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Epizootic Hemorrhagic Disease Outbreak Update

September 25, 2007

NOTE: Epizootic Hemorrhagic Disease (EHD) is common to white-tailed deer, but rarely affects other species. Domestic livestock could be exposed, especially cattle, but EHD causes only mild disease in sheep and cattle and EHD mortality in cattle is very rare.

NJDFW recommends hunters avoid shooting and consuming deer that show any EHD symptoms, even though the disease cannot be transmitted to humans. Since the disease can not be transmitted to humans, infected deer with no symptoms, which are harvested and consumed are not considered a health risk.(updated 10/19/07)

An outbreak of Epizootic Hemorrhagic Disease (EHD) in wild white-tailed deer, caused by an RNA virus transmitted by biting midges, began in the last week of August and first week of September in New Jersey. It was investigated on September 7, 2007 by the NJ DEP Division of Fish and Wildlife’s Office of Fish and Wildlife Health and Forensics (OFWHF) and deer project personnel when 15 deer were reportedly found by hunters scouting their hunting property comprising slightly less than 500 acres in Hillsborough Township, north of Amwell road, west of Millstone in Somerset County.

Several deer carcasses were found in varying states of decomposition. A fawn found at the site, which was recently dead showed gross lesions consistent with EHD (blue tongue, hemorrhaged conjunctiva of the eye, congested hemorrhagic lungs) and was collected for postmortem examination. Spleen and serum samples collected from the deer were submitted to Dr. David Stallknecht at the Southeast Cooperative Wildlife Disease Research Study at the University of Georgia for virus isolation and typing.

A search of 1 mile of the Royce Brook, the main drainage near the hunting property, by wildlife toxicologist and the wildlife pathologist on September 12 found 8 more deer, which had been dead approximately one week. On September 19, 2007 the diagnosis of EHD was confirmed with the isolation of serotype 2 EHD virus. A recumbent buck emitting fluid from the mouth was shot and reported to the pathologist by Hillsborough police. It was found just south of Amwell road and had lesions consistent with peracute EHD. Samples from that deer were sent for virus typing on September 20, 2007.

On September 17, 2007 the wildlife pathologist, investigated 12 deer deaths that hunters reported along the Manantico River drainage in Cumberland County. Two additional deer were found not previously reported by the hunters. All deer appeared to have been dead for 1 to 2 weeks. Additional anecdotal evidence of 6 dead deer found by hunters on another nearby drainage of Mud creek north of Union Lake in Pittsgrove Twp. was received but not investigated, since the deer were also reportedly 1 to 2 weeks old. Deer dead for more than 24 hours are unsuitable for virus isolation. Hunters were asked to immediately report any symptomatic or newly dead deer in the area.

A report of dead deer seen by fishermen floating in the Salem Canal near Carneys Point in Salem County around the first week of September was reminiscent of the first reports of the 1999 EHD outbreak in Salem County. This was again well after the fact and no samples could be collected.

A fourth report of approximately 15 dead deer found by canoeists on the Mullica River in Wharton State Park near Hammonton and Shamong was received by Central Law on 9/23/07 and will be investigated. The carcasses were reportedly found by smell.

This is the first time serotype 2 EHD has been found in New Jersey. In all previous outbreaks, in 1955 (Passaic River Drainage), 1975 (Paulinskill, Pequest River Drainages), and 1999 (Salem River, Rancocas River Drainages), type 1 was isolated. An estimated 4,000 deer died in the 1999 outbreak. Serotype 2 is commonly isolated from deer in Southern Florida, Texas and Mexico. Deer in these areas may have no clinical illness or mortalities. This may be due to their genetic innate resistance, the lower virulence of the strain of EHD virus and immunity from previous exposures. The deer in northern states appear to be more susceptible to experimental exposures and deer infected with serotype 1 do not develop immunity to serotype 2 and visa versa.

The locations and seasons of EHD outbreaks are more dependent on the density and distribution of the midges than the density of the deer herd. One species of midge (Culiocoides sonorensis previously named C. variipennis) has been identified as a vector of EHD in North America, although about 11 species may have the potential to transmit it. Suspect midges were found and collected at the Hillsborough site on mud flats, which serve as a prime breeding habitat. Cold weather will terminate midge activity and the EHD epizootic.

Identification of the cause of these outbreaks through virus isolation is important since the lesions and signs may mimic potential foreign animal diseases like foot and mouth disease, heartwater fever, rinderpest and andenovirus hemorrhagic disease. EHD may have a very short course with few signs (peracute), a longer period of clinical disease (acute) or a protracted course (chronic). The virus reaches maximum numbers in the blood of the deer 6 to 7 days after a bite by an infected midge and can circulate in the blood as long as 56 days if the deer doesn’t die. The virus causes blood clots and damage to the linings of the blood vessels causing leakage of serum and hemorrhages. Deer, which survive the infection, may develop ridges or bands on the hooves and in more severe chronic cases they may slough the hooves and develop secondary infections becoming lame and emaciated.

Deer with EHD in the fall are not usually emaciated. Sick deer from August through October which are unable to stand and are drooling or emitting foam from the mouth and nose could be suffering from EHD. Similarly those found dead in the water or near the water with no apparent wounds should be suspect EHD cases and the OFWHF should be notified immediately by calling 908-735-6398 or the nearest DFW Regional Office.

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Last Updated: October 19, 2007