Tissue samples taken last September from a Chilmark skunk and a Katama rat tested positive for tularemia, the rare disease that infected 15 people on the Island last year, killing one man who did not seek medical attention in time.

State health advisories warning people to wear dust masks when mowing the lawn or cutting brush may have put a dent in this summer's total for cases of tularemia, the rare disease that has an unexplained foothold on the Vineyard.

Are rabbits really to blame for last summer's outbreak of tularemia and for what could be a repeat performance this year?

Sam Telford, a parasitologist from Harvard University and the newest member of a team sent here to investigate why such a rare disease has taken hold on the Vineyard, doesn't think so. What's more, Mr. Telford is just as skeptical about the prevailing theory that most victims breathed in air particles contaminated with the tularemia bacteria.

State public health officials yesterday confirmed this year's third case of pneumonic tularemia, the rare and potentially fatal disease that killed a Chilmark man two years ago and has baffled scientists for the last three summers.

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.

The Vineyard's first tularemia case of the year, a 50-year-old male landscaper, may have contracted the potentially fatal disease after handling a dead rabbit he found while working in Edgartown, state public health officials said this week.

With six confirmed cases of tularemia and reports of Lyme disease coming in, the Vineyard has begun another season of documenting tick-borne illnesses.

Although cases are still being confirmed, official numbers will not be released until early next year. But initial reports from state public health officials and the Martha’s Vineyard Hospital indicate no slowdown in the high rates of tick-borne illnesses on Island.