Epizootic Hemorrhagic Disease In Michigan Deer
- Epizootic Hemorrhagic
Disease In Michigan Deer
By Steve Griffin
Local hunting and fishing gets so busy this time of year, it's easy
to ignore what's going on elsewhere. Sometimes, though, news brings a
shudder of recognition. A few years ago, a productive deer hunting
spot in Nebraska suddenly came up virtually deer-less.
Where we'd seen pretty good numbers of mature bucks and big does, we
were mostly seeing lone fawns. First one hunter, then another,
reported seeing an adult deer running with its lips rolled back, a
spot or 2 of blood visible. Several of us caught the sickening odor
of a decaying animal down near a marsh edge.
Epizootic hemorrhagic disease (EHD), we would learn, had pretty much
wiped out our hunting spot. Spread by tiny flying insects called
biting midges, EHD causes severe, flu-like symptoms in deer.
High fever sends deer toward water for relief, and that's often where
they die, often less than 3 days after becoming infected. Cattle can
suffer from it, but dogs and cats don't get it. EHD does not appear
to affect humans, but hunters are always urged to avoid contact with
sick animals. If deer survive the infection, they often have cracked
hooves or heavy hoof overgrowth.
A hard frost is said to kill off biting midges, ending that year's
outbreak. Whitetail populations recover, but it can take years.
This year, a news release reported EHD in west-central Indiana. Up to
30 EHD-killed deer were found there.
Then, a week or so ago, Michigan's DNR and Michigan State
University's Diagnostic Center for Population and Animal Health
confirmed 2 Allegan County deer infected with EHD. Their carcasses
were among about 50 dead deer found along southwest Lower Michigan
rivers and marshes. One was a free-ranging deer and 1 was privately
Bill Moritz, chief of the DNR's wildlife division, said Michigan
seldom gets hit with EHD, which he said is considered the most
important viral disease facing whitetails nationwide. It last struck
here in 1955 and 1974. "When all conditions are right -- weather,
virus and host -- the disease may occur," he said in a news release.
We're not alone. So far this year, besides Indiana, EHD has been
diagnosed in Oregon, Wyoming, Texas, Missouri, Illinois and Georgia.
If you find a dead deer near water, or if you shoot one with unusual
hoof growth or hoof damage, contact the nearest DNR office (Bay City,
Sanford or Gladwin, for most of us), or visit the DNR website at
From Patricia Doyle, PhD
A ProMED-mail post
International Society for Infectious Diseases
EHD is not uncommon in many states. EHD is an acute, infectious,
often fatal viral disease of some wild ruminants. This malady,
characterized by extensive hemorrhages, has been responsible for
significant epizootics in deer in the northern United States and
southern Canada. A similar hemorrhagic disease called bluetongue also
occurs in wild ruminants. The 2 diseases are antigenically different,
although there are similar clinical signs.
The first occurrence and subsequent identification of EHD occurred in
1955, when several hundred white-tailed deer ( Odocoileus
virginianus ) succumbed in both New Jersey and in Michigan. It was
considered a new disease of deer, and the name "epizootic hemorrhagic
disease" was suggested to describe its main clinical and pathological
Since the initial 1955 outbreak, this malady has occurred primarily
among white-tailed deer, although occasionally mule deer ( O.
hemionus ) and pronghorn antelope ( Antilocapra americana ) have also
The mode of transmission of EHD in nature is via a 'Culicoide biting
fly or gnat. 'Culicoides variipennis' is the most commonly
incriminated vector in North America. A common observation in
outbreaks involving large numbers of deer (as in Michigan, New
Jersey, and Alberta) is that they are single epizootics that do not
recur. Die-offs involving small numbers of deer (as experienced in
South Dakota and Nebraska) occur almost annually, and the disease
appears to be enzootic in these areas. All documented outbreaks of
EHD have occurred during late summer and early fall (August-October)
and have ceased abruptly with the onset of frost.
Clinical signs of EHD and bluetongue are similar. White-tailed deer
develop signs of illness about 7 days after exposure. A consistent
characteristic of the disease is its sudden onset. Deer initially
lose their appetite and fear of man, grow progressively weaker, often
salivate excessively, develop rapid pulse and respiration, and
finally become unconscious. Hemorrhage and lack of oxygen in the
blood result in a blue appearance of the oral mucosa, hence the
name "bluetongue". Between 8 and 36 hours following the onset of
observable signs, deer pass into a shock-like state, become
prostrate, and die.
The gross and histological lesions of EHD are characterized by
extensive hemorrhage, ranging from pin-point to massive in size, and
involve different tissues and organs in individual animals. No organs
appear to be exempt from hemorrhage, with the most regularly involved
being the heart, liver, spleen, kidney, lung, and intestinal tract.
Extensive hemorrhaging is the result of interference with the blood-
clotting mechanism together with degeneration of blood vessel walls.
Because of its very high mortality rate, EHD can have a significant
effect upon the deer population in a given area, reducing numbers
drastically. Hemorrhagic disease can be transmitted to other wild
ruminants. The EHD virus can infect domestic animals but rarely
causes disease. Presently there is no evidence that the virus crosses
Portions extracted from Roselake Wildlife Disease Laboratory site:
Patricia A. Doyle DVM, PhD
Bus Admin, Tropical Agricultural Economics
Univ of West Indies
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(as found at http://www.rense.com/general73/eepi.htm )