precautions, common sense, and good hygiene, including careful handling of feces and using proper parasiticides and medications to prevent fleas and other parasites, can further reduce the risk of zoonotic disease.

How are zoonotic diseases transmitted?

Transmission of a zoonotic disease can potentially occur when a person comes into direct contact with secretions or excretions--such as saliva or feces--from an infected dog. Additionally, some diseases may be contracted through a bite wound by an infected dog. Many zoonotic diseases can be transmitted from fleas or ticks (called vectors) to a person or a dog from another animal.

Who is at risk?

Most zoonotic diseases pose minimal threat; however, some humans are particularly at risk. Those with immature or weakened immune systems, such as infants, individuals with acquire immunodeficiency syndrome (AIDS), the elderly, and people undergoing cancer therapy, are more susceptible to zoonotic infections than others.

What are some common zoonotic diseases?

Bacterial Infections

Leptospirosis is a bacterial disease spread through the urine of infected animals. In people, the symptoms are often flu-like. The risk of getting leptospirosis through common contact with a dog is low; the primary mode of transmission is through contact with contaminated animal urine and swimming in contaminated water. Signs on dogs include fever, vomiting, abdominal pain, diarrhea, refusal to eat, severe weakness and depression, kidney disease and liver dysfunction. Risk factors for dogs include contaminated water and contact with deer, cattle, rats or raccoon urine. Leptospirosis can be treated with antibiotics. To prevent leptospirosis, vaccinate your dog, keep rodents under control, and keep away from areas of standing water. Note, however, that the vaccine does not provide 100% protection due to many strains of the bacteria and needs to be boosted annulally.

Parasitic Infections

Fleas are the most common external parasite of dogs. While fleas cannot thrive on humans, their bites can cause itching and inflammation. Fleas may also serve as vectors for zoonotic diseases. Flea-infested dogs may become infected with tapeworms from flea ingested while grooming. Children, albeit rarely, can also become infected with tapeworms from inadvertently ingesting fleas.

Some canine intestinal parasites, including roundworms and hookworms, can also cause disease in people. Children are particularly at risk due to their higher likelihood of contact with contaminated soil. Visceral larva migrans, a potentially serious disease that can affect the eyes and other organs, results from inadvertent consumption of roundworm eggs (e.g. when soiled fingers are placed in the mouth). Cutaneous larva migrans, an itchy skin disease, is caused by contact with hookworm-contaminated soil. Proper hygiene, including washing hands before meals, cleaning soil from vegetables, and reducing exposure to animal feces can prevent infection. Anti-parasite medications for puppies and annual fecal exams for adult dogs can reduce environmental contamination and the risk of human infection.

Fungal Infections

Ringworm is not caused by a worm at all; it is a skin infection caused by a group of fungi. Infected dogs most often come from environments housing large numbers of animals. In dogs, ringworm usually appears as a dry, gray, scaly patch on the skin. In humans, ringworm often appears as a round, red, itchy lesion with a ring of scale around the edge. Ringworm is transmitted by contact with an infected animal's skin or fur, either directly or from a contaminated environment. Infected dogs continuously drop fungal spores from their skin and fur; these spores, which remain capable of causing infection for many months, are difficult to eradicate from a household. Children are particularly at risk of infection. To reduce environmental contamination, confine infected dogs to one room until they are free of infection, then thoroughly clean and disinfect the household.

Protozoal Infections

Protozoans are single-celled organisms. The two most common protozoal diseases in dogs and humans are cryptosporidiosis and giardiasis. These protozoan parasites can cause diarrhea in both dogs and people, who usually become infected by a common source--for example, contaminated water--not by each other. To prevent the spread of infection, schedule annual fecal examinations for your dogs, and medicate infected dogs as directed by your veterinarian. Other preventive measures include wearing gloves while handling feces-contaminated material, washing hands afterwards, and boiling or filtering any surface water used for drinking. If your dog had diarrhea, bring it to your veterinarian for an examination.

Cryptosporidiosis is an infection of the gastrointestinal system caused by the parasite Cryptosporidium parvum. Symptoms include watery diarrhea, fever, abdominal cramps, nausea, and vomiting. Many infected individuals require hospitalization and IV fluid therapy to recover. Infection in immunosupressed individuals such as the very young.

Giardiasis is caused by the parasite Giardia, giardiasis is the most frequent cause of non-bacterial diarrhea in North America and the most commonly diagnosed intestinal parasite in humans in Oregon, with 00 to 800 cases reported each year. It is transmitted most frequently through contaminated water. The most common sign of giardiasis in dogs is diarrhea, which can be acute, chronic, or intermittant.

Viral Infections

Most viruses infect only their natural host species. Human viruses, like those than cause the common cold, infect only humans, while canine influenza virus infects only dogs.

Rabies: is a virual disease that can be passed from dogs to humans from the bite of an infected animal. Dogs are highly susceptible to rabies, which attacks the central nervous system, causing a variety of signs. Rabies is almost always fatal. In people, rabies infections usually occur when an infected animal bites a person. In order to protect human health, rabies vaccination of cats is required by law in many areas. Even if your dog is kept indoors, it is important to keep rabies vaccines current because dogs occasionally escape outdoors, and because rabid animals such as bats and raccoons occasionally enter houses. To further reduce your risk of rabies, avoid contact with wildlife and stray animals. See a doctor immediately if you receive an unprovoked bite by an animal.

Avian Influenza (H5N1): While the highly-pathogenic H5N1 strain of avian influenza has yet to be discovered in the US, it is expected to be found here in the future. In central Tailand, where the H5N1 strain has been found, dogs have tested positive for its antibodies, suggesting infection in dogs is likely. Keeping oets inside when possible and keeping an eye on what they might be consuming outside is their best protection.

What can I do to protect my dog and myself?

Common sense and good hygiene will go a long way toward keeping you, your family, and your cat free of zoonotic diseases. Here are a few simple precautions: