Hemorrhagic disease, spread by a virus and commonly seen during hot summer months, appears to be spreading more rapidly throughout the United States.
Hemorrhagic disease is caused by the caused by the EHD virus (EHDV) and bluetongue
virus (BTV). The virus can affect deer, sheep and cows, and is believed caused by a biting midge found around water sources. Because these animals need more water in summer, obviously, they’re going to be found around these sources. During times of drought or lower than normal rainfall, water sources may become smaller, concentrating the animals and increasing the chance of one or both viruses to be spread.
Northern and midwestern states are seeing more regular outbreaks of hemorrhagic diseases. Severe outbreaks the last five years have affected populations of white-tailed deer and other species, especially in the upper midwest.
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“It looks like [HD] has been expanding its geographic range over the last several years, in the northward direction,” John Fischer, unit director of the University of Georgia’s Southeastern Cooperative Wildlife Disease Study (SCWDS), said in this Wildlife Society News report about the northern expansion. SCWDS was founded in 1957 and helps state and federal wildlife agencies with diseases, research and data.
Hemorrhagic disease was first identified in 1955 but, like other viral diseases, may have been or probably was around much earlier. The disease has been found in almost every state in the U.S. but is primarily associated with the Southeast and upper Midwest. Why? Who knows?
From the report:
Not all deer populations across the United States are impacted equally. Researchers have found that, in the northeastern U.S. and the Midwest, the frequency of infection and the number of HD outbreaks tends to decrease farther north. Outbreaks that do occur in those areas, however, are typically more severe and result in a higher number of mortalities (Southeastern Cooperative Wildlife Disease Study). This regional pattern of disease might be the result of acquired immunity from a previous infection, maternal protective immunity, or an innate resistance that some southern deer populations may have developed to HD.
Hunters and landowners often find dead deer — unfortunately, they can smell them first — near creeks and watering sites during summer outbreaks. A few years ago when one of the hardest HD outbreaks hit in Tennessee, it was common to get a big whiff of rotting deer when approaching bridges over creeks. The creeks were dry or trickling and infected deer were searching for water. Many died along those creeks.
Creating watering holes that are not conducive to the infected midges is one way you can do something to counteract HD.
But while those findings are alarming, and distressing when different age classes of does and bucks are discovered, they’re not always indicative of a massive die-off of the population. From the report:
Rates of mortality during an HD outbreak rarely exceed 25 percent, and at this level, deer populations can usually recover relatively quickly. Although HD outbreaks haven’t yet impacted deer populations on a state or national scale, they can affect local populations. Though local populations will likely rebound over time, says Mark Ruder, research veterinary medical officer with the USDA-Agricultural Research Service, HD is still a cause for concern: “It’s a little bit dangerous of us to just completely dismiss the disease as not significant,” Ruder says. “We’re in a changing environment and we don’t know if … there could be other disease threats that move in and tip the scale.”
For the full Wildlife Society News report, click here.
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