October 01, 2016

Epizootic Hemorrhagic Disease (EHD) was first identified in 1955 when several hundred whitetail deer succumbed to it in both Michigan and New Jersey…

Prior to this there had been recorded deer die-offs in North America since 1890 that could possibly be attributed to EHD, but this is unknown. EHD is an acute and infectious viral disease that can cause a high mortality rate which in turn can create a significant impact on the deer population in a locality, and there is no effective treatment or control for it.

photo by Author photo.

The common vector for EHD is the midge (Culicoides biting fly) and when deer are bitten by small midges carrying the disease the onset can be quite sudden, with the deer showing signs of the illness in only a week after exposure. The deer will lose its appetite and even its fear of humans and will usually seek out and lie in bodies of water in an attempt to cool off due to a high fever. A majority of the dead deer due to EHD are found in wetland associated areas.

Although EHD is very similar to another virus called “Blue Tongue”, it is antigenetically different. As its name implies, EHD causes extensive hemorrhaging that involves different tissues, body organs and the intestinal tract, and once a deer shows the signs of the illness it can go down and die in only 8 to 36 hours. Some deer do recover from the virus, and if so they have developed antibodies which will readily resist EHD for the remainder of its life. However there must be a continual exposure to EHD in order for a particular deer herd to develop any extensive immunity to it (an example is the southeastern U.S. that has experienced a continual EHD situation).

Since 1955, Michigan has experienced sporadic EHD outbreaks in 1974, 2006, 2008, 2009, 2010, 2011, 2012 and 2013. Typically this only entailed 30 to 400 dead deer during each outbreak in localized areas with the exception of 2012 when nearly 15000 deer died in 30 (Lower Peninsula) counties. I have a friend who owns property along a river in that affected area and he can remember finding a large number of dead deer in 2012 and the deer herd in his area has yet to fully recover. There were no confirmed cases of EHD in Michigan during 2014 and 2015.

EHD is apparently a seasonal occurrence that only happens in late summer and early fall (August–October) that ends when the first frosts kill the midges. What seems to assist the spread of EHD is when there is a hot and dry summer, such as was the case with 2012 and this sort of atmosphere (as well as associated wetland areas) seems to be the midge’s cup of tea, as it tends to create an abundance of midges. What concerns me is the fact that this summer is very similar to 2012 in being hot and dry for an extended period. However I’m seeing far less midges this summer than I did during my frequent outings in 2012, but that is far from being a clinical observation and I’m certainly not making any assumptions.

The fortunate side to all of this is that EHD is not transmissible to humans and EHD affected venison is actually edible (although I highly doubt I’d want to dine on venison from a deer that had visible internal hemorrhaging from unknown causes).

I first met Sonja Christensen last summer when she contacted me and let me know about her EHD research project. Sonja is working on her PHD and is working with the Boone & Crockett Quantitative Wildlife Center within the MSU Department of Fisheries and Wildlife which also works closely with the MDNR. I wouldn’t describe Sonja as being a typical PHD candidate because she already has impressive credentials. Hailing originally from Minnesota she did her Undergrad at Minnesota State, and then received a Master’s Degree in Wildlife Science at Penn State (during which she live-trapped deer for research). From there she went on to be the “Deer Specialist” for the state of Massachusetts for four years. After deciding to pursue her PHD, she found herself on an elk research project in Montana for two years followed by going to MSU to do wildlife disease research. She is presently doing an outstanding job collecting important research data in regards to EHD in Michigan.

To better understand the dynamics of deer populations recovering from EHD, Sonja is comparing the affected Maple River area with the unaffected Cass River area. We have a lot more deer here in the Thumb today than the Maple River area as well as the dynamics are much different. Deer densities are usually more abundant along river corridors as is the case near the Cass River but it is just the opposite situation these days near the Maple River with a recovering deer population due to the effects of EHD.

One survey technique is called distance sampling where teams of (volunteer) observers head out a couple hours before sunset on set routes to count and record deer numbers (including the number of bucks and does as well how many fawns). Tools (which are provided) for the survey are binoculars, range finder, GPS and a simple but effective apparatus made with a ruler and protractor to figure in the angle at which deer are viewed. Everything goes onto a chart to be figured out later. I can tell you for a fact that if you enjoy driving around on a summer evening and watching and glassing deer it is a whole bunch of fun being a volunteer for this survey. (Sonja will truly appreciate anyone who wishes to volunteer for one evening a week next summer).

The other survey technique is blood samples that are collected from deer harvested by hunters during the various fall hunting seasons. Deer hunters who volunteer to do this receive sampling kits that have latex gloves and a plastic vial for collecting blood, which can be easily done when field dressing the deer. There is even a small form and a pencil in the kit for the hunter’s name, date and location of the kill and sex of the deer. I did this last fall with all the deer taken by my family and there is really nothing difficult about it. There is a drop box at the Cass City DNR Field Office and the samples are picked up regularly to test for any EHD antibodies.

Thus far, there have not been any blood samples from the Cass River area in the Thumb that tested positive for EHD antibodies. However there was one positive sample from the Maple River area last fall. It was from a four and half year old buck that had been alive in 2012 and had gotten EHD but recovered.

Sonja is looking for Thumb area deer hunters this fall who will volunteer to collect blood samples from their kills and the kits are readily available upon request (her contact info is chris625@msu.edu).

The late summer timeframe until the first October frost arrives is when EHD can rear its ugly head. If you see a deer that might be a possible EHD suspect (such as a live one totally unafraid of you and looking ill), or one that is laying dead or dying in a watery (especially a wetland) situation you should immediately notify the DNR (the Bay City DNR Office phone number is 989-684-9141 and if on the weekend call the RAP number that is 800-292-7800) or send Sonja an email (if it’s ever me, I’ll do both). This is a deer that needs to be tested and the public enjoying the outdoors during various pastimes are the very important “eyes” in this regard.

I certainly appreciate and applaud Sonja Christensen’s efforts in researching EHD and its effects to the Michigan deer herd. There was a time when I thought EHD was a very rare occurrence in Michigan, but the times are changing.