Found Injured Wildlife?

Contact a local
Wildlife Rehabilitator

For more information contact a WDFW Regional Office


Deer Hemorrhagic Diseases
(Bluetongue, Epizootic Hemorrhagic Disease)
September 2015

  • Hemorrhagic diseases (Epizootic Hemorrhagic Disease or Bluetongue) are common viral diseases of white-tailed deer, but rarely affect other species.
  • These diseases occur during the driest part of the year when conditions are favorable for the biting Culicoides gnats that transmit them. The gnats are found in wet, muddy areas where deer may congregate during late summer and early fall, especially in unusually warm, dry years.
  • The spread of these diseases is usually cut short with colder, wetter weather which spreads the deer out and away from gnat-infested areas; or by the first hard frost, which kills the disease-carrying gnats. Since the incubation period for these diseases is five to 10 days, afflicted deer may be observed for a couple of weeks after the first hard frost of fall.
  • Deer in the early stages of hemorrhagic disease may appear lethargic, disoriented, lame, or unresponsive to the presence of humans. As the disease progresses the deer may salivate excessively or foam at the mouth; have bloody discharge from the nose; lesions or sores on the mouth; and swollen, sometimes blue-tinged tongues. Oftentimes the disease kills the deer so quickly (within a day or two), that they may die in very good body condition. In other cases, they may not die, just become sick and stop eating, resulting in emaciation.
  • Other wildlife, like mule deer, elk, and bighorn sheep could be exposed to the disease but are usually not stricken like white-tailed deer.
  • Domestic livestock may also be bitten by the disease-carrying gnats. Cattle and sheep are seldom seriously affected by EHD, although sheep can be quite susceptible to Bluetongue.
  • Humans are not affected by these viruses. However, WDFW recommends hunters avoid shooting and consuming animals that are obviously sick.