A vast majority of diseased birds taken into clinics and rehabilitation centers have died. At City Wildlife, all the birds arrived with such severe symptoms that they died within days or their disease progressed to the point that they had to be euthanized. “Not being able to do anything but relieve the suffering of these birds has been a very emotionally taxing experience,” Dr. Chooljian wrote in an email.
Nearby, the Wildlife Center of Virginia was also overrun with sick birds that did not respond to medication. “I’ve never lost so many birds before,” said Jennifer Toussaint, the chief animal control officer at the center. Out of concern that the disease could be contagious to other birds, both City Wildlife and the Wildlife Center of Virginia now recommend putting the birds down on intake.
Although the cause of the disease officially remains a mystery, people have proffered a number of theories. On the internet, the favorite culprit is Brood X, the periodical cicadas that spent the last 17 years underground only to emerge this year in teeming, singing masses, around the time the bird disease emerged. Though many cicadas’ long-awaited bacchanalia has gone off without a hitch, others have fallen prey to a zombifying white fungus, which some have speculated could be the cause of the disease.
To Dr. Chooljian, the eye symptoms initially resembled those associated with the disease mycoplasma conjunctivitis, also called house finch eye disease. But the sick birds did not respond to the clinic’s usual treatments for house finch eye disease which, she added, does not cause neurological symptoms.
“Who knows at this point,” Dr. Casey said, adding that she does not want to rule out anything but doubts the cicada hypothesis. “In general, more of us are leaning toward an emerging bacterial infection,” she added, pointing to the eye lesions that seem similar to the bacterium-caused conjunctivitis.
The full results from the diagnostics lab may not come for several more weeks, according to Dr. Casey. The dead birds, their eyeballs and their flesh have been put through a battery of molecular tests for fungi, parasites and bacteria. There is still a possibility, however, that all these tests will be inconclusive, she said, adding that the diagnostics lab is holding on to a handful of corpses for retrospective testing in future years.