Canine Distemper Virus

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Different stages of the disease are associated with various clinical signs, usually involving some combination of the respiratory and/or gastrointestinal tract signs in the early stages, and the nervous system several weeks later. Not all stages occur in all dogs. Distemper is much less common than it was years ago, prior to the introduction of the distemper vaccination. The prognosis for dogs with distemper ranges from good to guarded. Some patients recover; some patients recover but have additional manifestations of the disease later in life; some dogs die from the disease or have such severe persistent signs that they must be euthanized.

Differential Diagnosis

Several diseases and disorders can appear similar to canine distemper.

The respiratory form of canine distemper must be differentiated from the following:

  • Kennel cough, or infectious tracheobronchitis, is a contagious respiratory disease of dogs that is manifested by coughing. This is a transient disease, and most dogs recover without severe complications.
  • Pneumonia due to other infections (bacterial, fungal) can present similarly to dogs with distemper.

    The gastrointestinal (GI) form of canine distemper must be differentiated from the following:

  • Other GI viral diseases including parvovirus and coronavirus
  • Bacterial enteritis including Campylobacter, Salmonella and Clostridia
  • Protozoal infections, specifically, Giardia
  • Ingestion of foreign bodies and toxins
  • Any non-infectious disorder that causes vomiting and diarrhea in dogs

    The central nervous system (CNS) form of canine distemper must be differentiated from the following:

  • Granulomatous meningoencephalitis is a progressive, inflammatory disease of the central nervous system of dogs. Many signs seen in this disorder may mimic the neurologic form of canine distemper.
  • Protozoal encephalitis is an inflammation of the brain, caused by one of the protozoal organisms (neosporosis, toxoplasmosis).
  • Cryptococcosis is a systemic fungal infection that affects particularly the respiratory and neurologic systems.
  • Lead poisoning commonly produces clinical signs that involve both the gastrointestinal tract and nervous system.
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    In-depth Information on Diagnosis of Canine Distemper

    Certain diagnostic tests must be performed for a definitive diagnosis of canine distemper and to exclude other disease processes that may cause similar symptoms. A complete history (vaccination status, travel pattern, environment, etc.), description of clinical signs, and thorough physical examination are all important to obtaining a diagnosis.

    There are certain characteristic changes that may be apparent on the physical examination that lead to a presumptive diagnosis of canine distemper. These include the following:

  • Pitting and discoloration of the enamel (white surface coating) of the teeth
  • Presence of rhythmic jerking of a single muscle or a group of associated muscles, called tics or myoclonus
  • Abnormally thickened and hard foot pads
  • Inflammatory changes in the retinas of the eyes that are compatible with distemper

    The following tests are recommended to confirm a diagnosis:

  • A complete blood count (CBC) may reveal a mild lymphopenia (a decrease in the number of lymphocyte white blood cells), particularly during the early stage of infection. Occasionally, thrombocytopenia (decreased platelets) is seen also.
  • A biochemical profile is usually within normal limits, although it may reveal changes in kidney and/or liver enzymes, electrolytes, blood sugar, and protein levels, depending on the stage of disease and degree of severity of disease present.
  • A urinalysis is helpful in determining the level of hydration on the patient.
  • Chest and abdominal X-rays are an important part of any baseline work-up. They may be normal, they may show evidence of pneumonia, and they may help rule out other causes of similar clinical signs.

    Your veterinarian may recommend additional tests to exclude or diagnose concurrent conditions. These tests are not always necessary in every case; however, they may be of benefit in certain individuals and are selected on a case-by-case basis. These include the following:

  • The ultimate diagnosis is based on demonstration of viral antigens (proteins) in scrapings and body fluids such as conjunctival smears, transtracheal washings, urine sediment, buffy coat (layer of white blood cells formed after blood is spun down), and cerebrospinal fluid (CSF). Their absence does not rule out infection, however.
  • Analysis and testing CSF obtained from individuals exhibiting neurologic signs may be useful in diagnosing distemper. Microscopic analysis of CSF may show increased numbers of lymphocytes and protein. Detection of high antibody titers for distemper in the CSF can provide supportive evidence of an active infection. Comparing the antibody titers found in the CSF to antibody titers found in the serum (blood) may also help support the diagnosis of distemper.
  • The measurement of antibodies to the distemper virus in blood may be helpful. Dogs that are able to mount an antibody response to the virus usually have titers that increase over a 2- to 4-week time period. A single elevated antibody titer taken at the beginning of the illness may be difficult to interpret, because it could represent antibodies produced by prior vaccination.
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