Distemper disease

Distemper is a serious viral infection, most often seen in dogs less than one year old. Highly effective vaccines have ensured that distemper is rarely seen in vaccinated pet dogs. It is still a problem in the UK in unvaccinated pets, particularly in urban areas. In other countries the disease is still a big killer of dogs.

Distemper is a large virus related to the virus causing measles in humans. Animals become infected by breathing in the virus following contact with an infected dog or contaminated environment.

Dogs that are infected usually develop the signs of disease 1-2 weeks after they are exposed to the infecting virus. The initial signs of infection are listlessness, reduced appetite and fever. Some dogs recover at this stage and become immune to further infection. In other animals the immune system becomes affected and secondary infections are common.

Respiratory signs such as breathing problems, coughing and snotty nasal discharge are common, and diarrhoea and vomiting may also develop. In severe cases the virus may enter the brain and seizures (fits) may develop. About half of all severely affected dogs will develop neurological signs ranging from blindness to inco-ordination to persistent tics.

Your vet will probably suspect that your dog might have distemper from the symptoms that you describe, the dog’s vaccination history and the findings on physical examination. A blood test that shows a severe decrease in the white blood cell numbers and possibly the presence of virus bodies in the cells will help to confirm the diagnosis.

It is possible to grow the virus outside the dog and your vet could send samples to a laboratory to identify the virus. However this is rarely done in practice. Results of the test can take a long time and the diagnosis will often be obvious without this test. If your pet recovers an increase in antibodies against distemper in the blood will be seen.

Currently, there is no direct treatment against the virus. Therapy is “supportive” and consists mainly of giving fluids by a vein in order to compensate for dehydration and correct for on-going losses of fluid by vomiting, diarrhoea and the refusal to drink during the disease.

In addition, dogs are treated with drugs to stop vomiting, and with antibiotics, to prevent secondary infection with bacteria. If seizures are present then drugs may be used to control these but euthanasia may be the best option in very severely affected animals.

Around 1 in 5 of all dogs infected with distemper will die from the disease (despite veterinary care). One of the biggest killers is the development of pneumonia due to a compromised immune system. The outlook is much worse in those where the brain is affected.

The disease is more severe in young pups and in those that have had no vaccination against distemper or have only just begun their vaccination regimen. Even in dogs that do appear to recover the prognosis must be cautious. Some go on to develop brain problems months or years after the episode.

It is essential to vaccinate your dog according to your vet’s recommendations. Pups that are born to vaccinated dams usually have antibodies from their mothers (maternal antibodies) that protect them against infection during the first few weeks of their lives. The pup is in danger after the level of maternal antibodies declines in his blood and that is when he should be vaccinated.

Maternal antibodies can interfere with vaccination so vaccination must be timed so that it is given as soon as maternal antibody levels start to drop and that time differs between pups. The vaccination is repeated in order to make sure that the dog has had an effective vaccine dose and to boost this effect.

To prevent the spread of infection, sick dogs should be isolated from other dogs and cages and pens should be properly disinfected and cleaned. Pups who have not completed their vaccination schedule should be prevented from any exposure to potentially infected animals or their environment.