Comparison of background histologic findings in cynomolgus macaques of Philippine vs. other Asian origin

STP 2026 -- Background histologic findings in cynomolgus macaques (Macaca fascicularis) have been documented and at some institutions are also tracked via historical control databases (HCDBs). Comparison of spontaneous histopathologic findings between macaques of Mauritian, Chinese, Vietnamese, and Cambodian origin has revealed relatively minor variations that do not impact suitability for use in toxicology studies. However, changes in the research animal supply chain may result in institutions acquiring macaques from different sources, such as the Philippines. Because discrimination of subtle test article related effects relies on identifying differences from background findings, it is necessary to establish that background findings do not drift with a change in source population, particularly in studies without contemporaneous control animals. In this report we compare the incidence of histologic findings in control cynomolgus macaques of Cambodian, Chinese, and Mauritian origin with those of Philippine origin. Our results support pathologists in making a nuanced interpretation of subtle findings and demonstrate to clients and other stakeholders the maintenance of scientific rigor despite changing research animal populations.