Tetanus toxemia is caused by a specific neurotoxin produced by
Clostridium tetani in necrotic tissue. Almost all mammals are
susceptible, although dogs and cats are relatively more
resistant than any other domestic or laboratory mammal. Birds
are quite resistant; the lethal dose for pigeons and chickens is
10,000–300,000 times greater (on a body wt basis) than that for
horses. Horses seem to be the most sensitive of all species,
with the possible exception of humans. Although tetanus is
worldwide in distribution, there are some areas, such as the
northern Rocky Mountain section of the USA, where the organism
is rarely found in the soil and where tetanus is almost unknown.
In general, the occurrence of C tetani in the soil and the
incidence of tetanus in humans and horses is higher in the
warmer parts of the various continents. Etiology and
Pathogenesis C tetani, an anaerobe with terminal, spherical
spores, is found in soil and intestinal tracts. In most cases,
it is introduced into the tissues through wounds,