A female house finch with house finch eye disease, a form of conjunctivitis, or pinkeye, that is caused by the bacteria Mycoplasma gallisepticum. House finches that contract the disease develop swollen, weepy eyes, become lethargic, suffer reduced vision, and may succumb to adverse weather or be caught by predators such as hawks and cats. The disease has led to an estimated population decline of 40 million house finches in its first five years.
National Science Foundation (NSF)-supported researchers at the Virginia Polytechnic Institute are studying the disease, in particular, why pathogens cause harm to the hosts they depend on and why are some life-threatening, while others only give you the sniffles? The research offers a model to help understand how diseases that threaten humans may change in virulence as they become more prevalent in a host population.
"This study is the first to confirm predictions that pathogens may evolve to become more deadly. The results are important for planning responses to events such as the bird flu outbreak in China," said Sam Scheiner, NSF program director for the joint NSF-National Institutes of Health Ecology and Evolution of Infectious Diseases Program, which funded the research.
André Dhondt, director of bird population studies at Cornell University, says "there's an expectation that a very virulent disease will become milder over time, to improve its ability to spread, otherwise, it just kills the host and that's the end of it for the organism." House finch eye disease has given researchers an opportunity to test this--and they were surprised to see it actually become worse rather than milder.
To learn more, see the NSF press release Evolution in the Blink of an Eye. (Date of Image: 2000s) [Image 1 of 6 related images. See Image 2.]