A new pathogen has been discovered by scientists investigating majordie-offs of pigeons native to North America, according to studies ledby the University of California, Davis, and the California Departmentof Fish and Wildlife.
Scientists were able to implicate this new parasite, along with theancient parasite Trichomonas gallinae, in the recent deaths ofthousands of Pacific Coast band-tailed pigeons. The die-offs occurredduring multiple epidemics in California's Central Coast and SierraNevada mountain ranges. Scientists named the new pathogen Trichomonasstableri.
Avian trichomonosis is an emerging and potentially fatal disease thatcreates severe lesions that can block the esophagus, ultimatelypreventing the bird from eating or drinking, or the trachea, leadingto suffocation. The disease may date back to when dinosaurs roamedthe earth, as lesions indicative of trichomonosis were found recentlyin T-Rex skeletons. The disease may also have contributed to thedecline of the passenger pigeon, whose extinction occurred exactly100 years ago.
Epidemics of the disease can result in the death of thousands ofbirds in a short amount of time. An outbreak in Carmel Valley killedan estimated 43,000 birds in 2007.
"The same parasite species that killed band-tailed pigeons during theoutbreaks were also killing the birds when there weren't outbreaks,"said lead author Yvette Girard, a postdoctoral scholar with theWildlife Health Center in the UC Davis School of Veterinary Medicineat the time of the studies. "This indicates there may be otherfactors at play in the die-offs."
"We are now investigating what triggers these die-offs, which may becaused by the congregation of infected and vulnerable birds duringcertain environmental conditions, or even spillover from anothernearby species," said principal investigator Christine Johnson, aprofessor with the UC Davis Wildlife Health Center.
Three band-tailed pigeons perch in Santa Barbara County. Researchers at UC Davis and the California Department of Fish and Wildlife have identified trichomonosis as a key factor in winter die-offs and the population decline of this native migratory game bird.
(Photo Credit: Courtesy Dianne Ricky)
Between winter 2011 and spring 2012, there were eight mortalityevents -- defined as more than five dead birds found in the samegeographic area during the same time frame. The study saidtrichomonosis was confirmed in 96 percent of dead, sick or dyingbirds examined at seven of the mortality events. This disease wasalso found in:
- 36 percent of band-tailed pigeons at wildlife rehabilitation centers
- 11 percent of hunter-killed band-tailed pigeons
- 4 percent of the birds caught live and released
"What makes this disease more troublesome for band-tailed pigeons istheir low reproductive rate -- about one chick per year -- and alsothat these events are occurring in the wintertime," said co-authorKrysta Rogers, an environmental scientist with the CaliforniaDepartment of Fish and Wildlife. "That means almost all the birdswe're losing during events are adult birds. They're being killedbefore they have the ability to reproduce in the spring."
Mortality events in band-tailed pigeons have been reported inCalifornia at least since 1945, but have increased during the lastdecade, with outbreaks reported in six of the last 10 years.
"Going into the study, we expected to find a single, highly virulentspecies of Trichomonas in birds sampled at outbreaks," Girard said."Having two species killing birds at these large-scale mortalityevents is surprising."
Necropsies of the birds were conducted at the California AnimalHealth and Food Safety Laboratory at UC Davis and the WildlifeInvestigations Laboratory at the California Department of Fish andWildlife.
Both studies were funded by the California Department of Fish andWildlife and the U.S. Fish and Wildlife Service.
The study naming the new species of parasite is published in thejournal International Journal for Parasitology: Parasites andWildlife. The study that explains how trichomonosis is affecting theband-tailed pigeon is published in the journal Infection, Geneticsand Evolution.
Source: University of California - Davis