Page 827 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

786 SECTION | XII Poisonous and Venomous Organisms

VetBooks.ir phospholipase A 2 , metalloproteases, and hyaluronidase, Staphylinidae (rove beetles), Tenebrionidae (darkling bee-
tles), Dermestidae (larder beetles), and Scarabaeidae
serotonin, a β-pore-forming compound, a hemolysin
(scarab or dung beetles) (Krinsky, 2002).
(γ-glutamyl transpeptidase), and histamine (Norris, 2004;
Undheim et al., 2015). In most cases, systemic toxicosis Blister beetles are elongate, soft-bodied specimens in
is not expected, although local necrosis may occur which the pronotum (section between head and wings) is
(Russell, 1996); a single case report exists of a human narrower than the head or wings. Two common blister
fatality from the bite of Scolopendra subspinipes (Norris, beetle species are potato beetles, one with orange and
2004). Signs generally subside within 48 h and rarely black longitudinal stripes and one black with gray wing
require more than symptomatic care (e.g., analgesics). margins (Goddard, 2003). Members of the genus Mele are
Millipedes do not bite but can emit irritating and foul- called oil beetles because they exude an oily substance
smelling secretions from repugnatorial glands; some spe- from their legs when disturbed. Oil beetles are approxi-
cies can spray these fluids over distances of several mately 20 25 mm long and black with no hind wings,
inches. These secretions are irritating to mucosal surfaces, giving the appearance that their wings are too short
particularly the eyes, and corticosteroids have been (Goddard, 2003).
recommended to decrease the inflammatory response Species that pose veterinary problems in the United
(Russell, 1996). States include the striped blister beetle (Epicauta vittata)
(Fig. 58.1), the black blister beetle (Epicauta pennsylvani-
ca), the margined blister beetle (Epicauta pestifera), and
Insecta: Insects
the three-striped blister beetle (Epicauta lemniscata), as
Introduction well as Epicauta fabricii, Epicauta occidentalis, and
Epicauta temexa. Of these, the most common species
Insect and insect-related problems are common in domes-
associated with toxicosis are E. occidentalis and
tic and wild animals. Insects such as lice, fleas, deerflies,
E. temexa (Stair and Plumlee, 2004).
horseflies, sand flies, mosquitoes, blackflies, and biting
midges may cause severe annoyance to animals because of
biting behavior. Members of several groups of insects can Mechanism of Action
inject venom when they bite or sting, most notably bees, The toxic principle in melioid beetles, cantharidin, is a
wasps, and ants. Bites or stings from insects such as bees, bicyclic terpenoid (Goddard, 2003; Stair and Plumlee,
ants, wasps, and chiggers may cause direct effects from 2004). The concentration of cantharidin present in beetles
venoms or may result in allergic host reactions resulting varies from 1% to 5% of the dry weight of the beetle.
from overresponsive host immune systems. Contact aller- Males always have higher concentrations because the
gies may occur when certain beetles or caterpillars touch male produces cantharidin and transfers a quantity to the
the skin. Other insects, such as blister beetles and certain female during copulation (Krinsky, 2002). Cantharidin is
caterpillars, produce toxins that can cause adverse reac- present in the hemolymph as well as in the clear, yellow
tions when they are touched or ingested (Durden and secretion that is exuded at the joints of the legs of these
Mullen, 2002). Respiratory allergies can result from inhal- beetles by reflex bleeding (Fig. 58.2).
ing allergic air-borne particles from cockroaches, fleas, or The mechanism of action of cantharidin may involve
other arthropods (Durden and Mullen, 2002). Some insects interference with enzyme systems responsible for active
invade the body tissues of their host. Various degrees of transport across mitochondrial membranes, resulting in
invasion may occur, ranging from subcutaneous infesta- membrane disruption and permeability changes.
tions to invasion of organs such as the lungs and intestine Mitochondrial damage results in cellular disruption,
(Durden and Mullen, 2002). Insects of veterinary impor- acantholysis, and vesicle formation. Cantharidin has also
tance are discussed below and outlined in Table 58.2. been shown to inhibit protein phosphatase 2A, resulting
in disruption of signal transduction and cell metabolism
Coleoptera: Meloidae (Blister Beetles) (Stair and Plumlee, 2004). Purified, crystalline cantharidin
Background is a potent vesicating agent that is readily absorbed
through the gastrointestinal mucosa and, to a lesser
More than 300,000 species of beetles have been
degree, the skin. It is eliminated unchanged through the
described, representing 30% 40% of all known insects.
kidneys (Krinsky, 2002).
Fewer than 100 species of beetles worldwide are known
to be of public health or veterinary importance. Most of
these are in the suborder Polyphaga. The species that Toxicity
have the greatest impact on the health of human and Adult blister beetles feed on flowering foliage, especially
domestic animals are in the following families: Meloidae blooming alfalfa (Medicago sativa). Blister beetles in
(blister beetles), Oedemeridae (false blister beetles), alfalfa fields contain enough cantharidin to provide lethal