Secret Infection in Birds Shortens Lifespan

A secret infection in migratory birds has been shown to speed up the aging process and shorten lifespan, according to a new study.

The infection in question, caused by malaria, may seem harmless, as it exhibits no symptoms of illness; however, results published in the journal Science say otherwise. The mild infection may not produce any obvious direct negative effects, but in the long run it can have serious consequences in the form of a shortened lifespan.

"If this is a general mechanism for any type of mild, chronic infection, which is quite possible, it will mean our study is of major interest to understand the impact that mild illnesses can have on other organisms, including humans," researcher Dennis Hasselquist at Lund University in Sweden said in a statement.

Researchers believe this rapid aging has to do with a mechanism linked to the chromosomes in the cells of infected individuals, specifically the telomeres, or ends of chromosomes, which protect the DNA from damage. The longer the telomeres are, the greater the chance of living a longer life. However, in malaria-infected migratory birds the telomeres shorten at a faster rate and therefore accelerate aging compared to healthy birds.

Until now, scientists didn't believe that mild infections had an effect on survival and reproduction. That is, until the Lund University team studied malaria in great reed warblers, a species of migratory bird that breeds every summer on Lake Kvismaren in Sweden and spends winters in tropical Africa.

They found that those with chronic malaria - despite an extremely low number of parasites in the blood and no signs of illness - produced half as many young during their lifetime as non-infected birds. What's more, given their shortened lifespan their total number of young was also significantly lower.

These great reed warblers may have seemed fine on the outside, with males singing the same as healthy males and females feeding their young just as intensively as other healthy mothers, and yet they were dying on the inside.

This study goes to show that scientists have yet to learn more about mild illnesses like malaria, and can use these findings to better understand underlying mechanisms in various organisms, including humans.

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