1
Q
Myotoxins
A
- Cause systemic destruction of muscle fibres (myolysis/rhabdomyolysis)
- Myoglobinuria is the by-product of broken-down muscle fibres and can cause secondary renal failure due to tubular necrosis
- Cause creatine kinase (CK) and potassium to be released into the systemic circulation
2
Q
Australia
A
- Home to 20 of the 25 most venomous snakes
- Most common envenomations in South East Queensland = Eastern Brown Snake (Pseudonaja textilis) and Red Bellied Black Snake (Pseudechis porphyriacus)
- The Dugite or Spotted Brown Snake (Pseudonaka affinis) is a highly venomous species commonly treated in practices in Perth, WA.
3
Q
Pathophysiology of Toxins
A
- Snake venom has many varying toxic properties depending on the species and geographical location of the individual snake
- Can include: myotoxins, nephrotoxins, neurotoxins, procoagulants, anticoagulants, haemotoxins, cardiotoxins and cytotoxins
4
Q
Myotoxins
A
- Cause systemic destruction of muscle fibres (myolysis/rhabdomyolysis)
- Myoglobinuria is the by-product of broken-down muscle fibres and can cause secondary renal failure due to tubular necrosis
- Cause creatine kinase (CK) and potassium to be released into the systemic circulation
5
Q
Nephrotoxins
A
- Secondary renal failure caused by myotoxins and haemotoxins.
- Haemoglobin & myoglobin block renal tubules causing tubular necrosis
6
Q
Neurotoxins
A
- Toxins that cause progressive flaccid paralysis of skeletal and respiratory muscles
- Interfere with neuromuscular junctions (presynaptic or postsynaptic)
- Postsynaptic neurotoxins are neutralised once antivenin administered; patient generally makes a quick recovery
- Presynaptic toxins cannot be reversed with antivenin; much slower recovery
7
Q
Procoagulants
A
- Extremely potent activators of blood clotting. This process is incredibly rapid and results in massive thrombosis and consumption of fibrinogen. The blood then cannot clot
- Characterised by profound coagulopathy and defibrination
- The coagulopathy is not reversed with antivenin
- Bleeding may occur from bite site, venepuncture sites, in the lungs, GIT, bladder etc.
(haematemesis, haemoglobinuria, haematochezia etc commonly observed)
8
Q
Anticoagulants
A
- Toxins impede coagulation of blood
- Characterised by coagulopathy WITHOUT defibrination
- Readily reversed with antivenin
9
Q
Haemotoxins
A
- Causes haemolysis (breakdown) of red blood cells
- Secondary renal failure/tubular necrosis
- Secondary hyperbilirubinemia
10
Q
Cardiotoxins
A
- Seen with taipan venom (Taicatoxins)
- Interferes with myocardial calcium channels
- Dysrhythmias
11
Q
Cytotoxins
A
- Localised reaction often experienced at the bite site
- Can cause swelling, inflammation, pain, and in severe cases necrosis of tissues
12
Q
Eastern Brown Snake
Pseudonaja textilis
A
- Varying colours of brown ranging from dark brown to orange with a slightly paler head. Pale ventral surface (cream, yellow/orange with blotches). Eyes have round pupils and distinguishing orange/brown brow ridge
- 17 midbody scale rows, divided anal scale
13
Q
Spotted Brown/Dugite Snake
Pseudonaja affinis
A
- Ranges from olive brown to grey with irregular (dark grey/black) spots on each scale
- 19 mid body scale rows, divided anal and subcaudal scales
14
Q
Red Bellied Black Snake (RBBS)
Pseudechis porphyriacus
A
- Uniform black head and body with pale brown snout. Bright lateral scales (often red or pink) fading to a paler colour on underside (orange or cream)
- 17 mid body scale rows, divided anal scale
15
Q
Identification of Common Snake Envenomation
A
- Presenting clinical signs
- Visualisation and scale count of presenting dead snake
- In house tests = Coagulation (Prolonged ACT or PT/APTT), Positive Snake Venom Detection kit
16
Q
Clinical signs of snake envenomation
A
- Dilated pupils
- Absent or slow pupillary light reflexes
- Hind limb ataxia
- Hypersalivation
- Vomiting
- Rapid respiration
- Depression
Module 7: Snakes and Ticks
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