Understanding canine distemper virus and increased risk during summer

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With longer days, warmer weather and a little more breathing room in the schedule, summer often feels like the perfect time to bring home a new dog.

At the same time, summer often brings a surge in dog shelter populations. Waves of spring-born puppies, combined with dogs of all ages, can overwhelm shelter space and force animals into close-contact conditions.

The close proximity can increase exposure to harmful diseases such as canine distemper virus, CDV, said experts with the Texas A&M Veterinary Medical Diagnostic Laboratory, TVMDL. Even with effective vaccines available, this highly contagious virus can sweep through shelters, posing a serious threat to vulnerable dogs waiting for a new home.

Understanding how this virus spreads, how it is diagnosed and the importance of veterinary guidance can avert devastating outcomes.

What is distemper?

Distemper can affect the respiratory, gastrointestinal and immune systems, and can sometimes cause neurological problems. This virus primarily affects dogs but can also infect other species, including ferrets, raccoons and wild cats such as mountain lions.

"It may start as mild respiratory signs, but it can explode into severe pneumonia and other issues," said TVMDL veterinary diagnostician Cathy Campbell, DVM. "Once it gets into the lymphatic tissue, which is the tonsillar area, then it's kind of like the virus is on a tissue superhighway from there, and it goes everywhere within the body."

With no cure and a highly contagious nature, canine distemper can spread rapidly and cause devastating, often life-threatening illness. Some dogs recover, but more than 50% do not survive. Dogs that do recover may later develop neurologic complications, including persistent rhythmic tremors known as chorea.

How it spreads

Like most contagious diseases, canine distemper spreads through airborne droplets, allowing it to move quickly between dogs. In kennels, oftentimes the virus can spread before a dog shows signs of infection.

"It's a little hard to control because you can have shedding of the virus before the onset of clinical signs," Campbell said. "And by the time you see clinical signs, it's going everywhere."

CDV is easily transmitted through respiratory secretions, so coughing, sneezing or even barking can release the virus into the air. It can also spread through direct contact with bodily fluids, such as ocular discharge and urine, as well as contaminated items like food bowls and bedding.

It's important to consider that adult dogs can also get the virus. Even after a complete puppy vaccination series, it's advised for dogs to get booster vaccinations every one to three years.

However, puppies younger than four months are the most vulnerable to CDV because their immune systems are still developing, and antibody protection from their mother fades before they are fully vaccinated.

"When you get a new puppy, you want to share this puppy and socialize this puppy," Campbell said. "But you have to be prudent about where it's exposed before they complete their series of vaccinations. For example, I don't recommend taking them to dog parks right away."

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Recognizing clinical signs

For pet owners, recognizing early signs of illness is critical. Distemper can initially look like other common diseases like parvovirus, kennel cough or pneumonia, which makes awareness especially important.

In addition to fever, lethargy, decreased appetite, coughing and sneezing, some other common signs include:

• Nasal discharge—clear to thick, may become crusty
• Difficulty breathing
• Pneumonia
• Ocular discharge (watery to pus-like)
• Vomiting
• Diarrhea
• Thickened footpads—"hard pad disease."

As the disease progresses, more severe neurological signs may develop, including:

• Muscle twitching
• Head tilt
• Tremors
• Seizures
• Paralysis

"Since the early signs of distemper can mimic other diseases, it is important to consider diagnostic testing from the initial onset instead of waiting to 'see how things go,'" Campbell said.

Protecting dogs from distemper

Even though there is no cure for CDV, the disease is very preventable.

Puppies should receive a full vaccine series starting at 6 to 8 weeks of age, followed by boosters as recommended by a veterinarian.

"No vaccine is 100% guaranteed to get a response from the immune system, but it has allowed us to manage this disease quite well and protect the vast majority of dogs," Campbell said.

Pet owners can also reduce risk by:

• Avoiding high-risk environments for unvaccinated puppies.
• Confirming vaccination policies at boarding or daycare facilities.
• Limiting exposure to unknown animals.
• Consulting a veterinarian before traveling or socializing.

Why testing matters

Diagnostic testing helps veterinarians identify the virus, rule out other illnesses, and make informed decisions about care and infection control. Accurate diagnosis is essential.

"Just because a dog has a snotty nose and goopy eyes doesn't always mean they have distemper," Campbell said. "And that's why we test to rule out."

TVMDL offers several options to assist veterinarians in diagnosing canine distemper:

• PCR testing: Detects viral genetic material. Results may reflect vaccination or natural exposure to the viruses.
• Antibody testing: Measures the body's immune response to distemper.
• Additional differentiation testing: Helps distinguish vaccine strain from wild-type virus when needed.
• Respiratory disease panel, PCR: Detects distemper along with other common respiratory pathogens using swab or tissue samples.
• Testing strategy may vary depending on the stage of disease and recent vaccination history.

Ensuring a safe start in a new home

While summer often marks a time when dogs are welcomed into new homes, it also creates an environment where disease can spread more easily.

With CDV posing a serious threat in high-risk environments, veterinarians play a critical role in guiding prevention and reducing risk. Following their recommendations can help ensure that bringing home a new canine companion is the start of a healthy future.

At TVMDL, providing reliable diagnostic support is part of that mission by helping ensure that when distemper is suspected, answers are clear, timely and actionable.

Key concepts

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Provided by Texas A&M University