Viruses: Distemper Overview

Cause and Pathogenesis of Distemper:

The genus “Morbillivirus” in the family “Paramyxoviridae” causes dog distemper. This virus is similar to viruses that cause measles and rinderpest. Distemper in dogs is a contagious disease and usually spreads via the air, contact with and contamination caused by an affected dog. Dogs may shed the virus for quite some time after recovery.

The respiratory system is initially invaded by the virus; it replicates in lymphatic tissues of the respiratory system and then spreads to the whole tract, gastrointestinal system, genital system, and at last reaches the central nervous system (CNS) and optic nerves. Viremia or presence of the virus in the blood is very common; therefore a generalized spread of the virus is seen with severe leukopenia & immune suppression.

Puppy distemper requires immediate treatment, since their immature immune system may not be able to effectively fight the disease, particularly during age 3 to 6 months.

Signs and Symptoms:

Dogs that are age 2 – 6 months are more susceptible to distemper.  Distemper signs and symptoms include fever which  is the initial sign of distemper in dogs, which occurs in two different phases. Initially a fever persists for 3 – 6 days along with leukopenia and anorexia.

A second phase of the disease is associated with a persistent fever which usually lasts for a week or more. In this phase of distemper disease, along with fever, serous nasal discharge, ocular (eye) discharge and loss of appetite can be noticed. This phase is described as generalized distemper in dogs, which involves respiratory, gastrointestinal and nervous system problems

Secondary bacterial complications, acute encephalomyelitis (inflammation of the brain and spinal cord), and other systemic problems may be seen in severe cases.

Dog distemper is also called “Hard Pad Disease”, this is because of severe hyperkeratosis (thickening) of the footpads and epithelial (outer skin layer) tissues of the outer plane surface of nose.

A neurological form of distemper may cause distemper signs such as: 

• twitching of the muscles locally 
• partial or complete paralysis of the hind limbs
•  convulsions

The course or length of the disease is usually not more then 10 days, but once a dog shows nervous symptom signs, the disease may persists for several weeks or months.

Diagnosis:

A review of the course of the disease, signs and symptoms, history and pathogenesis (development) of the disease should be an initial step toward diagnosis. The involvement of various systems and laboratory tests may reveal progressive leukopenia.

Distemper in dogs should be differentiated from toxoplasmosis, coccidiosis, and if the dog has dual or two infections clinically. The disease may also be confused with leptospirosis and infectious canine hepatitis. The paramyxo virus can thus be isolated from blood and culturing can reveal the exact condition a dog may be experiencing. Other options for differentiation and confirmations are determining antibodies level & resistance tests too.

Treatment:

A viral infection cannot be specifically treated; therefore a line of treatment usually involves prevention of secondary bacterial complications, resolving symptoms an supportive therapy.

Secondary bacterial infections can be treated or prevented by antibiotic therapy. Antibiotics which are potentially broad spectrum should be preferred. Sensitivity tests should be conducted prior to administration.

Fluid therapy is a primary requirement for treating distemper in dogs. Balanced electrolytes with glucose can be administered to affected dogs to restore these levels in the body and to help to reduce the chance of the onset of the neurological form of this disease.

Distemper symptoms may be treated by antipyretics (drugs which reduce fever), pain killers, nasal preparations and sometimes anticonvulsant drugs are administered.

In any case, mild or severe a combination of treatment options is only effective.

In cases where severe neurological involvement is seen, treatment is usually not effective. Glucocorticoids, NSAIDS and immuno suppressants have been used but the prognosis in these types of cases is very low.

There is also a homeopathic remedy available for an added level of support for the immune, respiratory, digestive systems while helping to reduce fever and keep body temperature normal. The product, Vi-Pro Plus, contains Bryonia to help keep the respiratory system clear and Echinacea purp (long history of immune system support). The manufacturer is a good source of additional information on distemper and clinical information that supports the use of the product.

Prevention:

Canine distemper modified live vaccine (MLV) can be administered in puppies when they are of 6 weeks, and then repeated every 2 – 4 weeks until dog reaches to an age of 16 weeks. Annual revaccination is highly recommended for reasons if the neurological form of distemper in dogs is ever suspected.

Successful immunization is only possible if modified live vaccine (MLV) is not interfered by maternal antibodies, other vaccinations as that of measles virus vaccine alone etc.