B. burgdorferi, a microscopic spirochaete similar to the microbe that causes syphilis, was unknown until the early Eighties. In the Seventies tenacious 'lay' observers were consistently highlighting, against a mass of expert opinion, the unusual symptoms of an illness. The perseverance of these members of the public forced the experts to investigate further, and the illness was eventually linked to the microbe.
This is the story of Lyme disease, a form of arthritis caused by B. burgdorferi, which is carried by ticks that usually live on deer. Around this time of year doctors are reminded that Lyme disease may occur over the summer in areas such as the New Forest. Although the chances of infection are very low and the disease can be cured with antibiotics, chronic pain and damage to the heart and nervous system may follow if the infection is not diagnosed and treated promptly.
The tale began in Connecticut in 1975, when a vigilant mother noticed that 12 children in the village of Lyme (population 5,000) had been diagnosed as having juvenile rheumatoid arthritis. Local doctors appeared unconcerned. So the woman, increasingly perplexed and worried, decided to report the matter to her state health department.
Around the same time, and quite independently, another villager telephoned the Yale Rheumatology Clinic announcing that there was an 'epidemic of arthritis' in her family. This pattern, too, had not been picked up by the otherwise meticulous health surveillance machinery of the state of Connecticut.
At first, officials were deeply sceptical about the Lyme claims. They were impatient with the villagers' demands that the mystery be investigated. Who had ever heard of arthritis appearing as an epidemic? Arthritis was not an infectious disease; it was a degenerative condition associated with ageing. There was no way in which it could spread around a community, like chickenpox or measles.
Fortunately, one research group at Yale did take the women seriously and began to monitor what was happening. By 1977 scientists were convinced that there was indeed an outbreak of arthritis in and around Lyme. As well as aching joints and a stiff neck, it caused headache and fever. It tended to begin in the summer and appeared several weeks after an unusual spot suddenly developed on the skin.
The first real clue to solving the mystery came from one patient who recalled having been bitten by a tick at the site of the spot. Gradually, researchers discovered that a particular type of tick, usually carried by deer, was in turn the carrier of the microbe that might cause the disease. Further detective work led to the isolation of a characteristic type of spirochaete from the tick. Antibodies against the microbe were also found in the blood of Lyme arthritis victims.
Researchers slotted the final piece into the jigsaw when they isolated the spirochaete from patients' blood. Dr Willy Burgdorfer and his colleagues reported these historic findings in the New England Journal of Medicine in March 1983. Shortly afterwards Dr Burgdorfer joined Louis Pasteur and other pioneer microbiologists in having a virulent microbe named in his honour.
Lyme disease has since been reported, mainly in sporadic cases, in parts of Britain, the Swiss Alps, southern Germany and Austria, the Russian Steppes and Australia. Descriptive records strongly suggest that the infection occurred in Europe earlier this century, long before it was properly identified.
In the US, more precise confirmation of its earlier existence has come from a new method of amplifying tiny quantities of DNA. By examining tick specimens in museum collections, researchers demonstrated that DNA characteristic of the spirochaete - and presumably, therefore, the parasite itself - had existed as early as the Forties.
It is in the US that Lyme disease poses by far its major threat to human health. As the journal Science commented recently: 'In the Northeast, where lawns are crawling with disease-carrying ticks and tens of thousands of people have fallen ill since the early 1980s, anxiety about Lyme disease runs high.'
In this part of the US, the white- footed mouse is a long-term 'reservoir' for B. burgdorferi. The deer tick acquires the spirochaete from the mouse and then passes it on in turn to humans. In California a different variety of tick, the western black-legged tick, transmits the spirochaete to humans.
Science has taught us much, comparatively quickly, about Lyme disease. But we should remember that what brought the problem properly to light, and triggered real research into the infection, was public, rather than professional, disquiet.