His team of Harvard scientists collected 5,000 dog ticks and trapped 35 skunks and raccoons on the Vineyard this summer. Now, parasitologist Sam Telford wants something more to bring back to the lab in Boston - human blood.

Mr. Telford is on the hunt for clues to the mystery of tularemia, the rare and potentially fatal disease that has infected 23 people on the Island in the last three years, killing one man in 2000 who didn't seek medical treatment soon enough.

Nearly all of the victims were landscapers or people who make a living working outdoors.

This Monday from noon to 4 p.m., Mr. Telford is inviting landscapers to the State Forest headquarters in Oak Bluffs to provide a blood sample and fill out a questionnaire.

"The problem is there are confirmed cases and then reports of cases. We're doing this kind of study to see whether the outbreak is continuing at the same level or whether it's going away," said Mr. Telford.

There's no cost for the confidential blood test, and participants will be notified of individual results.

Two years ago, Mr. Telford along with scientists from the federal Centers for Disease Control (CDC) drew blood samples from 165 landscapers. Ten tested positive for tularemia antibodies, a rate of six per cent.

The test results were surprising for two reasons, Mr. Telford said. For one thing, the rate of infection among landscapers is just half the overall rate of Lyme disease on the Island.

"Tularemia is supposed to be rare," he said. To have a community where tularemia is even half the rate of Lyme is "a remarkable thing," he said.

Another surprise yielded from that round of tests was the fact that two participants had high levels of antibodies - which suggested a recent exposure - but reported no symptoms.

This year, the official tularemia count is the lowest it's been since the outbreak was first reported back in 2000. The Massachusetts Department of Public Health (DPH) has confirmed just one case this year - a 41-year-old housepainter who was bitten by a dog tick back in June and recovered after two weeks in a Boston hospital.

The DPH is still trying to do follow-up blood tests on two other cases, both landscapers, aged 26 and 38.

"Initial tests would suggest those two are likely to be confirmed cases," said Bela Matyas, medical director of the epidemiology program at the department of public health.

On the animal front, though, the test results from Mr. Telford's monthly field studies are a little more shocking.

Among the 5,000 dog ticks plucked from Vineyard skunks and raccoons or dragged from Island fields, the rate of tularemia infection ranges from one to five per cent, depending on the location.

"In terms of dog ticks, we're still finding a remarkable rate of infection," said Mr. Telford.

A dog tick bite is supposed to be the most common way for humans to contract tularemia. They are a key to the puzzle, and Mr. Telford is now trying to figure out whether tularemia is passed on to successive generations of dog ticks.

"It may be inherited. The more adult ticks with the infection, the more progeny and tularemia will be around for a while," he said.

Another unanswered question is the role other carriers - skunks, raccoons, rats and rabbits, for example - are playing in the transmission of tularemia. Is the bacteria traveling from the mammals to the insects or vice-versa?

"We still need to get a good scientific answer to that," said Mr. Telford.

So far this summer, roughly half of the Island's skunk and raccoon population is testing positive for tularemia, according to the Harvard lab results.

Compared to field tests back in 2000, the Harvard study is yielding much greater evidence of tularemia in the Island animal population.

Of 40 animals trapped by the CDC in the summer of 2000, only two tested positive for tularemia - a skunk from Chilmark and a rat from Katama. Of more than 500 dog ticks collected from the Island that summer, only one tested positive for tularemia.

Mr. Telford's team doesn't kill the animals. Instead, they blast them with a spray of automotive starter fluid - whose active ingredient is ether - and then jab them with a hypodermic needle filled with anaesthesia.

After pulling ticks and drawing an eight-milliliter blood sample, the scientists are done and the rodents will be back in action.

"Much to the consternation of people out there - and we are sympathetic that there are more skunks and raccoons than needed - it doesn't help us to kill them," said Mr. Telford. "We capture them and give them an ear tag."

This Monday, though, Mr. Telford will shift his focus to the human population at the highest risk of contracting tularemia.

Of the 23 confirmed cases, 19 were either landscapers or people who worked outdoors. All but six of the cases have also been the pneumonic form of the disease, a fact that has earned the Vineyard a place in the medical history books.

No other place in the country has ever experienced an outbreak of pneumonic tularemia, which is believed to be more rare than the form contracted by a tick bite.

A CDC study in the New England Journal of Medicine published in November 2001 speculated that people who contracted pneumonic tularemia had likely inhaled particles of dirt or grass contaminated with the bacteria.

Public health advisories have warned landscapers to wear dust masks while they work to try to prevent breathing in air particles laced with tularemia. And while hardware stores reported that they were selling caseloads of dust masks early on in the outbreak, many landscapers simply refuse to wear one.

Yesterday, landscaper Roy Hope told the Gazette he rarely sees any workers in his trade strapping on a dust mask.

"It's tough to wear a mask in the middle of August. You'd pass out on the lawn," he said. Mr. Hope, who owns Island Wide Landscape, contracted tularemia several years ago.

"I had a 104-degree temperature and no health insurance so I waited ‘til the last minute," he said. His housemates convinced him to go the doctor, and he spent five days in the hospital on antibiotics.

Now, Mr. Hope is banking on his antibodies to ward off another encounter with tularemia. "I feel like Superman," he said as he stood outside Walter Ashley's equipment repair shop by the airport.

But while landscapers may not grab a mask, they are on the watch for the onset of a fever in the summertime. "Now, everybody knows," he said. "And it's the first thing the hospital checks."