8-Venoms & toxins Flashcards
1
Q
Venomous animals
A
- actively inject toxins into victim
- venom used for hunting and defense
2
Q
Poisonous animals
A
- secrete poisons, which are passive defense mechanisms
3
Q
Venom composition
three classes of compounds
A
- 1) LMW substances
- 2) Peptides
- 3) Enzymes
4
Q
LMW substances
A
- prostaglandins
- histamine
- epinephrine
often cause
- pain
- inflammation
- hypotension
5
Q
Peptides
A
- cause many direct toxic effects and allergy
- mellitin
- bungarotoxin
6
Q
Enzymes
A
*cause toxicity and allergy
- Hyaluronidase
- spreading and potentiating factor
- catalyzes the cleavage of glycoside bonds
- Collagenase
- breaks down capillary walls
- Protease
- degrades proteins and cause necrosis
7
Q
Hymenoptera
A
- bees
- wasps
- hornets
- fire ants
8
Q
Bees
A
- envenomate by stinging; stinger remains in skin in some spp
- can only sting once
- swarms of hives can be fatal
9
Q
Wasps/hornets
A
- can sting repeatedly
- highly social; often attack in groups
10
Q
Fire Ants
A
- bite, sting, or both
- some spray formic acid
11
Q
Bee venom
MOA
A
- 63 identified components
- 50% mellitin
- acts as detergent
- hemolytic
- pain and histamine release
- cortisol release
- 12% Phospholipase A2
- destroys membranes (major allergen)
- 3% hyaluronidase
- disrupts cell membranes
- 50% mellitin
12
Q
Wasps/hornets
MOA
A
- venoms contain peptides, enzymes, amines
- designed to trigger pain
- kinins
- primary pain-inducing substances
- some contain neurotoxins/alarm pheromones
- alerts swarm to an intruder
13
Q
Ant venoms
MOA
A
- complex mixtures
- largely alkaloids
-
Piperidine
- dermal necrosis
- cytotoxic
- hemolytic
- fungicidal
- insecticidal
- bactericidal
- animals with limited mobility affected most
- neonates
- juveniles
- disabled
14
Q
Bees, wasps, hornets
Clinical Signs
A
- Small local
- swollen, edematous, erythematous plaque at sting site
- Large local (regional allergic reaction)
- Anaphylaxis
- most common cause of death
- reported in dogs
- not documented in livestock
- most common cause of death
- Systemic toxicity
- uncommon
- caused by delayed hypersensitivity
- shock, hemolysis, rhabdomyolysis, hepatic and renal injury
15
Q
Bees, wasps, hornets
TX
A
1) Removal of retained stinger by scraping
* grabbing stinger with forceps may inject more venom
2) Cold compress to relieve swelling and pain
- antihistamines and corticosteroids
- questionable once lesion formed
- not contraindicated
3) Monitor patients for anaphylactic reactions
- treat promptly with epinephrine
- aggressive fluid therapy with balanced fluids: systemic toxicosis
*exposure to single stings is rarely fatal
16
Q
Fire Ants
Clinical Signs
A
- pain at sting site
- erythematous puritic papules in dogs
- generally resolve w/in 24 hours
- No reports of anaphylaxis
- Multiple stings may cause systemic signs similar to multiple wasp/bee stings
- Multiple envenomations causing systemic rxns/anaphylaxis manage similar to bee stings
- epi
- fluids
17
Q
Ticks
A
- Dermacentor, Ixodes
- Holocyclotoxin
- produced in salivary glands
- toxin production inc with time on host
- Dec ACh release at neuromuscular junction
- paralysis/weakness
- Dermacentor toxin may act on Na+ channels
18
Q
Tick tox
Clinical Signs
A
- May appear 6-14 days after attachment
- loss of appetite/voice
- incoordination
- ascending flaccid paralysis
- excessive salivating and vomiting
- respiratory distress
- death from respiratory paralysis
19
Q
Tick Tox
DX
A
- No def dx
- hx tick infestation
- presence of
- dermacentor
- ixodes
- ascending paralysis, loss of voice
20
Q
Tick tox
TX
A
- Supportive
- Atropine sulfate
- Anti-emetics
- Fluid replacement
- Oxygen
- Prognosis good if treated
21
Q
Toad poisoning
Cane Toad / Giant Toad
A
- All species of Bufo secrete toxins for defense and possibly protection from microorganisms
- B. marinus (Florida) and B. alvarius (California/Arizona)
- Eggs and tadpoles also toxic
- Dogs most commonly involved in toad toxicosis
- mouthing stimulates release of toxins
22
Q
Toad Tox
MOA
A
- Biogenic amines (histamine, etc)
- vasoconstriction, hypotension, hallucination, GI effects
- Bufogenins (bufotalin)
- inhibit sodium-potassium ATPase activity similar to cardiac glycosides (digitalis)
- potentially toxic cardiac arrhythmias
23
Q
Toad tox
Dx
A
- Clinical signs begin immediately
- hypersalivation
- foaming at the mouth
- head shaking
- vomiting
- Other signs
- hyperemic gums
- arrhythmias (bradycardia, sinus tachycardia, sinus arrhythmia
- neuro signs (convulsions, ataxia, hallucinations)
- can cause severe hyperkalemia
- death can occur in 15 minutes
24
Q
Toad tox
TX
A
- immediate oral decon w/ water
- activated charcoal if no seizures
- diazepam/barbiturates for seizures
- atropine
- for bradycardia
- NOT for salivation, may exacerbate arrhythmia
- propranolol/lidocaine or esmolol for arrhythmia
- fluid replacement for CV support
- digoxin specific antigen-binding frags (digoxin immune Fab)
- for neuro signs/hyperkalemia
- may be cost prohibitive
25
Black Widow
* Only females are toxic
* messy web
* venom contains alpha-Iatrotoxin
* creates pores in membranes allowing Ca++ entry
* releases massive amounts of neurotransmitter
* causes sustained muscle spasms
26
Black widow tox
Clinical signs
* Muscle cramping/spasms
* rapid weight loss
* abdominal rigidity
* restlessness, writhing
* vocalization
* hypertension
* tachycardia
* cats most sensitive to venom and eat spiders
* severe pain, vomiting, diarrhea, respiratory collapse
27
Black widow tx
Tx
* Control muscle spasms and pain
* Calcium gluconate
* muscle cramps
* Anti-venom
* supportive care: **respiratory**
28
Brown recluse
| (Loxosceles reclusa)
* Nocturnal, non-aggressive
* animals bitten when they lay on spider
* dogs most susceptible
* venom contains necrotizing enzymes
* **sphingomyelinase D**
* binds to cell membranes
* cleaves head off lipids
* causes tissue necrosis
* victim's immune response determines severity of lesion
29
Brown Recluse Tox
Clinical Signs
* Initial bite causes little to no pain
* 3-8 hours after envenomation
* red, swollen, tender, blister like formation
* bulls-eye and non-healing ulcer
* can be necrotic
* can cause
* hemolytic anemia, fever, weakness, leukocytosis
30
Brown Recluse tox
Dx
* Dx difficult if bite not witnessed
* brown recluse often blamed necrotic lesions of other origin
31
Brown recluse tox
Tx
* Dapsone: for dermal lesion
* inhibits neutraphil migration
* Treat with fluids and bicarb: hemoglobinuria
* Anti-inflammatories
* Antibiotics to prevent secondary infections
* Analgesics for pain
* Necrotic lesion
* clean with **burrow's soln (aluminum acedate)** or hydrogen peroxide
* debridement of necrotic tissue
* sx removal if site is questionable
* bandage
32
Snakes
* Elapidae vs Crotalidae
* Dogs and horses most common victims
* 25% bites are dry bites-look for CS plus bite marks
* Size of victim and amount of venom determine severity
* death due to resp paralysis
33
Eastern Coral Snake
Micrurus fulvius fulvius
* Small fangs, small heads, red next to yellow bands
* shy, non-aggressive and nocturnal
34
Eastern Coral Snake
Micrurus fulvius fulvius
MOA
* Venom mostly small polypeptides and enzymes
* bungarotoxin-neurotoxic
* prevents binding of ACh (similar to curare)
* causes paralysis
* binding of neurotoxin to postsynaptic receptor appears to be irreversible
* enzymes can cause
* local tissue decrosis
* myoglobinemia in cats
* hemolysis in dogs
35
Eastern Coral Snake
Micrurus fulvius fulvius
Clinical Signs
* Onset of CS may be delayed up to 12 hours: duration of effect prolonged
* CS
* Salivation (inability to swallow)
* Dyspnea, weakness, hyporeflexia, CNS depression, paralysis
* no def. dx test
36
Eastern Coral Snake
Micrurus fulvius fulvius
TX
* Antivenom if neuro signs
* anaphylaxis to antivenom possible
* Ventilation if respiratory function compromised
* Broad-spectrum antibiotics
* Symptomatic wound care
* Monitor patients for minimum of 24 hours
* cats recover in 7-10 days
* Prognosis good with prompt care
37
Pit vipers: Copperhead, Cottonmouth, Rattlesnakes
(Crotalids)
* heat sensing pit and hinged fangs, triangular head, elliptical pupils, retractable fangs
* Copperhead responsible for most bites
* Rattlesnakes cause most deaths
38
Snake bite
Clinical Signs
* Distinct fang marks
* Immediate swelling and bruising at site of bite
* Pain around bite
* Hypotension, shock, tachycardia, tachypnea
* Anticoagulation
* Tissue necrosis
* Cats
* more resistant than dogs
* often hide after bite (present later)
* Dogs
* seek companionship after bite, treated earlier
39
Snake bite
Tx
* Antivenom
* Supportive
* Copperhead
* antihistamines for inflammation
* Rattlesnake and moccasin bites
* fluids
* corticosteroids for shock
* glucocorticoid for inflammation
* **cutting, ice, tourniquets contraindicated**
40
Garbage/carrion toxicity
* Usually from protein rich foods during warm months
* leftovers
* moist foods
* Can be due to bacteria or preformed toxins
* **enterotoxins**
* **endotoxin**
41
Enterotoxins
* Salmonella, E. Coli, Bacillus, Strep, C. perfringens
* Bind to intestinal epithelium
* inc permeability
* causes fluid loss and dec absorption
* Cause vx/d, abdominal pain, stasis with gas accumulation, bowel distention
42
Endotoxin
* Lipopolysaccharide from G- cell walls
* Activates inflammatory processes and releases
* TNF
* Prostaglandins
* histamine
* causes circulatory collapse (shock)
* activation pancreatic enzymes and autodigestion
* pancreatitis
* activation of clotting cascade
* uncoupling oxidative phosphorylation in heart
43
Endotoxin
Clinical signs
* lethargy
* fever
* hypothermia
* diarrhea
* abdominal pain
* shock
* exremely bad smelling feces
44
Endotoxin
TX
* Limit absorption
* emesis
* support CV function
* Correct fluid/electrolyte imbalance
* Prevent bacterial proliferation and septicemia
45
Botulism
Clostridium botulinum
* Toxin extremely potent
* Prevents release of ACh at NMJ causing paralysis
* Very difficult to dx, can be circumstantial
* access to carrion
* garbage
* compost piles
46
Botulism
Clinical Signs
* Decreased tonge and tail tone
* weakness, dropping food from mouth, weak vocalization
* can be down but alert, tail wag still present
* bradycardia
* constipation, urinary retention
* progressive paresis
47
Botulism
DDX
* anticholinesterases
* ionophores
* snakeroot
* lead
* nitrate
* botulism
* atropine-like alkaloids
48
Botulism
TX
* Supportive
* Parenteral nutrition, IV fluids
* Resp support, O2
* Warm water enemas, bladder expression may be necessary
* determine source
* treat with antibiotics if theres a wound or toxicoinfectious
* antitoxin
* doesn't neutralize toxins in neurons
* made from horse serum (can cause hypersensitivity)
* do intradermal test first
* prognosis poor
