House Finches are often associated with the disease, but many species tested positive in the study. (photo by Errol Taskin)
Researchers working with the Cornell Lab of Ornithology have found that a bird eye disease which was previously thought to only infect finches is actually prevalent in many different species of birds that regularly visit US backyards.
Until now, the bacterium, known as Mycoplasma gallisepticum, was so commonly found in the red-colored House Finches that it was commonly called House Finch eye disease. It first appeared in North America in 1994 when birdwatchers started seeing birds with swollen, runny eyes visiting their feeders. André Dhondt, director of Bird Population Studies, says that a strain of the bacteria, usually found in poultry, was able to grow successfully in House Finches and has been mutating since it was first detected.
Dhondt’s team trapped nearly 2,000 individual birds from 53 species between January 2007 and June 2010, and tested them for evidence of current infections. Diagnostic tests revealed that 27 species of birds were infected by this bacterium, although the lab notes in the release that the actual number of species exposed to the bacteria could be even higher because the test for antibodies is known to produce false negatives. The lab also notes that not every bird species which tested positive in their study exhibited the conjunctivitis symptoms most commonly associated with the bacterium.
Black-capped Chickadees, though exposed to the mycoplasma bacterium, do not show symptoms of eye disease. (Photo by Shirley Gallant.)
Black-capped Chickadees, Tufted Titmice, and American Goldfinches were on the list of those which tested positive, as were some forest species, such as Wood Thrushes.
“That was another surprise,” stated Dhondt. “How on earth do Wood Thrushes get infected with mycoplasma? They’re not a feeder bird at all. Everyone has always assumed that feeders play a major role in the transmission of the disease and this study shows that’s not necessarily so.”
The lab has long notified homeowners of the need to keep feeders clean, and they are once again asking homeowners to be diligent in order to protect the further spread of the bacterium. The lab further notes that if you see sick birds, leave them alone, take down your feeders and clean them, being sure to wash your hands thoroughly afterward.
“The organism could mutate into a form that is much more virulent among other bird species and create a new epidemic,” Dhondt said. He also added that while they now know that many species of songbirds are exposed to Mycoplasma gallisepticum, investigators still do not know whether the bacteria in other species of songbirds are identical to that living in House Finches in the same area.
The paper, Diverse Wild Bird Host range of Mycoplasma gallisepticum in Eastern North America, is co-authored by André Dhondt, Jonathan C. DeCoste, and Wesley M. Hochachka from the Cornell Lab of Ornithology and David H. Ley of North Carolina State University. It was published in the journal PLOS One on July 25, 2014, and can be found online here.