August 3, 2009
Ouchless Wildlife Plague Vaccine, Shipwrecks And Coral Reefs And More
A new oral vaccine against sylvatic plague is showing significant promise in the laboratory as a way to protect prairie dogs and may eventually protect endangered black-footed ferrets who now get the disease by eating infected prairie dogs, according to results by a USGS researcher at the USGS National Wildlife Health Center. Sylvatic plague is an infectious bacterial disease usually transmitted from animal to animal by fleas. This exotic disease is usually deadly for black-footed ferrets and their primary prey, prairie dogs, resulting in local extinctions or regional population reductions. Along with other wild rodents, prairie dogs are also considered a significant reservoir of plague for other wildlife, domestic animals, and people in the western U.S. Prevention of plague in wild rodents by immunization could reduce outbreaks of the disease in animals, thereby reducing the risk for human exposure to the disease.
USGS scientists offered plague vaccine in food for voluntary consumption by 16 black-tailed prairie dogs. They also injected a plague vaccine into 12 other prairie dogs and then studied how much protection against plague the two kinds of vaccines offered. USGS researcher Dr. Tonie Rocke, the lead researcher of the project, found that the prairie dogs that "ate" their vaccine were better protected from the disease than the ones who were injected with a vaccine. These results, said Rocke, demonstrate that oral immunization of prairie dogs against plague provides significant protection from the disease, at least in the laboratory. Black-footed ferrets, of course, are one of the rarest mammals in North America. An oral vaccine, said Rocke, could be put into bait and delivered into the field without having to handle any animals, a process that is time-consuming, costly, and sometimes stressful for the animals. The same bacterium that affects ferrets, prairie dogs, and other rodents, is also responsible for human cases of plague. For more information, contact Dr. Tonie Rocke at 608-270-2451 or [email protected]
Shipwrecks Wrecking Coral Reefs? A Case Study at Palmyra Atoll National Wildlife Refuge:
For the first time, researchers have definitively shown that shipwrecks and other man-made structures increase the potential for large invasions of unwanted species into coral reefs, even comparatively pristine ones. These unwanted species can completely overtake a reef and eliminate native corals, dramatically decreasing the diversity of marine organisms on the reef. Coral reefs can undergo fast changes in their dominant life forms, a phenomenon referred to as phase shift. Scientists have speculated on many possible causes of phase shift, but this study is the first one to clearly show that a rapid change in the dominant life forms on a coral reef is associated with man-made structures.
In September 2007, USGS researcher Dr. Thierry Work, Dr. Greta Aeby from the Hawaii Institute of Marine Biology, and Dr. James Maragos from U.S. Fish and Wildlife Service studied a 100-foot vessel that wrecked in 1991 on isolated Palmyra Atoll in the central Pacific Ocean. They found extremely high numbers of an invasive species related to anemones and corals, Rhodactis howesii, on and around the shipwreck site. The density of this species progressively decreased with distance from the ship, and it was rare or absent in other parts of the atoll. Likewise, the researchers confirmed high densities of R. howesii around several buoys installed on the atoll in 2001.
Even though phase shifts can have long-term negative effects for coral reefs, eliminating organisms responsible for phase shifts can be difficult, particularly if they cover a large area. The extensive R. howesii invasion and subsequent loss of coral reef habitat at Palmyra highlights the importance of rapid removal of shipwrecks on corals reefs to help prevent reefs from being overgrown by invasive species.
"Why this phenomenon is occurring remains a mystery," said Work, a scientist at the USGS National Wildlife Health Center's Honolulu Field Station. One possibility, he said, is that iron leaching from the ship and mooring buoy chains, accompanied with other environmental factors particular to Palmyra Atoll, are somehow promoting the growth of Rhodactis. For more information, contact Dr. Thierry Work at 808-72-9250 or [email protected]
Society, Wildlife Disease and Wildlife Conservation: Oxymoron or Evolutionary Siblings?
Over the past 50 years, the field of wildlife disease as an issue for concern has exploded in significance, mostly because of the increased realization that most emerging human diseases are "zoonotic," that is, diseases that can spread from people to other animals or vice-versa. USGS emeritus scientist Dr. Milt Friend, in an invited talk at the Wildlife Disease Association conference, will explore how and why the field of wildlife disease research has changed over the last 50 years.
One of the biggest differences, says Friend, is that until very recently, wildlife disease was not an important focus for the wildlife conservation community. "Now, though, a new wave of social environmentalism and public concerns about emerging zoonotic diseases are placing increased pressure on wildlife agencies to address disease 'crises' involving wildlife," Friend says.
He emphasizes, however, that emerging zoonotic diseases often result in double jeopardy for wildlife: not only do wildlife often suffer direct negative effects from a disease, they also endure indirect effects associated with actions taken to reduce human risks by suppressing wildlife populations. In addition, says Friend, wildlife can also be jeopardized by actions taken if they happen to share diseases with domestic animals, even if those diseases do not pose a significant public health threat. "Conversely, within the wildlife conservation community, the role of disease as a factor for species extinctions is receiving increased worldwide attention," Friend noted. For more information, contact Dr. Milton Friend at 608-270-2488 or [email protected]
Disease Risks When Moving Wildlife to New Areas: Endangered Laysan Duck Cautionary Tale:
Laysan ducks, one of the world's most endangered waterfowl, are native to only the Hawaiian archipelago. For 150 years, Laysan ducks were restricted to an estimated 4 square kilometers of land on Laysan Island in the northwestern Hawaiian Islands. In 2004 and 2005, in an effort to rebuild the population, biologists released 42 Laysan ducks on Midway Atoll, located one day's boat ride from Laysan. By 2007, a breeding population was well established on Midway, reaching 200 ducks. However, in August 2008, more than half of the Midway duck population (181 ducks) was lost to a disease epidemic lasting 30 days. Necropsies (the animal equivalent of autopsies) on dead birds revealed botulism type C as a cause of the die-off.
Disturbingly, said Work, 3 ducks were also infected with a worm suspected to be Echinuria uncinata; this worm has been responsible for mass die-offs of Laysan ducks on Laysan Island. Work notes that this worm was either moved to Midway during translocations of ducks from Laysan, despite preventive treatment of all founding birds, or it arrived with migratory waterfowl. Either way, says Work, this epizootic highlights the disease risk to birds restricted to small island populations and the challenges associated with managing newly translocated endangered species. Frequent population monitoring for early disease detection and comprehensive wetland monitoring and management will be needed to offset the potential effects of avian botulism and parasitism on endangered Laysan ducks, Work said. The bigger picture, though, is that disease risks need to be closely examined for translocations of all kinds, especially in light of translocations being proposed for dealing with habitat range changes that affect endangered species due to climate change. For more information, contact Dr. Thierry Work at 808-72-9250 or [email protected]
Bat white-nose syndrome:
An emerging fungal pathogen? New research provides even more evidence that a previously undescribed, cold-loving fungus is associated with white-nose syndrome, a condition linked to the deaths of up to 1,000,000 cave-hibernating bats in the northeastern and mid-Atlantic states. Since the winter of 2006-2007, bat populations plummeted from 80 to 97 percent at surveyed bat-hibernation caves, called hibernacula. USGS microbiologist Dr. David Blehert and his colleagues identified the fungus last year, and have followed up by trying to determine if the fungus may be responsible for the deaths or if it is simply a side effect of another underlying disease. The researchers found that 90 percent of all bats they examined from suspected WNS sites had a severe fungal skin infection that did not just occur on the skin, but below it as well. The growth temperature requirements of the fungus are consistent with the core temperatures of cave-hibernating bat species throughout temperate regions of the world. Given the hundreds of thousands of hibernating bats found throughout the WNS-affected region, as well as the potential for the spread of this disease to other parts of the United States and Canada, white-nose syndrome represents an unprecedented threat to bats of the northeastern United States and potentially beyond. For more information, contact Dr. David Blehert at 608-270-2466 or [email protected]
Sick Fish May Get Sicker: Climate Change and Other Stresses Expected to Affect Entire Populations of Fish (see full press release on this subject at http://www.usgs.gov/newsroom/)
Entire populations of North American fish already are being affected by several emerging diseases, a problem that threatens to increase in the future with climate change and other stresses on aquatic ecosystems, according to a noted U.S. Geological Survey researcher giving an invited talk on this subject today at the Wildlife Disease Association conference in Blaine, Wash.
"A generation ago, we couldn't have imaged the explosive growth in disease issues facing many of our wild fish populations," said Dr. Jim Winton, a fish disease specialist at the USGS Western Fisheries Research Center. "Most fish health research at that time was directed toward diseases of farmed fish." In contrast, said Winton, recent studies in natural aquatic systems have revealed that, in addition to being a cause of natural death, infectious and parasitic fish diseases can produce significantly greater mortality in altered habitats leading to population fluctuations, extinction of endangered fish, reduced overall health and increased susceptibility to predation. For more information, contact Dr. Jim Winton at 206-526-6282, x328 or [email protected]
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United States Geological Survey