Biology Reference
In-Depth Information
exposure from prey that escape an initial attack. Escaping prey infected with organisms
from the attacking lizards thereby serve as vectors and spread the infection among the
lizards' oropharynx, possibly through communal feeding (Bull et al., 2010). As noted
by Bull et al. (2010), there is a paucity of knowledge about the natural history of these
lizards and their oral flora. Therefore, the functional role(s), if any, of oral bacteria, as
well as proposed toxin-induced shock and/or coagulopathy in bitten prey (Fry et al.,
2009b), requires confirmatory biomedical evidence in addition to careful field observa-
tions of predatory behavior, and the subsequent effects on prey such as buffalo, deer,
pigs, and the like.
There are two reports of “toxic” bites from one species of varanid lizard, the
desert monitor,
V. griseus
(Ballard and Antonio, 2001; Sopiev et al., 1987). These
reports described “toxic effects” such as dysphagia, dyspnea, chest discomfort, and
other signs/symptoms (Ballard and Antonio, 2001). However, these and similar cases
require careful evidence-based and physician-based evaluation (Weinstein et al.,
2010). Bites from large lizards may cause painful, freely bleeding wounds due to
physical trauma from the powerful jaws, and this certainly can induce anxiety with
additional somatic manifestations (see Section 4.5). Varanid, agamid, and iguanid
lizards are very common in private collections, and bites from some of these are
reasonably common. However, there are no well-documented reports from medi-
cal facilities recording the clinical evolution of such “toxic effects.” Instead, medi-
cally verified clinical sequelae of varanid and iguanid bites feature mechanical
trauma (severity may be related to the involved anatomical region) and infectious
complications (Weinstein et al., 2010). Presentations may include severe lacera-
tions, extensive soft tissue injury/cellulitis, and type I hypersensitivity (Bibbs et al.,
2001; Hsieh and Babel, 1999; Kelsey et al., 1997; Levine et al., 2003; Merin and
Bush, 2000). Increased relative bite performance is selectively favored in lizards and
is associated with increasing cranial size as well as ontogenetically related growth
of jaw adductor muscles (Herrel and O'Reilly, 2006). Therefore, larger specimens
inflict correspondingly more serious wounds. This is consistent with the greater
than 12 cases of bites inflicted by large varanids (Nile monitor,
V
.
niloticus
, Bengal
monitor,
V
.
bengalensis
, water or Salvator monitor,
V
.
salvator
, and lace monitor,
V. varius
) that were personally experienced, medically managed, or observed first-
hand by one of the authors (SAW). These cases presented as purely local wounds of
varying severity with reactive erythema and mild edema. Increased size of the vara-
nid responsible for the bite was associated with increased severity of the resulting
injury. Broad-spectrum antibiotic coverage (amoxicillin/clavulanate, 875/125 mg,
twice per day) was prescribed in one of three cases managed by SAW. None of these
three cases had any clinically significant sequelae (Weinstein et al., 2010).
Some investigators have noted the regional beliefs that have anecdotally assigned
toxicity to several taxa of lizards including varanids (Smith, 1935); geckos (leopard
gecko,
Eublepharis macularis
; Minton, 1964), and agamids (Ruppell's agama,
Agama
ruppelli orientalis
; MacCabe, 2009). The fearsome and factually unsupported repu-
tation of some of these may rival that of well-known medically important venomous
snakes. The innocuous gekkonid,
Eublepharis macularis
, is one of the most popu-
lar pet lizards in Europe, the USA, Canada, and parts of Asia. However, it is dreaded
among the Sindhis of West Pakistan, referred to as “khan” or “hun khun,” and is believed
