Reptiles

By:Ana Rebecca Joy T. Lucero

Rochelle GavinoAngeline Lacson

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

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”

Beaded Lizard

Gila Monster

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

Type of Exposure

• Accidental Dermal Bite

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.