Systemic herpesvirus infection in a puppy
Emily Brouwer
Animal Health Laboratory, University of Guelph, Guelph, ON.
AHL Newsletter 2024;28(2):28.
An English Bulldog breeder sought the services of a veterinarian after eight puppies from three different litters had died suddenly over an unspecified period of time. A four-week-old male puppy had stopped eating several days prior to death, and was treated with acyclovir and clavamox due to a history of herpesvirus infection in the kennel. The puppy died despite treatment, and was submitted to the Animal Health Laboratory for postmortem examination.
On gross examination, the puppy was in good body condition and had no significant external findings. On internal examination, innumerable 1-2 mm diameter flat red foci were identified in the renal cortices, which corresponded to segmental streaks of hemorrhage extending from cortex to medulla. Similar pinpoint to 1 mm diameter foci were randomly distributed throughout the hepatic parenchyma and the spleen (Fig. 1). The lungs were diffusely dark pink and firm.
Histologically, these foci in the kidneys, liver and spleen corresponded to foci of acute necrosis and hemorrhage (Figs. 2, 3). In the lung, there were similar foci of parenchymal necrosis with more widespread interstitial pneumonia. Very rarely, intranuclear eosinophilic inclusion bodies typical of herpesvirus were identified in areas of necrosis. Kidney was submitted for canid herpesvirus-1 PCR and was positive with a cycle threshold of 20.29.
Figure 1. Opened abdominal and thoracic cavities. The kidney and liver demonstrate multifocal to coalescing areas of necrosis and hemorrhage, characteristic of systemic canid herpesvirus-1 infection.
Figure 2. Kidney. Acute tubular necrosis with interstitial hemorrhage. H&E stain, 20X.
Figure 3. Liver. Acute hepatocellular necrosis and hemorrhage. H&E stain, 20X.
The combination of gross and histologic lesions is considered essentially pathognomonic for systemic canine herpesvirus infection in puppies. This fatal condition tends to occur in puppies less than four weeks of age, as younger animals have difficulty with thermoregulation and herpesvirus requires a cooler body temperature in order to replicate. Litter mortality rates are high, and clinical signs in affected puppies can include respiratory distress, nasal discharge, anorexia, vomiting, increased vocalization, seizures, and sudden death. Dams of infected litters may not show clinical signs or may have non-specific upper respiratory signs. Neonates can be infected in utero, during birth from maternal genital lesions, or from oronasal secretions of the dam. Similar to all herpesviral infections, the infection is life long, and periods of recrudescence in infected animals often coincide with periods of stress, such as pregnancy, or immunosuppression. AHL
References
1. Creevy KE, Evans JB. Canine herpesvirus infection. https://www.merckvetmanual.com/generalized-conditions/canine-herpesvirus-infection/canine-herpesvirus-infection Revised Nov 2022. Accessed May 17, 2024.
2. Schlafer DH, Foster RA. Female genital system. In: Jubb, Kennedy, and Palmer's Pathology of Domestic Animals, 6th ed. Maxie MG, ed. Elsevier, 2016; vol 3:431-432.