False-colour scanning electron micrograph of Leptospira sp. bacteria. Leptospira is one of a group of helical bacteria called spirochaetes, which contains many serious pathogens. The parasitic species L. icterohaemorrhagiae is the main causitive agent of leptospirosis (Weil's disease), but many other Leptospira species cause similar symptoms, attacking the liver (jaundice) or the meninges of the brain (meningitis). Infection occurs through contact with rodents, dogs & farm animals, so farmers, sewage workers & veterinary surgeons are particularly susceptible. Treatment is with penicillin. Magnification: x22,000 at 6x7 cm size, x11,000 at 35mm size.