State confirms six cases of tularemia this summer
Why the Island is a disease hot spot remains a mystery
There have been four confirmed cases of tularemia on Martha's Vineyard so far this year, a spokesperson for the state Department of Public Health (DPH) said Tuesday. That number is expected to increase to six once the results of blood tests permit definitive diagnoses in two cases now described as probable.
"Of the six, four are professional landscapers," said Bela Matyas, medical director of the DPH epidemiology program. "One is a construction-related worker who spends a lot of time working outdoors on Martha's Vineyard. And the sixth one is a retired individual who does landscaping on his own property but is not a professional landscaper."
All of the cases are the pneumonic, or respiratory form, of the disease. The pneumonic form of the disease is the most dangerous and if left untreated has a mortality rate as high as 60 percent. Tularemia, sometimes called rabbit fever, is caused by the Francisella tularensis bacterium.
In recent years, an unusually high number of pneumonic (airborne) tularemia cases have been diagnosed on the Vineyard. Exactly why remains a mystery despite research efforts.
Small wild animals, mainly rabbits, carry the bacteria that cause the disease. Pneumonic tularemia is thought to occur when bacteria from an infected animal becomes airborne when the dead animal or ground around it is stirred up during mowing, brush cutting, or excavating.
During past Island outbreaks, landscapers and brush cutters have been advised to wear masks while working outside. Caution and precaution was the message this week.
Dr. Matyas said DPH wants the public to be aware that the risk of respiratory tularemia continues to exist on Martha's Vineyard. "Professional landscapers appear to be at greatest risk, as they have been for many years, and we want to remind people to take proper precautions," said Dr. Matyas.
Based on past cases, the Katama area of Edgartown and Chilmark, in particular the Squibnocket area, appear to be the highest areas of risk. That does not mean other parts of the Vineyard are free of risk, Dr. Matyas said.
DPH recommends that before mowing or brush cutting workers should check the area to be cut and remove any carcasses; wearing of a mask is also recommended when stirring up lots of dust and clippings.
In a telephone conversation Monday, Donna Enos, Martha's Vineyard Hospital infectious control nurse, said all of the cases were contracted in June and July. She said that unlike some other diseases, it takes very few airborne particles for someone to contract a tularemia infection. Ms. Enos said the infection responds to specific antibiotic treatment when treated early enough.
According to the Centers for Disease Control, people can get tularemia many different ways: being bitten by an infected tick, deerfly, or other insect; handling infected animal carcasses; eating or drinking contaminated food or water; and breathing in the bacteria.
Symptoms of a tularemia infection are similar to those of a bad case of flu. They may include fever and/or respiratory symptoms; chest congestion, tightness, or pain; lethargy; cough; or chills.
Dr. Matyas said the symptoms of tularemia generally appear within several days to a week of infection. He said anyone with those symptoms should seek medical attention and let his or her doctor know that he or she has been involved in landscaping activities.
He said Island doctors are well aware of the symptoms and testing protocols. He said that although the recently identified cases had relatively mild symptoms of pneumonia, the doctors, being aware that they were landscapers, tested them for tularemia.
"And it allowed them to be identified much more quickly," said Mr. Matyas. He said quick diagnosis is important, because when not treated the disease can be life threatening.
A CDC report said that tularemia is endemic to Martha's Vineyard. Tularemia has been prevalent on the Island over the past several years and created something of a public health mystery because of the sudden upsurge in cases. The worst occurred in summer of 2000, when there were 15 cases confirmed on the Island and one death, the first confirmed tularemia death in the state since 1996. Local, state, and federal medical experts have been unable to provide any solid explanation for the outbreak of tularemia.
The characteristics of tularemia have also thrust it onto the front lines in the war on terror. Scientists around the world consider the bacterium a prime candidate for use as a bioterror agent because it occurs naturally and can be cultured.
The World Health Organization estimates that airborne dispersal of 50 kg (110 pounds) of F. tularensis over an urban area with 5 million inhabitants would kill 19,000 people and incapacitate a further 250,000.
In January 2005, researchers at Epivax, a Providence, R.I., based biotechnology company working under a grant from the National Institutes of Health (NIH), came to the Vineyard as part of a research study to develop a vaccine against the potentially fatal disease.
Information on tularemia is available on the Massachusetts Department of Public Health web site at www.mass.gov/dph.