Herpes Virus: Image courtesy of: The Universal Virus Database http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/

Canine Herpes Infection
Solving the Mystery of the Disappearing Litter

Article Courtesy of:
http://www.marvistavet.com/

Most of us are familiar with herpes viruses because of human herpes. Most of us know mucous membrane or fresh body secretion contact (Herpes I causes facial sores and is spread by kissing or sharing food utensils and Herpes II causes genital sores and is spread by sexual contact). In small animals, feline herpes probably gets the most press as it is responsible for at least 50% of feline upper respiratory infections. It is extremely contagious among cats and is readily spread through the respiratory secretions that are sneezed and sprayed by the infected cat. While canine and feline herpes viruses are closely related, infection cannot be transmitted across species lines. All herpes viruses have the ability to infect the host for life (retreating to the nerve ganglia of the nervous system), though symptoms only periodically emerge.

Canine herpes is more of a reproductive problem than a respiratory one; in fact, most infected dogs do not appear to get sick at all. Instead the infection manifests in the pregnancy as resorption of the litter of puppies, abortion, still birth, or death of puppies within a few weeks of life. Transmission occurs through direct contact (sexual contact will do it but the usual route is simply normal nosing, licking, and sniffing) between the infected and uninfected dog. For this reason, it is recommended that a pregnant female dog be isolated from other dogs for the last three weeks of pregnancy and the first three weeks after birth. Let’s say that again:

Puppies can be exposed before, during, or after birth. Just because one member of the litter is infected, this does not mean they all are. The incubation period is 3-7 days following infection. Once symptoms begin (shallow breathing, loss of appetite, vomiting) death follows within 48 hours. Infected puppies uniformly have low platelet counts and may show red spots called “petechiae” which actually represent small bruises.

WHAT TO DO WHEN ONE OF THE PUPPIES DIES SHORTLY AFTER BIRTH:
The necropsy (autopsy) is the only realistic means to finding out what happened. If you want to find out if the other litter members are at risk or if the mother dog can safely be bred again, the dead puppy should be examined.

• Place the remains in a zip-loc plastic bag and refrigerate until you can notify your veterinarian. If the placenta is available, it should be included.

• Expect the mother dog and remaining littermates to be examined and the dead puppy to be necropsied.

There are many causes for the loss of a near term or newly born litter of puppies: corona virus, parvo virus, toxoplasmosis, brucellosis, umbilical trauma, genetic disease, etc. Knowing what to do heavily depends on knowing what happened. Puppies that die from canine herpes have characteristic “inclusion bodies” in many tissues under the microscope. Inclusion bodies are essentially areas of heavy virus reproduction that are actually visible and unique in appearance. The presence of herpes inclusion bodies confirms the diagnosis.

BLOOD TESTING THE ADULT DOG:
The ability of an infected dog to maintain antibodies against canine herpes is variable. Some infected dogs show no antibodies after a couple of months and others have antibody levels persisting for years. If the history is suggestive or herpes then any herpes antibodies found in the bloodstream would be considered significant. Without the history of puppy loss, the presence of antibodies simply indicates past exposure to the virus. To get a better sense of how acute an exposure might be and whether or not the antibody level indicates active infection, a second antibody level can be drawn 10-14 days later. An active infection will show a fourfold rise in antibody level. In a breeding kennel situation, it maybe useful to know which dogs have been exposed and which ones haven’t so that the risks can be assessed. It is only the unexposed females that are at risk for infection during pregnancy and losing the litter. Checking pre-breeding titers is not a bad idea for both the male and female dog.

If the infection is less than 3 weeks old, it may be possible to actually culture the virus from swab from the nose or vagina. In general, confirming herpes infection in a dead puppy is much easier and faster than trying to confirm the infection in the adult dog.

SAVING THE REST OF THE LITTER:
Canine herpes is very bad news for puppies under three weeks of age. Often there is nothing that can be done to stop the sweep of this lethal virus. This does not keep us from fighting, however. Serum from a recovered female dog can be separated and injected into the puppies as a source of anti-herpes antibodies. Warming the puppies may help as the virus cannot survive at body temperature. Antiviral medications such as Acyclovir may help.

PREVENTION:
Fortunately, herpes viruses do not live in the environment (it dies at 68º F and is readily killed by common disinfectants); direct contact with an infected host or fresh secretions is needed. Still, once a dog is infected, it will be infected for life. Shedding virus is increased by stress. One more time: all mother dogs should be isolated from the final 3 weeks of pregnancy through the first 3 weeks after birth. In Europe, a vaccine is available for use during canine pregnancy (one dose at the time of breeding and a second 6-7 weeks later, to be repeated with each pregnancy).

Herpes is only a danger to the puppies when the mother is infected during pregnancy. Once the mother has been infected, subsequent pregnancies should be unaffected as she will have made enough antibodies to keep the virus in check.