(p. D6) The kakapo, a large flightless parrot that can live 95 years and perhaps longer, is dangerously close to extinction. Once found throughout New Zealand, the population has dwindled to fewer than 150.
Conservation biologists are doing everything they can to keep the kakapo from vanishing. And so, when they discovered a few years ago that a pair of captive kakapos were infected with tapeworms, they did the obvious thing: They dewormed the birds.
Hamish G. Spencer, a geneticist at the University of Otago in New Zealand, thinks that was unwise. If endangered species are going to escape extinction, he argues, they may need parasites to survive.
“Some of these parasites may turn out to be quite good for their hosts,” Dr. Spencer said.
. . .
Evidence accumulated over the decades for what came to be known as the hygiene hypothesis. Supporters argued that over the past two centuries, modern civilization has radically changed our relationship with our inner residents.
For millions of years, our evolving bodies had to strike a tricky balance. We depended on a powerful immune system to fend off deadly infections. But if the immune system were to attack indiscriminately, it could destroy the body’s beneficial bacteria, for example, or damage its tissues with relentless inflammation.
According to the hygiene hypothesis, our ancestors came to tolerate low levels of infection. They even came to depend on parasites to help the immune system develop properly.
. . .
It’s possible, Dr. Spencer said, that the lack of parasites may help explain why some species restoration projects have been disappointing. “There are a number of cases where reintroduced populations haven’t done very well,” he said. “It might be that their immune systems are not very good.”
. . .
A first step, Dr. Spencer said, would be to stop medicating captive animals so freely. “We are arguing against the idea that you just dose the hell out of everything before you put animals back in the wild,” he said.
For the full story see:
Carl Zimmer. “Parasites as Welcome Guests.” The New York Times (Tuesday, April 5, 2016 [sic]): D6.
(Note: ellipses added.)
(Note: the online version of the story has the date March 31, 2016 [sic], and has the title “Tapeworms and Other Parasites Can Make Good Guests.” The paragraph that starts “For millions of years,” appears in the online version, but not in the print version.)
For more on the hygiene hypothesis see the following academic article: