Biology Reference
In-Depth Information
are very infrequent. Aside from the hazard 1 species discussed previously, to date,
there are no data supporting the commercial development of antivenoms against
other colubrid species, although some authors have advocated this (e.g., Salomão
et al., 2003), or suggested that such a “serum” could avoid the adverse effects of
inappropriate provision of polyvalent antivenoms (e.g., anti-
Bothrops
spp.) for vari-
ous colubrid bites (particularly
Philodryas
spp.; Correia et al., 2010). The risks of
administering hypothetical antivenom in these cases would probably far outweigh
any possible minimal benefit, as the vast majority of documented bites from many
of these snakes feature insignificant or mild local effects. Commercial preparation
of antivenom against species associated with frequent bites resulting in mild-
to-moderate local effects in specific Third World regions (e.g.,
Philodryas
spp. in
Brazil) would be highly unlikely due to the unfavorable clinical risk/benefit profile
and the complete lack of any commercial profit margin. Indeed, procurement of
an adequate supply of safe, regionally specific antivenom against fully recognized
medically important viperid and elapid species in Third World locales of great need
is often a challenging, politically charged issue (Gutiérrez et al., 2006; Harrison
et al., 2009; White, 2009; Williams et al., 2010). However, it is important to note
that closer study and careful detailed reporting of clinical features of bites from these
diverse colubroids should be included in the ambitious, and much needed, proposed
global snakebite partnership/World Health Organization initiative.
As emphasized previously, the vast majority of these snakes inflict minor wounds
without medically significant effects. Cases that do feature notable local effects are
relatively uncommon and result from unclear etiology. Many people bitten by colu-
brid species have had prior contact with wild and/or captive snakes. This supports
the concept that Type 1 hypersensitivity plays a part in their causation. These hyper-
sensitivity reactions are due to classic IgE cross-linkage on mast cell and basophil
receptors and, possibly, binding of a pro-anaphylactic subtype of IgG
4
to other mast
cell-activating receptors. Medically significant local effects from many of these bites
are probably due to the action of Duvernoy's secretion components such as proteo-
lytic rhexic hemorrhagins and, in some individuals, hypersensitivity reactions.
There are only two well-documented cases of systemic effects after bites by
M. monspessulanus
(neurotoxicity) and
P. olfersii
(widespread ecchymoses).
Therefore, although uncommon, these species must be considered capable of inflict-
ing systemic envenomation. However, even though documented cases of bites by
B. irregularis
on Guam also have occasionally included systemic symptoms or signs
suggesting systemic involvement, there are too few data to firmly establish the risk.
This exemplifies the need for careful and cautious analysis of these cases along
with precise documentation founded on evidence-based data. It also emphasizes the
need for evaluation of these cases with due consideration of the verified identifica-
tion and natural history of the ophidian species involved in a given case. Similarly,
as CRISPS have been characterized from the Duvernoy's secretions of
H. angulatus
and
A. portoricensis
, as well as others, it is tempting to hypothesize a role for these
in the occasional reports of wound paresthesia associated with bites from these taxa.
However, it is important to avoid premature assignment of clinical risk based on lim-
ited biomedical data primarily derived from biochemical analysis of very restricted
