By Dr. Becker
Idexx Reference Laboratories has developed a canine distemper virus (CDV) test that determines whether a dog has the virus even though he's been recently vaccinated against it.
The reason for the test, according to Idexx, is to accurately diagnose dogs recently adopted from kennels and shelters who develop CDV symptoms within days of arriving at their new homes.
It's important for owners of recently adopted dogs and their vets to determine whether the new pet has distemper in spite of having been vaccinated.
Early diagnosis of distemper versus other less serious conditions can help pet owners and veterinarians be better informed and forewarned about possible neurologic problems down the road, as well as what types of treatment and therapy are most appropriate.
Canine Distemper Virus (CDV)
Canine distemper is one of the most dangerous infectious diseases in dogs.
CDV is second only to rabies in worldwide mortality rates.
CDV is actually closely related to human measles, and there was a time when puppies were given the measles vaccine to protect against distemper.
Despite its distinction as a canine virus, it infects not only puppies and unvaccinated dogs, but also other land-dwelling carnivores and marine mammals as well.
The severity of the infection depends on the strain, the host, and the animal's immune response and vaccination status.
Transmission of the virus happens primarily through exposure to respiratory secretions from infected dogs or by exposure to infected wildlife. It can also be spread though exposure to other bodily secretions like urine.
Viral shedding begins about seven days after infection and can continue for up to three months.
Fortunately, vaccines for canine distemper have dramatically reduced incidence of the disease in vaccinated adult dogs. Today, the disease is most common in locations with significant unvaccinated populations of dogs, or in wildlife reservoirs.
In the U.S., most victims today are puppies.
Often in the early stages of CDV infection there are no observable signs of illness, though the dog may have fever and a low white blood cell count.
If the dog's immune response is inadequate, eventually the virus moves to epithelial tissues and the central nervous system, and then one of three things typically occurs – the infection resolves on its own, the dog becomes a silent carrier, or the infection becomes systemic.
Silent carriers can infect other dogs. They may also develop thickening of the footpads and neurologic symptoms later on.
If a dog's immune system isn't adequate to defend against the infection, acute systemic illness will develop within a couple of weeks after exposure to the virus. Early symptoms can include:
- Mild conjunctivitis (eyelid swelling)
- Discharge from the nose and eyes
- Loss of appetite
As the infection progresses, there will be upper respiratory symptoms like coughing, shortness of breath and even pneumonia.
Gastrointestinal symptoms like vomiting, diarrhea with or without blood, and severe dehydration typically follow respiratory illness.
The severity of symptoms depends on the dog's immune response. In its mildest form, CDV is often confused with kennel cough. At the other end of the spectrum is sudden death as a result of the infection.
Some dogs who recover from systemic illness will go on to develop neurologic symptoms within one to two weeks. This can also occur around the same time in dogs who exhibited no symptoms of systemic illness.
In puppies infected in the womb or right after birth, there can be immediate, acute neurologic signs with no other symptoms present.
Neurologic impairment can also appear alongside systemic illness, or take months or even years to develop.
Symptoms depend on the area of the nervous system involved and can include:
- Involuntary muscle twitching
- Seizure episodes sometimes called 'chewing gum fits'
- Lack of coordination of muscle movements
- Partial or complete paralysis of limbs
- Brain disturbances and eye problems
Unfortunately, neurologic symptoms are typically not reversible and are often progressive.
Preventing Canine Distemper
Insuring your dog receives her puppy shots in a timely manner is the best way to prevent CDV as well as the other potentially fatal canine diseases for which we administer core vaccines.
The new American Animal Hospital Association (AAHA) vaccination guidelines now recommend re-vaccination for distemper every three years. However, the AAHA also makes note that CDV vaccines are known to provide protection against the disease for at least five years.
My recommendation for healthy dogs who were vaccinated by 16 weeks of age is to have your dog titered to test her immunity to the core diseases (distemper, parvo and, if indicated, adenovirus) every three to five years. Re-vaccinate only if for some reason the titer indicates your pet is not sufficiently protected against a particular disease – and allow only re-vaccination for the specific disease in question versus a combo vaccine.
The second thing I recommend, as always, is that you make sure your pet's immune system is balanced and functional. The best way to accomplish this is by feeding your carnivorous canine species-appropriate nutrition. Keep her well-exercised and at a healthy weight.
It's also very important that your pet's immune function isn't compromised by unnecessary vaccinations, overprescribed veterinary drugs and excessive use of heartworm and flea/tick preventives.