Biomedical Engineering Reference
In-Depth Information
It was not too long ago that microbiologists classified spirochetes among
the protozoa [46]. We now know that the spirochetes are bacteria with a
peculiar morphologic feature that is characteristic of every member of the
class. As mentioned in the overview chapter (Chapter 4), Class Spirochaetes
are Gram-negative organisms, and have an inner and outer membrane.
Spirochetes are long, helical organisms with an axial flagellum that runs
between the inner and the outer membranes. In this location, motion of the
flagellum twists the entire organism, and this twisting motion accounts for
the motility of the organism.
Most of the members of Class Spirochaetes require direct transmission
from an animal reservoir, either through a bite of a louse (Class Hexapoda),
tick (Class Chelicerata), rat (Class Craniata), through intimate sexual contact
with an infected human, or through close skin-to-skin contact with another
human (e.g. yaws). The exception is Genus Leptospira.
Spirochaetes
Spirochaetales
Leptospiraceae
*Leptospira
Spirochaetaceae
*Borrelia
*Treponema
Brachyspiraceae (formerly Serpulinaceae)
*Serpulina
*Brachyspira
Spirillaceae
*Spirillum
Numerous species of Genus Leptospira can cause leptospirosis; also known
as Weil disease, Weil syndrome, canicola fever, canefield fever, nanukayami
fever, 7-day fever, rat catcher's yellows, Fort Bragg fever, and pretibial
fever. The disease produces a bacteremia, with consequent splenitis and
infection of multiple organs. Jaundice is a common feature of the disease.
Leptospirosis is transmitted to humans through contact with the body fluids
of infected animals. Drinking water or eating food that has been contamin-
ated with infected urine is a common route of transmission. A wide range of
animals may carry the infection, but rats and mice are usually considered the
most important hosts. Though leptospirosis is a rare disease, it can occur just
about anywhere in the world, often as localized outbreaks. Nepal has been a
frequent site of leptospirosis outbreaks.
Borrelia burgdorferi causes Lyme disease. It is transmitted by the bite
of infected deer ticks. The rates of Lyme disease infections are increasing
in the USA. Though the disease my occur anywhere, it is found most often
in the Northern hemisphere. In Europe, most cases of Lyme disease are
caused by Borrelia afzelii and by Borrelia garinii. It is likely that newly
