By SHAWNE K. WICKHAM Sunday News Staff What if the debilitating illness that sickens hundreds of New Hampshire residents every year comes from a different strain of bacteria than the one that causes Lyme disease in other states? Could that help resolve the ongoing controversy over testing and treatment of an illness that often continues even after patients are treated with antibiotics? Some medical experts say it's possible. Dr. Jose Montero, state epidemiologist at the Department of Health and Human Services, said there are many diseases that can cause similar symptoms and even cross-react in diagnostic tests — such as West Nile virus, Eastern equine encephalitis and St. Louis encephalitis, which are all transmitted by mosquitoes. "It may be in the realm of possibility that something similar may be happening to these particular patients," he said, referring to Lyme disease patients who have chronic symptoms, even after treatment. "It may be that we are missing some other thing that looks similar and causes a similar illness but as yet has not been identified." Indeed, scientists have discovered that some patients who get Lyme disease also become co-infected — apparently from the same tick bite — with other tick-borne diseases, including babesiosis and erlichiosis. Such co-infections can make diagnosis and treatment more problematic, doctors say. Different types of Lyme? Dr. Rex Carr, a Lebanon physician who treats numerous Lyme disease patients, noted there are different strains of the "borrelia" spirochete that causes Lyme disease; Europe sees different strains than the one identified as the cause of illness in Lyme, Conn., he said. Here's his theory about why some New Hampshire patients test negative for Lyme disease, despite having numerous symptoms of the illness: "There's probably more than one bacteria causing the disease that we're seeing. In other words, it may not be Lyme, Connecticut, Lyme disease, and that's why the disparity in the testing." He noted several years ago, health department officials in Missouri began tracking an illness that looked a lot like Lyme disease, with a similar rash and flu-like symptoms. But patients tested negative for Lyme disease; the look-a-like illness became known as Master's disease, after the family doctor who first started studying it. The CDC refers to this new illness as "Southern tick-associated rash illness" (STARI), and attributes it to the bite of the lone star tick in southeastern and south-central states. The agency, on its Web site, notes that a spirochete, distinct from the one that causes Lyme disease, has been detected using DNA analysis. Different spirochetes Meanwhile, a study published in an obscure medical journal — Vector-Borne Zoonotic Diseases — in the spring of 2001 reported the discovery of "a species of Borrelia spirochetes previously unknown from North America has been found to be transmitted by Ixodes scapularis ticks." Those are the black-legged ticks that transmit Lyme disease in Eastern states, including New Hampshire. The study found the spirochete was distinct from the one that causes Lyme disease, but closely related to a group of spirochetes found in similar ticks in Japan. The study found the new spirochete in ticks from Connecticut, Rhode Island, New York and New Jersey. The study concluded that "further work is needed to determine the potential health significance of yet another zoonotic agent transmitted by this tick species." Other possibilities Paul Mead, a medical epidemiologist at the Centers for Disease Control, said he can't rule out the possibility that another bacteria is causing a Lyme-like illness in New Hampshire. But he said the antibody testing done to detect Lyme disease would "likely" still turn up positive for another strain of the bacteria. "One of the strengths of serologic testing is that it can produce cross-reactions, so if you are infected with a closely related organism you will often test positive," he said. "Now, is it possible that there's some borrelia which is a very weird mutant and quite a bit different and causing these symptoms? It's possible, but it could also be a bacteria or a virus or any number of other things," he said.