Victims were spotted living close to tiny ticks in urban margins

Polly Murray's son and Judith Mensch's daughter both suffered from swollen joints, fever, sore throats, headaches, fatigue and depression. Neither mother was satisfied with the local physician's label on their children's condition, JRA (juvenile rheumatoid arthritis). The first took her evidence for an epidemic of similar symptoms in Lyme, Connecticut, to Alan Steeve of Yale University. When Steeve plotted the frequency of acute arthritis and similar complaints in Lyme, East Lyme and Haddam, he noted that the illness was not limited to children (Polly Murray herself had been sick during the 15 years they lived in Lyme, and even the dog suffered swollen joints); that it correlated with grassy woodlands; and that most of the afflicted fell ill in summer or early autumn. Not a single patient - and there were more than 50 in Steeve's first cohort published in 1977 - resided in the heavily populated urban areas of Connecticut. On the other hand, at least one in four recalled that they had been bitten by ticks.

The symptoms of Connecticut's mysterious "Lyme disease" - the subject of Arno Karlen's book - had broadened by the time Steeve published his 1979 paper. They included a travelling rash (erythema migrans), heart problems and nervous disorders, and they were found among thousands of victims, many of whom lived beyond the borders of Connecticut. Not long after Steeve's paper, the medical profession recognised a commonality with northern European illnesses: ACA (acrodermatitis chronica), EM (erythema migrans) and ECM (erythema chronicum migrans), among others.

The Biography of a Germ compellingly describes the source of the problem, which was essentially a symbiosis, or living together, of very different types of organisms, and its history.

The Murray house in the 1920s was surrounded by "sparse vegetation and a few lone trees". By the 1970s, "the land about our house was thick with trees, wild roses, barberry, bittersweet, wild grapevines and other vegetation". In summer, Polly and her neighbours might pick a dozen ticks a day off their children and pets - "seed ticks" - tiny nymphal stages of the deer tick.

It took Willy Burgdorfer, a Swiss-born medical researcher who had studied tick-borne diseases since the 1950s, to make the connection between habitat and illness. A lethal summer illness especially prevalent in the Bitterroot River valley of the western Montana Rockies was called "spotted fever", "black measles" or "mountain fever". A rash of spots covered the body of the victim, even the palms of the hands and the soles of the feet.

Burgdorfer knew that the deforestation that had transformed the countryside into grazing and mining country had also converted the landscape into an ideal habitat for mice and ticks. He knew, of course, of the pioneering work of Howard Ricketts, who had proved that tiny bacteria, later called Rickettsia , were transmitted from female to female via the ovaries of the Rocky Mountain wood tick.

When ticks became rare and their habitats and those of the small mammals they bite were replaced by Rocky Mountain shopping malls and asphalt parking lots, the "spotted" fevers disappeared. When woods, shrubs, grass and other suburban greenery reappeared, the Rocky Mountain spotted fever re-emerged too.

Burgdorfer also knew, having enjoyed a fine European education, that as long ago as 1948 Carl Lennhoff, and in 1949 Sven Hellstrom, both Swedes, had suggested that "erythema chronicum migrans with meningitis" was probably caused by a tick-borne spirochete bacterium sensitive to antibiotics. In 1981, he requested that dog ticks and deer ticks be sent to him for investigation. From a deer tick midgut smear he saw relatively large irregularly coiled bacteria that he recognised at once as spirochetes.

When he dissected more than a hundred ticks collected at Shelter Island, off the Long Island coast of New York, he found that two thirds of them bore spirochetes. Shelter Island provided wonderful scrubby grassy woodland habitat for both deer mice and deer. Burgdorfer obtained blood samples from patients from Shelter Island and saw that antibodies indicated that these people had been exposed to the same spirochete bacteria carried by the ticks. After he published his findings in 1982, the elusive spirochete, a bacterium that is only "the silhouette of a corkscrew" unless it is stained with heavy metals and studied with a powerful high-magnification electron microscope, was named in his honour Borrelia burgdorferi . (The insect-borne borrelias were named for bacteriologist Amedee Borrel in the late 1800s.)

B. burgdorferi is related to other Borrelia bacteria whose presence has been correlated with symptoms of relapsing fever carried by soft ticks or lice. But it was Alan Barbour's development of media (liquid food containing vitamins, amino acids and other specific chemicals) that could grow B. burgdorferi that led Burgdorfer to the definitive cause of Lyme disease. The recent work of the Norwegians, O. and S-H. Brorson, that proves Borrelia enters the encysted state refractory to antibiotics and invisible even to microscopists with "spirochete eyes", could not have been accomplished without Barbour's liquid medium. As we have found in our research with free-living spirochetes (which, like most spirochetes, cause no disease), they are elusive bacteria.

Karlen's account is a delightful and witty page-turner. Certainly, it is not a scientific book at all; it commits the typical sins of the medical literature - glibness, sloppiness and factual errors. However, the curious reader forgives the ardent author in the same way that one does not expect a physician telling a complicated story at a cocktail party to be accurate. From the dust-jacket hype that claims a sex life for the spirochete (which has none) and a tree of life for Linnaeus (Linnaeus was a Christian who never subscribed to any evolutionary tree of life) to the folk classification employed by the author (the living world is divided into four kinds of life: plants, animals, germs and people), the reader is warned to remain sceptical. This simply written annal of medicine should be read for what it is: an informative, charming, serendipitous and sometimes opinionated talk that successfully transmits the historical and environmental activities of the Borrelia spirochete in generating disease symptoms. The details of Karlen's story are not to be taken too literally.

Lynn Margulis is professor in the department of geosciences, University of Massachusetts, Amherst, United States.