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Crotalus atrox
General Details, Taxonomy and Biology, Venom, Clinical Effects, Treatment, First Aid , Antivenoms
Crotalus atrox  ( Western Diamond Rattlesnake  )  [ Original photo copyright © Dr Julian White ]
Family: Viperidae
Subfamily: Crotalinae
Genus: Crotalus
Species: atrox
Common Names
Western Diamond Rattlesnake
Local Names
Vibora de Cascabel , Vibora Serrana , Coon-Tail Rattler
North America + Central America
Mexico, United States of America
Taxonomy and Biology
Adult Length: 1.10 m
General Shape
Large in length, heavy bodied rattlesnake with a short tail and horn-like segmented rattle. Can grow to a maximum of about 2.34 metres ( but very rarely exceeding 1.80 metres ). Head is large, broad and very distinct from narrow neck. Eyes are medium to moderately small in size with vertically elliptical pupils. Dorsal scales are keeled.
Recorded up to about 2500 metres but rarely above 1500 metres in mesquite grassland, desert, pine-oak forest, tropical deciduous forest and thorn forest.
Terrestrial and diurnal snake.
Feeds on a variety of small mammals, rodents lizards and occasionally birds.
Species Map
Small (Approx 20k) version
Average Venom Qty
175 to 325 mg ( dry weight ), U.S. Dept. Navy (1968) ( Ref : R000914 ).

200 to 300 mg ( dry weight ), Minton (1974) ( Ref : R000504 ).
General: Venom Neurotoxins
Possibly present but not clinically significant
General: Venom Myotoxins
Not present
General: Venom Procoagulants
General: Venom Anticoagulants
General: Venom Haemorrhagins
Zinc metalloproteinase
General: Venom Nephrotoxins
Not present
General: Venom Cardiotoxins
Not present
General: Venom Necrotoxins
Secondary necrotoxic activity only
General: Venom Other
Nucleosides & nucleotides
Clinical Effects
General: Dangerousness
Severe envenoming possible, potentially lethal
General: Rate of Envenoming: 60-80%
General: Untreated Lethality Rate: 10-20%
General: Local Effects
Marked local effects; pain, severe swelling, bruising, blistering, necrosis
General: Local Necrosis
Potentially may occur
General: General Systemic Effects
Variable non-specific effects which may include headache, nausea, vomiting, abdominal pain, diarrhoea, dizziness, collapse or convulsions
General: Neurotoxic Paralysis
Classic neurotoxicity is rare, if present, likely to be minor, but secondary peripheral neuropathy may occur.
General: Myotoxicity
Not likely to occur
General: Coagulopathy & Haemorrhages
Very common, coagulopathy + haemorrhagins causing bleeding is major clinical effect
General: Renal Damage
Rare, usually secondary effect
General: Cardiotoxicity
Unlikely to occur
General: Other
Shock secondary to fluid shifts due to local tissue injury is likely in severe cases
First Aid
Description: First aid for bites by Viperid snakes likely to cause significant local injury at the bite site (see listing in Comments section).
1. After ensuring the patient and onlookers have moved out of range of further strikes by the snake, the bitten person should be reassured and persuaded to lie down and remain still. Many will be terrified, fearing sudden death and, in this mood, they may behave irrationally or even hysterically. The basis for reassurance is the fact that many venomous bites do not result in envenoming, the relatively slow progression to severe envenoming (hours following elapid bites, days following viper bites) and the effectiveness of modern medical treatment.
2. The bite wound should not be tampered with in any way. Wiping it once with a damp cloth to remove surface venom is unlikely to do much harm (or good) but the wound must not be massaged.
3. All rings or other jewellery on the bitten limb, especially on fingers, should be removed, as they may act as tourniquets if oedema develops.
4. The bitten limb should be immobilised as effectively as possible using an extemporised splint or sling; if available, crepe bandaging of the splinted limb is an effective form of immobilisation.
5. If there is any impairment of vital functions, such as problems with respiration, airway, circulation, heart function, these must be supported as a priority. In particular, for bites causing flaccid paralysis, including respiratory paralysis, both airway and respiration may be impaired, requiring urgent and prolonged treatment, which may include the mouth to mask (mouth to mouth) technique of expired air transfer. Seek urgent medical attention.
6. Do not use Tourniquets, cut, suck or scarify the wound or apply chemicals or electric shock.
7. Avoid peroral intake, absolutely no alcohol. No sedatives outside hospital. If there will be considerable delay before reaching medical aid, measured in several hours to days, then give clear fluids by mouth to prevent dehydration.
8. If the offending snake has been killed it should be brought with the patient for identification (only relevant in areas where there are more than one naturally occurring venomous snake species), but be careful to avoid touching the head, as even a dead snake can envenom. No attempt should be made to pursue the snake into the undergrowth as this will risk further bites.
9. The snakebite victim should be transported as quickly and as passively as possible to the nearest place where they can be seen by a medically-trained person (health station, dispensary, clinic or hospital). The bitten limb must not be exercised as muscular contraction will promote systemic absorption of venom. If no motor vehicle or boat is available, the patient can be carried on a stretcher or hurdle, on the pillion or crossbar of a bicycle or on someone's back.
10. Most traditional, and many of the more recently fashionable, first aid measures are useless and potentially dangerous. These include local cauterization, incision, excision, amputation, suction by mouth, vacuum pump or syringe, combined incision and suction ("venom-ex" apparatus), injection or instillation of compounds such as potassium permanganate, phenol (carbolic soap) and trypsin, application of electric shocks or ice (cryotherapy), use of traditional herbal, folk and other remedies including the ingestion of emetic plant products and parts of the snake, multiple incisions, tattooing and so on.
Treatment Summary
Rattlesnake bites can cause major, even fatal envenoming. All cases require urgent assessment and management. For larger species, about 20% will have an ineffective bite, with no local or systemic envenoming, so will not require antivenom and may not require prolonged observation. This figure will be higher for the smaller species, which are generally unlikely to cause a severe bite. All other cases, with any degree of local or systemic effects, require extended observation and may require IV antivenom (Crofab), the amount partly dictated by the severity grading. Beware fluid shifts causing shock, coagulopathy and bleeding, kidney damage and necrosis of the bitten area.
Key Diagnostic Features
Variable severity local pain, swelling, blistering, ± necrosis. Systemic effects may include coagulopathy, bleeding, renal failure, rarely myolysis &/or mild paralysis
General Approach to Management
All cases should be treated as urgent & potentially lethal. Rapid assessment & commencement of treatment including appropriate antivenom (if indicated & available) is mandatory. Admit all cases.
Antivenom Therapy
Antivenom is the key treatment for systemic envenoming. Multiple doses may be required.
1. Antivenom Code: SAmPRO01
Antivenom Name: Polyvalent crotalid antivenom ( CroFab ), Ovine, Fab
Manufacturer: Protherics Inc. (US)
Phone: ++1-615-327-1027
Address: 5214 Maryland Way
Suite 405
Tennessee 37027
Country: U.S.A.
2. Antivenom Code: SAmIBM06
Antivenom Name: Antivipmyn
Manufacturer: Instituto Bioclon
Phone: ++56-65-41-11
Address: Calzada de Tlalpan No. 4687
Toriello Guerra
C.P. 14050
Mexico, D.F.,
Country: Mexico
Crotalus atrox ( Western Diamond Rattlesnake ) [ Original photo copyright © Dr Julian White ]
Larger version
Crotalus atrox ( Western Diamond Rattlesnake ) [ Original photo copyright © Dr Julian White ]
Larger version
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