Occasionally a deer "dieoff" is reported to state wildlife biologists. Usually 5 to 20 deer are noted and experts are called in to analyze the situation. There are many diseases of deer and some of these (and other factors) cause many deer deaths in a brief time. Most frequently involved is hemorrhagic disease. Virus-produced, this one shows up in 6 of 10 years in Virginia. Only lab analyses are necessary to confirm the disease, but there is a recognizable set of symptoms:
- sloughing hooves (on 2 or more feet)
- ulcers in the deer's mouth
- scars on the rumen lining.
The Southeastern Cooperative Wildlife Disease Study operates out of Athens, Georgia, and does studies for state agencies. In a recent report, their scientists observed that the comment of 1967 is still true: this disease remains a major unresolved problem. There are no known treatments or prevention.
The virus is transmitted by the biting midges (genus Culicoides). There may be an intermediate reservoir. It is likely that when the midge populations are low, the deer are inoculated by small "doses" given the fawns by midges. When there are swarms of midges (for reasons we do not think anyone yet knows) then the virus may overpower the deer's defense system. The hidden (chronic) disease becomes acute and die-offs are seen.
In my fundamental population model, I hold that "crowding stress" operates. It has not been demonstrated in many large animals. The concept is that when animals are crowded (their perceived density goes past a threshold, then they are stressed). This is chronic stress. Their adrenal glands are enlarged and may become become dysfunctional. This prevents their immune system from working well. The hemorrhagic disease virus that is present in their system gains status and overpowers the deer. The ultimate form of death is respiratory failure. It is a long pathway from biting midges to adrenal glands, but one of the fascinations of wildlife studies is their complexity and parallels. A solution to one problem, may lead to solutions in entirely unsuspected areas.
Hunters and others may help work on solving this problem by:
- Making observations and records on biting midges (when they occur, where, abundance, etc.)
- Reporting deer with the above set of symptoms (road-kill deer as well as during the hunting season)
- Encouraging and supporting research on it at Virginia Tech and elsewhere.
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This Web site is maintained by R. H.
Giles, Jr.
Last revision January 17, 2000.
