Feeding deer associated with a human and deer illnesses

Friday, July 10, 2009

You might call it the Bambi syndrome. Well-intentioned people who love deer think they are helping them by setting out food, usually corn. That practice is known as "recreational feeding." Corn is also sometimes used to bait deer to make it easy for hunters to kill them.

Jay Gaylen, owner of Hart's Family Center in Eureka Springs, said they sell quite a bit of deer corn.

"In the wintertime we sell more than in the summertime because there are more people trying to help the deer out in the winter," Gaylen said.

But feeding the deer does more harm than good. It can lead to deer overpopulation that can wreak havoc to the ecosystem. And it can kill the deer people are trying to help.

Deer feeding is definitely involved with a number of diseases, said Kevin Keel, DVM, PhD, Dipl. ACVP, a wildlife pathologist with the SE Cooperative Wildlife Disease Study in the College of Veterinary Medicine at the University of Georgia.

Bovine TB

"Bovine tuberculosis (TB) is a prime example," Keel said. "It is caused by a bacterium called Mycobacterium bovis. This bacterium is similar to the agent of human tuberculosis and can cause a generally milder disease in humans. It originally spilled over into deer from cattle, but has since been maintained in deer in a corner of Michigan. The occurrence of bovine tuberculosis in deer in Michigan is directly correlated with the practice of baiting deer. The more deer are fed, the greater the number with bovine TB."

Another good example is bovine brucellosis in and around Yellowstone National Park. Like bovine tuberculosis, this is a cattle disease that originally spread to elk and later to bison. In the Greater Yellowstone Area, elk and bison are artificially fed in the winter.

"This has led to high populations and a dense, focal accumulation of animals in the winter," Keel said. "This also happens to be the time when elk with brucellosis exhibit one of the principal signs of the disease, abortions. The aborted fetuses and placentas are heavily laden with the Brucella abortus, the bacteria causing the disease. These can contaminate the feed grounds so that animals may be infected while feeding, but other elk are often curious and will lick or nibble at the aborted material. This is a situation that greatly encourages transmission of the disease and the feed grounds certainly contribute to persistence of this disease in the Greater Yellowstone Area."

Chronic Wasting Disease

Another concern is Chronic Wasting Disease (CWD), which is the mad cow variant in deer. CWD is of double concern because there are worries that eating deer meat contaminated with CWD could cause human illness. With deer meat an important part of their diet for many people, this is a huge concern.

There is an organization called Arkansas Hunters Feeding the Hungry that last year harvested 1,000 deer that were sent to food banks and other charitable organizations. The Arkansas Game and Fish Commission says one deer can provide meals for between 50 and 100 people.

Keel said the practice of feeding deer is a concern with CWD because it is likely spread in a fecal-oral manner and persists in the environment.

CWD -- a tough study

"However, CWD is such a slowly progressive disease that it is much harder to investigate and we haven't been able to show the tight correlations with feeding that we've demonstrated with bovine tuberculosis and bovine brucellosis," Keel said.

The closest CWD has been found to Northwest Arkansas is western Kansas and northern Illinois.

Interstate transportation of captive deer and elk has been stopped in most states.

Other problems with feeding of deer include the syndrome of hair loss in white-tailed deer.

"We've also seen a number of deer with unusual swelling of the muzzle that seems to be associated with feeding," Keel said.

Another concern is, in some areas, the deer population has been linked to the prevalence of Lyme disease in people.

"This is not because deer carry the agent, but because they are an essential host in the life cycle of the tick that transmits the Lyme disease agent," Keel said. "However, this is a very complicated issue and the density of rodents, the intermediate hosts of the ticks, also has to be taken into account. Some studies found that tick density increased with deer density at a broad scale but others report that deer density is a poor predictor of tick abundance, probably due to the effect of rodent populations. Complete removal of deer is associated with elimination of the ticks, but that is not a realistic option unless you live on a small island."

The lone-star tick

Current evidence indicates a definite association between deer density and human diseases transmitted by the lone-star tick. Keel said white-tailed deer are the principal host for all life stages of the lone star tick and the abundance of the ticks and deer are tightly linked. Several human diseases (human monocytotropic ehrlichiosis, /Ehrlichia ewingii/ehrlichiosis and southern tick-associated rash illnesses) are known to be transmitted by lone star ticks or, in the case of southern tick-associated rash illness, are suspected to be transmitted by lone star ticks.

"These diseases were not recognized until the 1980s and 1990s and their emergence is likely associated with increasing populations of white-tailed deer," Keel said. "I should also add that I do a great deal of work on deer health and generally assess density dependent problems. Higher deer populations contribute not only to some infectious diseases, but also to greater parasite burdens that can impact deer health. Lungworms and parasites of the gastrointestinal tract are mostly responsible and are higher in areas of high deer density. These parasites can cause significant problems in deer particularly in younger animals."

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