Infectious Diseases in Dogs

Protect Them From These Common Conditions

Dogs on walk

 Your Personal Camera Obscura/Getty Images

Bringing a new dog into the family can be an exciting experience. But just like children, they are a huge responsibility. It is important to understand what it takes to care for a dog, and that includes knowing what conditions may affect them. This article discusses some common conditions that dogs can get, how they are treated, and what can be done to prevent their occurrence.

Canine Distemper

Canine Distemper Virus is a highly contagious disease in dogs. It is closely related to the Measles Virus in humans. If left untreated, this disease can be potentially fatal. The virus is shed in most body secretions, including urine. The infected dog typically spreads the disease through coughing infected secretions, that are inhaled by the new host. Dogs that have not been vaccinated against distemper are most commonly affected.

Symptoms include eye and nasal discharge, fever, lack of appetite, and a cough that sometimes develops into pneumonia. Calluses of the nose and footpads and neurologic symptoms may also occur. Humans can contract Canine Distemper, but it does not cause any illness. Treatment is symptomatic and supportive. The best prevention for dogs is vaccination.


Giardia are single-celled protozoal organisms that can cause intestinal infection in dogs. Although rare, Giardia can be passed to humans. Dogs in group settings, like kennels, shelters, or daycare, are most commonly affected. Giardia have two forms: the trophozoite and the cyst. The trophozoite is the parasitic form that lives within the host (dog), swimming around and attaching to the intestine. The cyst is the contagious form and lives in the environment.

Symptoms include continual or intermittent diarrhea and occasional vomiting. In many cases, there are no symptoms. Diagnosis used to be difficult, but in recent years, an in-house test was created making the process easier. The most successful treatment includes a broad spectrum dewormer prescribed by a veterinarian. Because cysts can stick to the infected dog's fur, they can be a source of re-infection. So a bath should be given during the course of treatment. Environmental decontamination is also recommended. To help prevent the spread of Giardia cysts, prompt and frequent removal of feces and disinfection, limits environmental contamination. Cysts are inactivated by most quaternary ammonium compounds, steam, and boiling water.

Kennel Cough

Canine Infectious Tracheobronchitis, commonly referred to as Kennel Cough, is another highly contagious disease. Exposure to a number of viral and bacterial organisms can cause Kennel Cough. This condition typically affects dogs in group settings like kennels and shelters. An infected dog sheds infectious bacteria and/or viruses in respiratory secretions. These secretions become aerosolized and float in the air where they can be inhaled by a healthy dog.

Symptoms include a characteristic harsh, hacking cough. This cough usually doesn't last long and may not require treatment. Uncomplicated Kennel Cough may last about a week or two. It entails frequent coughing fits, but otherwise, the dog acts and feels fine. Sometimes the cough can progress to life-threatening pneumonia. Symptoms, in this case, may include poor appetite, fever and listlessness. Diagnosis is usually made using history and symptoms. Radiographs may be taken to rule out pneumonia. Good nutrition and hygiene may shorten the dog's recovery. In more severe cases of Kennel Cough, antibiotics and cough suppressants may be helpful. The best prevention is vaccination.


Canine Parvovirus, also known as parvo, is a highly contagious virus that mainly affects young dogs. It is a common cause of acute gastrointestinal illness. If left untreated it can be fatal. Parvo is shed in the feces of infected dogs within four to five days of exposure, throughout the period of illness, and up to two weeks after clinical recovery. Puppies and young adult dogs that have not been fully vaccinated are most at risk.

Symptoms may include depression, lack of appetite, dehydration, and fever. As the condition worsens, vomiting and bloody diarrhea develop, usually within 24 to 48 hours. Severely affected dogs may show signs of shock, sepsis, and even death. Diagnosis is based on history and symptoms. There is also an in-house test that can help detect exposure to the virus. Treatment is supportive and symptomatic. The best prevention is vaccination and avoiding exposure of incompletely vaccinated dogs to unvaccinated dogs. Because parvovirus can remain viable in the environment for up to two months, disinfectants with oxidizing activity such as accelerated peroxide compounds or sodium hypochlorite, are recommended.


Ringworm is an infection of skin, hair, or nails caused by a type of fungus known as a dermatophyte. Ringworm is zoonotic, meaning, it can be passed to humans. Infection can come from direct contact with an infected symptomatic animal, direct contact with an asymptomatic carrier, or contact with spores in the environment. Infection is transmitted when spores bind to irritated skin. Skin lesions typically appear one to three weeks after exposure.

Infected dogs usually develop bald, scaly patches with broken hairs. They may also develop acne-like bumps on the skin. The most common sites affected by Ringworm are the face, ear tips, tail, and feet. Ringworm is diagnosed by fungal culture, examination with an ultraviolet lamp, and direct microscopic examination of hair or skin scale. Ringworm infections often clear on their own. But, some dogs may need treatment. Medicated shampoos and dips, and anti-fungal medication, may help to speed recovery. They may also prevent further spread of the fungus in the environment. Diluted bleach can be used to clean the pet's environment. If you suspect you or someone in your household has become infected with Ringworm, please contact your doctor for further instruction.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
Article Sources
The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Canine Distemper. American Veterinary Medical Association.

  2. Giardia and Pets. Centers for Disease Control and Prevention.

  3. Tracheobronchitis (Bronchitis) in Dogs. Merck Veterinary Manual.

  4. Canine Parvovirus. Merck Veterinary Manual.

  5. Ringworm (Dermatophytosis) in Dogs. Merck Veterinary Manual.