Biology Reference
In-Depth Information
increased collected volumes; procurement of some species of snakes, etc.), perceived
lack of medical importance, and very limited economic support for these investiga-
tions—an unfortunate reality partly derived from a rigid narrowmindedness on the
part of many funding organizations that effectively limit the advancement of many
“nonmainstream” research disciplines.
Published reports describing the effects of bites from some of these snakes have
been hindered by: limited numbers of well-documented reports; a large amount of
disseminated anecdotal information (occasionally perpetuated in the literature and
on the Internet without verification); misidentification and/or unverified identity of
snakes involved in reported cases; a common lack of qualified and critical clinical
analysis and misinterpretation of reported/observed effects; frequent lack of thor-
oughly considered differential diagnoses for aberrant cases; and publication of many
of these reports in nonclinically refereed journals or periodicals. Due to these flaws,
critical assessment of a large proportion of these published cases reveals limited
quality data available for risk analysis, and thus results in generally low evidence-
based scores (Table 4.1).
Dispholidines or natricids that have inflicted life-threatening or fatal human
envenoming all produce consumptive coagulopathy/DIC resulting in hemorrhagic
diathesis. Unlike the medically significant effects of bites from most other non-front-
fanged colubroids, the procoagulant and proteolytic/hemorrhagic toxins present
in the venoms of these species exhibit clear functional correlation with the clinical
effects observed in envenomed patients. Acute kidney injury figures in many of these
cases and is often poorly responsive to diuretics and/or dialysis. There are commer-
cial antivenoms available against venoms of two of these species ( D. typus and R.
tigrinus ). However, it is fortunate that these life-threatening bites are relatively rare,
as these antivenoms may be very difficult to obtain.
Management of envenomation from highly toxic species without antivenom,
such as Thelotornis spp., consists of supportive measures. The use in management
of heparin and antifibrinolytics is contraindicated by available evidence, but some
unproven therapies (e.g., synthetic protease inhibitor, SPI) do not appear to exac-
erbate bleeding in Gram-negative endotoxemic coagulopathy and therefore may be
used in selected cases of hazard level 1 colubrid envenoming. Replacement ther-
apy with FFP, cryoprecipitate, and/or platelets is controversial but may be required
according to clinical need. Patients envenomated by these species often exhibit ane-
mia that requires treatment with repeated PRBC transfusions. The role in manage-
ment of plasmapheresis or exchange transfusion is unclear. These procedures are
unlikely to be of benefit. Although the respective pathological mechanisms/processes
are distinctive, some coagulopathic envenomations by these species may share some
similar pathophysiology and therefore some basic clinical management with that of
Gram-negative endotoxemia.
Although bites from Thelotornis spp. are rare, effective antivenom against T.
capensis is desirable. It might provide some protection against envenomation by
congeners, and could be useful in a research context as well. However, develop-
ment of such antivenom is extremely unlikely as it would be nonprofitable and bites
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