Introduction

• Cause: canine herpesvirus-1.
• Signs:
  • In adult: mild infection of the respiratory and genital tracts.
  • In neonates: severe, generalized, usually fatal infection: part of 'fading puppy' syndrome.
• Diagnosis: usually post-mortem in neonate.
• Up to 80% of dogs have serum antibodies to CHV.
• Prevention is via good husbandry and hygiene in breeding kennels.
• Treatment: unrewarding, anecdotal.
• Prognosis: poor for neonates, good for adults.

Pathogenesis

Etiology

• Canine herpesvirus-1 (CHV-1) Canine herpesvirus, family Herpesviridae.
• Reported to exist in the United States, Canada, Australia, Japan, England and Germany.

Predisposing factors

• Lack of maternally-derived antibody, eg delayed suckling or naive bitches with no titer.

• Poor hygiene/husbandry in breeding establishment; failure to isolate bitches during pregnancy and in the immediate post partum period.

• Lack of thermoregulation in canine neonates.

Specific

• Naive bitch with recent CHV infection.

Pathophysiology

• Aerosol infection → replication in nasal or oropharyngeal epithelium and lymph nodes. This leads to viremia → localization in reticuloendothelial cells.
• Systemic infection → petechiation of renal cortex, liver, lungs and lymph nodes, pulmonary edema, splenomegaly and effusions.
• Infection of eye → retinal dysplasia, panuveitis or retinitis.

• Infection via respiratory or genital tract → placental infection, placentitis, abortion or fetal mummification.

• Aerosol infection → replication in upper respiratory tract → damage to epithelial cells → inflammatory response with serous nasal discharge. Infection of tracheobronchial epithelium (may) → rhinitis Rhinitis.
• Viremia may occur, but the virus does not localize in tissues.
• Conjunctivitis may develop.

Timecourse

• Incubation period 2-7 days.
• Some puppies born dead.
• Some puppies die at 2-21 days old.

Epidemiology

• Herpesviruses may cause persistent or latent infections.
• Latent infection may follow either clinical (any form) or inapparent infection.
• Latency is established at the site of original infection, and is lifelong.
• Maternally derived antibody protects against neonatal disease, but not against inapparent infection.
• Virus is shed in nasal or genital secretions.
• Up to 80% of healthy dogs have antibodies.
• Can be a significant problem in breeding kennel without proper management.
• Replication of CHV is inhibited at adult core body temperature (39°C) - pups over 3 weeks of age do not develop systemic disease.
• CHV replicates at 37°C, therefore infects the upper respiratory and genital tracts of adult dogs.
• Puppies thermoregulate poorly, therefore may support systemic CHV replication → generalized infection.
• Infection of genital tract of bitch leads to infection of puppies in utero or during passage through vagina.
• Puppies may also be infected by inhalation of virus during contact with other puppies or the bitch, or from fomites.
• Severity directly related to amount of maternal derived antibody present in pups.

Diagnosis

Treatment

Prevention

Outcomes