TB infection in the nonhuman primate biomedical model: tip of the iceberg?

Biomedical research in the 21st century increasingly relies on pathogen-free nonhuman primates (NHPs) to model human pathophysiology. Despite adherence to protocols designed to maintain pathogen-free colonies, reports of tuberculosis regularly appear. We hypothesize that, undetected by standard screening protocols, mycobacteria of the Mycobacterium tuberculosis complex (MTBC) continue to circulate in established NHP colonies and may, in addition, be periodically reintroduced with newly imported animals. The tuberculin skin test (TST), the accepted standard screening test for tuberculosis, relies on the host's immune response to detect infection, but empirical data suggest that TST lacks both specificity and, particularly in certain NHP species and in immune compromised animals, sensitivity. In order to improve the detection of MTBC infection in NHP colonies we propose new screening protocols that incorporate molecular methods to detect mycobacteria. These new tests do not rely on the host's immune response and may allow for strain typing of the pathogens - enhancing our ability to elucidate patterns of disease transmission. Moreover, the ability to rapidly and noninvasively collect specimens could lead to an improved appreciation of the burden of MTBC circulating in populations of NHPs and humans, including drug-resistant strains, data that are invaluable to public health efforts.