Just when you thought prions couldn’t get any scarier, you find out that some birds can pass the infectious proteins intact through their digestive systems. Yes, crows can pick up prions from eating infected meat, and then pass those prions on in their feces. This cheery news is courtesy of Kurt VerCauteren and his colleagues at the United States Department of Agriculture.
Prions are infectious misfolded proteins. Normally, malfunctioning proteins are simply discarded or dismantled, but not so with prions. Upon introduction into a cell, these peptides induce other proteins to misfold as well. In other words, prions are communicable despite having no genetic material. This rampant misfolding results in a number of incurable, deadly neurological diseases known as transmissible spongiform encephalopathies (TSEs). An example would be bovine spongiform encephalopathy, a.k.a. mad cow disease.
Wild animals also succumb to prions and are often scavenged by crows. To test whether prions can be spread by foraging crows, the researchers fed some captured wild American crows the brains of mice infected with prions. The crows’ feces were collected, radiated to kill microbes, diluted, and injected back into mice. 100% of the unfortunate mice treated in this manner came down with TSE. If this doesn’t sound ominous, let me remind you that crows can travel far distances and are indiscriminate poopers.
Kurt C. VerCauteren, John L. Pilon, Paul B. Nash, Gregory E. Phillips, & Justin W. Fischer (2012). Prion Remains Infectious after Passage through Digestive System of American Crows (Corvus brachyrhynchos) PLoS ONE : doi:10.1371/journal.pone.0045774