Envenomation Flashcards
(22 cards)
What are the toxins of Elapid snake
- Neurotoxins (presynaptic = phospholipase A2 preventing release of Ach / post-synaptic = antagonists of Act receptor)
- Hemolytic toxins
- Hemostasis toxins
- Cytotoxins
What tick species are involved in tick paralysis
- Dermacentor variabilis / Dermacentor andersoni in the US
- Ixodes holocylus in Australia
What is the action of the toxin responsible for tick paralysis
- Inhibits depolarization in the distal segments of motor neurons
- Blocks the release of Ach at the neuromuscular junction
Name some enzymes contained in crotalinae snake venom
- Hyaluronidase ->connective tissue breakdown
- Phospholipase A2 -> cytotoxicity (RBC) + anti-Xa activity
- Thromboxane -> thrombocytopenia
- Snake venom metalloproteinases -> platelet dysfunction
What are the effects of crotalinae snake venom on coagulation factors / proteins
Pro-coagulant:
- Activators of factors II, V, X
- Thrombin-like enzymes
Anti-coagulant:
- Inhibitors of factors II, IX, X
- Activators of protein C
- Plasminogen activators
- Fibrinolytic enzymes
Name one rattlesnake causing severe neurological signs
Mojave rattlesnake
What RBC morphology abnormalities are expected in a patient with crotalinae snake envenomation
Echinocytosis, spherocytosis
What are the Crotalinae antivenoms made of? What are the different types?
Immunoglobulin G against the different antigens
- Whole IgG antivenom: ACP = Antivenin (Crotalidae) Polyvalent, Rattler Antivenin
-> also contains contaminants (albumin, globulins, IgM), higher risk of reaction - Fab antivenom: CroFab (Fab1 ; monomer), Antivipmyn & VenomVet (F(ab’)2 ; dimer)
-> less antigenic but faster clearance, formulation as a dimer increases half life + allows 2 antigen binding sites
How to differentiate the venomous Eastern coral snake from the non-venomous Scarlet king snake
For the Eastern coral snake the red and yellow rings are adjacent (yellow - black - yellow - red - yellow - etc) vs. red and yellow are separated by black in Scarlet king snake
“Red on yellow kill a fellow, red on black, venom lack”
What are the different toxins of Elapid venoms
- Neurotoxins -> presynaptic (phospholipase A2), post-synaptic (Ach receptor antagonists)
- Procoagulant toxins -> group C prothrombin activators (= analog of XaVa) or group D prothrombin activators (= analog of Xa, requires patient’s Va)
- Anticoagulant toxins -> phospholipase A2
- Myotoxins -> phospholipase A2
- Hemolytic toxins -> phospholipase
- Local acting cytotoxins (rare in North America / Australia)
(North American Coral snakes mainly cause severe paralysis and occasional hemolysis)
When could FFP transfusion be indicated following snake envenomation
Not for Crotalinae snakes (mechanism of coagulopathy is not a factor deficiency and FFP can worsen thrombosis) ->should resolve with antivenoms
For Elapid snakes, only if coagulopathy is persistent after antivenom administration and causes life-threatening hemorrhage (more cases of coagulopathy can be due to factor consumption)
Name some examples of Crotalinae snakes / Elapid snakes. Which ones are the most common in the US?
- Crotalinae snakes
- Rattlesnakes (Crotalus spp)
- Copperheads and Water moccasins (Agkistrodon spp)
- Pygmy rattlesnakes and Massasaugas (Sistrurus spp) - Elapid snakes
- Coral snakes (Micruroides, Micrurus)
- Brown snakes (Pseudonaja)
- Black snakes (Pseudechis)
- Copperheads (Austrelaps)
- Death adders (Acanthophis)
- Taipan (Oxyuranus)
- Tiger snake (Notechis)
Mostly Crotalinae snakes in North America with some Coral snakes (in the south)
What is the possible toxicity of Loxosceles spiders (= loxoscelism syndrome)
- Local necrosis of tissues around the bite (potentially leading to extensive wounds) = cutaneous loxoscelism
- Rarely intravascular hemolysis = systemic loxoscelism
What are the main signs associated with lactrodectism (= widow spider envenomation)? What species is more sensitive?
- Mostly severe diffuse pain
- Muscle rigidity progressing to paresis
- Possible arrhythmias, bronchoconstriction, GI signs
Cats are more sensitive
What toxins are present in scorpion venom
- Histamine
- Serotonin
- Acetylcholinesterases
- Phospholipase
- Hyaluronidase
- Neurotoxins
- Protease inhibitors
What species of scorpion can cause envenomation in North America
Centruroides (Bark scorpion)
What are clinical signs of scorpion envenomation
Mostly secondary to binding to voltage-gated sodium channels on neurons -> hyper excitability
- Pain
- Numbness
- Seizures
- Sympathetic stimulation: tachycardia, hypertension, mydriasis
- Parasympathetic stimulation less common: bradycardia, salivation, lacrimation, vomiting
What treatment is recommended in case of hypertension secondary to scorpion envenomation
Alpha1-antagonists (prazosin, phenoxybenzamine)
What are clinical signs of Bufo toad toxicosis
- Hypersalivation
- Hyperemic mucous membranes
- Seizures
- Arrhythmias (Digitalis effect)
What is the primary allergen of bee / wasp venom
Bee venom: Phospholipase A2
Wasp venom: Antigen 5 (also contains phospholipase A)
What is the number of bee / wasp stings that can be lethal in mammals
20 stings/kg
Beyond causing anaphylaxis, what systemic effects can bee and wasp venoms cause
- Neuro: ataxia, facial paresis, seizures
- Rhabdomyolysis
- Hypotension
- ARDS
- Secondary IMHA / ITP
