Breaking Down the Hemorrhagic Disease Outbreak

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Published on: Jun. 17, 2013

is unlikely to be a permanent reservoir for the disease in Missouri.

One question remains: How and where does the HD virus survive over winter? While there are several theories, none have been proven.

Implications for Humans and Other Wildlife

Hemorrhagic disease is not infectious to humans or non-ruminant animals like dogs and cats. Therefore, the virus itself poses no threat to humans. However, secondary infections in deer arising from the effects of the HD virus can pose human health risks if consumed or improperly handled. This provides further justification for normal precautionary measures to be taken when field dressing, butchering, and preparing venison to reduce any potential health risks. The Department of Conservation recommends not consuming venison from known diseased animals.

While infrequent, domestic ruminant species, like cattle and sheep, can become susceptible to specific HD viruses dependent on the animal species. For example, cattle can exhibit varying severity of symptoms from either EHD or blue-tongue, but it is infrequent. However, domestic sheep are generally unaffected by EHD, but bluetongue can have serious health implications.

Weather Intensified the Outbreak

The intensity of the 2012 HD outbreak in Missouri was a result of several weather conditions. While it is only a theory that warm winters allow the virus to be maintained from one year to the next, the 2011–12 winter was the third-warmest winter on record in Missouri. In March of 2012 the rainfall was slightly above average, causing the ponds and other water bodies to fill with water, which would provide ample breeding area for midges during the summer. Plus, March 2012 was the warmest on record at 14 degrees warmer than the long-term average! This warm weather continued, making the 2012 spring the warmest on record and likely causing midges to become active much earlier than normal.

Weather extremes continued into the summer with a combination of record heat and drought conditions, causing ponds and other water sources that filled up during early spring to dry up. The exposed mud flats created the ideal breeding areas for midges. The drought conditions also caused deer to visit these water sources more often because of lower water content in the plants they consumed and fewer free-standing water sources. Furthermore, nutrification of these sites because of livestock loafing in small ponds results in increased midge production. Additionally, both deer and midges are most active at dawn and dusk, further increasing the

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