Infection and the brain

It was Louis Pasteur who first showed that microorganisms could affect the mental state of humans in injecting the virus causing rabies to animals.

It has been known from a century that chronic bacterial infection, namely, Treponema pallidum, the causative agent of  syphilis can cause dementia.

Historical evidences indeed show that spirochetal infection can not only reproduce the clinical but also the pathological hallmarks of Alzheimer’s disease.

Importantly, by the use of Penicillin, syphilitic dementia was virtually eradicated.


Spirochetes are peculiar, helically shaped spiral bacteria, which are the causative agents of various  human diseases. They possess endoflagella, which distinguish them from other bacteria.

Treponema pallidum is the causative agent of syphilis.
Borrelia burgdorferi is the causative agent of Lyme disease.
Between other Borrelias, Borrelia recurrentis causes relapsing fever.
Various virulent oral Treponema spirochetes are predominant pathogens of periodontal disorders and are highly prevalent in the population.
Spirochetes have a particular affinity for the nervous system.

Various types of spirochetes are involved in Alzheimer’s disease

There is a statistically strongly significant association between spirochetes and Alzheimer’s disease fulfilling Hill’s criteria in favor of a causal relationship.

All types of spirochetes: P < 0.001 ( = 2.8x10-18); 95% CI: 60.
Periodontal pathogen spirochetes: P < 0.001 (p = 3.6x10-4); OR = 30, 95% CI:2.8.
Borrelia burgdorferi: P = 1.4x10-4; OR = 17.9; 95% Cl: 2.6.

There are more than 60 different species of oral spirochetes. Several of them are predominant periodontal pathogens. They can disseminate to the brain and many other organs. Species-specific antigens and DNA of six different oral Treponemes were detected in the brain in Alzheimer’s disease. Different oral Treponemes can co-infect together. Oral Treponemes can co-infect with Borrelia burgdorferi.