Canine Distemper

Canine distemper is a contagious, incurable, often fatal, multisystemic viral disease that affects the respiratory, gastrointestinal, and central nervous systems. Distemper is caused by the canine distemper virus (CDV). Canine distemper occurs worldwide, and once was the leading cause of death in unvaccinated puppies. Widespread vaccination programs have dramatically reduced its incidence. CDV occurs among domestic dogs and many other carnivores, including raccoons, skunks, and foxes. CDV is fairly common in wildlife. The development of a vaccine in the early 1960s led to a dramatic reduction in the number of infected domestic dogs. It tends to occur now only as sporadic outbreaks. Young puppies between 3 and 6 months old are most susceptible to infection and disease and are more likely to die than infected adults. Nonimmunized older dogs are also highly susceptible to infection and disease. Nonimmunized dogs that have contact with other nonimmunized dogs or with wild carnivores have a greater risk of developing canine distemper. Infected dogs shed the virus through bodily secretions and excretions, especially respiratory secretions. The primary mode of transmission is airborne viral particles that dogs breathe in. Dogs in recovery may continue to shed the virus for several weeks after symptoms disappear, but they no longer shed the virus once they are fully recovered. It is possible for humans to contract an asymptomatic (subclinical) CDV infection. Anyone who's been immunized against measles (a related virus) is protected against CDV as well. Macrophages (cells that ingest foreign disease-carrying organisms, like viruses and bacteria) carry the inhaled virus to nearby lymph nodes where it begins replicating (reproducing). It spreads rapidly through the lymphatic tissue and infects all the lymphoid organs within 2 to 5 days. By days six to nine, the virus spreads to the blood (viremia). It then spreads to the surface epithelium (cell lining) of the respiratory, gastrointestinal, urogenital, and central nervous systems, where it begins doing the damage that causes the symptoms. Early symptoms include fever, loss of appetite, and mild eye inflammation that may only last a day or two. Symptoms become more serious and noticeable as the disease progresses. The initial symptom is fever (103ºF to 106ºF), which usually peaks 3 to 6 days after infection. The fever often goes unnoticed and may peak again a few days later. Dogs may experience eye and nose discharge, depression, and loss of appetite (anorexia). After the fever, symptoms vary considerably, depending on the strain of the virus and the dog's immunity. In utero infection of fetuses is rare, but can happen. This can lead to spontaneous abortion, persistent infection in newborn puppies, or the birth of normal looking puppies that rapidly develop symptoms and die within 4 to 6 weeks.