Epizootic hemorrhagic disease recently caused deaths in the Minnesota Zoo’s reindeer herd. Officials say the virus that causes the disease is transmitted between deer by biting midges, or gnats, which are most active in the first frost of the fall. EHD is fatal in deer and it can also affect other hoofed mammals.
Source: Fox 9, Apple Valley, MN, September 17, 2020. Link.
Also see: Epizootic hemorrhagic disease, Minnesota Department of Natural Resources. Link. EHD was not found in Minnesota wild deer until September 2019 but it is common in the Midwest. Wisconsin, Nebraska, Iowa, Illinois, Michigan and Ohio report EHD mortalities almost every year.
EHD is seasonal and most often occurs during drought-like conditions in the late summer and early fall. Frost will kill the virus and midge that carries it, ending the potential infection period.”