Wildlife diseases spread on land and water


By John Hayes - Pittsburgh Post-Gazette



PITTSBURGH — Since late-August thousands of fish have washed up on the shores of Pymatuning Reservoir. The fish kill, described as “significant,” has impacted just one species, the common carp.

Last week a Minnesota testing lab confirmed what biologists from the state Fish and Boat Commission had suspected. The cause is koi herpes virus, a disease that since the 1990s has killed fish in the carp family in Europe, Asia, the Middle East and North America.

“Wherever it hits, it hits a large number of carp,” said Tim Wilson, a biologist with the state Fish and Boat Commission. “In the United States it’s hitting, checkerboarding, all over the place.”

KHV is a carp-specific virus that cannot be contracted by humans or other fish species. It is spread fish-to-fish, secreted through the skin and waste. Wilson said that because most carp are bottom feeders, the virus may also be transmitted orally.

The washups have occurred in Ohio and Pennsylvania jurisdictions of the co-managed impoundment. Dan Bickel, manager of Pymatuning State Park in Pennsylvania, said none of the dead fish were found near the spillway, a popular tourist attraction where visitors toss bread to mooching carp numbering in the thousands — so many that gulls can walk across the carp without touching the water. Wilson said the virus had not spread to sanctuary waters on the north end of the lake.

“Fortunately we’re seeing fewer fish washing up in the last week, and as the lake cools we’ll see even less,” he said.

Researchers aren’t sure why but recent studies showed that KHV kills carp only when the water temperature is between 64.4 degrees and 82.4 degrees.

“Above or below that the fish can survive,” Wilson said. “I believe any fish that survives can develop an immune response. Next year the carp population will be down significantly — the hope is any that survive will have developed that immunity.”

The standard statewide fish consumption advisory for recreationally taken sport fish, one meal or one-half pound per week, has not been increased for fish caught at Pymatuning Reservoir. Wilson said dead carp continue to be collected for more testing at University of Minnesota’sAquatic Invasive Species Research Center and other labs.

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Since August, as many as 1,000 white-tailed deer may have died from a viral disease that has spread through southwestern Pennsylvania. The state Game Commission is monitoring the spread of epizootic hemorrhagic disease in parts of Allegheny, Beaver, Butler, Lawrence and Washington counties.

The outbreak began shortly for the early archery deer season now underway in Wildlife Management Unit 2B. The statewide archery deer season opens Sept. 30. Trusso said hunters may find temporary pockets with fewer deer within the impacted counties, but the populations will rebound in 2018.

EHD cannot be contracted by humans or their pets, but could threaten some livestock. Game Commission biologist Samara Trusso said the current outbreak is smaller than some recent flare-ups.

“Compared to previous outbreaks, and in the scale of looking at total deer numbers, this is a blip,” she said.

The epizootic hemorrhagic virus is common among North American deer but occurs more frequently in southern states where the midges that carry it have a longer lifespan. It cannot be spread deer-to-deer through contact, water or waste. Symptoms include a disheveled appearance, lethargy, disorientation, drooling and bloody patches of skin. There is no remedy for EHD, but some deer survive. Those that die succumb to extensive hemorrhages 5 to 10 days after contracting the disease.

Trusso said the dead deer are often found near water.

“We can’t be sure but we think infected deer are attracted to water because they’re feverish and trying to cool their body down,” said Trusso. “They’re also dehydrated — it’s a hemorrhagic disease and they’re losing fluid.”

A 2007 EHD epidemic is believed to have killed 1,500 to 2,000 deer in nine counties including Allegheny.

“That was the worst we’ve ever had,” Trusso said. “In fact, 2007 was the biggest outbreak ever recorded in the United States. I was driving through parts of Greene county and you’d roll down the window and the smell of death was in the air.”

The outbreak will end when the midges are killed off by the first hard frost, Trusso said. But EHD can kill indirectly.

“Their rumen — a part of the stomach that helps them digest all the green browse — begins to slough off and they may not digest well,” she said. “Late in the season hunters and nature watchers may see some emaciated deer and some may die in late winter. But generally if they make it to that point they’re going to survive.”

The symptoms of EHD are similar to those of chronic wasting disease, a more serious problem for Pennsylvania deer, but the illnesses are not related.

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Sightings of sick or dead deer should be reported to the Pennsylvania Game Commission Southwest Region office at 724-238- 9523.

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By John Hayes

Pittsburgh Post-Gazette