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reported in mice injected with Duvernoy's secretion of T. e. vagrans (Jansen, 1987).
Confirmation of these reported pathophysiological effects is needed.
From field observations, Finley et al. (1994) suggested that the buccal secretions
of T. e. vagrans may have a digestive function. These authors based their hypoth-
esis on the observed partial depilation of a vole ( Microtus mexicanus ) while the ani-
mal was being grasped and swallowed by a 68-cm T. e. vagrans . In addition, Jansen
(1987) reported that buccal secretions of T. e. vagrans exhibited antibacterial proper-
ties as has been described for venoms from several species of elapids and viperids. 5
4.2.3.3 Conclusion and Assessment of Thamnophis spp.
Most bites inflicted by Thamnophis spp. are insignificant. However, bites from these
taxa can cause puncture wounds/lacerations, mild edema, erythema, and, occasion-
ally, ecchymosis. The very low yields of Duvernoy's secretions, as well as the sparse
lethal potency data indicating very low toxicity, underscore the lack of any signifi-
cant medical risk from these snakes.
Assessment of Thamnophis spp. based on available evidence: Hazard
Level 4 (typically only mild lacerations, reactive erythema and edema, and rarely
mild ecchymoses).
4.2.4 Genus Heterodon spp.: Background and General Features of
Documented Bites
Concerns about the potential toxicity of bites by hognose snakes ( Heterodon spp.;
four species; for photos of three of these species (see Plates 4.24A-C, 4.25A-D,
and 4.78A and B ) have been expressed at least since the late nineteenth century
(Blatchley, 1891; Schneck, 1878). Recently assigned to the family Dipsadidae,
subfamily Heterodontinae, most of these snakes are anuran (frogs and particularly
toads) specialists, while H. nasicus (western hognose, Plate 4.24A-C; see also Plate
4.91B-F later Section 4.5.1.1) in particular will prey opportunistically on a wider
variety of animals ( Table 4.2 ). Another genus popular in private collections, hognose
snakes (most commonly, H. nasicus ; Table 4.1 ) can inflict bites that produce mild-
to-moderate local effects ( Table 4.1 ; see Plate 4.24D-J). Almost all of these cases
involved protracted bites sustained during feeding of captive snakes. It is notewor-
thy that several of these cases featured local effects (edema, blistering, ecchymoses,
joint stiffness, or other joint dysfunction) that lasted for weeks to months (Weinstein
and Keyler, 2009). To date there are no reports of systemic effects from bites by any
Heterodon spp. (Weinstein and Keyler, 2009; Table 4.1 ).
5 Antimicrobial components identified in and/or purified from some elapid and viperid venoms have
included well-known enzymes such as L-amino oxidases (Stiles et al., 1991) as well as novel peptides
(Gomes et al., 2005; Nair et al., 2007). As noted when considering the relative paucity of information
about numerous specific components of Duvernoy's secretions and venoms of most non-front-fanged col-
ubroids, the lack of idenitifed antimicrobial activities of these secretions may reflect the comparatively
limited research of these, rather than absence of these substances from these secretions/venoms.
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