Newly Discovered Parasite Threatening Band-Tailed Pigeons

A newly discovered parasite is threatening band-tailed pigeon populations, giving scientists a clue as to why there have been so many die-offs in North America, a new study says.

Trichomonas stableri is the new pathogen responsible for the epidemic sweeping through the Pacific Coast, killing thousands of band-tailed pigeons in California's Central Coast and Sierra Nevada mountain ranges. Not only that, but the ancient parasite Trichomonas gallinae is also implicated in the recent deaths.

The recent epidemic spreading among this species is Avian trichomonosis, a potentially fatal disease that creates severe lesions in the birds, either in the trachea - causing suffocation - or in the esophagus - preventing them from drinking and eating.

Scientists believe the debilitating disease may have been related to the decline of the passenger pigeon 100 years ago - an extinct species that other researchers are currently attempting to bring back to life.

"We are now investigating what triggers these die-offs, which may be caused by the congregation of infected and vulnerable birds during certain environmental conditions, or even spillover from another nearby species," principal investigator Christine Johnson, a professor with the UC Davis Wildlife Health Center, said in a statement.

Between winter 2011 and spring 2012, there were several mortality events involving the band-tailed pigeon, and trichomonosis was confirmed in 96 percent of the dead, sick or dying birds. It also infected 36 percent of birds in rehabilitation centers, 11 percent of hunter-killed band-tailed pigeons and 4 percent of the birds caught live and released.

Band-tailed pigeon die-offs are not something out of the ordinary, but they have increased within the last decade - outbreaks have been reported in six out of the last 10 years.

And unfortunately for these birds, they are more susceptible a die-off caused by this disease, compared to other birds.

"What makes this disease more troublesome for band-tailed pigeons is their low reproductive rate," explained co-author Krysta Rogers. "That means almost all the birds we're losing during events are adult birds. They're being killed before they have the ability to reproduce in the spring."

The new pathogen is described in the journal International Journal for Parasitology: Parasites and Wildlife, and the study describing how trichomonosis is affecting the band-tailed pigeon is published in the journal Infection, Genetics and Evolution.