Here’s how West Nile is spread — and what symptoms to look for after a mosquito bite
This summer’s record rains have affected fishing, camping, hiking, picnicking and many other outdoor activities. For most of us, those interruptions have been minor inconveniences, but for the state’s bird populations the heavy rainfall is causing big trouble.
The warm, wet weather has created perfect mosquito habitat, and lots of it. Mosquitoes carry West Nile virus, which can infect birds, horses, people and many other species. It is particularly deadly to some species of birds.
The disease is also responsible for the death of two Pennsylvania residents already this year — one in Lancaster County and one in Lebanon County. In Lancaster County alone, infected mosquitoes have been discovered in nearly 300 different locations. According to most estimates, virus positives identified so far in 2018 have put this year on track to be the worst ever for West Nile virus in the state.
“There have been more positive West Nile virus samples from mosquitoes this year, 4,609, than any other year since DEP started keeping track in 2000,” Pennsylvania Department of Environmental Protection Press Secretary Neil Shader noted. “The wet weather, especially with the periodic flooding in various parts of the state, has created excellent conditions for mosquito populations and higher prevalence of WNV as a result.”
West Nile virus has been found in more than 250 species of birds, however, it is very hard on crows, blue jays, ruffed grouse and raptors. Most birds that die from the disease are usually not discovered, so the true total is not known. Evidence suggests that West Nile virus has been responsible for declines in ruffed grouse, crows, blue jays, robins, bluebirds, chickadees, tufted titmice and house wrens.
In Centre County, the birds that tested positive this year were multiple crows, one broad-winged hawk, one red-tailed hawk, and one great horned owl. These results were primarily from sick birds brought to Centre Wildlife Care in Port Matilda.
“We continue to treat sick birds, and we have had some success, but all of the crows have died,” Centre Wildlife Care rehabilitator Robyn Graboski said. “Unfortunately, the crows were just too far gone when they were brought in for us to save.”
“Centre County didn’t have too many positives through the middle of the summer,” Centre County West Nile Virus Coordinator Robert Bloom said. “However, things just blew up in late July.”
Thus far in the county, 46 mosquitoes, 13 birds, four horses and two humans have tested positive for West Nile virus. This number grows almost daily.
WNV was initially isolated in the West Nile province of Uganda in 1937. It reached the United States in 1999, and was first identified in Pennsylvania in 2000. The virus was found in 19 counties that year, but by 2003, WNV was found in all 67 Pennsylvania counties.
Eight human deaths were recorded in the state that year. The number of counties with “positives” varies from year to year. According to the state website, WNV has been detected in 63 counties so far this year, including Centre, Blair, Cambria, Mifflin, Union, Lycoming and Huntingdon.
Across the Keystone State, the following statistics for West Nile virus have been compiled for the past five years: 2017 - 49 counties; 2016 - 41 counties; 2015 - 56 counties; 2014 - 40 counties; and in 2013 - 42 counties. Centre County reported the presence of the disease every year since 2010.
While numbers across the state are terrible, some counties have been more fortunate than others. “Although this is the worst year statewide, Adams County has fewer positives,” said Steph Summers, Mosquito-Borne Disease Control Program Coordinator for Adams County. “Two dead birds that were reported here tested negative, but we have had 77 positive mosquito samples and one horse.”
Summers supplied much of the data used in this column. Bloom noted that Centre County was also lucky.
“If you look at how amplified the virus is across the Commonwealth this year, Centre County seems to have avoided the worst,” Bloom said.
The hunting season for ruffed grouse begins on Oct. 13. That species, probably more than any other, has been negatively impacted by WNV. “Our hunter-reported flush rates for last season were .88 birds per hour — our lowest rate in 52 years,” said Lisa Williams, ruffed grouse biologist for the Pennsylvania Game Commission. “Grouse brood numbers looked good in June, but by the time we get to July and August we are just not seeing any broods. We have had successive years with widespread West Nile virus.”
The prognosis does not look good for the coming grouse season. Williams urges hunters and the general public to be on the lookout for dead ruffed grouse — even road kills — and report them. “Since so few dead grouse are found outside of hunting season, these samples are of a very high value. Please call the regional office for the Pennsylvania Game Commission to report dead grouse.”
In Centre County the phone number for the Northcentral Region is 570-398-4744. This will aid Williams in her research efforts. In addition, ruffed grouse cooperators — hunters who willingly compile data for the Game Commission — are collecting blood samples from their harvested grouse.
Williams also noted that large functioning wetland systems do not appear to be the problem, but rather temporary pools that do not contain tadpoles, dragonflies newts and other mosquito eaters.
“This isn’t a call to drain all of the swamps,” Williams clarified. “We are studying the problem and hope to make the best management decisions based on our research.”