Canine Herpes Virus

Canine herpes virus (CHV-1) is a common infection in dogs but its important role in neonatal mortality has only recently been recognised.  

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. Alternatively puppies may be born normally and then 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 Bronchotracheitis).

Does herpes virus only affect dogs?

Different strains of herpes virus can cause disease in many species including cats where 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 are known to die of CHV infection. The puppies can die at any time during the pregnancy. Sometimes 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 just under the skin or actual vesicles. These signs in the adult usually clear very quickly but can reappear at the time of the next oestrus.

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 dangerous levels in as little as three months post infection. Infection is then likely to 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.

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 also during mating. Frequently there are transient small haemorrhages under the skin of the penis.

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 utero?

No.  If the bitch is actually shedding virus at the time of birth puppies can contract infection during or immediately after being born. 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 some countries such as 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 protect the puppies during that vital postnatal period. The vaccine is currently unavailable in Australia but may become available in the near future.

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?

Good hygiene practices should be implemented and the puppies kept warm.

How is infection confirmed in the puppy?

In the bitch blood samples two or three weeks apart showing a rise in antibody titre indicates active infection. This can be more reliable than post mortem on a dead puppy since sometimes the virus can be difficult to demonstrate.