A recent survey of ticks on the Cape has revealed the prevalence of Powassan, a lesser known but potentially fatal disease carried by deer ticks. But despite a growing list of tick-borne diseases in the region, there are no plans to invest in widespread tick surveillance on Martha's Vineyard.

Deer ticks in the northeast are known to carry five diseases that may lead to human illness, including Lyme disease, which affected at least 4,080 people in the state last year. The state Department of Public Health (DPH) reports only nine cases of Powassan since 2013, but that includes one fatality.

Efforts on the Island have recently turned to deer culling as a way to reduce the incidence of Lyme and other tick-borne illnesses, since deer provide habitat at a key stage in the ticks’ life cycle. The approach would likely reduce the risk of Powassan as well.

Island biologist and tick expert Richard Johnson emphasized the importance of prevention, even as new diseases like Powassan enter the fold. “It doesn’t change what people should do,” he said this week. “They still have to take all the same personal precautions. And we’ve got to do something about the deer and the deer ticks.”

Experts agreed, though, that the list of tick-borne diseases in the region will likely grow as the tick population expands and testing continues.

The Cape Cod Cooperative Extension, which focuses on public education, teamed up with the UMass Laboratory of Medical Zoology in Amherst in 2007 to begin testing ticks for various diseases, and recently added Powassan to the list. The survey this spring revealed the pathogen in ticks at six sites between Falmouth and Truro.

Powassan has been documented in the region since the 1990s, but the survey revealed higher-than-expected rates, especially in Truro, where about 10.5 per cent of sampled ticks carried the disease. Infected people may not always show symptoms, as is typical for the flavivirus genus, which includes West Nile and Eastern Equine Encephalitis. But those who do develop an illness may experience severe symptoms, including encephalitis, or inflammation of the brain. About 10 percent of those cases are fatal, according to the Centers for Disease Control and Prevention.

The virus was first identified in woodchuck ticks in Powassan, Ontario, in the 1950s, and later found on the Cape and Islands. Tufts University professor and tick expert Sam Telford began looking for it after a patient on Martha’s Vineyard was diagnosed with a severe illness in 1994. He later found it on Cape Cod and in Connecticut, although the local strain is associated with deer ticks and white footed mice, not woodchucks. He has since found it everywhere he has looked, including last fall on the Vineyard.

“I’ve known about this for a long time,” Mr. Telford said, arguing that increased surveillance on the Vineyard would only reconfirm the obvious.

Meanwhile, the DPH has endorsed the Cape’s tick surveillance program, which offers some of the only local data related to Powassan. “We are at the state where we are starting to really learn more about the prevalence of the virus in ticks, at least in certain areas,” DPH epidemiologist Catherine Brown said this week.

The UMass laboratory has tested more than 20,000 ticks from around the country over the last 10 years, with significant growth since 2013. Dukes County residents have submitted 128 ticks, with 25 positive tests for Lyme, nine for Anaplasma, and seven for Babesia microti, among others. None of those ticks were tested for Powassan; 10 were found to have multiple diseases.

A $50 fee covers testing for all but Powassan, which costs an extra $99. But an agreement between Barnstable County and the laboratory, along with a grant from Cape Cod Healthcare, has lowered the cost to $15 for Cape residents. The extension is also seeking funds to offset the cost of Powassan testing.

Laboratory director Stephen Rich said the program gives doctors another tool for diagnosis, as well as providing a level of tick surveillance in the country. Tests usually come back within five business days, which he said provides a real-time benefit for diagnosis. Residents are asked their age and sex, town of residence, and where the tick was attached, among other things. Children and the elderly tend to get the most bites, Mr. Rich said, and ticks may attach just about anywhere on the body.

The town of Gosnold has also partnered with the UMass lab and provides free tick reporting for its residents. Sixteen of the 128 ticks from Dukes County, beginning in 2013, were sent by Gosnold residents. But Island towns and the county as a whole have yet to develop such a partnership.

Mr. Telford said the UMass program would be a “tremendous waste of money” for the Island, in part because the same prevention measures would apply. “People are getting tick bites every day,” he said, noting that the chances of illness depend largely on how long the ticks stay attached. “If you pull them off right away, you are not going to get infected,” he said.

But surveillance may have long-term benefits as well.

“We fully expect there will be more viruses, there will be more pathogens, and there will be more varieties of the existing pathogens the more we look,” Mr. Rich said. “But no one has looked in a largely systematic fashion. There is no surveillance program like what we’re doing, so we’re filling an important gap.” He added that with a growing archive of frozen samples, the laboratory will be able look back and see if a newly identified disease had already been present in certain areas.

Meanwhile, Mr. Telford is tracking down yet another deer tick disease in the state, which would bring the total to six along the coast. But rather than raising alarm, he noted a decline in tick-borne illness on the Vineyard since 2013, attributing it to education and preventive efforts since around 2010. “It’s fantastic news,” he said, adding that he expected the numbers for 2015 to be even lower.

“Prevention is key,” Mr. Telford said. “That’s the most important thing.”