Natural History of Inhalation Melioidosis in Rhesus Macaques (Macaca Mulatta) and African Green Monkeys (Chlorocebus Aethiops)

Burkholderia pseudomallei, the causative agent of melioidosis, is recognized as a serious health threat due to its involvement in septic and pulmonary infections in areas of endemicity and is recognized by the Centers for Disease Control and Prevention as a category B biothreat agent. An animal model is desirable to evaluate the pathogenesis of melioidosis and medical countermeasures. A model system that represents human melioidosis infections is essential in this process. A group of 10 rhesus macaques (RMs) and 10 African green monkeys (AGMs) was exposed to aerosolized B. pseudomallei 1026b. The first clinical signs were fever developing 24 to 40 h postexposure followed by leukocytosis resulting from a high percentage of neutrophils. Dyspnea manifested 2 to 4 days postexposure. In the AGMs, an increase in interleukin 1β (IL-1β), IL-6, IL-8, gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α) was observed. In the RMs, IL-1β, IL-6, and TNF-α increased. All the RMs and AGMs had various degrees of bronchopneumonia, with inflammation consisting of numerous neutrophils and a moderate number of macrophages. Both the RMs and the AGMs appear to develop a melioidosis infection that closely resembles that seen in acute human melioidosis. However, for an evaluation of medical countermeasures, AGMs appear to be a more appropriate model.