There's much evidence that in Minnesota, Chronic Wasting Disease in whitetail deer is linked to captive deer herds.
Now another disease, often fatal for deer, has been detected in a captive herd. This is the first time the disease has appeared in deer, captive or wild, in Minnesota.
The Minnesota Board of Animal Health, which oversees domestic and captive animal diseases, has issued the following press release:
The Minnesota Board of Animal Health has confirmed the first cases of Epizootic Hemorrhagic Disease (EHD) in Minnesota deer. Six of seven animals in a small herd of captive white-tailed deer in Goodhue County died of the disease earlier this month. The remaining buck appears healthy at this time and is showing no clinical signs associated with this disease. This is the first detection of this disease in a Minnesota deer, yet it is widespread across North America. It has previously been detected in two Minnesota cattle in Brown County (2012) and Murray County (2013).
“This virus is transmitted between deer by biting midges, or gnats, which are most active in the fall before they are killed by the first frost of the season,” said Board of Animal Health Senior Veterinarian, Dr. Mackenzie Reberg. “These bugs can’t travel far on their own and we’re concerned by this detection because the herd owner hasn’t moved deer onto the property for several years.”
The quick and suspicious deaths of the animals earlier this month alarmed the owner, who worked with their veterinarian to submit tissues from the carcasses to the Iowa State Veterinary Diagnostic Laboratory to determine the cause of death. EHD was confirmed by the USDA’s National Veterinary Services Laboratory.
EHD affects members of the deer family, Cervidae, and there are no known health risks to people. Many different deer species may be infected with EHD, and white-tailed deer are highly susceptible, and experience high rates of mortality. Most die within 36 hours of clinical signs, which can include: fever, anorexia, lethargy, stiffness, respiratory distress, oral ulcers, and severe swelling of the head and neck. Sporadic cases occur in other species of cervids and hoofstock. There is no specific treatment or vaccine available in the U.S.
The Board has notified the Minnesota Department of Natural Resources of the confirmed cases in southeastern Minnesota.
Cornell University's Wildlife Health Lab has more on the disease here, and Outdoor Life published an explainer in 2012.
It's unclear what the relationship between the outbreak and farming is, though a 2013 Quality Deer Management Association article Can We Prevent EHD? notes:
EHD and bluetongue are spread in cattle, deer and other ruminants by several species of a tiny flying insect in the genus Culicoides. Call it a gnat, a midge, a no-see-um, or any other local name, this is the tiny fly with the big bite. Three species are the primary vectors, or transmitters, of HD viruses, but one of them is considered the most significant vector and the one we know the most about: Culicoides sonorensis.
Now retired, Ed Schmidtmann spent most of his career as a researcher with the Arthropod-Borne Animal Diseases Research Unit, part of the USDA Agricultural Research Service. Ed studied insects and ticks that transmit diseases, and sonorensis was one of his special interests. If there is a way to reduce midge numbers and thus reduce the spread of HD, it relates to their breeding habitat: the shallow margins of ponds.
The worm-like larvae of all Culicoides species are tiny – about 2 to 4mm long (the height of a capital letter in the text you are reading right now). After hatching from eggs, the larvae live in submerged mud at the very edge of shallow standing waters. They are found in water less than 2 inches deep. The ideal water is warm, sunlit, high in organic matter, high in nutrients and low in oxygen (“eutrophic” is the scientific term for this low-quality water). Disturbed mud is also ideal. Thus, perfect conditions for midge reproduction are created in the typical cattle pond, where cattle disturb and disrupt the shallow margin of the water and prevent plant growth while also defecating and urinating in the water, increasing eutrophication.
“If I wanted to find the larvae of this insect, I’d look in a cattle pond,” said Ed. “Captive deer create the same kind of situation, it isn’t just cattle.” ...
The organization recommends methods to eliminate muddy shallow margins on ponds and other water sources created or enhanced for whitetails.
Outbreaks in northern states are more problematic than those in the south, according to Northern Plains hit hard by deer-killing disease, an Associated Press article from 2012:
. . . In southern states where deer have a history of exposure to EHD, death rates from the disease are relatively low, said David Stallknecht with the Southeastern Cooperative Wildlife Disease Study, which has been tracking EHD for more than 30 years.
Whitetail in northern states are more likely to die because they lack the antibodies from previous exposures needed to help fight off the disease, said Stallknecht, a professor in the College of Veterinary Medicine at the University of Georgia. . . .
Captive deer and CWD
The press release is a timely reminder that Minnesota's captive farmed deer are problematic for the state's wild deer herd, which is a treasured cultural heritage in the state.
Here's the vote on a floor amendment to pause approval of new farms until 2020, taken from the Recent Chronology on Chronic Wasting Disease at The Minnesota Legislature:
That was last year. This spring we reported Legislative Auditor's report on Board of Animal Health oversight of deer farms isn't pretty and CWD: Post Bulletin outdoors columnist Eric Atherton nails it on casual corruption of BAH.
The Rochester Post-Bulletin's AgriNews reported that the DNR's plan outlines more strict rules for deer farms, but captive deer and elk farmers are pushing back.
Photo: The cycle of EHD. Image via Cornell Wildlife Health Lab - Cornell University.
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