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Study Reveals Impact of Cold Temperatures on Bird Pink Eye Pathogen

Recent research indicates that the pathogen responsible for a form of bird pink eye can survive significantly longer on bird feeders during winter months compared to summer, without diminishing its potency.

“In lower temperatures, birds have a much longer opportunity—up to seven days—to encounter this pathogen on feeders,” explained Sara Teemer, a doctoral candidate in biological sciences, set to graduate in May. “In contrast, during warmer periods, that timeframe is reduced to just two days.”

Teemer’s research, published in the journal Ecosphere, focuses on the effects of Mycoplasma gallisepticum, a pathogen that leads to a specific type of conjunctivitis in birds. The findings highlight that at cold ambient temperatures, this pathogen remains infectious on bird feeders for up to a week, significantly exceeding previous observations. This is particularly concerning for house finches during colder months, as they increase their food consumption to maintain body heat, coinciding with a scarcity of natural food resources.

The study uncovered another critical detail: the severity of the disease in birds was greater when the pathogen was incubated on feeders exposed to lower temperatures compared to those at warmer temperatures.

“It was quite surprising to find that the pathogen we swabbed from bird feeders after a week still caused disease as severe as if it had just been transmitted from an infected bird,” noted Dana Hawley, a biological sciences professor and co-author of the study.

To arrive at these findings, researchers conducted experiments using feeders in controlled laboratory settings simulating typical winter and summer temperatures in Southwest Virginia. They inoculated the feeders with the pathogen and later assessed the remaining viable pathogen cells and the resultant disease severity in birds over time.

“Outbreaks of mycoplasmal conjunctivitis in house finches tend to occur during the winter months, coinciding with when birds heavily depend on feeders for energy to survive the cold,” Teemer said, also affiliated with the Global Change Center. “Given that past studies have shown the pathogen can spread from feeders, I was particularly interested in the role colder temperatures might play in its endurance and transmission.”

The transmission of this pink eye pathogen occurs through direct contact or when an infected bird sheds pathogenic cells at feeding ports, potentially infecting other birds. While some wild birds can recover, others may fall prey to predators due to impaired vision. All birds used in this study, however, made a recovery.

Documented outbreaks of this pathogen have been occuring in Eastern house finches since 1994, leading to a significant population decline of over fifty percent, from which they have not yet recovered. Nonetheless, house finches remain one of the predominant backyard bird species, making them an important subject for research.

“While the pathogen clearly affects bird survival and their potential for population growth, it is not a species that raises conservation alarms,” Hawley noted, also associated with the Fralin Life Sciences Institute Global Change Center.

Gaining insight into how ambient, or environmental, temperatures influence pathogen longevity in the absence of a host could provide valuable information about the impact of non-living factors in ecosystems on disease transmission and management strategies aimed at curtailing spread.

Hawley suggested that bird enthusiasts with feeders can play a role in lessening the pathogen’s transmission among house finches by maintaining cleanliness.

“Our research indicates that cleaning feeders is particularly effective during colder periods,” Hawley stated, underlining the importance of regular maintenance. “We recommend wiping down perches and feeding ports at least once a week with a bleach solution to eliminate pathogens present.”

Looking ahead, the research team plans to investigate other environmental elements that may influence the pathogen’s longevity and capacity to cause disease on feeders, including humidity and exposure to ultraviolet light. Gaining a comprehensive understanding of how the pathogen survives outside a host is crucial for developing methods to limit its spread.

Despite these findings, researchers advise against removing bird feeders right away.

“I keep a bird feeder in my yard throughout the year because it offers vital support to birds and creates a connection to nature for those who maintain them,” Teemer emphasized. “Provided it is done responsibly, both birds and people benefit from feeding them.”

Other contributors to the study, funded by the National Science Foundation, included Alicia Arneson, a Ph.D. student in Hawley’s lab, along with Edan Tulman and Steven Geary from the University of Connecticut, Storrs.

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