Zootoxins (Bufo Toad and Snake Venom) (Shokry) Flashcards
What are the toads in the Bufo family?
- Cane or marine toad
- Colorado river toad
What toxins does the Bufo toad carry?
- Catecholamines (dopamine, norepinephrine, epinephrine) and serotonin
- Bufotenine
- Bufogenins
- Bufotoxins
- Indole alkylamines
Where are the bufo toad toxins stored in the animal?
Parotid glands
What toxin from toads is a Schedule I substance because it has an hallucinogenic effect?
- Bufotenine
- Indole alkylamines are similar to the hallucinogen LSD
What’s unique about bufagenins and bufotoxins?
Cardioactive steroids similar to digitalis
What species are most suspecptible to Bufo toad intoxication?
Dogs
- Cats and ferrets can also be poisoned
What is the most common season and time for bufo toad intoxication?
- Summer season
- Evening (most toads are nocturnal)
What’s the toxic dose of bufo toads?
1 mg/kg of secretions cause poisoning signs
Where are Bufo toxins absorbed and distributed?
Mucous membranes of mouth, gastric mucosa, conjunctiva, and open skin wounds and distributed all over body (including CNS)
What is the MOA of Bufo toad intoxication?
- Direct irritation of mucus membranes
- Main organs affected: heart, blood vessels, and CNS
- Bufotenine and bufotoxins → digitalis-like effect by inhibiting Na/K-ATPase
- Indole alkylamines → hallucinogenic
- Bufotenine → vasoconstriction and hallucinogenic
What are the clinical signs associated with Bufo toad intoxication?
- Irritation of oral mucosa (hypersalivation [foaming], brick red mucous membranes, vocalization and vomiting)
- Neurological signs (disorientation, ataxia, circling, seizures, opisthotonos, hyperthermia, and coma)
- Cardiovascular (tachypnea, tachycardia, cardiac arrhythmia, or bradycardia and collapse)
Are there lesions associated with Bufo toad intoxication?
No
↑ in hemoglobin content, PCV, blood glucose, BUN, alkaline phosphatase, serum potassium, calcium, and phosphorous are consistent with what zootoxin?
Bufo toad toxin
What is the DDX for bufo toad intoxication?
Disease causing seizure, cardiac toxicity, caustic, and hyperthermia
DDX for diseases/toxins causing seizures?
- Bufo toad toxin
- Metaldehyde
- Theobromine
- Cholinesterase inhibitor
- Idiopathic epilepsy
- Infectious meningioencephalitis
What toxins can cause cardiac toxcity?
- Bufo toxin
- Digitalis toxicity
- Poisonous plant with cardiac glycosides (gossypol or oleander)
DDX for toxins that are caustic?
- Bufo toxin
- Acids/alkalis
- Detergents
- Bleaches
What is the treatment for bufo intoxication?
- Flush mouth with running water
- Activated charcoal
- Seizures: diazepam, phenobarbital, propofol, glucocorticoid, furosemide, and mannitol
- Atropine (bradycardia, as bronchodilator, and decrease secretions [contraindicated w/ tachycardia])
- Tachycardia/arrhythmia (B blocker, lidocaine/procainamide for ventricular)
- Digoxin (may bind bufagenins and bufotoxins)
- Supportive therapy (fluid therapy, famotidine [H2 blocker for caustic toxin effect])
What are the poisonous snakes of North America?
- Pit vipers, Crotalid family
- Coral snakes
What are the pit vipers?
- Rattlesnake
- Copperhead
- Cottonmouth, water moccasins
What are the general characteristics of pit vipers?
- Have temp sensitive pit between eyes and nostrils
- Broad, triangular head
- Vertical pupils with prominent ellipitical slits
- Retractable fangs of upper jaw
What toxins are in snake venom?
Combination of enzymatic and nonenzymtic proteins and amino acids
- Nonenzymatic proteins and peptides are “killing fraction”
What species is most susceptible to snake venom? Which is most sensitive?
- Dogs are most susceptible (also cats and horses)
- Dogs are most sensitive (but cats more severely affected)
What are the sources for pit vipers?
ALL US STATES (except Maine, Aslaska, and Hawaii)
- Most bites due to Copperheads
Of the pit vipers, which are the most toxic?
Rattlesnake > cottonmouth > copperhead
- Severity depends on venom potency, amount, and season (April-October)
What is the MOA of snake venom?
PRIMARY effect is hypocoagulation
- Hyalurondiase cause venom to spread
- Phospholipase A2 disrupt cell membranes, uncouples oxidative phosphorylation, and releases vasoactive amines
- Enzymatic and nonenzymatic proteins have hematoxic (procoagulant, anticoagulant ), cardiotoxic, and neurotoxic effects
What are the clinical signs of pit viper envenomation?
Envenomatous
- Ecchymosis
- Puncute worund
- Fang mark
- Bleeding
- Edema
- Swelling
- Petechia
- Necrosis
Nonenvenomatous
- Mild local signs
- No systemic signs
- Normal laboratory findings
How long does it take to see pit viper clinical signs?
Onset may be rapid or delayed for several hours
Lab shows echinocytosis, hemolysis, hemoconcentraiton, increased or decreased coagulation time, hypokalemia, and liver and renal failure. What zootoxin is this consistent with?
Pit viper envenomation
How is snake venom toxin detection in tissues?
Not practical
Treatment for snake envenomation?
ANIMAL NEEDS TO BE IMMOBILIZED
- First aid: keep calm, keep bite below level of heart, monitor swelling, avoid incision and suction of bite site to decrease venom absoprtion
- Polyvalent crotalid antivenin: available for dogs, can cause allergic reaction (antiphylactoid therapy)
- Diphenhydramine IV: reduce allergic rxn to antivenin and sedates
- Fluid therapy
- Blood transfusion
- Broad-spectrum antibiotics
- Control pain with fentanyl
- Maintain airway and treat shock
What is contraindicated in pit viper treatment?
Corticosteroids and NSAIDs
T/F: if your dog gets a snake bite but has the rattle snake vaccine, you do not need to bring it in to be treated
False Still considered an medial emergency
What are the characteristics of coral snakes?
- Black head with alternating bands of black, yellow (or white) and red
- Small head with rounded pupils
- Short fixed front fangs
- Require chewing action to inject venom
What is the MOA of coral snake envenomation ?
- Local tissue rxn and destruction by hyaluronidase, proteinase, ribonuclease, desoxyribonuclease, and phospholipase
- Primary effect is neurotoxic
- Nondepolarizing neuromuscular blockade, CNS depression, muscle paralysis, and vasomotor activity
- Hemolysis with severe anemia and hemoglobinuria reported in dog
Clinical signs with coral snake envenomation ?
- CNS depression, quadriplegia with decreased spinal reflexes, respiratory paralysis, hypotension, and ventricular tachycardia
- Dogs also can have hemolysis, anemia, hemoglobinuria, and may salivate excessively (not seen in cat)
- Aspiration pneumonia can be a complication
Elevated fibrinogen and CK RBC morphological changes, anemia, and hemoglobinuria What zootoxin is this associated with?
Coral snake envenomation
What is your dddx for coral snake envenomation ?
- Tick paralysis
- Botulism
- Myasthenia gravis
Treatment for coral snake envenomation ?
- Micrurus fulvius antivenin
- Life support and symptomatic therapy as in pit vipers
