Hemorrhagic Disease in Whitetail Deer
A. Jacques Fuselier, DVM, DABVP, DACT
Paul Whittington, DVM
Anyone who has been involved with the deer industry for longer than a day knows the devastation Hemorrhagic Disease has on a deer herd. The term “Hemorrhagic Disease” refers to infection with either Bluetongue virus (BTV) or Epizootic Hemorrhagic Disease virus (EHD). Both of these viruses belong to the Orbivirus family and cause very similar signs.
Both BTV and EHD are transmitted by the biting Midge (gnat). Other modes of transmission are suspected but not scientifically confirmed. There are several different serotypes of BTV and EHD known worldwide. In Louisiana, we have confirmed the presence of BTV types 1, 10 and 12, and suspect type 2. Also, we have confirmed EHD types 1, 2, and 6. Unfortunately, there is no reliable “cross protection” between each serotype of virus. This means that if a deer survives an infection from one type of BTV or EHD and develops immunity to that type, then gets infected with another type of BTV or EHD, it will not be protected or have any immunity towards that new type. However, one study shows that deer with immunity to EHD – 1 will not get as sick when exposed to EHD – 2 and fewer deer will show clinical signs compared to those that do not have EHD – 1 immunity. This would suggest that there is at least partial immunity between these types of EHD.
These viruses are life-threatening to deer and are difficult to treat. The most common clinical signs we see are oral ulcers, lack of appetite, excessive drooling, lameness, respiratory distress, neurologic disease, and death. Deer usually die within 72 hours of the development of any of these signs, often in spite of treatment attempts. It is important to have a veterinarian do a necropsy (autopsy) on deer that die. This will confirm if the deer had EHD or BTV or if it died from some other cause. It is also beneficial to find out which type of EHD or BTV is affecting your deer. This will help your veterinarian to tailor treatment plans and prevention plans for your herd.
Although most people use an autogenous vaccine from Newport Labs, we do not have an approved, commercially available vaccine for deer in the U.S. The autogenous vaccine does appear to provide some herd-level protection, but is not as effective as we would hope for. Currently, it is best to have a vaccine made specifically for the type of virus that is affecting your herd. Ideally, there would be a vaccine that would be efficacious for the types of virus that are most commonly isolated in Louisiana. In order for that to happen, we would need farms to go through the process of submitting samples for virus detection, identification, and typing. If we had this, we could have an understanding of the distribution of virus throughout the state and develop a bank of viruses that can be used to develop a better vaccine. Until then, appropriate insect control and early treatment remains our best defense against these diseases. There is also a myth that people are creating deer that are genetically resistant to these viruses. We do not have any scientific proof that this is happening. Deer may be able to pass on immunity from doe to fawn for the specific type of virus that your deer have been exposed to from year to year, but that does not protect them against the other types of EHD or Bluetongue that may be introduced to your farm.
We recommend that you develop a relationship with a veterinarian who knows the specifics of these viruses so that you have a partner in this difficult fight against this horrible disease. Drs. Fuselier and Whittington are always available for evaluation and consultation.
Whittington Veterinary Clinic – 1101 W. Port St., Abbeville, LA 70533 – 337-893-8522