Canine herpesvirus (CHV-1) is a highly infectious agent and a recent study showed that more than 80% of dogs in England have been exposed to the virus at some time in their lives. The main route of transmission appears to be oronasal from infected puppies or from nasal or vaginal excretion of adults.

For most dogs CHV is not thought to cause any significant problem and as a consequence has largely been ignored. However, it is now clear that CHV can be a significant cause of death in young puppies as well as causing smaller litter size and weight.

The outcome in the foetus/puppy depends largely on the time of infection:

> early pregnancy - foetal death/mummification

> mid pregnancy - abortion

> late pregnancy - premature birth

> birth to 2-3 weeks of age - death within 1 or 2 days - FADING PUPPY SYNDROME

> puppies older than 2-3 weeks seldom become severely ill.

Typical signs of a fading puppy are:

> anorexia

> soft stools progressing to diarrhoea

> painful abdomen: the puppies cry continually with paddling limb movements until they die

> sometimes dyspnoea; vomiting or salivation.

Older puppies and adults may develop respiratory signs - CHV is one agent responsible for kennel cough.

Puppies can become infected in utero, during birth or by contact with the bitch's saliva. Older animals which survive probably have a lifelong infection. The virus can undergo latent infection and reactivation and further shedding can be induced by immunosupression or stress.

There is no reliable antemortem test to detect animals which are infected. Diagnosis is difficult in adults as the virus is quite labile and excreted only occasionally and in small amounts, while antibody levels are often very low or undetectable. Diagnosis of CHV infection in puppies is usually made at post mortem. There is no treatment or cure. Age resistance appears to be mainly a matter of body temperature: the virus grows best at temperatures just below that of normal dogs, so puppies less than 3 weeks old, which generally cannot yet regulate their own temperature, are most at risk of generalised disease. This is one reason why it is important to keep young puppies warm.

There is a vaccine in the UK launched by Merial Animal Health. This vaccine, Eurican Herpes 205 cannot prevent infection but if given during pregnancy has been shown to significantly improve fertility rates and reduce early puppy deaths. Bitches that already have the virus can still be vaccinated. The vaccination protocol is to give one dose anytime between the onset of heat and 7-10 days after the presumed date of mating. A second dose is given 1-2 weeks before the expected date of whelping. This protocol is repeated at any subsequent mating.

Peter Cockett BSc BVetMed DVR CertSAO MRCVS

Hollygrove English Setters