to report a case of erythema migrans in America. His patient, a fellow physician, had been bitten by a tick while grouse hunting in central Wisconsin, and the rash grew outward from the site of the bite, eventually encircling much of his chest, right armpit, and back. Scrimenti treated the symptoms with penicillin. In his brief published report, he echoed Hellerstrom’s guess that it might have been caused by a spirochete, but Scrimenti hadn’t been able to find one.
This is all part of the medical groundwork that was available—though not conspicuously available—when doctors at the Yale School of Medicine heard about the cluster of juvenile arthritis cases in Lyme, Connecticut. One of those doctors was Allen C. Steere, a first-year fellow in the rheumatology division. Rheumatology is the science of joint disorders such as rheumatoid arthritis, which is an autoimmune condition, not an infectious disease. Juvenile rheumatoid arthritis, Steere recognized, should not be occurring in any such cluster. It didn’t pass from one patient to another. It didn’t infect people through their drinking water. It didn’t fly on the wind like Q fever . . . did it?
Steere and his colleagues followed out the cases brought to their attention, did some further epidemiological legwork, found many more cases in roughly the same area, and began calling the syndrome “Lyme arthritis.” Steere’s group also took note of the associated symptom among a sizable fraction of the patients: a circular red rash. Other medical practitioners, in Connecticut and nearby parts of New York, also saw cases of this peculiar skin inflammation and began wondering. Was it caused by an insect bite? Was it the same condition, erythema migrans, that had been described in the literature from Europe? About that point, in the summer of 1976, a field biologist named Joe Dowhan, working in a forested area some miles east of Lyme, pulled a tick off his leg and dropped it into a jar. Dowhan had noticed the bite because, unlike most other tick attachments he’d experienced in his career, it registered as a small, painful nip. Three days later, he developed a rash. As the red circle grew, he remembered having seen an article about Allen Steere’s work. So he called, got an appointment, sat through an exam, and then handed Steere the tick.
Dowhan’s specimen was identified as Ixodes scapularis, commonly known as the deer tick, an arthropod widely distributed throughout the eastern and midwestern United States. This became an important but ambiguous clue in the Lyme disease story, leading both toward insight and into confusion. The insight came first. Fieldwork along the lower Connecticut River revealed that Ixodes scapularis ticks were far more numerous in small woodlands and brush on the east bank of the river—the bank on which sat the village of Lyme—than on the west bank. That finding, combined with the fact that human cases also were far more common on the east bank, pointed further suspicion at the “deer tick” as a vector of what even Steere and his rheumatologist colleagues, having dropped the term “Lyme arthritis,” were now calling “Lyme disease.”
The confusion grew more slowly. If the “deer tick” carried the pathogen (whatever it was) and infected people like Joe Dowhan by biting them, then the abundance of human cases must reflect the abundance of ticks, and the abundance of ticks must reflect the abundance of deer in those suburban woodlands of coastal Connecticut. Yes?
No. This was an ecological system with the intricacy of chess, not a board game with the clarity of checkers, and its cause-and-effect relations weren’t nearly so simple. The “deer tick,” as later research has shown, lives a complicated life.
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Willy Burgdorfer meanwhile made his crucial discovery of the pathogen itself, giving a name and a biological identity to the agent responsible for the mysterious clusters of cases.
Burgdorfer was a Swiss-born and Swiss-trained microbiologist with a shovel-wide jaw, a cagey smile, a great domed head like Niels Bohr, and a deep interest in medical entomology. He did his doctorate on a tick-borne spirochete, Borrelia duttonii, which in Africa causes an illness called relapsing fever. By the time he finished that project, Burgdorfer had dissected thousands of ticks to scrutinize their innards. He had also invented a quick, practical technique for determining whether a given tick carries spirochetes: snip off a leg and look through a microscope at the body juice (hemolymph) that dribbles out. Emigrating to the United States, in 1952 he joined the Rocky Mountain Laboratory, in Hamilton, Montana, the same facility where