Canine Distemper

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 Basics

Overview

• Contagious disease that appears suddenly (acute) or over a moderate amount of time (known as “ subacute”), characterized by fever and a variety of signs involving the eyes, central nervous system, and respiratory, urogenital, and gastrointestinal tracts; often a fatal disease
• Caused by the canine distemper virus
• Affects many different species of the order Carnivora; mortality rate varies greatly among species

Signalment/Description of Animal
Species :

• Most species of the order Carnivora—including dogs, fox, wolves, hyenas, weasels, ferrets, mink, raccoons, skunks, and civets
• Large cats in Californian zoos and in Tanzania

Mean Age and Range : Young animals are more susceptible to infection than are adults

Signs/Observed Changes in the Animal

• Fever—first fever occurs 3 to 6 days after infection, may go undetected; second fever several days later (and intermittent thereafter),usually associated with discharge from the nose and eyes, depression, and lack of appetite (known as “ anorexia”)
• Gastrointestinal and/or respiratory signs follow, often enhanced by secondary bacterial infection
• Central nervous system signs—occur in many infected dogs; often, but not always, after generalized (systemic) disease; depends on the virus strain; either sudden (acute) gray or white matter disease (“gray matter” is the nerve tissue of the brain and spinal cord that contains the nerve cell bodies;  “white matter” is the part of the brain and spinal cord that contains nerve fibers covered with myelin, a fatty covering that increases conduction of nerve impulses)
• Gray-matter disease—affects the brain and spinal cord; may cause inflammation of the meninges (the membranes covering the brain and spinal cord; inflammation of the meninges known as “meningitis”), seizures, stupor, hysteria, and wobbly, incoordinated or “drunken” appearing gait or movement (known as “ ataxia”); dogs may die in 2 to 3 weeks, recover (associated with prompt immune response), or progress to white-matter disease  
• White-matter disease—variable signs of disease involving multiple locations of the central nervous system; commonly see weakness and wobbly, incoordinated or “drunken” appearing gait or movement (ataxia) secondary to spinal cord disease; occasionally may see twitching or contraction of a group of muscles (known as “myoclonus”); some dogs die 4 to 5 weeks after initial infection; some dogs may recover with minimal central nervous system injury Inflammation of the optic nerve (the nerve that runs from the back of the eye to the brain; condition known as “optic neuritis”) and lesions in the back of the eye (known as the “ retina”) may occur
• Hardening of the footpads (known as “hyperkeratosis”) and nose—some virus strains; but relatively uncommon
• Abnormal development of the enamel layer of the teeth (known as “ enamel hypoplasia”) after neonatal infection is common

Causes

• Canine distemper virus (closely related to the measles virus and the seal and dolphin distemper viruses)
• Incompletely altered, modified live canine distemper virus vaccines (rare)

Risk Factor : Contact of animals that have not been vaccinated or have not responded to vaccinations with animals that are infected with canine distemper virus (dogs or wild carnivores)

Treatment
Helath care

• Inpatient treatment in isolation, to prevent infection of other dogs
• Supportive treatment
• Intravenous fluids—cases with lack of appetite (anorexia) and diarrhea
• Once fevers and secondary bacterial infections are controlled, patients usually begin to eat again
• Carefully clean away discharges from the nose and eyes

Activity

• Limited
• Depends on the extent of gastrointestinal involvement

Medications
Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive.

• Antiviral drugs—none known to be effective in treating canine distemper viral infections
• Antibiotics—to reduce secondary bacterial infection, because canine distemper virus decreases the ability of the animal to develop a normal immune response (known as “ immunosuppression”)
• Medication to control seizures (known as “ anticonvulsant therapy”)—phenobarbital, potassium bromide

Patient Monitoring

• Monitor for signs of pneumonia or dehydration from diarrhea in the sudden (acute) phase of the disease
• Monitor for central nervous system signs, because seizures generally follow

Preventions and Avoidance

• Routine vaccination against canine distemper virus is key to prevention and avoidance; series of vaccinations administered initially followed by periodic booster vaccinations, as directed by your pet’s veterinarian 
• Avoid infection of puppies by isolation to prevent infection from wildlife (such as raccoons, fox, skunks) or from canine distemper virus-infected dogs

Possible complications

• Secondary bacterial infections, frequently involve the respiratory and gastrointestinal systems
•  Possibility of occurrence of central nervous system signs for 2 to 3 months after discharge from the eyes and nose has subsided
• Seizures
• Death

Expected Course and Prognosis

• Depend on the strain of virus and the individual host response—animal may be infected, but have no signs of disease (known as a “subclinical infection”) or have signs of disease involving various areas of the body; the infection may be fatal or non-fatal
• Mild central nervous system signs—patient may recover; twitching or contraction of a group of muscles (myoclonus) may continue for several months or indefinitely
• Death—2 weeks to 3 months after infection; mortality rate approximately 50%
• Euthanasia—owner may elect euthanasia, if or when nervous system signs develop; indicated when repeated seizures occur
• Fully recovered dogs are not carriers, as they do not shed canine distemper virus

Key Points

• Mortality rate is about 50%
• Dogs that appear to recover from early signs (such as discharge from the eyes and nose) may later develop fatal central nervous system signs
• Fully recovered dogs are not carriers, as they do not shed canine distemper virus
• Routine vaccination against canine distemper virus is key to prevention and avoidance; series of vaccinations administered initially followed by periodic booster vaccinations, as directed by your pet’s veterinarian

Source : Tilley, Larry P. and  Francis W.K. Smith Jr.2007.The 5-Minute Veterinary Consult: Canine and Feline (The 5-minute Veterinary Consult Series)