Affects: Dogs
Canine distemper (CDV) (sometimes termed "footpad disease") is a viral disease that affects a wide variety of mammal families, including domestic and wild species of dogs, coyotes, foxes, pandas, wolves, ferrets, skunks, raccoons, and felines, as well as pinnipeds, some primates, and a variety of other species. CDV does not affect humans.
In canines, CDV affects several body systems, including the gastrointestinal and respiratory tracts, the spinal cord, and the brain. Common symptoms include high fever, eye inflammation and eye/nose discharge, labored breathing and coughing, vomiting and diarrhea, loss of appetite and lethargy, and hardening of the nose and footpads. The viral infection can be accompanied by secondary bacterial infections and can eventually present serious neurological symptoms.
Canine distemper is caused by a single-stranded RNA virus of the family Paramyxoviridae (the same family of viruses that causes measles and mumps in humans). The disease is highly contagious via inhalation. Morbidity and mortality may vary greatly among animal species, with up to 100% mortality in unvaccinated populations of ferrets. In domestic dogs, while the acute generalized form of distemper has a high mortality rate, disease duration and severity depend mainly on the animal's age, immune status, and the virulence of the infecting strain of the virus. Despite extensive vaccination in many regions, it remains a major disease in dogs and was the leading cause of infectious disease death in dogs prior to a vaccine becoming available.
Clinical Signs: In dogs, signs of CDV vary widely, from no signs to mild respiratory signs indistinguishable from kennel cough to severe pneumonia with vomiting, bloody diarrhea, and death.
Commonly observed signs are a runny nose, vomiting and diarrhea, dehydration, excessive salivation, coughing and/or labored breathing, loss of appetite, and weight loss. If neurological signs develop, incontinence may ensue. Central nervous system signs include a localized involuntary twitching of muscles or groups of muscles, seizures with salivation, and jaw movements commonly described as "chewing-gum fits," or more appropriately as "distemper myoclonus." As the condition progresses, the seizures worsen and progress to grand mal convulsions, followed by the death of the animal. The animal may also show signs of sensitivity to light, incoordination, circling, increased sensitivity to sensory stimuli such as pain or touch, and deterioration of motor capabilities. Less commonly, they may lead to blindness and paralysis. The length of the systemic disease may be as short as 10 days, or the start of neurological signs may not occur until several weeks or months later. Those few that survive usually have a small tic or twitch of varying degrees of severity. With time, this tic usually diminishes somewhat in its severity.
Diagnosis: The above signs, especially fever, respiratory signs, neurological signs, and thickened footpads, occurring in unvaccinated dogs strongly indicate CDV. However, several febrile diseases match many of the signs of the disease and only recently has distinguishing between canine hepatitis, herpes virus, parainfluenza, and leptospirosis been possible. Thus, finding the virus by various methods in the dog's conjunctival cells or foot pads gives a definitive diagnosis. In older dogs that develop distemper encephalomyelitis, diagnosis may be more difficult, since many of these dogs have an adequate vaccination history.
An additional test to confirm distemper is a brush border slide of the bladder transitional epithelium of the inside lining from the bladder, stained with Diff-Quik. These infected cells have inclusions which stain a carmine red color, found in the paranuclear cytoplasm. About 90% of the bladder cells will be positive for inclusions in the early stages of distemper.
Treatment: No specific treatment for the CDV is known. As with measles, the treatment is symptomatic and supportive. Care is geared towards treating fluid/electrolyte imbalances, neurological symptoms, and preventing any secondary bacterial infections. Examples include administering fluids, electrolyte solutions, analgesics, anticonvulsants, broad-spectrum antibiotics, antipyretics, parenteral nutrition, and nursing care.
Prevention: A number of vaccines against CDV exist for dogs (ATCvet code: QI07AD05 (WHO) and combinations) and domestic ferrets (QI20DD01 (WHO)), which in many jurisdictions are mandatory for pets. Infected animals should be quarantined from other dogs for several months owing to the length of time the animal may shed the virus. The virus is destroyed in the environment by routine cleaning with disinfectants, detergents, or drying. It does not survive in the environment for more than a few hours at room temperature (20–25 °C), but can survive for a few weeks in shady environments at temperatures slightly above freezing. It, along with other labile viruses, can also persist longer in serum and tissue debris.
Despite extensive vaccination in many regions, it remains a major disease of dogs.
To prevent canine distemper, puppies should begin vaccination at 6–8 weeks of age and then continue getting the "booster shot" every 2–4 weeks until they are 16 weeks of age. Without the full series of shots, the vaccination does not provide protection against the virus. Since puppies are typically sold at the age of 8–10 weeks, they typically receive the first shot while still with their breeder, but the new owner often does not finish the series. These dogs are not protected against the virus, so are susceptible to canine distemper infection, continuing the downward spiral that leads to outbreaks throughout the world.
Outcome: The mortality rate of CDV largely depends on the immune status of the infected dogs. Puppies experience the highest mortality rate, where complications such as pneumonia and encephalitis are more common. In older dogs that develop distemper, encephalomyelitis and vestibular disease may be present. Around 15% of canine inflammatory central nervous system diseases are a result of CDV.