Canine Herpes Infection
Solving the Mystery of the Disappearing Litter
Most of us are familiar with herpesviruses because we have heard of human herpes. Medications to suppress herpes outbreaks are advertised on television and educational programs are in place in schools and communities. In humans, there are two herpesviruses: herpes I, which causes facial sores and is spread by kissing or sharing food utensils, and herpes II, which causes genital sores and is spread by sexual contact. Herpesviruses have the ability to hide in the body’s nerve ganglia, where they are safe from the immune system, periodically emerging and causing symptoms. Herpes infection is generally considered to be permanent and outbreaks of symptoms are generally associated with stress.
In fact, our pets must deal with their own herpesviruses. In cats, herpes is a respiratory virus accounting for nearly 50% of feline upper respiratory infections. Feline herpes is very contagious and is a common problem wherever cats are housed in groups.
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; the virus affects the unborn and newborn.
Herpes infection manifests in pregnancy as resorption of the embryos, abortion of the fetuses, stillbirth, or death of puppies within a few weeks of life. Transmission occurs by direct contact (sexual contact will do it but the usual route is simply normal nosing, licking, and sniffing) between the infected and uninfected dogs. 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: Any pregnant female dog should be isolated from other dogs for the last three weeks of pregnancy and the first three weeks after birth. If she gets infected during this period, the litter is likely to be lost.
Puppies can be exposed before, during, or after birth. Just because one member of the litter is infected does not mean they all are. The incubation period is 3 to 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 that actually represent small bruises.
What to do when one of the Puppies Dies Shortly after Birth
The necropsy (autopsy) is the only realistic means of 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-lock plastic bag and refrigerate it 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 have a necropsy (veterinary word for autopsy).
There are many causes for the loss of a near term or newly-born litter of puppies: coronavirus, parvovirus, toxoplasmosis, brucellosis, umbilical trauma, genetic disease, etc. Knowing what to do heavily depends on knowing what happened. Puppies who 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 visible and unique in appearance. The presence of herpes inclusion bodies confirms the diagnosis.
Blood Testing Adult Dogs
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 of herpes, then any herpes antibodies found in the bloodstream would be considered significant. Without the history of puppy loss, antibodies simply indicate 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 to 14 days later. An active infection will show a four-fold rise in antibody level. In a breeding kennel situation, it may be useful to know which dogs have been exposed and which have not 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 titers before breeding 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 swabs 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.
Recently a PCR test (a test for herpesviral DNA) has been developed for dogs. This test is likely to become the diagnostic test of choice.
Saving the Rest of the Litter?
Canine herpes is very bad news for puppies under age 3 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.
Fortunately, herpesviruses do not live in the environment (they die at 68º F and are readily killed by common disinfectants); direct contact with an infected host or fresh secretions is needed for transmission. Still, once a dog is infected, she 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 to7 weeks later, to be repeated with each pregnancy).
Herpes is only a danger to the puppies when the mother is infected during pregnancy or shortly after delivery. Once the mother has been infected, subsequent pregnancies should be unaffected as she will have made enough antibodies to keep the virus in check.
- Canine herpes only causes symptoms in unborn or newborn puppies and they usually do not survive infection.
- The mother dog will not appear sick.
- Problems only occur for the puppies when an uninfected female becomes infected during pregnancy. Females infected long before pregnancy do not lose their litters to herpes.
- Herpes is a common canine infection and is spread not only by sexual contact but via oral and nasal secretions.