EFFECTS OF VALACYCLOVIR IN CATS INFECTED WITH FELINE HERPESVIVUS-1

Objective-To determine whether orally administered valacyclovir can be used safely and effectively to treat cats with primary, feline herpes virus 1 (FHV-1) infection. Animals-14 specific-pathogen-free adult cat s. Procedure-Cats were infected with FHV-1 strain 87-727 (300 mu l, 10 (7) plaque-forming units/ml) by ocular and nasal inoculations, and wer e treated every 6 hours with dextrose (controls) or valacyclovir (60 m g/kg of body weight, PO). Virus shedding from both eyes and the oropha rynx was monitored every 2 days by virus isolation, and subjective cli nical scores were assigned daily for ocular and nasal discharge and co njunctival hyperemia. Urinalysis, CBC, and serum biochemical analysis were done prior to inoculation, and on days 2, 5, 7, 9, and 12 of infe ction. Differences in CBC and serum biochemical indices between groups were compared, as were differences between preinfection values and ma ximal postinfection values, rectal temperature, and scores for disease severity. Results-All cats developed acute conjunctivitis and rhiniti s typical of FHV-1 infection. Beginning between days 6 and 9, valacycl ovir-treated cats became noticeably more lethargic and dehydrated than did cats of the control group. Total WBC and neutrophil counts were s ignificantly lower in cats of the valacyclovir group. The experiment w as terminated on day 12 for humane reasons. Histologic changes attribu table to FHV-1 infection were similar in all cats. Additional histolog ic abnormalities seen only in the valacyclovir-treated cats were coagu lative necrosis of the renal tubular epithelium, centrilobular atrophy and hepatic necrosis, and severe bone marrow depression. Conclusions- Cats appear to be uniquely sensitive to the toxic effects of valacyclo vir, and even high doses appear not to suppress FHV-1 replication in a cutely infected cats. Clinical Relevance-Use of valacyclovir is of que stionable value in cats with acute FHV-1 infection and, at high doses, the drug may be toxic.