Rare but potentially deadly deer tick virus found at high levels at a Clearfield County park
By now, many Pennsylvania residents are familiar with the threat of Lyme disease, caused by the bite of a black-legged tick – or deer tick – infected with a certain bacteria. Now, another pathogen in the same tick is an emerging concern in the state. It’s called DTV or Deer Tick Virus.
When ticks infected with DTV transmit the virus to humans, many will have no symptoms. But, according to the CDC, many patients treated for DTV or Powassan virus, as it is also known, develop severe disease such as encephalitis or meningitis. About 12% of those have died and approximately half are left with long-term health problems. There is no medication to treat the infection.
Recently, a high percentage of ticks infected with DTV were detected at the Lawrence Township Recreational Park in Clearfield County.
The Allegheny Front’s Kara Holsopple spoke with Christian Boyer about DTV. He supervises the tick surveillance and testing program in Pennsylvania in the Vector Management Program at state’s Department of Environmental Protection.
Kara Holsopple: How rare is DTV in Pennsylvania or in our region?
Christian Boyer: Deer Tick Virus is still pretty rare. We started looking for it in 2019 as more of a rare pathogen in the tick populations. We were able to find it back then and we have found it every year since. However, we’ve not found it in high numbers. This recent finding in Clearfield County, that kind of blew it out of the water as far as infection rates go.
Holsopple: The deer tick virus is a type of Powassan virus?
Boyer: That’s correct. It was first isolated in Canada in 1957 in Powassan – that’s how it got its name. More recently it has been found in the northeastern part of the country and in the Upper Midwest, and that coincides with where the deer ticks – the black-legged ticks – are found.
DTV and Powassan virus are the same thing. Powassan virus is mainly transmitted by the groundhog tick and sometimes the squirrel tick. DTV gets its name from being transmitted by the deer tick. It’s a different lineage of Powassan virus. However, in humans, it will come up positive for Powassan virus.
Holsopple: DEP reported that 92 percent, or 23 out of 25 sampled ticks, were positive for DTV at that park in Clearfield County. How worrying is that infection rate?
Boyer: We’ve never seen an infection rate that high before, and in the literature the highest that we can find is 25 percent. It’s concerning that we have an infection rate that high at that community park. We call them hot spots of DTV activity and that has been seen in other states as well. We’re not exactly sure why we find these hotspots.
Last year, we found [a hotspot] in Bradford County, where we had an infection rate of 11 percent, which is extremely high, and also 4 percent in Schuylkill County. The statewide average for Deer Tick Virus was 0.6 percent last year for the entire state.
But we do find these hotspots, and we’re trying to do some things looking at some environmental site characterization to see if we can kind of link what might be happening where DTV tends to be so high in some of these areas and not in others.
Holsopple: What are some of your theories about that?
Boyer: We really don’t know. We’re just trying to advance the scientific literature and just put some more thoughts out there and try to figure out why we’re seeing these hotspots.
We’re looking at the vegetation type. Does that play a role in increased habitat for rodents when that’s where Powassan virus or deer tick virus is maintained? So we’re looking at those types of things just to try to advance some type of scientific literature to get a bunch of brilliant minds on it to see if we can’t figure out what’s going on.
Holsopple: Like Lyme disease, are the ticks infected with DTV from rodents?
Boyer: That’s where most, if not all, of these tick-borne pathogens that make people sick are maintained – in the rodent and small mammal populations. They’re the reservoir for all these pathogens.
Holsopple: Were you randomly studying that site in Clearfield County or how did you come to learn about the infection rate there?
Boyer: Pennsylvania has a tick surveillance program that we focus on the black-legged tick– [in the winter] the adult population and in the summertime, we focus on the nymphal population. The main focus is on that tick because of its implications on human health, so this is something we do every year, twice a year, looking at different life stages of the black-legged tick.
We focus on areas where people are going to visit, public use areas such as county parks, state parks, state forests and state game lands. This site was selected – it has been sampled in the past couple of years. It’s kind of up to the individual biologists where they would like to go so we get a better idea of a county-wide distribution of pathogen prevalence. We have found other pathogens at that park, however, we have never found DTV at that park in the past.
Holsopple: Is DTV spreading across the state?
Boyer: I don’t think we can say that it’s spreading across the state. We have found it across the state. Last year, we found it in a total of nine counties. And this year, again, we found it in nine counties. However, our testing is ongoing and our surveillance is ongoing for this adult survey that we’re doing currently.
It’s been found in all parts of the state, but I can’t say that it’s necessarily spreading. I think it’s here, it’s just finding it.
[Over the last three seasons DTV has been detected in these Pennsylvania counties: Adams, Allegheny, Butler, Bradford, Clearfield, Crawford, Columbia, Dauphin, Fayette, Lancaster, Mifflin, Monroe, Montgomery, Pike, Philadelphia, Schuylkill, Washington, Wyoming, and York.]
Holsopple: How do ticks transmit the virus to people?
Boyer: All these pathogens are transmitted by the bite of a tick. Transmission can occur for DTV to a human in 15 minutes, whereas it takes a lot longer for these other bacterial infections. The incubation period of when symptoms might show up in a person is much longer, up to 10 days to two weeks.
Holsopple: What are the symptoms and how serious is it?
Boyer: You have mild flu-like symptoms to begin with for any of these tick-borne or mosquito-borne pathogens that we have in the state. You’ll have a headache, fever, body aches, potentially nausea, and vomiting.
The thing with DTV is that it can be transmitted in as little as 15 minutes, so it’s the most serious tick-borne pathogen we have in the state in that a lot of the cases will turn into a neuroinvasive disease. Up to 91 percent of people who have symptoms will develop neuroinvasive diseases, such as encephalitis, which is swelling of the brain, and even more concerning, for around 12 percent of those people who develop severe neuroinvasive disease, it will end in fatality.
Holsopple: What’s being done to control DTV in the park in Clearfield County?
Boyer: We’ve gotten the word out to the local leadership, the township leadership and the county commissioners. We have hung signs at the site. They are Lyme disease signs right now, however, we’re developing our own DTV-specific sign so that we can hang them up at these parks or anywhere where hotspots are identified of Deer Tick Virus.
We do intend to do some kind of control work at the park. We’ll look to spray with a product that has been used by the mosquito control program for many years once the snow cover is off and the ticks become a little bit more active. That will probably occur in the early spring.
We also intend to place tick tubes around the park. Tick tubes basically look like toilet paper rolls that have cotton balls put in them that are impregnated with permethrin, which is an acaricide. Mice will come in and pull out the cotton balls to use as nesting materials and take them back to their nests. In doing that, they will be treated for the ticks and will kill the ticks.
So our approach is a two-fold approach by treating the mice and killing the ticks that are attached to the mice that are picking up these pathogens and also targeting the adult tick population to try to reduce the number of ticks, and by doing that, reducing the incidence of DTV at the park.
According to the DEP, there are no vaccines to prevent or medicines to treat Powassan viruses. Preventing a tick bite is the best way to protect yourself.
- Apply tick repellents containing permethrin to clothing, and EPA-registered insect repellents such as DEET to exposed skin before entering the outdoors. Reapply as needed according to product label instructions.
- Wear light-colored outer clothing and tuck shirts into pants, and pants into socks.
- Walk in the centers of trails, and avoid wooded and brushy areas with low-growing vegetation and tall grasses that may harbor ticks.
- After returning home, remove all clothing, take a shower, and place clothing into the dryer on high heat to kill any lingering ticks. Examine gear such as backpacks for ticks.
- Conduct a full-body tick check using a hand or full length mirror, including hidden areas such as the scalp, ears, armpits, belly button, and between the legs.
- Check over any pets exposed to likely tick habitats each time they return indoors.
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