In the twentieth century, men toiling in British and American coal mines relied on a primitive alert system for imperceptible dangers: the bright canary bird. Miners toted the caged birds into the depths of the earth to serve as early warnings against poisonous and potentially fatal gas leaks. If the tiny birds suddenly slumped in their cages due to the presence of odorless and colorless carbon monoxide, miners would beat a hasty retreat to safer, cleaner air. Today the expression “canary in the coal mine” refers to early warning sentinels, those early casualties most susceptible to lurking and imperceptible dangers. But the use of animal sentinels has extended far beyond the limited usefulness of a single caged canary, and public health officials now pay close attention to the collective health of animal populations in close proximity to human settlements for the purpose of monitoring nascent challenges to public health and to detect environmental and infectious threats to man.
Trypanosoma cruzi parasites, the causative agent of Chagas disease, in the hindgut of a triatomine bug. Triatomines are also known as kissing bugs for their tendency to blood feed near mouths. Image: CB Beard et al. (2003) Chagas Disease in a Domestic Transmission Cycle in Southern Texas, USA. EID. 9(1).
