News Release 

Citizen science data tracks battle of birds vs bacteria

Cornell University

Research News



"We have an escalating arms race," said Cornell Lab researcher Wesley Hochachka, first author of "Host Population Dynamics in the Face of an Evolving Pathogen," which published April 5 in the Journal of Animal Ecology. "Finches who become infected but survive acquire some immunity to that version of the bacteria and its predecessors. The bacteria evolve to get around the strengthened finch immunity. Then birds acquire immunity to the latest strain, and the cycle keeps repeating.

The study's authors believe that acquired immunity - when the immune system creates antibodies in response to an infection - is actually driving the arms race between the birds and the bacteria. They said imperfect acquired immunity, just like imperfect vaccines against human pathogens, creates the conditions needed to favor the proliferation of new strains of the bacteria that can overcome immunity acquired against existing strains of bacteria.

Immunity can also develop through genetic changes to the house finches, but this would be a relatively slow process, requiring multiple years for genetically novel and resistant finches to become widespread. In contrast, genetic changes to the bacteria can proliferate within hours - so fast that populations of house finches can't possibly evolve a defense quickly enough.

"We should really pay more attention to the role that acquired immunity can play in the dynamics of disease in any animal," Hochachka said. "Interactions can be much more complicated when both the host and the disease are able to change rapidly."



The finch eye disease dynamic has parallels to human health and the use of vaccines to give people acquired immunity to diseases. Here also, imperfect immunity - vaccines that do not provide perfect protection - are believed to accelerate the spread of new strains of pathogens against which vaccines are ineffective.

"The emergence of new diseases is going to keep happening," Hochachka said. "We just have to develop methods and systems for dealing with it as best we can when a lethal disease appears."


