Canine herpesvirus (CHV), or Varicellovirus canidalpha1, belongs to the subfamily Alphaherpesvirinae within the Herpesviridae family. This significant pathogen affects domestic dogs, notably neonates, and is likely to be globally distributed with varying prevalence across different geographic regions. While there is a need for more recent data on the seroprevalence of CHV in the United States, historical records indicate that less than 10% of randomly selected dog populations were positive. Nevertheless, the prevalence can be as high as 100% in shelters and kennel settings with high-density dog housing.
The pathogenesis of CHV involves a complex interplay between viral factors and host immune responses. The virus primarily targets the respiratory and genital mucosa, progressing to infection, replication, and often leading to clinical manifestations. A remarkable characteristic of CHV is its capacity for establishing latency, primarily in sensory ganglia, such as the trigeminal ganglia, following the initial infection. During this asymptomatic period, the virus remains dormant, with the infected dog showing no clinical signs of illness. Viral reactivation from latency can occur, triggered by stressors like parturition or animal transportation, immunocompromising disease, or immunosuppressive therapy. It may lead to viral shedding in secretions from the genital and respiratory tracts. The asymptomatic nature of latency may pose diagnostic challenges. Despite these, understanding the characteristics of CHV latency is crucial for managing the disease, as it plays a central role in maintaining the virus within canine populations.
The clinical manifestations of CHV infection range from mild to severe, depending on the animal’s age. This virus predominantly impacts puppies, particularly those under three weeks of age, often resulting in elevated mortality rates within the affected litter. Infected puppies may manifest systemic infection, presenting intense respiratory distress and neurological disorders, ultimately leading to sudden death. Pathological observations on deceased puppies include multifocal areas of necrosis and hemorrhagic regions in most organs, including lung, liver, brain, and intestine, with the kidney being the classically affected organ. In addition, the presence of enlarged lymph nodes and spleen can be noted. While nonpregnant adult animals often present mild respiratory symptoms and conjunctivitis, pregnant bitches may undergo reproductive failure, manifested as abortion, stillbirths, or the birth of weak and nonviable puppies.