Page 982 - Problem-Based Feline Medicine

974 PART 11 CAT WITH AN ABNORMAL GAIT

Treatment The toxin action on the presynaptic terminal of the
neuromuscular junctions results in initial outpouring
Gastric lavage and administration of activated charcoal of the neurotransmitters (acetylcholine and norepi-
are useful to remove unabsorbed toxin. nephrine) followed by depletion of acetylcholine
reserves at motor nerve endings. This may result in
Airway maintenance, oxygen therapy and mechanical
paralysis of voluntary muscles.
ventilation may be required.
The accompanying widespread release of cate-
Hypotension is treated with fluid resuscitation (up to
cholamines causes hypertension.
50–60 ml/kg of crystalloid replacement fluids) with or
without peripheral vasoconstriction via norepineph-
rine (0.2 μg/kg/min) or dopamine (5–10 μg/kg/min Clinical signs
CRI)
Erythema, edema and localized swelling at the bite
Etamiphylline (210 mg IM per cat), a cardiac and res- site occur within seconds to minutes after the bite.
piratory stimulant, has benefited some cases. The pain increases in intensity within 5–15 minutes,
causing generalized hyperaesthesia, vocalization, chew-
ing or licking at the bite site and holding of the affected
RED-BACK SPIDER ENVENOMATION limb off the ground; swelling of the limb may occur.
(AUSTRALIA) (LATRODECTUS MACTANS
HASSELTI) AND BLACK WIDOW SPIDER Pain may appear widespread for example abdominal
ENVENOMATION (USA) (LATRODECTUS pain, causing abnormal postures such as hunched
MACTANS) appearance, and may occur within 30–60 minutes of
the bite.
Classical signs Malaise, depression and vomiting may ensue.
● Pain and swelling initially localized to the Restlessness, tremors and weakness especially of the
area of the spider bite. Pain may spread to affected limb are common, and usually occur within
remote areas over 30–60 minutes and may 3 hours, but could be up to 24 hours
include abdominal pain.
Tachycardia and hypertension occur in several cases.
● Vomiting is a variable sign.
● Agitation, muscle weakness, and
incoordination occur later (1–24 hours). Diagnosis
● Muscular tremors and tachycardia.
A presumptive diagnosis is based on the history of sud-
den onset of severe pain in a cat with access to spi-
ders or finding a collapsed cat with no coagulation
Pathogenesis
defects near where red-back or black widow spiders
Pain is produced at the spider bite site and beyond via have been found.
an unknown mechanism which is presumed to be
related to the presence of algesic agents (e.g. hista- Differential diagnosis
mine, 5-hydroxytriptamine, bradykinin). These act
directly on nociceptors to promote the formation of Snake bite envenomation typically displays coagula-
prostaglandins and other inflammatory mediators tion defects as well as flaccid paralysis without obvi-
which may act in synergism with the venom compo- ous pain. Hindleg paralysis associated with poor
nents to enhance pain production. circulation is a feature. Cold, purple-blue skin and
absent pulses are typical.
Venom is a protein (alpha-latrotoxin) of 130 000 dal-
tons molecular weight, which is predominantly neu- Trauma can usually be differentiated if other injuries
rotoxic in action. are evident.