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VetBooks.ir Chapter 58

Terrestrial Zootoxins

Sharon M. Gwaltney-Brant, Eric Dunayer and Hany Youssef

INTRODUCTION face exposure to potential zootoxins on a frequent basis.
Bites and stings from arthropods and snakes certainly can
The animal kingdom is populated by a vast variety of
occur in any species, and the potential for oral exposure to
creatures whose main focus in life is to live to see tomor-
animals such as poisonous toads, snakes, or insects will vary
row. To this end, many animals have developed chemical
with the region and environment. Clinically significant zoo-
means of defense and/or food procurement. Every phylum
toxins can affect various vital organs, such as nervous, car-
within the animal kingdom contains species that produce
diovascular, and reproductive and developmental systems
poisons or venoms. Poisons are compounds produced in
(Dorce et al., 2009; Gwaltney-Brant, 2017).
nonspecialized tissues as secondary products of metabo-
lism that accumulate in the host animal or that accumulate
ARTHROPODA
in predators following ingestion of prey. Poisonous ani-
mals, therefore, lack means of actively delivering these Araneae: Spiders
chemical compounds to others—exposure generally
requires oral contact (rarely dermal) in order for another Introduction
animal to become poisoned. In contrast, venoms are pro- At least 30,000 species of spiders are distributed through-
duced in specialized tissues or glands, and venomous ani- out the world (Goddard, 2003). Spiders have eight seg-
mals have developed a variety of venom apparatuses mented legs and bisegmented bodies composed of head/
(stingers, teeth, etc.) to deliver their venom to target thorax (prosoma or cephalothorax) and abdomen (opistho-
animals—a process termed envenomation. soma) (Lucas and Meier, 1995b; Goddard, 2003). Venom
Most venoms and poisons are not composed of a sin- is stored in two glands located in the cephalothorax and
gle chemical substance but, rather, are mixtures of a vari- empties through fangs (chelicerae) located at the rostral
ety of chemical compounds that often act synergistically end of the prosoma (Lucas and Meier, 1995b). With the
to produce their toxic effects. Typical constituents include exception of spiders in the family Ulobiridae (found in
peptides, amines, serotonin, quinones, polypeptides, and Australia), all spiders are capable of inflicting an enveno-
enzymes (Russell, 2001). These compounds are collec- mating bite via fangs. Most spider envenomations, how-
tively termed toxins (the science of the study of toxins is ever, are likely to cause few signs other than local
termed toxinology), and toxins produced by members of swelling and pain. Anaphylaxis and other allergic reac-
the animal kingdom are collectively termed zootoxins. tions to venom components are possible (Goddard, 2003).
Not every exposure to a poisonous or venomous ani- Although there is disagreement in the literature, it appears
mal will necessarily result in a toxicosis (Meier, 1995). that fewer than 100 spider species can inflict a bite of
Within a species, variations in size, age, sex, season, toxin medical significance (Lucas and Meier, 1995b).
composition, and geographic location can result in zoo-
toxins with relatively more or less toxicity. Similarly, the
Widow Spiders (Latrodectus spp.)
animal exposed to the zootoxin may be more or less sus-
Background
ceptible to toxicosis based on its age, weight, sex, state of
health, and degree of exposure. Latrodectus spp. are found throughout the world. These
Compared to other means of injury or illness in animals, spiders are identified by a red, yellow, or orange
envenomation or poisoning from zootoxins is relatively rare hourglass-shaped marking on the ventral abdomen of the
in domestic animals, due largely to the protection afforded female. Males and immature females are brown; imma-
by animal owners. Wildlife, on the other hand, probably ture females do not have the hourglass marking. The

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