Canine distemper is a viral disease. It affects domestic dogs and several species of wildlife such as raccoons, wolves, foxes and skunks. Canine distemper is contagious and has no known cure. In domestic dogs, young, non-vaccinated puppies are most susceptible to the disease. The virus belongs to the Morbillivirus class of viruses. This means it is a relative of the human measles virus.
SYMPTOMS AND TYPES
The infective virus can be found in secretions from the eyes and nose, and in urine and feces. It can therefore be spread in several ways – through the air during indirect contact (e.g. utensils, bedding), or direct contact with an infected animal. The time between infection and disease is 14 to 18 days, however, a fever may occur from 3 to 6 days after infection. Initially, the virus attacks the dog’s tonsils and lymph nodes. It replicates itself in these tissues for approximately 7 days and then attacks the nervous, respiratory, urogenital and gastrointestinal systems.
Initial symptoms of canine distemper include an elevated body temperature (above 103.5°F or 39.7°C), reddened eyes and a watery discharge from the nose and eyes. More developed symptoms include lethargy, tiredness and eventually anorexia. At this stage, coughing, vomiting and diarrhea may also occur. In the extreme stages of the disease, the virus affects the other bodily systems, particularly the central nervous system (CNS); the dog may begin having seizures, fits and paralysis.
Some strains of the virus can cause an abnormal enlargement or thickening (hyperkeratosis) of the foot pads and sometimes the nose . This symptom gives canine distemper its colloquial name of “hard pad disease”.
In animals with weak or compromised immune systems, death can result 2 to 5 weeks after the initial infection.
CAUSES
If live vaccines are not properly attenuated, or the incorrect type of vaccine is administered, this can
inadvertently transmit the disease to the animal, however, this is a rare route of transmission. If your dog’s respiratory or gastrointestinal systems have a bacterial infection, this can increase his vulnerability to distemper. In particular, non-immunized dogs that have contact with an infected animal or its environment (e.g. bedding, bowls, toys) are at great risk of contracting the disease.
DIAGNOSIS
Diagnosis of canine distemper requires biochemical tests and urine analysis. These may reveal a reduced number of lymphocytes (white blood cells that function in the immune system), a disease called “lymphopenia”.
Blood serology tests may identify positive antibodies produced by the immune system to combat the virus, however, this test cannot distinguish between antibodies that have occurred due to vaccination or exposure to a virulent virus. Viral antigens (proteins produced by the virus) may be detected in urine or vaginal tests.
Skin associated with hair, mucous (from the nose) and the epithelium of the foot-pad may also be tested for antibodies.
If it is suspected that the infected animal has developed pneumonia, radiographs may be used. Brain lesions can be detected by computerized axial tomography (CAT) and magnetic resonance imaging (MRI) scans.
TREATMENT
There is no cure for canine distemper and there are no antiviral drugs effective in treating the disease. Treatment for the disease is therefore directed toward alleviating the symptoms. For example, intravenous fluids may be used to to support an animal that has become anorexic, dehydrated or has diarrhea. Regular clearing of discharge from the eyes and nose may be required. Antibiotics should control the symptoms caused by secondary bacterial infections, and phenobarbitals and potassium bromide may be required to control convulsions and seizures. The CNS should also be monitored for seizures and related neural disturbances.
LIVING AND MANAGEMENT
A dog’s prognosis for surviving canine distemper is dependent on several factors such as the strain of the virus and the capability of the dog’s immune system. Recovery is possible, although seizures and other fatal CNS events can occur 2 to 3 months after recovery. Fully recovered dogs are not infective – they do not spread or carry the virus.
PREVENTION
To prevent canine distemper, ensure your dog is routinely vaccinated and immediately isolated from any infected animals. New-born pups have under-developed immune systems and therefore particular care must be taken not to expose them to the virus. The virus does not survive in the environment for more than a few hours at room temperature. It is destroyed by routine cleaning with disinfectants, detergents, or drying. However, it can survive for several weeks in shady environments at temperatures slightly above freezing. It can also persist longer in serum and tissue debris.