Herpesvirus in Dogs
What is canine herpesvirus?
Canine herpesvirus or canine herpes is a systemic, often fatal disease of puppies caused by canine herpes virus (CHV). CHV is seen most commonly in Asia and Europe in dogs, coyotes, and wolves.
CHV does not cause infection in humans. It may remain latent or hidden and quiet in tissues after a dog is infected and may be passed on to other dogs, particularly to fetuses developing in the mother's uterus. Stress or other illness may cause recurrence of illness in a dog that has previously been infected. The incubation period in puppies is four to six days, after which clinical signs develop or sudden death occurs.
What are the clinical signs of canine herpesvirus infection?
The most common clinical signs occur in puppies under four weeks of age. Litter mortality (death) rates are high in CHV. In puppies, clinical signs include difficulty breathing, a thick nasal discharge, loss of appetite (anorexia), grayish yellow or green soft, odorless stools, persistent crying, seizures, and sudden death. Puppies that appear to be mildly affected often later develop neurological signs or blindness.
"Litter mortality (death) rates are high in CHV."
Most adult dogs have clinical signs that are nonspecific, including: coughing and sneezing caused by upper respiratory infection, miscarriage, and lesions on the external genitalia. Infections affecting the eyes can cause squinting, recurrent ocular (eye) discharge, conjunctivitis, and corneal ulcers.
How does a dog become infected with CHV?
Young females and their puppies are at greatest risk. Direct contact between infected and non-infected dogs causes transmission of the virus. Since the virus is widespread, the risk of infection is relatively great. Closed breeding kennels that experience a sudden increase in miscarriages should be tested for CHV.
How is canine herpesvirus diagnosed?
Diagnosis is usually based on clinical signs in affected dogs. The diagnosis can be confirmed by performing a post-mortem examination of tissues from stillborn puppies or puppies that die suddenly. In some cases, two blood samples can be collected two weeks apart showing a rise in immunity (antibody count) to the virus.
It is important to differentiate CHV from other diseases that cause similar clinical signs. These diseases include brucellosis or toxoplasmosis (both potentially infectious to humans), bacterial infections in the mother or puppies (including mastitis or breast infection), canine parvovirus type 1, canine distemper, and canine adenovirus type 1 (canine hepatitis). Puppies that die suddenly should have a post-mortem examination to diagnose the specific cause of death.
What is the treatment and prognosis for canine herpesvirus?
Treatment is usually unsuccessful and most infected puppies die before medical help can be sought. Antiviral drug therapy is generally ineffective. Immune sera from recovered females (i.e., blood containing antibodies) may be beneficial in reducing puppy deaths if it is administered before the onset of illness.
"Immune sera from recovered females (i.e., blood containing antibodies) may be beneficial in reducing puppy deaths if it is administered before the onset of illness"
Treatments for CHV eye infections include controlling secondary bacterial infections and pain with topical antibiotics and pain relievers. Antiviral eye drops such as idoxuridine and trifluridine can be used as well.
How can I prevent CHV?
The disease may be prevented by avoiding contact with infected dogs. This is particularly important for pregnant females. There is currently no vaccine available in the United States or Canada. In Europe, a vaccine is available, and has been shown to reduce puppy death from CHV. Good hygiene has been proven to dramatically reduce deaths in puppies. Adult dogs that are infected often have a short duration of clinical signs and recover without medical intervention. However, these adult dogs often develop latent infections (or become carriers) and may periodically shed and spread the virus throughout their lives. CHV is most dangerous to young and developing puppies. In these cases, death is unfortunately the most common outcome.
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