The canine parvovirus is a small virus which is particularly virulent and can affect all species of dogs, although it cannot cross species to infect other animals or human beings. It is present throughout the world and although only identified in the last forty years when a new, particularly lethal strain developed, it is usually sensitive to medications that can treat the disease. Additionally, most dogs have been exposed to it at some time and therefore have built up a certain level of immunity.
The parvovirus is spread very easily as it is present in the environment and is difficult to eradicate. It is usually picked up by a dog licking infected areas where there have been infected stools, either by eating food from the floor or from grooming itself, or from play-biting other puppies and dogs that have come into contact with the virus.
The virus attaches itself to the first cluster of lymph tissue in the throat and multiply to the extent that they are carried unfiltered by the lymphatic system throughout the body, and infect bone marrow and the intestine. Once the bone marrow has been compromised and the dog's immune system compromised, it will then attack the rest of the body: particularly the intestine where it destroys the small villi or finger-like projections which are part of the digestive system and absorb nutrients from the intestine. The damage extends to the blood supply to the intestine, leading to large amounts of blood appearing in the inevitable diarrhoea, severe dehydration, and subsequent general septicaemia as the virus migrates through the intestine into the bloodstream.
As the immune response has been compromised by the virus attacking the bone marrow, treatment will consist of helping the dog to survive while its own immunity builds up again to be able to fight the disease. Treatment should take place at the veterinary surgery, where a schedule of continuous intravenous therapy can be started and antibiotics given to attack the secondary bacterial infections in the body. Anti-emetics (anti-nausea) drugs can also be given since the dog will be feeling extremely nauseous.
Anti-inflammatory drugs may also be given, together with plasma transfusions from a dog who has an immunity and which may help the patient to kick start its own immune system back into play.
Treatment is likely to extend over six to seven days while the dog can build up strength again and start fighting the disease on his own; with all the care outlined above it is highly likely that he will manage to survive. However it should be said that most veterinary experts suggest that if a patient has not improved by any significant degree at the end of four days, then the prognosis is likely to be extremely poor.
The most effective prevention is vaccination. This cannot be given whilst a puppy is still weaning or for a short time afterwards, and a vet should always give a blood test to detect its immune status before starting a course of vaccinations.
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