Zoonoses Associated with Dogs

This document provides information on various diseases that can be passed from dogs to humans. Often these diseases do not make the animal appear sick but can cause serious illness in humans. Persons with specific medical conditions such as a chronic illness, immunodeficiency and pregnancy may be at higher risk of developing disease or complications from a zoonotic disease and should consult with their physician before working with animals. The diseases associated with dogs include rabies, capnocytophagosis, ringworm and external parasites, tularemia, brucellosis, leptospirosis, campylobacterosis, salmonellosis, cryptosporidiosis, giardiasis, infections with pathogenic E. coli, echinococcosis, cutaneous and visceral larval migrans, yersiniosis, mange, and MRSA. Additional information on zoonotic diseases can be found on the Center for Disease Control and Prevention Website, Healthy Pets, Healthy People.

Diseases associated with direct contact or bites:

Rabies is a fatal viral infection that can be transmitted by bites, scratches, and mucus membrane exposure from an infected animal. Dogs can be infected from contact with wildlife such as bats, skunks, and raccoons. Infected animals often exhibit neurological symptoms and unusual behavior. There is an effective vaccine available for people and most domestic animals including dogs. Dogs that have not been vaccinated for rabies and those with undiagnosed neurological disease should be treated with caution to avoid bites and scratches. If a person is bitten or scratched by a suspect animal, they should seek post-exposure rabies prophylaxis from a medical professional immediately. Persons who routinely work in high risk activities should be vaccinated against rabies.

Capnocytophaga canimorsus is a bacterium commonly found in the mouth of healthy dogs and cats and can be transmitted to people by biting. People may develop a local bacterial infection or life-threatening sepsis. Pre-existing liver disease, alcoholism and immunodeficiency indicate a higher risk of sepsis.

Dermatophytosis is a fungal skin infection commonly known as “ringworm” and is seen in both animals and people as scaly round areas of hair loss. Transmission of ringworm is by direct skin-to-skin contact with an infected animal.

Diseases associated with vectors or contaminated materials:

External parasites such as fleas, ticks, lice and mites are occasionally transmitted by close contact with an infested dog or handling infested bedding. Animals and animal housing areas should be routinely treated for external parasites.

Mange (aka Sarcoptic mange) is a skin disease caused by mites. Dogs can get infested with these mites after direct contact with affected dogs or contaminated bedding and will experience skin irritation with severe itching and self-inflicted wounds, and alopecia (loss of hair). People can get mild skin irritation after contact with infested dogs, but these mites cannot reproduce on humans, so the condition is resolved spontaneously after the mites die in a couple of days.

Tularemia is a bacterial infections of wild rodents and rabbits that occasionally infect dogs and people via tick or deer fly bites, by skin contact with infected animals, body fluids and tissues, ingestion of contaminated water, or inhalation of contaminated dust. Dogs that hunt rodents and rabbits may be at higher risk of becoming infected. Infected dogs may not show signs of illness or can experience high fever, swollen lymph nodes, reduced appetite, and lethargy. If the infection becomes generalized, the dog can have stiffness and reduced mobility. Tularemia in humans initially presents as a fever, headache, swollen lymph nodes and possibly a rash.

Leptospirosis is a bacterial disease of wild rodents and rabbits that occasionally infect dogs that hunt or drink contaminated water. The bacteria are typically shed in the urine of infected animals. Signs in dogs include fever, lethargy, reduced appetite, vomiting, diarrhea, conjunctivitis (red eyes), jaundice (yellow skin or eyes), or changes in urination (reduction or increase). The disease can progress in dogs to kidney or liver failure, bleeding of the lungs, and possibly death. People acquire the infection by accidental ingestion and contact with urine or other body fluids (except saliva) from infected animals or materials such as bedding. The organism can also infect through abraded skin. In people, the disease causes fever, headache, abdominal and muscle pain, vomiting, diarrhea, jaundice, and rash. In more severe cases, it can cause hemorrhagic pneumonia, liver and kidney failure and can lead to death.

Brucellosis caused by Brucella canis causes reproductive disease in dogs but may be also carried by normal animals. It can be transmitted by close contact with infected animals, tissues and body fluids. Disease in people is rare.

Salmonellosis, campylobacterosis, cryptosporidiosis, giardiasis and infections with pathogenic E. coli are acquired by contact and accidental ingestion of fecal material from infected animals. Echinococcus (canine tapeworms) and visceral larval migrans (canine roundworms) are parasitic infections in dogs which are also transmitted to humans by accidental ingestion of infected fecal material. Cutaneous larval migrans (canine hookworm) occurs when parasitic larvae penetrate bare skin and cause a local skin reaction. This primarily occurs from walking barefoot in areas contaminated with dog feces. Animals infected with these bacterial, protozoal and parasitic diseases typically have diarrhea, but some animals may show no symptoms of disease. Symptoms in people include abdominal pain, diarrhea, and fever.

Plague caused by Yersinia pestis is endemic in wild rodents in the Southwest. Plague is uncommon in dogs and if they are infected with the bacterium, they usually are asymptomatic but can become ill and can transmit the disease to humans. Dogs and people can acquire the infection by flea bites and contact with infected animals or their fluids and tissues. Signs of the infection in dogs may include fever, low appetite, apathy, swollen lymph nodes, vomiting, and diarrhea. Dogs can develop plague pneumonia and have cough or difficulty breathing Disease in people can be severe and requires prompt medical diagnosis and treatment. Symptoms can include high fever and chills, headache, malaise, swollen lymph nodes, and pneumonia. Plague is primarily found in the Southwestern United States and is unlikely to be diagnosed in dogs in the Northwest.

Methicillin-resistant Staphylococcus aureus (MRSA) are bacteria that have acquired resistance to certain antibiotics. They can be found on the skin of healthy animals and people, where they can opportunistically cause infections. Cats normally do not have signs of disease, but they can have infections in the skin, and respiratory and urinary tracts. People can get infected after direct contact with animals carrying these bacteria. If people are not treated, the infection can progress to septicemia and affect other organs including the lungs.

Avoid direct contact with feces and urine and use gloves and handwashing to avoid accidental oral ingestion of animal waste. Any animal with diarrhea should be suspect of having a zoonotic disease.

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Individuals with exposure to animals and animal environments may develop allergic reactions to animal proteins (allergens). Approximately 20-30 percent of individuals working with laboratory animals will develop an allergic reaction to animal proteins and 5-10 percent of individuals will develop asthma. Personnel may be exposed to allergens through inhalation and contact with skin, eyes and mucous membranes. Animal allergens may be present in animal dander, hair, skin, urine, saliva, serum and any contaminated feed or bedding materials. Risk factors for developing an allergic reaction include history of previous allergies to animals. The signs and symptoms of an allergic reaction are nasal discharge and congestion, conjunctivitis, tearing and eye itching, skin redness, rash or hives and lower airway symptoms (coughing, wheezing and shortness of breath). Individuals with symptoms suggestive of an allergic reaction related to a workplace allergen should report their concerns to their supervisor and consult a physician.

Transmission of zoonotic diseases from animals is primarily by direct contact, ingestion, indirect contact with insect vectors and contaminated inanimate objects, or inhalation of aerosolized materials. We can protect ourselves from most diseases by using the following procedures:

Handle animals appropriately and safely to avoid bites and scratches.
Thoroughly wash any bite or scratch wounds and report injuries.
Do not eat, drink, apply cosmetics or use tobacco products while handling animals or in animal housing areas.
Wear gloves when handling animals, animal tissues, body fluids and waste and wash hands after contact.
Wear dedicated protective clothing such as a lab coat or coveralls when handling animals. Launder the soiled clothing separate from your personal clothes and preferably at the animal facility.
Wear respiratory protection when appropriate.
Keep animal areas clean and disinfect equipment after using it on animals or in animal areas.

Most importantly, familiarize yourself about the animals that you will be working with and the potential zoonotic diseases associated with each species. If at any time, you suspect that you have acquired a zoonotic disease, inform your supervisor and seek medical care.

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**Prepared by Office of the Campus Veterinarian and the Office of Research Assurances January 2021

References

Centers for Disease Control and Prevention. Healthy Pets, Healthy People.(https://www.cdc.gov/healthypets/pets/dogs.html)
Runfola JK, House J, Miller L, et al. Outbreak of Human Pneumonic Plague with Dog-to-Human and Possible Human-to-Human Transmission — Colorado, June–July 2014. MMWR Morb Mortal Wkly Rep 2015;64(16):429–434.