Biologists Monitor White-tailed Deer Deaths
Recent reports of white-tailed deer deaths in southwestern North Dakota have wildlife biologists on the alert for a possible reoccurrence of epizootic hemorrhagic disease or EHD. To date, approximately 45 dead deer have been reported since the first of September. Aerial flights conducted by the State Game and Fish Department along the Little Missouri River and Cedar Creek yielded an additional 12 dead white-tailed deer.
"It appears that EHD could be the culprit," said Jacquie Ermer, disease biologist at the North Dakota Game and Fish Department's Riverdale office. "However, its presence has not yet been verified."
If it is EHD, occurrences appear to be on the edge of a more serious outbreak in northwestern South Dakota. So far, game and fish officials say losses are not significant enough to warrant suspension of antlerless licenses that are still available in affected units, or to justify refunding licenses already sold.
Only four reports yielded carcasses that were fresh enough for sampling, according to Bruce Stillings, big game biologist, Dickinson. Three of those samples were negative for the virus, with results of the fourth still pending.
EHD is a natural virus spread by a small biting fly - culicoides variipenis. Historically, EHD has been reported from more than 32 states and provinces across North America. It surfaces periodically in southwestern and western North Dakota, and primarily affects white-tailed deer. Sometimes the incidents are isolated and affect few animals. In other cases the disease is spread over a large geographic region with significant white-tailed deer mortality in localized areas.
Historically, EHD events are most noticeable in western North Dakota when high whitetail populations combine with a hot and humid late summer and early fall, which creates ideal breeding conditions for the culicoides fly. The last severe outbreak occurred in 2000, when the disease ranged through many counties south of Interstate 94 and west of the Missouri River.
White-tailed deer populations in the southwest are high again this year, Ermer said, and that part of the state has been hot and dry. "We are concerned and will continue to follow up on reports, and will keep the public informed if anything changes," Ermer said.
EHD causes dehydration and a high body temperature, causing deer to seek water prior to death. Some dead deer reported were found in or near water, Ermer confirmed, but said the carcasses were too badly decomposed for testing. To isolate the EHD virus, and many other disease agents, the animal cannot have been dead for more than 24 hours. "I would urge outdoor enthusiasts to report sick or dead deer to the North Dakota Game and Fish Department as soon as possible," Ermer emphasized.
Other clinical and behavior symptoms may include respiratory distress; swelling of head, neck, and tongue; lesions on tongue and roof of mouth; indifference to humans; and in later stages, hemorrhaging from body orifices.
Deer losses to the disease occur every year and are sometimes significant in localized areas, especially during dry years. Most deer that die from the disease are infected before the first hard frost, which kills the biting midges that spread the disease.
EHD is not a danger to humans. However, Ermer said, "Hunters should not shoot or consume a deer if it appears sick, rather contact the department."
Presently there is nothing that can be done to prevent EHD in deer populations, Ermer said. "Our best defense against EHD is to maintain deer populations below a level where disease becomes a major mortality factor," she added, "and the best proven method of doing that has been through a legal and regulated harvest."
Game and fish personnel also took fresh samples for chronic wasting disease testing. Signs of CWD - which so far has not been detected in North Dakota - can appear similar to EHD, however, the diseases are very different. Both diseases may cause the deer to become weak, depressed, or lose their appetite, but EHD kills a deer much quicker and is spread through a biting fly. CWD works slowly and is likely spread through close contact with other deer. CWD is most likely caused by an infectious protein called a prion that may be spread through feces, urine, or saliva. Deer are able to develop immunity to EHD, but not CWD.
Observations of sick or dead deer could increase in the coming weeks as hunting seasons continue to open and more hunters are in the field. Persons finding dead or sick deer should contact the game and fish department immediately, Stillings said, due to time constraints in obtaining fresh samples for testing. "Reports from the public will also assist the department in determining the distribution and severity of the outbreak," he said.