Introduction:Canine distemper virus (CDV) can infect not only dogs, but wild canids (wolves, coyotes, foxes), exotic felids (lions, jaguars, cheetahs), and other animals (bears, skunks, raccoons, and ferrets). Canine breeds that seem to be more at risk include the Arctic breeds (Samoyeds, Malamutes, Huskies), Greyhounds, and Weimaraners. Among domestic dogs, the group most at risk is unvaccinated puppies.
Causative Agent: Distemper is caused by a virus of the Paramyxovirus family and is closely related to the virus that causes measles in humans.
Clinical Signs: Symptoms vary widely and are dependant on many factors. Lethargy, anorexia, fever, discharge from the eyes and/or nose, and coughing are common in mild cases. In more severe cases, the animal will often experience vomiting and diarrhea, straining to defecate, dehydration, and sudden death. Seizures, balance problems, weakness or paralysis, and involuntary twitching of the muscles are all possible and tend to worsen with time. Weeks to months after apparent recovery, some dogs will begin to have additional problems with the nervous system. There is no way to predict which dog will develop nervous system problems, but those that do usually have a much poorer outcome.
Disease Transmission: Natural infection is spread through respiratory secretions of infected animals. These infections can occur in many kennel situations. Transmission to the fetus through the placenta can occur even with mild or inapparent infections in the mother.
Diagnosis: A definitive (precise) diagnosis of CDV infection is challenging. Several specific tests have been developed for the detection of CDV to aid in the definitive diagnosis of the disease; however, a presumptive (preliminary) diagnosis is usually made based on history and symptoms of the animal. If an exact diagnosis is needed, samples can be taken and sent to a laboratory. These samples may include serum, biopsies, and cerebrospinal (spinal cord) fluid. While the samples are being evaluated by the laboratory, blood work and X-rays are often used to help put together a treatment plan, and supportive care should be started immediately.
Treatment: Treatment for CDV infection consists mainly of supportive care, because no specific therapy exists which will seek out and destroy the virus itself; the animalís own immune system must accomplish this task. Therapy includes antibiotic therapy to fight secondary infections (especially respiratory infections such as pneumonia), fluid therapy to correct dehydration, anti-emetic therapy to help alleviate vomiting, anti-convulsive therapy to aid in management of seizures and other neurologic problems, and occasionally, steroid therapy if swelling of the brain is thought to be a complication.
Prevention: Vaccination remains the most effective method of preventing CDV infection in dogs. A vaccine made for dogs from human measles virus is sometimes used as the very first vaccination in puppies 6-9 weeks of age. This vaccine gives protection at a time when the routine canine distemper vaccine often fails due to antibodies obtained from the motherís milk. This measles vaccine is not given to puppies older than 9 weeks of age. Healthy puppies and adults older than 9 weeks should receive a modified live virus (MLV) canine distemper vaccine. Most varieties of the MLV distemper vaccine involve a living virus that has been attenuated or altered to avoid causing the disease. However, in very rare circumstances have allowed these live viruses can revert to their infective forms and cause serious infection. For example, vaccination of female dogs during pregnancy or the first few days after delivery has resulted in distemper infection of the puppies. Also, puppies suffering from parvo or other serious infections should not be vaccinated against distemper with a living virus vaccine, because there have been cases of vaccine-caused infections reported. Only healthy puppies and adults should receive this vaccine. See A900 for additional information on passive immunity and MLV vaccines.