Dog - Herpes Virus

Canine herpes virus (CHV) is a common infection in dogs. It is important because of the role it plays in canine neonatal mortality (death of newborn puppies).

Recent work has shown that more than 80% of dogs in the UK have been exposed to the virus at some time in their lives.

Why is the virus important?

CHV is now regarded as a major cause of neonatal death – fading puppy syndrome. Affected bitches often show signs of reduced fertility or are infertile due to abortion, stillbirth or re-absorption of their foetuses as a result of this virus. Sometimes puppies may be born normally and then 'fade' and die a few days after birth as a result of the action of the virus.

In adult dogs CHV is also one of the causes of kennel cough (infectious bronchitis).

Does herpes virus only affect dogs?

Different strains of herpes virus can cause disease in many species. In cats it is one of the major components of so-called 'cat flu' syndrome. Feline herpes virus (FHV) is also known as feline viral rhinotracheitis (FVR) virus and is one of the two major viruses incorporated into current cat flu vaccines.

In man another type, herpes simplex, is responsible for so-called 'cold sores'.

Is a bitch ill when she has fading puppies?

There are often no signs of illness in bitches that have puppies that subsequently die of CHV infection. The puppies can die at any time during the pregnancy. Occasionally the bitch shows typical signs of adult CHV infection with upper respiratory tract infection, coughing and a watery nasal discharge. Since in adult dogs the virus also causes genital problems there may be sores on the vulva, usually in the form of tiny haemorrhages (bleeds) just under the skin or actual vesicles (small blisters). These signs in the adult usually clear very quickly but can reappear at the time of the next oestrus (season).

Does the bitch not pass immunity on to her puppies?

If the bitch has had CHV infection just prior to or at the time of mating it is possible that she may confer sufficient immunity to her offspring that they show no evidence of infection. However the bitch's immunity to CHV is not long lasting. Circulating antibody levels fall to non-protecting levels in as little as three months post infection. Infection can then recur, particularly during periods of stress, e.g. during pregnancy and whelping. Very high levels of circulating maternal antibody are required to provide protection for the litter. Fortunately this is now possible in the UK with the use of a licensed vaccine (see below).

What about the male dog?

If adult male dogs show signs of upper respiratory disease (kennel cough) they spread it by coughing and sneezing and the bitch can be infected during mating. Male dogs may also show transient small haemorrhages (bleeds) under the skin of the penis which can infect the bitch at mating.

As with the bitch the dog can also have latent infection and shed the virus when under any stress.

Are the puppies only infected in the uterus?

No. If the bitch is actually shedding virus at the time of birth puppies can contract infection during or immediately after birth. They can show signs in 2-3 days and be dead in a fortnight.

How can infection be prevented?

A vaccine is now available in the UK (Eurican Herpes 205) which allows active immunisation of bitches. Two doses of the vaccine are required, the first being given either during oestrus or 7-10 days after mating with the second injection given 1-2 weeks before whelping. This has been shown to significantly increase the number of live pups from an infected bitch and also to protect puppies during the vital postnatal period.

Does vaccination prevent adult dogs acting as carriers?

No, unfortunately because of the short lasting nature of the immunity re-vaccination has to be repeated for each pregnancy. Infected adults still act as carriers and shed the virus.

What else can be done to protect the puppies?

It is known that the virus does not replicate in a temperature of 39ºC (102ºF) or above. Any newly born puppies, particularly if they appear weak, should be kept very warm, preferably around 40ºC (104.5ºF).

How is infection confirmed in the puppy?

In the bitch blood samples two or three weeks apart showing a rise in antibody numbers indicates active infection. In many cases however death of puppies at or shortly after birth is the first indication of a problem. Under those circumstances full post mortem examination of one or more of the puppies is essential in order to get a definative diagnosis, although sometimes demonstration of the causal virus can be difficult.