Biology Reference
In-Depth Information
Aside from possible efficacy of
R. tigrinus
antivenom for envenomation by the
congener,
R. subminiatus
, no data currently available support provision of any non-
specific antivenom for any non-front-fanged colubroid bite. As detailed in the previ-
ous sections, the only antivenoms available against any of these snakes are prepared
against two hazard level 1 species (
D. typus
and
R. tigrinus
;
Table 4.3
). There is no
clinical evidence of paraspecific protection afforded by any polyvalent or nonspecific
monovalent antivenom against the effects of any non-front-fanged colubroid species.
Further, as summarized in
Table 4.1
and in Section 4.1, the vast majority of bites
from many of these species feature only mild local effects. In addition, even medi-
cally significant bites from species that occasionally produce moderate local effects
(e.g.,
Philodryas
spp.,
H. nasicus
;
Table 4.1
and Section 4.1), would not merit the
risks of antivenom therapy if specific antivenoms were available. As described in
Section 4.5.1.1, inappropriate provision of antivenom for insignificant, nonvenomous
snakebites have sometimes produced life-threatening anaphylaxis.
It is also important that medical personnel (particularly in regions where such
bites more frequently occur) should realize that no specific antivenoms are available,
and that non-front-fanged colubroid bites rarely if ever justify the risk of this treat-
ment. For example, in the case of a
Boiruna maculata
bite in Brazil, the pediatric
patient was given polyvalent anti-
Bothrops
spp. antivenom although the snake had
been positively identified (Santos-Costa et al., 2000;
Table 4.1
and Section 4.5.1.1).
Similarly, a 17-year-old male bitten by a
P. patagoniensis
presented with moderate
edema, erythema, and mild ecchymoses of the right hand was given eight ampoules
of anti-
Bothrops
spp. polyvalent antivenom (Correia et al., 2010). This unfortunate
patient then suffered a moderately severe antivenom reaction due to an unnecessary
and useless treatment for this bite.
Polyvalent antivenoms are often used to treat serious envenomation inflicted by a
“presumed” species of unidentified elapid or viperid. In many cases, as long as the
likely species responsible is covered by the antivenom and/or established paraspe-
cific protection has been determined and is inclusive of the suspected species, this
would be a reasonable approach barring a firm identity of the snake. The main con-
cerns regarding this approach are whether the antivenom contains a significant neu-
tralizing titer of antibody against medically important toxins present in the venom
of the envenomating species and the likely larger volume required for effective
treatment (greater risk of antivenom reactions, etc.). However, treatment of a pre-
sumed hazard level 1 colubrid species such as
D. typus
must be based on a care-
ful history, clinical assessment, and investigations, as effective treatment is founded
on monospecific anti-
D. typus
antivenom therapy. In one case of presumed
D. typus
envenomation, provision of SAIMR polyvalent antivenom was predictably ineffec-
tive (Bajaj et al., 1980), as it was when also used to treat
T. capensis
envenomation
(Beiran and Currie, 1967).
A few investigators have described
in vitro
antigenic cross-reactivity between
various non-front-fanged colubroid Duvernoy's secretions and commercial antiven-
oms against viperid and elapid venoms (Boquet and Saint Girons, 1972; Minton and
Weinstein, 1987; Weinstein and Smith, 1993). However, it was uncertain whether these
immunological cross-reactions had any clinically protective value and therefore were
