How Distemper Affects Dogs
Canine distemper is a highly contagious and potentially deadly viral disease that primarily affects young dogs between 3 and 6 months of age. It also can affect wildlife. The virus usually settles in a dog’s respiratory tract first, replicates there and then spreads through the lymphatic system and the blood to other parts of the body. Once an animal is exposed to the canine distemper virus (by inhaling respiratory secretions or coming into direct contact with infected saliva, urine or fecal matter), the virus replicates in cells lining the respiratory tract. Eventually, virus-infected cells spread throughout the body, especially to the lymph nodes and other lymphoid tissue. Cells of the skin, gastrointestinal tract, urogenital tract and central nervous system are commonly infected as well. Neurological signs usually do not begin until at least several weeks after the respiratory and gastrointestinal symptoms are resolved.
Symptoms of Distemper in Domestic Dogs
Distemper tends to cause multisystemic signs in domestic animals. “Multisystemic” means signs throughout the dog’s body, instead of only local symptoms. Affected dogs typically have a fluctuating fever accompanied nasal and ocular (eye) discharge, coughing, diarrhea, vomiting, inappetance, lethargy and hardening and thickening of the nasal planum and foot pads. Depending upon the dog’s level of immune system development, central nervous system signs may follow. Affected dogs are also susceptible to developing secondary opportunistic bacterial infections.
Owners of dogs with distemper may notice some or all of the following symptoms:
- Fever, which may wax and wane
- Nasal discharge
- Ocular (eye) discharge
- Lack of appetite (inappetance; anorexia)
- Weight loss
- Difficulty breathing (dyspnea)
- Hard, thickened foot pads (hyperkeratosis of the hairless part of the foot)
- Hard, thickened nasal planum (hyperkeratosis of the hairless part of the nose)
- Muscle spasms or twitching (chorea)
- Inability to walk in a straight line
- Profuse salivation
- Abnormal jaw movements
- Retinal atrophy
- Hypoplasia of the tooth enamel (“distemper teeth”)
- Chronic encephalitis
- Pneumonia (interstitial)
- Demyelinating encephalomyelitis
- Seizures, convulsions
The central nervous system signs that often follow systemic illness are especially common in wild carnivores affected by distemper. As a dog’s immune system becomes weakened by the distemper virus, opportunistic bacteria can cause secondary bacterial infections as well.
Symptoms of Distemper in Wild Animals
The canine distemper virus can infect wild animals as well as domestic ones. Distemper has been reported in coyotes, foxes, ferrets, skunks, raccoons, lions and other wild cats. Wild carnivores seem to develop abnormal neurological and behavioral signs more frequently than do infected domestic dogs. In some cases, affected wild animals become quite aggressive, disoriented and have an apparent lack of fear, suggestive of rabies. Other common neurological signs in wild animals are convulsive movements of the head and paws and aimless wandering. The animal may develop a purulent conjunctivitis and nasal discharge (puss discharge from the eyes and nose), and its eyelids may be adhered together with a crusty exudate. They may have diarrhea, labored breathing and an overall unkempt appearance, and they often become severely dehydrated. Weakness and emaciation have been associated with end-stage cases of distemper in wildlife.
Dogs At Increased Risk
Distemper targets young puppies between 2 and 6 months of age, although dogs of any age can be affected. There is no recognized sex or breed predisposition for this disease. Unvaccinated animals, puppies born to a mother infected with the virus (transplacental infection) and young dogs going through periods of extreme stress or immunosuppression are at increased risk of developing clinical symptoms of distemper. Also, dogs that are exposed to wildlife may also have a heightened risk of contracting the disease.