by Jessica Vogelsang, DVM
When you hear the word “herpes,” most people automatically think of the human version of the disease. More specifically, they think of herpes simplex virus, which comes in two forms: HSV-1 and HSV-2. Although this dominates our attention, the family of herpesviruses is much larger and affects many animals, including dogs and cats.
The symptoms caused by different types of herpesviruses are varied; in humans, it is responsible for a variety of diseases, from shingles and Epstein-Barr to oral or genital lesions.
In cats, herpesvirus is a significant cause of upper respiratory infection. And in the dog, it is known as the reproductive disease leading to fading puppy syndrome.
How Common is Canine Herpesvirus?
The herpesvirus itself is very common in canines. Its prevalence in the population is estimated to be about 70%, but this does not mean the majority of dogs show signs of disease.
Like most herpesviruses, after the initial period the virus goes latent in the body and the dog seems outwardly unaffected.
What Age Group is Most Affected by Canine Herpesvirus?
By far, the most seriously affected age group is very young puppies in the 1-3 week age-period. In fact, canine herpesvirus is the leading cause of death in newborn puppies.
Dogs of any age can be infected, however, though the signs in mature dogs are usually nonexistent or mild compared to what is seen in puppies.
How is Canine Herpesvirus Transmitted?
A dog is infected by coming in contact with an affected dog’s oral, nasal, or vaginal secretions. Unlike other viruses, such as parvo, which is very hardy in the environment, herpesvirus is relatively unstable outside of the host, so close contact is required for transmission.
Puppies may be infected in utero or as they are delivered at birth. The virus replicates in the mucosa of the oral cavity and throat and enters the bloodstream from there.
What are the Symptoms of Canine Herpesvirus?
The most severe symptom, sudden death, occurs most often in young puppies one to three weeks old. However, this has been seen in puppies up to six months of age whose immune systems are not yet fully matured. In these cases, the puppies present with a very quick period of illness and death, usually in less than a day. This may be preceded by a variety of clinical signs, such as lethargy, decreased interest in nursing, conjunctivitis, diarrhea, or skin lesions. The organs most severely affected are the lungs, liver, and kidneys.
In older dogs with a mature immune system, herpesvirus often causes no clinical signs at all, although they still can shed the virus and infect other dogs. If signs do occur, herpesvirus may present as an upper respiratory infection with symptoms of kennel cough. Dogs may have eye symptoms such as conjunctivitis or corneal ulcers. Pregnant dogs may spontaneously abort. Once the acute infection is cleared, the virus remains latent in the body and can be reactivated by stress or immunosuppressive drugs.
How is Canine Herpesvirus Diagnosed?
Herpesvirus can be diagnosed by testing blood, tissue samples, or taking swabs of mucous membranes. Unfortunately, in puppies this testing is usually done post-mortem due to the rapid onset of disease. As it is a leading cause of sudden death in neonates, clinicians usually have a high index of suspicion for herpesvirus before confirming it through these diagnostic tests.
How is Canine Herpesvirus treated?
There is no cure for herpesvirus. Treatment is limited to supportive care and symptomatic management. In adults the symptoms are usually self-limiting, but in affected puppies the prognosis is guarded to poor even with treatment. In puppies who have been exposed but have not begun to show clinical signs, some clinicians may recommend keeping those puppies in a warmed, humidified environment that the virus is less likely to proliferate in.
How Can Owners Prevent Transmission of Canine Herpesvirus?
No vaccine for canine herpesvirus is available in the United States. If a female has been exposed to the virus prior to pregnancy, she will have antibodies in her blood that are passed to the puppies in the colostrum. These puppies may still be infected with the virus but do not become ill. The greatest risk to litters is when an exposure occurs for the first time in the three weeks prior to birth up through the three weeks after birth. For this reason, pregnant dogs should be isolated from other dogs during that six week period.
Any person coming in contact with the pregnant dog should be careful with their disinfection protocols to keep puppies safe. The virus is rapidly destroyed in the environment through the use of disinfectants, so maintaining a cleaning protocol is an important part of health management.
Once you’ve seen a litter affected by fading puppy syndrome, you never forget it. It is a terrible disease that leaves puppy owners and veterinarians feeling helpless. Fortunately, many cases can be prevented with foresight and management of pregnant dogs, so with luck it will never be a disease you have to witness.