Reptiles By: Ana Rebecca Joy T. Lucero Rochelle Gavino Angeline Lacson
Dec 25, 2015
Objectives
• To be able to know the toxins present in reptile venoms and their corresponding effects.
• To be able to understand how envenomation occurs in different reptile species.
• To know what safety measures & treatment must be done when envenomation happens.
Introduction/Definition
• Reptiles – cold-blooded egg-laying vertebrates that has
an outer covering of horny scales or plates- Includes snakes, lizards, crocodiles, and turtles
Snakes - any limbless scaled reptiles with a long tapering body and with salivary glands often modified to produce venom which is injected through grooved or tubular fangs
Lizards – are reptiles that typically has a long body and tail, four legs, movable eyelids, and a rough, scaly, or spiny skin.
Crocodiles - large carnivorous thick-skinned long-bodied semi-aquatic reptiles
Turtles - a slow-moving reptile, enclosed in a scaly or leathery domed shell into which it can retract its head and thick legs.
Introduction/Definition
Venom - a poisonous substance secreted by
animals
Envenomation– the process by which venom is injected into
some animal by the bite (or sting) of a venomous animal
Lizards
• Family : Helodermatidae • Genus : Heloderma
»Beaded Lizard (H. horridum)»Gila monster (H. suspectum)
Are the only lizards known to have evolved an overt venom delivery system Heloderma means "studded skin" (Ancient Greek: hêlos—the head of a nail or stud and dérma meaning skin.) Horrĭdum, is the Latin word meaning “rough or rude”
Type of Poison
• (1.) Neurotoxin– a substance which inhibits the functions of neurons– Action: damage neurons so that they cannot function. attack the signaling capability of neurons blocks the release of various chemicals interfering with the methods of reception/transmissions/sending of false signals
– Effect : Neuromuscular paralysis dizziness drooping eyelid (ptosis) paralysis of one or
more extraocular muscles (opthalmoplegia) flaccid facial muscle paralysis inability to swallow paralysis of larger muscle groups paralysis of respiratory muscle asphyxiation coma death
Type of Poison
• (2.) Hemotoxin– are toxins that destroy red blood cells ,disrupt blood clotting,
and/or cause organ degeneration and generalized tissue damage
– Effect : swelling necrosis (tissues/organs) cardiovascular damage
loss of blood pressure death
Type of Poison
Constituents of Lizard Venom•Hyaluronidase
– “spreading factor”– Hydrolase enzyme that degrades hyaluronic acid – Result: increase tissue permeability
facilitates venom diffusion into tissue– Hyaluronic acid – mucopolysaccharide that is an
important component of connective tissue
Type of Poison
• Serotonin– Neurotransmitter– Mediates inflammation, vasodilation ,smooth muscle
activity and cause platelet aggregation– Neurons Serotonin signal
smooth muscle activityproduce relays
produce
Type of Poison
• Monoamine Oxidase– Break-down excess neurotransmitter (e.g. serotonin)– Normal: Abnormal: neurotransmitter neurotransmitter
synaptic gap synaptic gap
Normal levels of MAO enzymes levels of MAO = activity
excess neurotransmitter levels of neurotransmitter flushed out /deactivated flushed out / deactivated
Type of Poison
• Phospholipase A2
- disrupts the release of neurotransmitter in nerve synapses blocks acetylcholine release parasympatholytic effect
Increase heart rate Mydriasis/cycloplegia/decreased lacrimation Reduce secretion relaxation- indirect degranulating effect on mast cells histamine
inflammationincrease permeability
of capillaries
Type of Poison
• Gila Toxin
- “lethal factor”- 3-5% of venom volume- action : release bradykinin from kininogen- effects : bradykinin inflammation
vasodilation fall of blood pressure bronchoconstriction dry cough natriuresis fall of blood pressure contraction of uterus smooth muscle
Type of Poison
Helotherime- “hypothermic toxin”- Action: inhibits Ca+ influx from sarcoplasmic reticulum- Result : muscle relaxation- Effect : lethargy , partial paralysis of rear limbs, intestinal distention, lowering of body temperature
Type of Poison
Helodermatine - “hypotensive enzyme”
- kinin-like activity induce vasodilation and contraction of smooth muscle
- effects: dose-dependent decrease of the arterial blood pressure.
Mechanism of Poisoning
Venom Glands capillary action release of venoms through (Venom storage) the ducts in large teeths(Lower Jaw) (Lower Jaw)
Gilas/beaded lizards latch onto their victims & chew to allow neurotoxins to move through grooves in their teeth and into the open wound
Mechanism of Poisoning
Venom
Open wound release
LOCAL EFFECTS Hyaluronidase Phospholipase A2 Other Proteolytic
enzymes
increased tissue permeability inhibits cellular respiration local tissue damagedeeper penetration cell membrane destruction spread of other venomTissue necrosis inhibits platelet aggregation components
inflammatory response (release of histamine)
SYSTEMIC EFFECTS Gila Toxin Helotherime Helodermatine Pain, hypotension hypothermia, lethargy, hypotension
Clinical Manifestations
– Pain– Edema ( caused by Histamine & Bradykinin)– Hypotension– Nausea– Vomiting– Weakness/ muscle paralysis– Diaphoresis (excessive sweating)-caused by
serotonin
Target Organ
• Neurotoxins– Nervous System (neurons,neurotransmitters)– Muscles (skeletal,smooth)
• Hemotoxins - Circulatory system
- Blood vessels,blood,tissues
Antidote/Treatment
No antivenin is commercially available. Treatment is supportive.First Aid : Disengage the lizard that is still attached to the victim Irrigate the bite site w/ 2% Lidocaine Probed the wound w/ 25-gauge needle to detect any embedded tooth Diazepam – useful in sedating agitated or painful patient Analgesic Broad Spectrum antibiotic
*co-amoxiclav / doxycycline*prevents infection of wound
Assessment & Monitoring- development of hypotension/shock
Antidote/Treatment
Suction or compression may impede venom movement, they are unproved.
Cryotherapy, tourniquet, and excision are dangerous and should not be used.