The Harvard scientists who spent the last four days on the Vineyard collecting clues that could help them solve the Island's biggest medical mystery came armed with an unusual tool kit: an aerosol can of automotive starter fluid, two flowerpots painted blue, a bag of apples and an empty can of Diet Coke.

It's a weird mix of stuff, but then again, the outbreak here in 2000 and 2001 of a rare disease called tularemia seems to demand some weird science.

For almost three years, the tularemia cases here - 19 in all, one of them fatal - have stumped the experts. Epidemic intelligence teams from the federal Centers for Disease Control (CDC) have flown to the Vineyard three times, looking for answers.

But after all that, the only thing scientists could say with any certainty was that landscapers are the highest risk group for contracting the disease. The CDC believes that the 14 victims who came down with the rarer, pneumonic form of tularemia must have inhaled the bacteria while mowing a lawn or cutting brush.

The disease is more commonly passed on by the bite of a dog tick, which transmits the disease from infected animals to humans.

One landscaper who got sick two years ago remembered running over a dead rabbit carcass a week or two before coming down with flu-like symptoms.

While there have been no confirmed cases yet this year, state public health officials are now waiting on a second round of blood tests that would determine whether two landscapers who fell ill with symptoms of pneumonia two weeks ago really had tularemia.

If that test comes back positive in the next two to three weeks, the CDC will very likely dispatch another team of scientists to the Vineyard.

"We still have an extremely high interest in the situation," said Dr. David Dennis, medical epidemiologist and coordinator of the tularemia program at the CDC's division of vector-borne infectious diseases in Fort Collins, Colo. "Martha's Vineyard poses a very intriguing question. Why is this the only place we've identified with clustered primary inhalational pneumonic tularemia? It has a research imperative there."

The tularemia cases on the Island are entirely unique. No other place in the country has experienced an outbreak of pneumonic tularemia, much less two. In 1978, another outbreak infected 15 people.

Heightening interest in the Vineyard tularemia mystery, said Harvard parasitologist Sam Telford, are two facts: "Because this place is the playground of the wealthy, and two, because [tularemia] is on the list of bioterrorist agents, it's high on the list for people."

Indeed, the bacteria is potent even in very small amounts. The dead rabbit that Mr. Telford picked up on the side of the road in Chilmark Monday definitely had tularemia.

"We opened it up and looked at its spleen. It had white spots on it," he said. "Looked like tularemia to me."

That infected spleen probably contained 10 trillion tularemia bacteria, Mr. Telford added. "But 10 to 25 bacteria alone are enough to cause an infection," he said.

Mr. Telford's Jeep Wagoneer sports a faded bumper sticker that reads "I Brake for Road Kills." But when he stops to bag one, he wears gloves and stays upwind.

Since Monday, Mr. Telford and his team of scientists have been trapping skunks, dragging for dog ticks and catching deer flies in an attempt to find some evidence of how and where tularemia exists on the Island.

"This thing doesn't entirely disappear from the Vineyard. There are years when there are no cases," said Mr. Telford. "We'd love to know where it hides and what causes these big outbreaks."

Scientists know surprisingly little about the disease, which is commonly known as rabbit fever. Rabbits are well-known carriers, but they die from the disease. What puzzles people like Mr. Telford is how the disease can persist when the bacteria is so deadly.

"It's a very strange parasite because it kills most of its hosts," he said. "The clever parasite doesn't."

The pneumonic form of the disease can have a mortality rate as high as 60 per cent if left untreated.

Tularemia bacteria is also hardy. According to the CDC study published last November in the New England Journal of Medicine, the bacteria "can survive in water, soil and decaying animal carcasses. The organism persists in water and mud for as long as 14 weeks, in straw for six months and in oats for four months."

Last year, Mr. Telford joined up with the CDC investigation and quickly pinpointed rats as a potential culprit in keeping tularemia going on the Island. According to the medical literature, he said, rats don't die from tularemia.

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. But the CDC tested 11 rats, and Mr. Telford has tested 15. All were negative. Of more than 500 dog ticks he collected from the Island, only one tested positive for tularemia.

Scientists believe that most of the victims were exposed to tularemia along the south shore, specifically in the Squibnocket area and Katama.

This week, Mr. Telford's group also focused on Cow Bay in Edgartown, where they believe two other victims could have been exposed. Finding the source is akin to locating the proverbial needle in the haystack.

As Mr. Telford put it, tularemia bacteria is not all over the Vineyard, but rather much more localized.

"This infection occurs in natural foci. It could be very small patches," he said. "If you're unlucky to step in that small patch, that's the exposure."

Of course, Mr. Telford would love to be so unlucky as to find one of those hot spots.

This week, they zeroed in on skunks and deer flies, also known to carry the bacteria. Tularemia has been called "deer fly fever," but according to Mr. Telford, no one has ever analyzed deer flies on the Island for tularemia.

Here's where the weird science comes in.

It turns out that flowerpots painted blue and turned upside down on broom handles are the ideal trap for the flies. Scientists in Florida invented the contraption. "They tried all colors," said Mr. Telford. "For some reason, blue works best, and it's a six-inch pot, not four-inch."

Zenda Berrada, a microbiologist who worked with the CDC in Fort Collins for five years, and her sidekick, Amber Shani, a medical student at Penn State, were in charge of fly collection, both near Squibnocket and then again at Felix Neck in Edgartown.

After about an hour walking the trails at Felix Neck Wednesday morning, they came back with dozens of deer flies stuck to the adhesive on the flowerpots.

They were a little embarrassed by their gear, but the task seemed a far cry better than what they were doing at 7 a.m. on a farm in Katama. That was the skunk hour, when the Harvard team went out to check traps baited with sliced apples the night before.

It was a good harvest - 15 traps and five skunks. Mr. Telford wore yellow foul-weather gear and threw plastic bags over the traps. "That's so if they let go, it doesn't go in your face," he said.

The next precaution was the can of starter fluid - active ingredient, ether. Mr. Telford walks across the field, lifts up a corner of the bag and sprays for about three seconds.

"You let them sit about five minutes," he said. Then he loads up some syringes with anaesthetic. Mr. Telford calls it "jabbing."

Pretty soon, he's emptied out five traps, dropping the limp-bodied skunks onto clear plastic bags in the field. Heidi Goethert, a doctoral student in parasitology from Harvard, and the two other women put on latex gloves, grab tweezers and get down to work.

Some skunks are covered in dog ticks, and their job is to pluck them all and drop them into small zip-lock baggies. There's a faint smell of skunk in the air. Small planes from the Katama airfield buzz overhead, and the baggies fill up with dog ticks - from the tiny to the grossly engorged.

The ticks will go back to the lab for testing; Ms. Shani will cut off their legs and run them through a DNA test to detect tularemia.

But out in the field, there's one more sample needed - blood. Mr. Telford makes the rounds, drawing vials of about eight milliliters. Over and done in about a half hour, and the skunks are already stirring.

The Harvard team has no trouble gaining access to Island properties when they tell homeowners they need to bag some skunks. What Mr. Telford neglects to tell them is that the skunks won't be euthanized.

They're tossed in a cardboard box and moved elsewhere in the field. One is a little bit too awake for the ride so Mr. Telford just scoops it out of the box and walks off into the tall grass.

He's not the least bit squeamish around skunks. "I grew up with poisonous snakes," he said. "My dad worked with the World Health Organization, and we lived all over. I grew up trapping snakes."

By the time the skunk trapping is over, it's time to load up the Jeep, which doubles as a field laboratory, full of charts and test tubes. Mr. Telford tosses the used needles into a Coke can, a makeshift sharps container.

They'll be back again in a month's time to do it all over again. It's a long shot whether the data will turn up anything.

"There are lots of maybes with this," said Mr. Telford. "That's what makes it fun."