Fatal Epizootic Hemorrhagic Disease Cases Rise in North Central Ohio
ASHLAND — Ashland, Richland, and Knox counties in Ohio continue to experience an uptick in reported deer sickened or killed by epizootic hemorrhagic disease (EHD).
As of September 23, the Ohio Division of Wildlife (ODW) has documented 20 cases in Ashland County, 18 in Knox County, and 14 in Richland County.
The ODW regularly updates a detailed map tracking these confirmed reports of dead or ill deer across the region. This monitoring is critical in assessing the progression of the disease each week.
Current Status of EHD in Ohio
On September 9, Clint McCoy, an experienced deer biologist with the Ohio Division of Wildlife, delivered a virtual briefing outlining the current severity and spread of EHD within the state.
McCoy described the 2025 outbreak as Ohio’s most significant to date, with cases expected to rise until the arrival of the season’s first hard freeze, which typically slows midge fly activity—the primary vectors of EHD.
During his presentation, McCoy noted that among approximately 5,000 reports of deceased or ill deer, 22 counties had confirmed EHD infections in free-ranging deer populations. This figure has since increased to 32 counties with roughly 8,200 reported cases as of September 23.
Southeast Ohio remains the hardest hit region, particularly Athens, Meigs, Washington, Morgan, Noble, and Monroe counties.
Expanding Range and Impact of EHD
McCoy highlighted a northward expansion of EHD since the 1980s. Northern deer populations typically exhibit lower immunity due to less frequent exposure compared to southern populations, resulting in more profound outbreaks when the virus arrives.
The pathogen’s history in Ohio began with a severe outbreak concentrated in southeast Ohio in the early 2000s, followed by a spread northward into central regions by 2007 and scattered cases statewide by 2012.
Historically unpredictable in both location and intensity, EHD is increasingly becoming endemic in Ohio, occurring annually with varying impact.
Factors Driving the 2025 Outbreak
McCoy attributes this year’s particularly intense outbreak to a convergence of environmental factors that favor the breeding of Culicoides midges, the tiny insect vectors responsible for transmitting EHD virus through their bites.
- Warmer spring temperatures accelerated midge fly breeding earlier in the year.
- Above-average rainfall in July created numerous standing water pools, ideal for midge larvae development.
- In August, diminishing precipitation left shallow muddy water pools, which sustained midge habitats.
These combined conditions created optimal environments for a significant vector population surge, escalating viral transmission to deer.
Wildlife Implications and Outlook
While outbreaks remain inherently unpredictable, this pattern emphasizes the critical role of vector ecology and climatic variables in wildlife disease dynamics.
McCoy anticipates that ongoing exposure will gradually foster increased immunity within Ohio’s deer herds, promoting resilience against future EHD events. However, until that time, these outbreaks result in substantial mortality, impacting local deer populations and hunting communities alike.
Continued surveillance and reporting are essential in managing and understanding the long-term effects of EHD across Ohio’s diverse deer habitats.
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