Hamer Research Team Collaborates to Protect Endangered Whooping Crane Populations from Vector-Borne Parasites

Whooping Crane at Aransas Wildlife Refuge. Photo by Dave and Liz Smith.

Whooping Crane at Aransas Wildlife Refuge. Photo by Dave and Liz Smith.

A collaboration among Dr. Gabriel Hamer’s Research Team in the Department of Entomology, the College of Veterinary Medicine and Biomedical Science, and the International Crane Foundation is helping to save the whooping crane populations by studying vector-borne parasites in both whooping and sandhill cranes in the United States and Canada.

PhD student and veterinarian Miranda Bertram is leading the project, and works closely with Gabe as well as Dr. Sarah Hamer of the Department of Veterinary Integrative Biosciences, and Dr. Barry Hartup of the International Crane Foundation and Department of Surgical Sciences at the University of Wisconsin.

In this project, the team is studying the ecology and epidemiology of both bird species with a special interest in vectored pathogens such as Haemosporida, which includes avian malaria, as well as other parasites that are vectored by biting flies.

Hamer said that the goal is to find out the diversity and seasonal occurrence of parasites in cranes as a first step to determine whether the parasites are limiting the population growth of whooping cranes. To do this, Hamer’s team is studying whooping cranes, as well as using sandhill cranes as a surrogate species. The use of a surrogate species is a useful approach when studying an endangered species, since access to large numbers of individuals that are endangered is not attainable.

Sarah Hamer, left, and Miranda Bertram performing a necropsy on a sandhill crane in the TX panhandle. Photo by Gabe Hamer

Sarah Hamer, left, and Miranda Bertram performing a necropsy on a sandhill crane in the TX panhandle. Photo by Gabe Hamer

He said that the sandhill cranes are an appropriate species to study for the project because they are more common in the region they are studying, and some populations of sandhills co-mingle regularly with whooping cranes. He also said that sandhill cranes are a legal game species and are actively hunted in Texas, which allows the group to perform necropsies on large numbers.

Some populations of sandhill cranes share territory with whooping cranes on breeding, migration and/or wintering grounds, and are likely exposed to the same vectors and parasites. “Being able to necropsy sandhill cranes give us some indications of how the different parasites affect sandhill crane health, and that provides clues to whooping crane health, since the two crane species are closely related,” Bertram said.

Between December 2009 and July 2013, blood samples from whooping cranes were collected as part of a telemetry and health assessment study. In addition, sandhill crane populations were studied between November 2012 and this past January. Hamer said the samples collected from the assessment and necropsy studies were then subjected to PCR analysis and DNA sequencing in order to detect Plasmodium and Haemoproteus DNA.

The whooping crane blood samples were collected at various sites throughout the Aransas National Wildlife Refuge in Texas and the Wood Buffalo National Park in Canada. The sandhill crane blood samples were collected from several locations, including the Texas Panhandle around Canyon, Texas, and the Texas Gulf Coast around Francitas. Additionally, to allow them to test hypotheses about similarities in parasite occurrence between the two avian species that may relate to sharing the same environments, the group is also studying a population of sandhills from central,New Mexico, near Bosque del Apache National Wildlife Refuge, that has no spatial overlap with the whoopers.

According to preliminary results, the team found that more than half the whooping cranes and three-fourths of the sandhill cranes studied were infected with haemosporidian parasites, Bertram said. The phylogenetic analysis showed that many of the Haemosporida linages in the cranes grouped with previously reported parasites found in other areas in other bird species, although the primary lineage infecting the cranes appears to be undocumented genetically.

Describing the vector-borne blood parasites associated with the birds is a first step toward understanding their importance in overall avian health. Eventually, these data will be important for preventing disease-related population declines or declines due to stress from landscape modifications.

“As human activities modify the landscape, we are potentially degrading habitat required by the whooping crane,” Bertram said. “As whooping crane populations become stressed and as habitat is modified, the transmission of parasites and pathogens might increase and further compromise bird health.”

Hamer said that with this study they are hoping to keep crane populations healthy by identifying parasites that might be limiting population growth, which will allow management intervention strategies to minimize exposure to parasites. “Biting flies, specifically black flies, are known to directly impact the breeding success of experimental populations of whooping cranes in Wisconsin because they are a nuisance to the birds. As a result, vector control programs have been established to reduce the direct harm caused by black flies. Our study extends this work by showing that black flies and other biting flies like mosquitoes also indirectly impact cranes by serving as,vectors and exposing them to a suite of parasites that can cause problems.”

“Very little is known about whooping crane parasites, especially avian malaria. Studies in other bird species have shown that infection with avian malaria reduces reproductive success and population growth, and the parasites could have a similar impact on the cranes,” Hamer said. “We hope to identify where transmission is occurring and by which vectors, in order to provide managers the option to consider vector control to reduce exposure to parasites like avian malaria.”


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