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Toxicology Final > Reptiles > Flashcards

Reptiles Flashcards

1
Q

what is envenomation?

A

injection of poisonous material by sting, spine, bite or other means

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2
Q

venomous reptiles come from what order?

A

squamata - includes lizards and snakes

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3
Q

where are venemous lizards found? what genus do they belong to?

A

north and central america, belong to Heloderma genus

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3
Q

what members of the venomous reptiles are represented in the western hemisphere?

A

members of the Crotalidae and Elapidae

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4
Q

H. suspectum and H. cinctum

A

Gila moneters, members of Heloderma

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4
Q

H. horridum

A

mexican beaded lizard

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5
Q

snakebites in companion animals

A

150k dogs and cats in north america annually

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6
Q

99% of snakebites come from what animals?

A

Crotalidae - pit vipers

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7
Q

why are dogs more likely to get a snake bite?

A

because of their inquisitive nature- come more in contact with them

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8
Q

Elipidae

A

Coral snakes

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9
Q

coral snakes

A

Elipidae

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10
Q

red touching black

A

safe for jack

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10
Q

the 2 genera of coral snakes are indigenous to where?

A

U.S

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11
Q

red touching yellow

A

kill a fellow

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12
Q

what 2 genera of coral snakes Elipidae are indigenous to the US?

A

Sonoran coral snake: Micururoides euryxanthus
Texas coral snake/eastern coral snake/south florida coral snake: Micurus fluvius

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13
Q

why are interactions between coral snakes and domestic animals less common than with pit vipers?

A

North American coral snakes tend to be shy, non-aggressive and nocturnal

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14
Q

Micuroroides Euryxanthus

A

Arizona coral snake/Sonoran coral snake

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15
Q

Micrurus Tener

A

Texas coral snake

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15
Q

Micrurus Fulvius

A

Eastern Coral snake

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15
Q

venom delivery of coral snakes

A

not very efficient- length of bite will determine deliverance
- short, fixed front fangs that are partially membrane covered
- 60% don’t result in venom deliver!

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16
Q

what amount of coral snake venom is lethal to a large dog?

A

1-2mg (4-5mg) is lethal in humans

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17
Q

how much venom does a large coral snake contain?

A

20mg of venom: but size of snake correlates to the amount of venom

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18
Q

PK/TK of coral snake venom

A
  • uptake delayed by hours
  • onset of neuro signs is delayed- 12+ hrs
  • binds irreversibly
  • can take 14 days to clear body!
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19
Q

coral venom PK in cats

A

in envenomated cats, clinical improvement began at 36 hours, recovery of limb motion after 48 hours

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20
Q

MOA of coral snake venom

A

neurotoxic! with not much swelling
- several neurotoxins involved, nondepolarizing neuro-muscular blockers. net effect is a “curare-like” syndrome (Flaccid paralysis)

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21
Q

clinical signs of coral snake venom

A

neurotoxic with little tissue reaction or pain at bite site
CNS depression, muscle paralysis, vasomotor instability, emesis, salivation, decreased spinal reflexes
maybe: intravascular hemolysis, anemia, hemoglobinuria, altered RBC

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21
Q

coral snake venom in dogs

A

hemolysis with severe anemia has been reported

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22
Q

clinical signs of coral snake venom in cats

A

acute ascending flaccid quadriplegia, CNS depression, reduced nociperception
- aniscoria, absent spinal reflexes, hypothermia have all been reported

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23
Q

you see a dog for a presumed snake bite. the dog presents with excessive salivation, quadriplegia and CNS depression. there is little swelling at the bite site. what is your suspicion?

A

coral snake bite

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24
Q

what was the only definitive treatment for coral snake bites?

A

Antivenin (Wyeth labs)- has been discontinued

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25
Q

how do you treat coral snake toxicity?

A
  • adequate supportive care!!
  • compression bandage around and over bite site
  • clinical signs may be delayed by 12 hrs! patient should be hospitalized for min of 24 hrs
  • be prepared to respond to respiratory collapse, dysphagia, aspiration pneumonia: ventilatory support!!
  • broad spectrum abx are generally recommended
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26
Q

why should coral snake bite pts be hospitalized for a minimum of 24 hours?

A

because clinical signs may not happen until 12 hrs after

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27
Q

what meds can you give a coral snake bite patient?

A

broad-spectrum abx
may need respiratory/ventilatory support

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28
Q

what is a possible anivenin treatment for coral snake

A

Coralmyn: new, made in Mexico, lyophilized antivenom of polyclonal abs from horses immunized with black banded coral snake venom. available for vetmed with USDA import permit

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29
Q

coral snake envenomation

A
  • rare: 1% of all snake bites
  • venom delivery is only 40%
  • dogs most likely recipients
  • neuro effects and “curare-like” paralysis
  • onset of effects are delayed and long-lasting
  • supportive txt, prognosis fairly good
  • major complication is aspiration pneumonia :(
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30
Q

Crotalidae

A

pit vipers

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31
Q

what genera do pit vipers (Crotalidae) belong to?

A
  1. Crotalus: rattlesnakes
  2. Sisturus: pygmy rattlesnakes and massasauga
  3. Agkistrodon: water moccasins/cottonmouths/copperheads
32
Q

where are pit vipers found?

A

every state in the US except for Hawaii, Maine and Alaska

33
Q

most pit viper bites are inflicted by what snakes?

A

copperheads- Agkistrodon- live thruout Southeastern US

34
Q

99% of snakebites to animals in North America are by what species

A

pit vipers

35
Q

pit viper envenomation

A
  • very efficient- strike super fast
  • venom given by rotating front fangs downward and stabbing forward
  • muscle contraction of venom glands delivers venom thru fangs
36
Q

what is a “dry” bite?

A

no venom delivered: 25% of time. defensive bites are more often dry, offensive bites deliver a controlled amount of venom

37
Q

what are agonal bites?

A

pit viper bite that delivers the entire venom load- most dangerous!

38
Q

severity of a pit viper bite is related to

A

volume and toxicity of venom, as well as location

39
Q

toxicity of venom is most severe in what pit vipers? (descending order)

A

rattlesnake > water moccasin > copperhead
toxicity of rattlesnake venom varies widely

40
Q

____________ will dictate uptake of poison into systemic circulation

A

location of the bite- also based on perfusion of that tissue region

41
Q

PK/TK of pit viper venom

A
  • may take weeks for venom to be cleared
  • response depends on snake, volume of venom, species of recipient
42
Q

MOA of pit viper venom

A
  • NOT to kill but to immobilize and pre-digest tissues
  • mixture of enzymatic and nonenzymatic proteins
  • minimum of 10 enzymes in a specific venom
  • 3-12 nonenzymatic protein/peptides in a specific venom: nonenzymatic fractions are the killing fraction and are 50x more potent
43
Q

what comprises pit viper venom?

A

complete mixture of enzymatic and nonenzymatic proteins
- minimum of 10 enzymes in a specific venom
- 3-12 nonenzymatic protein or peptides in a specific venom
- nonenzymatic fractions are the killing ones! 50x more potent

44
Q

what are the 3 types of rattlesnake venom in North American snakes?

A
  1. Classic diamondback venom
  2. Mojave A rattlesnake venom
  3. Intergrade - multiple species
45
Q

classic diamondback rattlesnake venom

A

causes markred tissue destruction, coagulopathy, hypotension

46
Q

mojave A rattlesnake venom

A

no tissue destruction or coagulation but induces severe neurotoxicosis: more potent

47
Q

intergrade venom in multiple species

A

contains both neurotoxins and classic venom components

48
Q

clinical signs of pit viper toxicity

A
  • initially see marked regional swelling: ecchymosis/petechiation
  • swelling and heavy haircoat could obscure wounds!
  • local tissue response doesn’t always = severity
  • delayed onset of clinical signs
  • marked hypotension develops early
  • progressive swelling up to 36 hrs
49
Q

what clinical sign of pit viper envenomation develops early?

A

marked hypotension

50
Q

additional clinical signs of pit viper envenomation

A

tachycardia, shallow respirations, lethargy, nausea, obtundation, muscle fasciculations, increased salivation, painful lymph nodes

50
Q

where are dogs typically bitten? what kind of bite?

A

head or front legs
- usually a defensive strike
- seek humans right after, thus bite presents early

51
Q

where are cats typically bitten? what kind of bite?

A
  • cats often bitten in torso
  • usually an offensive strike in response to “playing”
  • presents later due to hiding
52
Q

where are horses usually bitten?

A

nose, marked tissue necrosis is possible

53
Q

clinical pathology of pit viper venom

A
  • baseline blood counts and serum chemistries: repeat at 6, 12, 24 hrs
  • early high levels of Creatine Phosphokinase can indicate severe envenomation: marker of tissue/muscle damage
  • coagualation parameters should be monitored
  • urinalysis: hematuria or rhabdomyolysis
53
Q

where are cattle often bitten?

A

muzzle or tongue
tissue necrosis and secondary infection can be an issue due to later ID of envenomation

54
Q

what diagnostic test is often indicative of pit viper envenomation?

A

evidence of echinocytosis on a non-EDTA blood smear or one drop of blood mixed with a drop of saline
- caused by phospholipases in venom that alter membrane structure of RBCs

55
Q

treatment of pit viper envenomation

A
  • keep calm, bitten area should be below heart level if possible
  • circumferential measurements above, below and at bite site monitored at least 6 hours
  • severity score to monitor severity
  • IV crystalloid fluid therapy started
  • broad-spectrum abx in species susceptible to clostridial infx
  • diphenhydramine to calm animals and allergic reactions
56
Q

what medical txts can be used for pit viper envenomation?

A
  • antivenin! CroFab single vial
  • IV crystalloid therapy: combats hypovolemic crisis
  • broad-spectrum abx
  • diphenhydramine to calm and forllergic rxns
57
Q

what is the primary cause of death from pit viper envenomation? what txt helps combat this?

A

cardiovascular collapse from hypovolemic shock: IV crystalloid therapy helps combat!

58
Q

severity score of pit viper envenomations

A
  • pulmonary system
  • cardio system
  • local wound
  • GI system
  • hematologic system
  • CNS
    total possible score: 0-20
59
Q

what is the only proven treatment for pit viper venom?

A

IV antivenin! CroFab: Equine origin. typical dose is a single vial, epi should be ready to treat anaphylactic events, diphenhydramine can also be used

60
Q

antivenin is approved for treatment of what snake envenomation?

A

pit viper! stops swelling, reverses coagulopathy, thrombocytopenia, improves muscle strength

61
Q

vaccine for venom?

A

rattlesnake one is being developed- western diamondback rattlesnake, but is not preventive. does enhance recovery tho! not recommended tho

62
Q

prognosis of pit viper envenomation

A

with early medical intervention, most survive
large animals often survive initial effect, but are at risk of death from tissue damage and infection because of delayed recognition

63
Q

venemous lizards?

A

only ones in north and central america are members of genus Heloderma

64
Q

mexican beaded lizard

A

Heloderma horridum

65
Q

gila monster

A

Heloderma suspectum

66
Q

lizard envenomation?

A
  • do not inject- released from venom glands on lower jaw, flows up teeth thru capillary action
  • degree of envenomation is related to duration of bite
  • lizard sometimes still hangs on to patient!
    venom is for defensive purposes only
67
Q

MOA of lizard venom

A

mix of biologically active proteins- no neurotoxins and don’t affect coagulation

68
Q

clinical signs of lizard venom

A
  • extreme pain at bite site- ouchhh
  • significant bleeding from teeth that break off into wound
  • edema around wound
  • hypotension/tachycardia w resultant weakness
  • regional muscle fasciculations
69
Q

what does lizard venom NOT cause?

A

tissue necrosis! but secondary infection can be a sequela esp if tooth fragments are embedded

70
Q

feline lizard victims clinical signs

A

tachypnea, tachycardia, vomiting- likely as result of pain

71
Q

treatment of lizard venom

A
  • pry lizard off!
  • hospitalize and monitor
  • no specific antivenin available
  • txt is supportive; IVF, narcotics/fentanyl for pain, lidocaine for wound and check for lizard teeth
  • broad spectrum abx for secondary infx
72
Q

prognosis of lizard envenomation

A

good, single largest predictor is duration of bite. longer bite = more venom delivered
- patients w cardiac or pulmonary conditions are at greater risk
- federally protected- don’t let pets bother them!

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Toxicology Final (4 decks)

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