Biology Reference
In-Depth Information
Australian elapids (Goldstein et al., 1979; Parrish et al., 1956; Williams et al., 1954).
In a study of 100 taxa of venomous and nonvenomous snakes, 406 strains of 72 bac-
terial species were cultured (Lam et al., 2010). The Chinese cobra,
N. atra
, harbored
the greatest number of microbial species.
Does
Clostridium tetani
Occur in the Ophidian Oropharynx?
Some authors assert no evidence of
C. tetani
in the ophidian oropharynx (Daley and
Alexander, 2010), while others state that it does occur and tetanus prophylaxis (in
Western countries tetanus toxoid booster and wound care) should always be pro-
vided to victims of snakebites (Akubue, 1997; Omogbai et al., 2002). The perceived
absence of
C. tetani
is also asserted in a pharmaceutical company information insert
that was supplied with anti-Eastern coral snake (
Micrurus fulvius
) antivenom
26
(Wyeth Inc., Philadelphia, PA, USA). However, several cases of tetanus after seri-
ous envenomation by
N. nigricollis
(black-necked spitting cobra),
Echis ocellatus
(West African saw-scaled or carpet viper), and
Cryptelytrops
(
Trimeresurus
)
albola-
bris
have been reported (Habib, 2003; Suankratay et al., 2002). Fatal cases of tetanus
have been reported after Malayan pit viper (
Calloselasma rhodostoma
) envenomings
(Reid et al., 1963; Tantanun, 1957), and Parrish (1957) reported a case complicating
a water moccasin (or cottonmouth,
Agkistrodon piscivorus
) envenomation. Although
10 taxa of
Clostridium
spp. were isolated from the oropharynx of
T. albolabris
,
C. tetani
was not found (Suankratay et al., 2002). It can be observed that microbial
surveys of the ophidian oropharynx are far from complete, and detection as well as
culture of anaerobic organisms can be difficult. Another consideration is the micro-
biological shifts/population changes in the colonizing bacterial flora (Blaylock, 2001).
Snakebite-related tetanus may also be a result of wound contamination, or inocu-
lation with organisms derived from prey that has transiently colonized the snake's
dentition. Rare cases of tetanus complicating snakebites might have been due to the
relatively infrequent presence of
C. tetani
in the ophidian oropharynx, but whatever
the source of the pathogen, deep and necrotic snakebite wounds are an ideal medium
for this and other anaerobic organisms. Thus, potential exposure to tetanus toxin
27
justifies provision of tetanus toxoid in cases of medically significant snakebite. This
includes bites inflicted by colubroids that produce significant local effects. In Third
World communities or in the event of other circumstances in which previous immu-
nization may be lacking, treatment, whenever possible, should include administra-
tion of tetanus g-globulin (250-500 U, i.m., in the opposite extremity in which toxoid
is administered, or 3,000-10,000 U if clinical tetanus is suspected).
26
Aside from archived ampoules, this antivenom is no longer available, and a new anti-
Micrurus
antive-
nom (Coralmyn
®
) is under review for possible use in treatment of
Micrurus
envenoming in the USA.
27
Tetanus results from the action of tetanus toxin, a 150- kDa heterodimeric metalloprotease that hydro-
lyzes some of the major proteins that regulate exocytosis of neurotransmitters from inhibitory inter-
neurons of the central nervous system. The toxin causes tonic skeletal muscle spasms followed by
contractions. The initial muscle stiffness often involves the jaw (“lockjaw”) and/or neck, followed by gen-
eralized contractures that may result in respiratory paralysis and death.
