Distemper Outbreak

distemper picWhat is Distemper?

Canine distemper is a disease that primarily affects the respiratory, intestinal tract, and nervous system of dogs. Among the virus-induced diseases in dogs, the mortality rate of distemper is second only to that of rabies. The virus is highly contagious and is passed directly from dog to dog by close contact but can also be spread through bodily excretions like urine and faeces. Detergents and heat easily kill the virus. The virus dies within minutes in a warm environment but can persist for weeks at cooler temperatures.

What are the symptoms of distemper?

Young, unvaccinated dogs aged 3 to 6 months are most often infected with distemper although any dog without full immunity is susceptible. Nasal discharges containing virus are aerosolized by sneezing, thereby spreading the virus. The virus establishes itself in the nasal passages of a susceptible dog, multiplies, and spreads through the body. Dogs develop a fever approximately a week after infection but this fever may not be noticed. Two weeks after infection, the virus produces severe damage to the cells of the nasal passages, eyes, lungs, and intestinal tract. These damaged tissues commonly become secondarily infected with bacteria. This combined infection with virus and bacteria produces loss of appetite, fever, a snotty nose, thick discharge from the eyes, pneumonia, and diarrhoea. The virus infects the pads of the feet, producing a hard, scaly thickening referred to as “hard pad” disease. The virus also damages the immune system, thereby interfering with the body’s ability to fight off the infection.

If the bacterial component of the infection can be controlled with antibiotics, the dogs may appear normal for 2 to 3 weeks but signs of brain and spinal cord disease can still occur. Half of the dogs with distemper develop neurologic disease. The canine distemper virus is attracted to and grows well in nervous tissue. The damage done to the brain and spinal cord can result in epileptic seizures and/or localized seizures of the head often called “chewing gum fits.” Damage to the spinal cord can produce weakness and paralysis. Nerve damage may also produce involuntary twitching of the legs. Most dogs with neurologic disease die or are euthanized.

What tests are needed?

Making a definite diagnosis of distemper can be difficult if the dog does not develop the typical snotty nose–pneumonia syndrome; most commonly we make a presumptive diagnosis based on the immune status, history and clinical examination.

After the initial 14 days of the infection, the virus is difficult to identify in swabs of infected tissues. Increasing antibody titres against distemper in dogs that have not been vaccinated strengthen the suspicion of distemper. It is especially difficult to diagnose distemper in dogs with nervous system signs that have not had the other typical signs of distemper.

What treatment is needed?

Currently, no drugs are available to treat the distemper virus, so treatment is largely supportive and may include antibiotics, intravenous fluid therapy and symptomatic treatment for vomiting, diarrhoea, cough etc. Anti-seizure and anti-inflammatory medications may be required in some cases. The antibiotic treatment can relieve many of the signs of disease but does not prevent the virus from entering and damaging the brain and spinal cord.

Nursing care; good-quality, palatable food; and a stress-free environment are helpful in improving appetite and general well-being. Because the treatment options are limited, prevention by vaccination is the prime strategy.

Vaccines against distemper should be started when puppies are weaned. If the mother has been vaccinated or recovered from an exposure to distemper, she will pass protection (antibodies) against distemper to her puppies in her milk. These maternal antibodies protect the pups for a few weeks after birth. The amount of antibodies passed from the mother to her pups depends mainly on the level of the mother’s antibodies. The antibodies not only protect the pups from distemper but also interfere with the pups’ response to vaccination. As long as the pups have maternal antibodies, they cannot be successfully vaccinated.

Vaccines should be started soon after weaning, at 6 to 7 weeks of age, and given on 3 occasions at 3-4 week intervals. Thereafter the vaccination should be given on an annual basis to maintain optimum levels of immunity. This scheme of vaccination has proved effective in preventing this lethal disease.