Merck Manual

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Pet Owner Version

Canine Herpesvirus


Kate E. Creevy

, DVM, MS, DACVIM-SAIM, College of Veterinary Medicine & Biomedical Sciences, Texas A & M University

Reviewed/Revised Jun 2018 | Modified Oct 2022

Canine herpesviral infection is a severe, often fatal, disease of puppies. In adult dogs, it may be associated with upper respiratory infection, eye disease, an inflammation of the vagina marked by pain and a pus-filled discharge (in females), or inflammation of the foreskin of the penis (in males).

The disease is caused by a canine herpesvirus that occurs worldwide. Transmission usually occurs by contact between susceptible puppies or dogs and the infected oral, nasal, or vaginal secretions of their dam or oral or nasal secretions of affected dogs. Transmission may also occur prior to birth.

The disease is most severe in newborn puppies less than 3 weeks old. Death due to the infection usually occurs in puppies 1 to 3 weeks old, occasionally in puppies up to 1 month old, and rarely in puppies as old as 6 months. Typically, the onset of illness is sudden, and death occurs after an illness of less than 24 hours. If signs are seen, they may include lethargy, decreased suckling, diarrhea, nasal discharge, eye disease, and rashes. Puppies do not typically have a fever. Older dogs exposed to the virus may develop mild inflammation of the nasal passages (which may contribute to "kennel cough"), eye disease, or inflammation of the genitals. Infections in pregnant dogs may be associated with abortions, stillbirths, and infertility.

Laboratory tests are used to diagnose the virus. Unfortunately, treatment is usually not effective. Treatments may be more effective in puppies that have been exposed to infected dogs but do not yet shown signs. As with other types of herpesviruses, the infection remains within the body of infected dogs for the rest of their lives, intermittently causing signs. Adult dogs often experience mild signs that improve without treatment.

No vaccine is available. To best protect puppies from infection, pregnant dogs should be kept away from other dogs during their last 3 weeks of pregnancy and during the first 3 weeks after the puppies are born. In addition, people in contact with dogs during this time should wash their hands thoroughly and often. Infected female dogs develop antibodies, and litters born after the first infected litter receive antibodies from the mother in the colostrum. Puppies that receive these maternal antibodies may be infected with the virus, but show no signs of disease. The outlook for puppies that survive early infection with canine herpesvirus is guarded because the disease can cause irreparable damage to the lymph nodes, brain, kidneys, and liver.

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