Canine distemper is a highly contagious, systemic, viral disease of dogs worldwide.
The disease is more typically reported in young puppies (3 to 6 months of age) or unvaccinated or immunocompromized adults.
Neurological signs may be present without other clinical symptoms. Adult dogs often present with progressive tetraparesis, altered mental status and blindness. Optic neuritis can occur, and affected dogs can show signs of acute blindness, circling and seizures.
Long-term symptoms include odontodystrophy (enamel hypoplasia), hyperkeratosis of the footpads ('hardpad' disease) and epithelium of the nasal plane may also be observed. In young dogs following post-distemper infection, dental impaction, partial eruption, oligodontia, enamel hypoplasia and dentin hypoplasia may be observed.
Chronic distemper encephalitis is marked by ataxia, compulsive movements such as head pressing or continual pacing, and incoordinated hypermetria, may be seen in adult dogs without a history of signs related to systemic canine distemper. The development of neurologic signs is often more progressive. Although canine distemper antigen has been detected in the brain of some dogs with ODE by fluorescent antibody staining, dogs with ODE are not infectious and replication-competent virus has not been isolated.
Thymic atrophy is a consistent postmortem finding in infected young puppies. Depending on the degree of secondary bacterial infection, bronchopneumonia, gastroenteritis, and skin pustules may also be present.
Histologically, canine distemper virus produces necrosis of lymphatic tissues, interstitial pneumonia, and cytoplasmic and intranuclear inclusion bodies in respiratory, urinary, and GI epithelium. Lesions found in the brain of dogs with neurologic complications include neuronal degeneration, gliosis, demyelination, perivascular cuffing, nonsuppurative leptomeningitis, and intranuclear inclusion bodies predominately within glial cells.
Diagnosis is usually established by a combination of clinical signs augmented with fluorescent antibody staining, ELISA, PCR and necropsy with histopathology.
No single treatment is specific or uniformly successful. Dogs may recover completely from systemic manifestations, but good nursing care is essential. Because of the highly infectious nature of the virus, multiple pup households hold a high risk of spreading to uninfected pups, and euthanasia should be considered to minimize further spread of the disease.
Vaccinations are essential to minimize outbreaks, especially in kennels, pet shops and large dog populations.
Canine distemper virus is not resistant to disinfectants, but is easily transmitted through aerosols and has a wide host range. Wild canids are thought to act as reservoirs for fresh outbreaks of the disease.
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