Vineyard tularemia cases on the rise
By Erich Luening
Contributing writer
WEST TISBURY - This year has seen the highest rate of confirmed tularemia infections on Martha's Vineyard since an outbreak in 2000, according to state health officials.

Eight cases of tularemia have been documented this year. In the flare-up in 2000, there were 15 cases. In all, there have been up to 36 confirmed cases on the island over the past five years, said Dr. Fredric Cantor of the Massachusetts Department of Public Health.

Tularemia is a potentially serious illness that occurs naturally in the United States. It is caused by the bacterium Francisella tularensis found in animals - especially rodents, rabbits and hares - according to the Centers for Disease Control and Prevention.

Tularemia, or ''rabbit fever,'' can be contracted through a bite of an infected dog tick; when an open sore or cut comes in contact with the bacteria; or by inhaling the highly infectious spores thrown off by an infected animal or by soil near the animal.

The skin-contact version of tularemia creates a lesion on the skin and can also lead to swollen lymph nodes and flulike symptoms.

''The clinical presentation of tularemia depends upon the how and where it entered the body, if it was inhaled on a small particle, inhaled with a larger particle, eaten, cut in skin, tick bite or mucous membrane exposure,'' Cantor said. ''Martha's Vineyard has a particularly high percentage of people infected by the airborne form of the disease.''

Left untreated, about 7 percent of pneumonic tularemia cases in humans are fatal. Only three of the eight newest cases on the island are of the pneumonic type, according to Cantor.

The latest rash of infections have been seen in people who work outdoors.

Almost all cases to date, Cantor said, have been in people exposed to the outdoors through landscaping, caretaking and gardening work.

Most of the infected people reported they were not wearing a protective mask while performing those activities.

Cantor said Martha's Vineyard has just the right mix of conditions to support the tularemia bacterium, which is very resistant in the environment.

''There seems to be a lot of animal activity on the island as well as environmental conditions like proper soil and water balances that allow (the bacterium) to survive outside of the animal,'' he said.

Because of the number of infections on the island since the 2000 outbreak, Martha's Vineyard has been at the center of numerous studies on tularemia.

Researchers on the island
Health researchers and scientists from the Massachusetts Department of Public Health, the CDC and Harvard and Tufts universities have traveled to the island several times searching for clues to the outbreak.

Currently, the DPH, Tufts and Rhode Island-based vaccination developer EpiVax are conducting research on the island.

Tufts researchers have been closely monitoring dog ticks, which carry the tularemia bacterium, as part of their longtime study of deer ticks and Lyme disease.

Sam Telford, a Tufts University associate professor and epidemiologist, said his study found a boost in the dog tick population on the island in 1999, just before the major tularemia outbreak in 2000.

''The dog tick population has remained high ever since,'' Telford said.

Environmental factors
Telford's study is now looking closer at the ''environmental factors (that) exist on the island that brings the bacterium in contact with humans,'' he said.

DPH and Tufts researchers are working to trace the steps of recently infected residents to find what environmental factors were in place at the time of their exposure. They are paying particular attention to mud puddles, as tularemia can live a long time in water.

EpiVax is using blood samples taken this year from about 20 infected island residents to develop a vaccine for the pneumonic form of tularemia in its Rhode Island labs.

The National Institutes of Health awarded EpiVax an $831,000 grant last fall to develop a tularemia vaccine, as part of a counterterrorism initiative unveiled last summer by President Bush.

Potential weapon
The tularemia bacterium is naturally occurring and can be cultured, which makes it a likely bioweapon.

During World War II, tularemia was studied as a potential biological weapon by the Japanese as well as by the United States and its allies, according to the Vaccination News Web site.

Tularemia was one of several biological agents stockpiled by the U.S. military in the late 1960s, all of which were destroyed by 1973, according to Vaccination News.

In an e-mail, EpiVax project manager Julie McMurry wrote: ''The unusually large number of new infections on the Vineyard this year is unfortunate and underscores the need for an effective tularemia vaccine.''

She added that her company hopes to have a vaccine candidate evaluated in animals in one year and evaluated in humans in three to five years.