CANINE DISTEMPER

Canine distemper is a very serious viral disease that affects animals in the families Canidae,Mustelidae, Mephitidae, Hyaenidae, Ailuridae, Procyonidae, Pinnipedia, some Viverridae and Felidae(though not domestic cats; feline distemper or panleukopenia is a different virus exclusive to cats). It is most commonly associated with domestic animals such as dogs and ferrets, although it can infect wild animals as well. It is a single-stranded RNA virus of the family paramyxovirus, and thus a close relative ofmeasles and rinderpest. Despite extensive vaccination in many regions, it remains a major disease of dogs.

INFECTION

Puppies from three to six months old are particularly susceptible. Canine distemper virus (CDV) spreads through the aerosol droplets and through contact with infected bodily fluids including nasal and ocular secretions, feces, and urine 6–22 days after exposure. It can also be spread by food and water contaminated with these fluids. The time between infection and disease is 14 to 18 days, although there can be a fever from three to six days postinfection. 

Canine distemper virus tends to orient its infection towards the lymphoid, epithelial, and nervous tissues. The virus initially replicates in the lymphatic tissue of the respiratory tract. The virus then enters the blood stream and infects the lymphatic tissue followed by respiratory, Gastrointestinal,urogenital epithelium, the Central Nervous System, and optic nerves. Therefore, the typical pathologic features of canine distemper include lymphoid depletion (causing immunosuppression and leading to secondary infections), interstitial pneumonia, encephalitis with demyelination, andhyperkeratosis of foot pads.

The mortality rate of the virus 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 do develop distemper encephalomyetilis, vestibular diseasemay present. Around 15% of canine inflammatory central nervous system diseases are a result of CDV.

DIAGNOSIS

The above symptoms, especially fever, respiratory signs, neurological signs, and thickened footpads found in unvaccinated dogs strongly indicate canine distemper. However, several febrile diseases match many of the symptoms of the disease and only recently has differing between canine hepatitis, herpes virus, parainfluenza and leptospirosis been possible. Thus, finding the virus by various methods in the dog's conjunctival cells gives a definitive diagnosis. In older dogs that develop distemper encephalomyetilis, diagnosis may be more difficult since many of these dogs have an adequate vaccination history. 

The most reliable test to confirm distemper is a Brush Border slide/smear of the bladder transitional epithelium of the inside lining from the bladder, stained with Dif-Quick. These cells will always have inclusions. Inclusions in these cells which will stain a carmine red color and be para nuclear in the cytoplasm of infected cells. About 90% of the bladder cells will be positive for inclusions in the early stages of distemper. This is good for at least the first 21 days from onset of the disease. After this point, it gets harder to detect as the disease progresses further in the stages and the physical clinical signs will become quite obvious.

PREVENTION

There exist a number of vaccines against canine distemper for dogs (ATCvet code: QI07AD05 and combinations) and domestic ferrets(QI20DD01), which in many jurisdictions are mandatory for pets. The type of vaccine should be approved for the type of animal being inoculated, or else the animal could actually contract the disease from the vaccine. A dog who has eaten meat infected with Rinderpest can also sometimes receive temporary immunity. Infected animals should be quarantined from other dogs for several months due 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.