Incidentally, the spirochaetes bacterium that causes syphilis has a similar mode of action and can also lodge in the brain, potentially remaining active for years.

Brain abnormalities
The leaky-brain theory also accounts for some of the highly specific neurological abnormalities found in Lyme patients-including Bell's palsy, lymphocytic meningitis, meningo-encephalitis and cranial neuritis-not to mention the less specific CFS/ME and 'brain fog'.

"The neurological and psychiatric manifestations of Borrelia are so numerous that it is called the 'new great imitator'," says Dr Frederic Blanc, of the University of Strasbourg, France. "Every part of the nervous system can be involved: from central to peripheral nervous system, and even muscles" (Med Mal Infect, 2007; Mar 8; Epub ahead of print).

In fact, as long as 10 years ago, LD was firmly characterized as a 'neuropsychiatric illness'. Reviewing the whole history of the disease, a team of psychiatrists at New York's Colum-bia University found Lyme disease to be responsible for "a broad range of psychiatric reactions", including paranoia, dementia, schizophrenia, bipolar disorder, panic attacks, major depression, anorexia nervosa and obsessive-compulsive disorder (Am J Psychiatry, 1994; 151: 1571-83). Since then, tests have discovered reduced blood flow in the brains of chronic LD sufferers, explaining the impaired mental functioning that afflicts so many victims of the disease (Neuro-psychiatry Clin Neurosci, 2003; 15: 326-32).

The autism connection
The most dramatic mental condition thought to be caused by Lyme disease is autism. A rare condition 50 years ago, autism now affects one in every 150 American children, according to the latest figures from the CDC. But why should Lyme disease be implicated? One of the first clues was that the psychological symptoms of LD are similar to those of autism.

Six years ago, the above-mentioned Columbia University psychiatrists found that children with Lyme disease have "significantly more cognitive and psychiatric disturbances . . . resulting in psychosocial and academic impairments" (J Neuropsychiatry Clin Neurosci, 2001; 13: 500-7).

There are other clues, too. As already mentioned, syphilis, which is caused by a similar spirochaetes as in LD, in the womb is known to cause autism. Furthermore, autistic children are known to have many metabolic dysfunctions which are shared by victims of LD, in particular, chronically low counts of CD57 natural-killer (NK) cells.

Of course, scores of theories have been proposed for the cause of autism, among which vaccine damage is perhaps the best known. But LD may be involved there, too. "It is possible that the two are conjoined in damage, and the long-term effects of Borrelia could hamper the body's ability to mount a significant, timely response to vaccines," says Dr Geoffrey Radoff, of the Alternative Medical Care Center of Arizona. "This could explain the higher incidences of adverse reactions to vaccinations in children with autism (Townsend Lett Docs, 2007; April: 78-81; online only).

However, some children appear to be born with autism, so how could Lyme disease be involved there? Although the research has yet to be done in humans, studies of farm animals have shown that Borrelia can pass through the placental barrier into the womb and even into breast milk. This makes it possible for an infected mother to pass on the disease to her newborn child, in whom it could present as autism.