Determination of the presence of Mycobacterium avium on Guam as a precursor to reintroduction of indigenous bird species

Abstract

Eight of 11 native forest bird species on Guam were extirpated by the introduction of the Brown Tree Snake Boiga irregularis. Emergency measures necessary to rescue the Guam subspecies of Micronesian Kingfisher Halcyon cinnamomina cinnamomina from extinction involved translocation and captive breeding in American mainland zoos. Soon after the establishment of a captive breeding population, the kingfisher demonstrated a high degree of susceptibility to avian tuberculosis (ATB), a disease that proved to be a major threat to the preservation of the species. The cause of ATB is Mycobacterium avium which produces a prolonged course of infection in kingfishers and other birds. Kingfishers infected with M. avium are difficult to detect until late in the course of the disease, thereby potentially posing a risk of transmitting ATB to the Guam captive population of Guam Rails Gallirallus owstoni, if kingfishers are repatriated. M. avium is considered to be ubiquitous in nature. However, there are no reported mortalities due to ATB in any bird species on Guam. In this study, six of twenty-one cultures yielded Mycobacterium spp., two of which were further identified as M. avium. Since this study demonstrates that M. avium already exists on Guam, repatriating kingfishers to Guam poses no threat of introducing a new pathological agent to the island's ecosystem. Strict quarantine procedures along with rigorous animal husbandry protocols should minimize risks of repatriating infected kingfishers to Guam, and prevent transmission of ATB to the captive population of Guam Rails and other bird populations on Guam.