Clinical disease associated with simian agent 8 infection in the baboon.

Simian agent 8 (SA8) is an alphaherpesvirus that was first reported as a spontaneous natural infection in a captive baboon colony in 1988. It was first isolated from an African vervet monkey in 1958 and was classified as a simian agent. Simian agent 8 was later isolated from a baboon rectal swab specimen in 1969 and from an oral lesion in a vervet monkey in 1972. Restriction endonuclease analysis was used to identify the virus as SA8. In a 1-year period, 70 baboons housed in two outside 6-acre breeding corrals developed lesions principally on the genitalia and oral cavity. The incidence was the same for males and females, with recurrence rate, severity of the lesions, and duration for the lesions to resolve being greater in the female baboons. Lesions involving the mouth, tongue, and lips were most commonly observed in the juvenile population. The lesions tended to start as small multiple papules or vesicles, which advanced to large pustular or ulcerative areas. Using an every-other-day treatment regimen consisting of Nolvasan cleaning and procaine penicillin G injections, it took an average of 14 to 21 days for the lesions to resolve totally. Thirty-seven percent of the baboons with herpetic lesions experienced another episode of SA8 infection, usually within 1 year of development of the primary lesion. Several complications have been documented to be associated with SA8 infections. Partial or total vaginal obstruction is most common, leading to impaired breeding performance and pyelonephritis. A vaginal corrective surgical procedure has been developed to allow these females to return to productive breeding status within the colony. Penile urethral obstruction, also causing pyelonephritis, was observed in the male baboons. A case of sciatic neuritis was reported in a baboon that presented with self mutilation of the foot; viral isolation revealed the etiologic agent to be SA8. Four female baboons with chronic SA8 infections went on to develop perineal neoplasms. This is an economically important disease entity in captive baboons because it causes severe morbidity, decreased reproductive performance, and ultimately death in 1% of the baboon colony each year. The baboon is a promising animal model in which to study genital herpes as it relates to disease in human beings.