Distemper in Dogs
by: Laura McLain Madsen DVM
What is distemper?
Distemper in dogs is caused by canine distemper virus (CDV), a virus which is related to the measles virus in people. Distemper infections can be fatal. As well as dogs, CDV also infects ferrets, foxes, wolves, bears, lions and Siberian tigers. The so-called “distemper” seen in domestic cats is actually caused by feline panleukopenia virus, a completely different virus. Thanks to wide-spread vaccination programs, veterinarians don’t see as many cases of dog distemper these days, but it was very common a few decades ago.
How is distemper in dogs transmitted?
Distemper virus particles are shed by an infected dog primarily through respiratory secretions (sneezing, coughing, nasal discharge). It can also be transferred across the placenta from a bitch to her puppies. Another dog coming into contact with the virus particles can become infected. Outside of the body the virus can only survive a few hours in warmer environments, but can survive for weeks in freezing temperatures.
Which dogs are at risk?
Puppies are most susceptible, especially between 3-6 months. A young puppy will receive some antibodies against the virus from its mother through the milk (colostrum), but those antibodies will diminish over time. If the puppy is exposed to the virus after the antibodies diminish, it is likely to become infected.
As well as puppies, any dog which has not been properly immunized is at risk of contracting distemper. The basic vaccines given to puppies and adult dogs (DHPP, DA2PPL, “five-way,” “seven-way,” etc.) protect against distemper, as well as canine parvovirus, another potentially fatal infection in dogs. Distemper outbreaks are seen in shelters, breeding kennels and puppy mills.
What are the symptoms of dog distemper?
Canine distemper virus can cause a range of symptoms, both short-term and long-term. About a week after infection, dogs will show a fever. Within another week, the virus spreads to many organs and tissues in the body, including eyes, brain, lungs, intestines and skin. Symptoms vary quite a bit depending on the virus strain, age of the dog, and general immune system status of the dog.
Mild cases may only show decreased appetite, watery nasal discharge, and a mild cough. Severe cases may show fever, severe nasal discharge, sneeze, cough, eye infections, diarrhea, vomiting, crusty nose and paw pads (“Hard Pad Disease”), dehydration, and death.
Neurologic symptoms can be seen at the same time as the severe respiratory and gastrointestinal symptoms, or can develop weeks to months later. Neurologic symptoms include tremors, myoclonus (persistently tense and twitching muscles), seizures (especially seizures of the face muscles called “chewing gum seizures”), weakness, loss of equilibrium and neck pain.
A syndrome that is occasionally seen in puppies infected with CDV is called hypertrophic osteodystrophy (HOD). In HOD, the virus attacks the bones, especially near the growth plates of the leg bones in large-breed puppies. The bones will be swollen and painful and the puppies usually have a fever and loss of appetite.
Distemper virus also attacks the developing teeth, so a puppy which recovers from distemper will likely have abnormal or missing teeth and fragile tooth enamel on the adult teeth once they grow in. Abnormal enamel makes the dogs more prone to tartar build-up and broken teeth.
In some dogs which appear to have fully recovered from infection, the virus can lie dormant in the central nervous system and cause neurologic problems later in life (“Old Dog Distemper” or “Old Dog Encephalitis”).
How is distemper in dogs diagnosed?
Diagnosis can sometimes be tricky. Your vet may make a presumptive diagnosis based on classic symptoms (coughing, sneezing, crusty paw pads). Your veterinarian may recommend various diagnostic tests including:
• Complete blood count (CBC): may show a low level of white blood cells due to destruction by the virus, or an elevated white count if secondary bacterial infection is present.
• Blood chemistry panel to check blood sugar, electrolytes, kidney function and liver function.
• Chest x-rays to look for pneumonia.
• Broncho-alveolar lavage or tracheal wash to obtain samples for bacterial culture if pneumonia is present.
• Spinal tap and CSF (cerebrospinal fluid) analysis if symptoms of encephalitis are present.
• Specific blood tests through a referral laboratory to detect antibodies against the virus, or to detect the virus itself. There can be both false positive (a positive test result in a dog which does not have distemper) and false negative (a negative test result in a dog which is actually infected) results.
• Immunohistochemistry: a specialized test performed on tissue samples, such as a paw pad biopsy or autopsy samples.
Is distemper contagious to other pets or people?
Canine distemper is highly contagious to dogs and ferrets. All puppies and young ferrets should be immunized between 8-16 weeks of age to protect them. Canine distemper is not contagious to cats or people.
Dogs should be isolated for 4-6 weeks after recovery from distemper to avoid contagious spread to other dogs in the community. Areas where the infected puppy has been housed should be thoroughly cleaned and disinfected. Most disinfectants will kill the virus, including bleach (Clorox®) diluted one part bleach to thirty parts water. (Use a regular cleanser first to remove any debris, and then allow the diluted Clorox® to sit for ten minutes before rinsing.)
What is the treatment for distemper?
Unfortunately no antiviral drugs are effective against distemper in dogs, so treatment is mainly supportive. Secondary infections (bacterial infections that develop on top of the viral infection) are controlled with broad-spectrum antibiotics such as ampicillin, enrofloxacin (Baytril®), amoxicillin/clavulanic acid (Clavamox®), metronidazole (Flagyl®), azithromycin (Zithromax®) and cefazolin. (Note: Baytril® is technically not recommended for use in puppies due to a slight possibility of cartilage side-effects, but many veterinarians routinely use it in cases of life-threatening infections, when the benefit outweighs the risk.)
Intravenous fluids are given to prevent or correct dehydration. If pneumonia is present, treatments may include oxygen therapy (delivered through an air-tight cage, mask, or nostril tube), nebulization (having the puppy breathe in a vapor of saline and antibiotics), and coupage (gently thumping on the pup’s chest to loosen mucus). High-quality nutrition is important.
Other medications that may be needed on a case-by-case basis include anti-nausea drugs like maropitant (Cerenia®), anticonvulsants like phenobarbital or diazepam (Valium®), corticosteroid anti-inflammatory drugs like prednisone, and anti-arrhythmic drugs like procainamide or mexilitine for myoclonus.
What is the prognosis?
The prognosis for distemper in dogs is guarded. Even with ideal treatment with hospitalization, IV fluids and supportive care, some dogs may deteriorate and die. If the dog survives the initial bout with distemper, it is impossible to predict when or if neurologic symptoms will develop. If neurologic symptoms are present they are unlikely to improve, although dogs can learn to adjust to myoclonus or equilibrium problems.
How can I prevent my dog from getting distemper?
All puppies should receive distemper-parvo immunizations. Typically the vaccines are given at 8, 12 and 16 weeks of age, with a booster one year later and then periodically throughout the dog’s life.
Unfortunately, in rare cases, vaccination with a MLV distemper vaccine (modified live virus; the type that is primarily used in veterinary medicine) can cause symptoms of distemper, including HOD (particularly in Weimaraners) and neurologic symptoms. These are very rare side effects: the risk of complications from vaccination is less than the risk of acquiring a fatal infection from being unvaccinated. If you are concerned about the risks, ask your vet about an alternative recombinant vaccine (Recombitek® by Merial).
Distemper in dogs isn’t nearly as common as it used to be, but regular immunizations of all puppies and dogs are still necessary to prevent distemper outbreaks.
Return from Distemper in Dogs to Dog Health