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Canine herpes virus (CHV)
Canine herpes virus (CHV) is an alphaherpesvirus affecting dogs worldwide, and is a well-known agent of lethal neonatal canine infections and the fading puppy syndrome. The virus is very common and it has been found all over the world. The prevalence of the infected dogs depends on the region, from 20% to 98% of the infected dog rate. Conducted studies have shown following geographical seroprevalence of CHV: 88% in England, 80% in Norway, 45.8% in Belgium, 39.3% in the Netherlands ad 39.3% in Turkey. Because virus can change into latent stage, infected animals, which are still contagious, may show seronegative status, due to which any seroprevalence study shows underestimated infection rates. The virus is not contagious for humans.
Transmission
CHV is composed of an enveloped viral DNA which is sensitive to UV light, high temperatures and lipid solvents, such as ether or chloroform, and most of disinfectants. This makes the virus unstable outside of the host organism, so for the transmission a close contact is required. CHV lives in the reproductive and respiratory tract of the infected dog. Transmission is mediated through oral, nasal, or seminal or vaginal fluids of the infected dog, of which oronasal transmission is considered as the main route of infection. A stud can transmit the virus to the bitch, or vice versa. Puppies usually get infected through contact with the birth canal or from nasal and oral fluids of the mother.
Symptoms
New-born puppies typically start displaying the canine herpes virus symptoms between the ages of 1 and 3 weeks. Visible symptoms include persistent crying, dull and depressed attitude, loss of appetite, soft yellow-green stool, and abdominal pain. The highest viral concentrations in the infected puppies are localized in the adrenal glands, kidneys, lungs, spleen and liver. Puppies mostly die before the development of the neurological signs. In puppies older than 5 week and in the adult dog, CHV usually does not cause any harmful symptoms, but may cause upper respiratory and ocular infection. However, in female dogs, canine herpes virus infection is associated with reproductive problems, such as lowered conception rate, fetal resorption, abortion, stillborn puppies or small litter size. The herpesvirus pathology depends on factors influencing the dog’s immunity, such as age, pregnancy, stress, immunosuppressive therapy and accompanying disease.
Overall, symptoms associated to CHV infection in puppies include:
- Sudden death of new-born puppy
- Weakness, depressed attitude
- Persistent crying
- Lack of appetite
- Discomfort in the abdomen
- Soft, yellow-green feces
- Cold puppies
- Respiratory difficulties, nasal discharge
- Hemorrhages, such as nose bleeds and small bruises
- Older puppies may develop nervous system abnormalities, including blindness and seizures
In adult dogs, herpes virus infections include:
- Often there are no symptoms visible
- Respiratory and ocular infections
- Reproductive problems
- Abortion
Treatment
Unfortunately, there is no available cure for herpesvirus, and the treatment is limited to management of the symptoms. In affected puppies the survival prognosis is poor even with given treatment. It is recommended to keep infected puppies warm, due to viral sensitivity to temperature.
References:
Krogenaes A et al (2014): A serological study of canine herpesvirus-1 infection in a population of breeding bitches in Norway. Acta Vet Scand. 56(1): 19.
Ronsse, V., Verstegen, J., Thiry, E., Onclin, K., Aeberlé, C., Brunet, S., & Poulet, H. (2005). Canine herpesvirus-1 (CHV-1): clinical, serological and virological patterns in breeding colonies. Theriogenology, 64(1), 61–74.
Papageorgiou KV, Suárez NM, Wilkie GS, McDonald M, Graham EM, Davison AJ (2016) Genome Sequence of Canine Herpesvirus. PLoS ONE 11(5): e0156015. https://doi.org/10.1371/journal.pone.0156015
Ledbetter, E. C. (2013). Canine herpesvirus-1 ocular diseases of mature dogs. New Zealand Veterinary Journal, 61(4), 193–201. doi:10.1080/00480169.2013.768151
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