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Disease Risks to Whooping Cranes and Sandhill Cranes

Whooping cranes are critically endangered and exist in a single natural migratory population in the wild.  This population spends the summer in Canada and winters along the Texas Gulf Coast. The number of whoopers has increased from a fewer than 20 in 1941 to a current estimate of 304 individuals, but the population remains at risk. A natural disaster or disease outbreak could have a major impact on the crane population, so it is important to learn which disease agents currently infect crane populations. We use non-invasive sampling approaches (i.e., collection of freshly voided fecal samples from the refuge) and classical and molecular parasitology techniques to characterize the parasite communities that infect the wild whoopers as a first step in determining which parasites may impact population growth.

Sandhill cranes are closely related to whooping cranes. Sandhill cranes share habitat and migration routes with whooping cranes, so they are likely exposed to the same diseases. Through partnering with hunters and field biologists, we perform field necropsies hunter-harvested sandhill cranes to search for visible signs of disease and take samples of all the organs and blood to test for a number of parasites, viruses, and toxins. In doing so, we are evaluating the sandhill crane as a surrogate species for the whooping crane for understanding population-level infection.  Surrogate species can be very useful in endangered species research because sample sizes are, by definition, very limited when working with a species of conservation concern.

After two winter seasons of sampling, we found that almost 30% of whooping crane fecal samples are positive for a protozoan parasite called coccidia. This is an important finding because the same species of coccidia has caused severe disease and death in captive crane chicks, and may be impacting population growth in the wild.  The most common parasitic worm we have found in sandhill cranes is a fluke infecting the trachea in over 40% of sandhill cranes. We have also detected protozoan blood parasites in almost 60% of whooping cranes and sandhill cranes; these parasites are spread by blood-sucking vectors. Once we obtain the genetic signatures of these parasites, we can link them to similar parasites that cause disease in other populations of wild birds.

In collaboration with the Schubot Center, Department of Poultry Science, Department of Entomology, Department of Veterinary Integrative Biosciences, Texas Parks and Wildlife Department, USGS Patuxent Wildlife Research Center, and the International Crane Foundation, we are currently sequencing the genome and transcriptome of the whooping crane and sandhill crane. Once analyzed, the genomes will be freely available to researchers and will provide a background for further understanding crane health and disease.

We aim to use our data to assist in whooping crane conservation and sandhill crane management so future generations can continue to enjoy these magnificent birds. We greatly appreciate financial support from the United States Fish and Wildlife Service, Region 2, Division of Migratory Birds- Avian Health and Disease Program; American Association of Zoo Veterinarians- Wild Animal Health Fund; The Cooper Ornithological Society; and the Schubot Center.