Page 831 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Terrestrial Zootoxins Chapter | 58 789

VetBooks.ir erythrocytes are usually present in the urine, yielding a posi- a modification of the ovipositor apparatus and is found
only in female bees and wasps. Venom secreted from
tive occult blood reaction.
specialized cells in the acid glands is transported to the
Gross lesions may be minimal with massive dose inges-
tion. In more protracted cases, oral ulcers, vesication and venom sac reservoir via small tubules. One-way valves
desquamation of patches of the distal esophagus, erosion in the bulb of the venom apparatus control the flow of
and ulceration of the gastrointestinal tract, mucus in the venom during envenomation. At the time of venom
renal pelvis, and renal cortical hemorrhages may be seen. injection, the alkaline gland contributes a secretion that
Hyperemia and hemorrhages are seen in the urethra and enhances the toxicity of the venom. The stinger of the
bladder mucosa. Ventricular myocarditis, pulmonary honeybee is covered with retrograde barbs that cause the
edema, petechial hemorrhages of serosal surfaces, hepato- stinger to remain impaled in thick-skinned victims.
megaly, and splenomegaly may also be present. The initial When this occurs and the bee attempts to withdraw, the
microscopic lesion is acantholysis of mucosa of the gastro- entire stinger apparatus is pulled from the bee, resulting
intestinal tract, epithelium of the urinary tract, and endothe- in death of the honeybee.
lium of vessels (Krinsky, 2002). Other microscopic lesions Honeybee venoms are complex mixtures of proteins,
include myocarditis, renal tubular nephrosis, and degenera- peptides, and small organic molecules (Akre and Reed,
tive changes in the kidneys and digestive tract. 2002). Phospholipases and hyaluronidases present in the
Cantharidin may be detected in urine, tissues (kidney venom account for the majority of allergic responses to
and blood), gastrointestinal contents, and the dried bee- bee venoms in humans and likely other animals as well.
tles themselves by high-pressure liquid chromatography Phospholipase A 2 is one of the most lethal peptides in
or gas chromatography mass spectrometry. Cantharidin honeybee venom (Schmidt, 1995). Mellitin is a membrane
is excreted rapidly and may not be present in disruptive compound that increases the susceptibility of
detectable amounts after 4 or 5 days following ingestion cell membranes to the damage caused by phospholipases
(Krinsky, 2002). within the venom (Akre and Reed, 2002). Mellitin can
also cause pain, trigger hemolysis, increase capillary
Treatment blood flow, increase cell permeability, and enhance
spread of venom constituents within tissue. Mellitin, in
There is no specific treatment. The administration of
combination with phospholipase and a mast cell degranu-
either activated charcoal or mineral oil via a gastric tube
lating peptide, triggers the release of histamine and sero-
may aid animals that have consumed a small dose or are
tonin. In mice, mellitin was found to be the primary lethal
in the early stages of poisoning. General supportive ther-
component of honeybee venom (Schmidt, 1995). Apamin
apy should include correction of fluid loss and electrolyte
is a neurotoxin that blocks calcium-activated potassium
imbalances, particularly hypocalcemia and hypomagnese-
channels and has been associated with transient peripheral
mia (Krinsky, 2002). Broad-spectrum antimicrobial ther-
nerve effects in humans after bee stings (Saravanan et al.,
apy may be necessary to counter secondary bacterial
2004). In cats, bee venom can cause contraction of bron-
invasion from the gastrointestinal tract avoiding amino-
chiolar muscles.
glycosides and other medications that are potentially
Like honeybees, vespid wasps (including yellow jack-
nephrotoxic or excreted via the kidney.
ets and hornets) produce venoms containing peptides,
enzymes, and amines designed to trigger pain (Akre and
Hymenoptera: Bees, Wasps, and Hornets Reed, 2002). The primary pain-inducing substances are
Background kinins; however, other compounds present in vespid
venom, such as serotonin, histamine, tyramine, catechola-
More than 20,000 species of bees are distributed
mines, and acetylcholine, can contribute to the pain as
throughout the world (Fowler, 1993). Native honeybees
well as local vasoactivity. Several of the constituents of
in tropical Southeast Asia were the source of the domes-
vespid venom can act as allergens and trigger allergic
tic honeybee, Apis mellifera. Africanized honeybees
reactions. Some vespid venoms contain neurotoxins or
(Apis mellifera scutellata)area subspeciesofthe com-
alarm pheromones that alert the swarm to an intruder.
mon honeybee native to Africa that has spread from
South and Central America into south Texas, New
Mexico, Arizona, Nevada, California, and Puerto Rico
Toxicity
(Akre and Reed, 2002).
Honeybees can inflict only a single sting, but an animal
attacked by a swarm or hive of bees may sustain multiple
Mechanism of Action stings and the cumulative envenomation may be lethal.
There are numerous variations in the venom apparatus of The Africanized honeybee (A. mellifera scutellata) pre-
members of Hymenoptera (Fowler, 1993). The stinger is sents a special case. Although its venom is no more toxic