Treatment & Prevention
There is no cure for an animal that has CHV – infection is probably lifelong and can flare up repeatedly during periods of stress. Antiviral drugs such as acyclovir have shown very limited efficacy and are expensive.
Some work has shown variable success by injecting infected puppies with the serum of immune bitches. Early intervention appears vital and will depend on the immune status of the donor.
The disease is most clinically significant in unborn and newborn puppies. Infection takes place transplancentally, during birth and soon after birth. Therefore caesarean birth cannot guarantee freedom from infection. It can also be transmitted from mother to pup as an aerosol (droplet infection). However, good hygiene and quarantine measures between breeding units will reduce the viral burden within the environment and reduce the incidence of secondary bacterial infections.
CHV multiplies rapidly when body temperature falls below 37oC (99oF). This explains why puppies in the first three weeks of life are worst affected, as they have poor ability to regulate body temperature. The ideal body temperature of 39oC (101.5oF) can be maintained with the use of infra-red heat lamps, though it is important not to overheat the mother.
As the greatest amounts of virus are shed in the first hours post partum, colostral antibody is the most important factor in reducing disease incidence in the puppy. Even seropositive (previously exposed) bitches do not produce significant amounts of neutralising antibody, and therefore it is necessary to boost the immune system prior to whelping.
Previous exposure to CHV will not confer lasting immunity. The virus becomes latent until the circulating antibody levels fall, which can occur in as little as three months. It will then reappear during periods of stress, particularly whelping and overcrowding. High levels of maternal circulating antibody are required to provide protective levels in colostrum.