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What Causes Hemorrhagic Disease? How Is Hemorrhagic Disease Spread?

Hemorrhagic Disease

Hemorrhagic Disease

Hemorrhagic Disease: In the Southeast and in Virginia, Hemorrhagic Disease is the most significant infectious disease of white-tailed deer, and outbreaks occur virtually annually.

What Causes Hemorrhagic Disease?

Epizootic hemorrhagic disease (EHD) and bluetongue virus are two related viruses that can cause hemorrhagic sickness. In North America, we have seen two strains of the EHD virus and five strains of the bluetongue virus. Since the symptoms of diseases caused by these viruses are similar, the term “hemorrhagic disease” is commonly used in place of the individual virus’ name.

How Is Hemorrhagic Disease Spread?

It is impossible to contract hemorrhagic fever just by touching someone with the virus. Culicoides flies, which are very small and biting, are the vectors. Biting midges are a frequent term for these insects, although they are also known by other names depending on where they are found.

When Does Hemorrhagic Disease Occur?

When the biting midges are plentiful, the hemorrhagic disease tends to break out around the middle of August and continue through the end of October. There is an abrupt end to HD epidemics when freezing temperatures kill the midges that spread the disease. Little is known about how the viruses survive the winter when the midges are dormant.

What Are The Signs Of Hemorrhagic Disease?

The virulence (severity) of the virus and the length of time it has been in the deer’s system both play a role in determining the outward symptoms. The majority of infected deer show no signs at all or relatively minor ones. The symptoms of a sick shift as the condition worsen. Animals may initially experience lethargy, fever, head, neck, tongue, and eyelids swelling, and respiratory distress.

Extremely deadly virus strains can cause death in deer in as little as 1-3 days. When deer live longer, they often develop health problems associated with old age, such as lameness, loss of appetite, and reduced activity. It is common to find dead or dying deer near water in late summer or early fall.

When Should You Suspect Hemorrhagic Disease?

When a sudden and unexpected death of a deer occurs in late summer or early fall, it is prudent to assume HD. Due to the high fever the deer experience in the early stages of the disease, it is not uncommon to see dead or dying deer near water (e.g., laying on or near the sides of ditches, streams, lakes, rivers, etc.).

What Should I Do If I Find What I Think Is A Dead Or Dying Hemorrhagic Disease Deer?

Do not approach the animal, nor should you try to kill or remove it. If you know where the animal is and want to report it, call the Department at (804) 367-1000 or write down the address of the nearest office and send a letter describing the situation. Offices may be reached at (540) 961-8304 in Blacksburg, (434) 392-9645 in Farmville, (540) 899-4169 in Fredericksburg, (434) 525-7522 in Lynchburg, (276) 783-4860 in Marion, (540) 248-9360 in Verona, and (804) 829-6580 in Charles City.

Each year, the Department collects reports on HD mortality, noting the area and approximating the total number of animals lost to the disease. Please be aware that the Department will not send anyone to investigate the HD report unless there are unusual circumstances.

How Many Deer Will Be Lost?

Virginia suffers from HD regularly, but the disease’s prevalence and impact can vary significantly yearly (see the graph below). There have been minor incidences here and there and large epidemics in 1999, 2002, 2005, and 2014, among other years. Losses during an outbreak of HD are typically under 25% of the population but have been as high as 50% on rare occasions.

As of this writing, HD has not caused the extinction of any deer populations. The Department’s research suggests mild winters, hot summers, and a June drought are three environmental drivers of HD activity in eastern Virginia. It is hypothesized that a lack of June precipitation creates optimal breeding sites for midges (mud flats) and lowers deer’ food and water sources, concentrating deer on the landscape and raising their physiological stress.

What Is The “Hoof Disease” I Hear Deer Hunters Talk About Related To Hemorrhagic Disease?

Many infected deer eventually recover, as was already mentioned. Fever at the outset of the disease often causes development pauses in the hooves and subsequent peeling or sloughing of the hoof walls in these animals that manage to survive (see photo). If a deer is found during Virginia’s general firearms deer season with sloughing/splitting hooves on two or more feet, the deer likely had HD a few months prior.

Was The Hemorrhagic Disease Outbreak Caused By Overpopulation?

However, the correlation between deer density and HD severity is not as plain and dry as one might hope. Regardless of deer density, an infection within a deer population could be affected by factors such as the number of immune deer, the severity of the virus, the proximity of cattle, or the number of midge vectors. But it’s reasonable to assume that dense deer herds will be more conducive to viral spread than less dense ones.

Are Livestock Affected?

Unlike the apparent impact of EHD and bluetongue viruses on white-tailed deer, determining the significance of these agents to domestic animals is more challenging. Infected cattle usually show no symptoms, although some may experience lameness, painful mouths, and reproductive issues due to the bluetongue virus.

Bluetongue virus can be carried temporarily in cattle. Cattle and EHD are less well understood. Isolation of the EHD virus from diseased cattle and subsequent investigations showing general antibody levels in cattle suggest that this virus is widely circulated. Sheep raised in a home setting have it much more manageable. While EHD seldom manifests in sheep, bluetongue can cause severe illness.

Will Livestock Become Infected From Deer?

Deer, cattle, and sheep have all been shown to contract the same virus simultaneously. When the disease is found in deer, it’s a sign that infected biting midges are in the area, putting other animals, including deer and livestock, in danger. Disease transmission from deer to livestock, or vice versa, has not been demonstrated, but once virus activity begins, both livestock and deer have the ability to feed an outbreak. Additionally, deer have not been reported as long-term EHD or bluetongue virus carriers.

Will Hemorrhagic Disease Recur?

Yes. Historically, there have been noticeable divides in the frequency of HD incidents across the state of Virginia. Tidewater and Piedmont physiographic zones also experience HD annually, while the former is more heavily affected. Greater HD activity is observed in the southern and central Piedmont regions than in Piedmont’s northern and southwestern areas. Rare HD cases have been reported west of the Blue Ridge in Virginia.

Can People Become Infected with Hemorrhagic Disease?

People are not at risk of coming into contact with infected animals, eating venison from infected deer, or being bitten by infected biting midges. Infected or abscessed deer may not be fit for human food if they develop HD.

What Can Be Done To Prevent Hemorrhagic Disease?

However, there is now very nothing that can be done to either stop or slow the progression of HD. Maintaining deer herds at levels intermediate to below the environment’s carrying capacity will reduce the likelihood of serious problems. The same is true for most white-tailed deer parasites and illnesses.

Recreational deer hunting, including harvesting antlerless deer if necessary, is the best and only realistic method of managing deer populations. Although reports of deer deaths due to HD tend to raise concerns, historical data shows that local deer populations can withstand a certain amount of mortality before being completely wiped out and that the outbreak can be contained by the approach of cold weather.

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