Cambodia - Very Venomous Snakes Found - Trimeresurus macrops

Trimeresurus macrops ( Dark Green Pit Viper ) 

Original photo copyright © Dr Anita Malhotra

Family: Viperidae

Subfamily: Crotalinae

Genus: Trimeresurus

Species: macrops

Common Names: Dark Green Pit Viper , Large-eyed Pit Viper , Kramer's Pit Viper

Local Names: Ngu khiaw Hang Mai

Region: Southeast Asia

Countries: Cambodia, Thailand, Vietnam

Trimeresurus macrops ( Dark Green Pit Viper ) Original photo copyright © Dr Julian White

Taxonomy and Biology

Adult Length: 0.40 m

General Shape: Small in length, moderately slender bodied snake with tapering prehensile tail. Can grow to a maximum of about 0.75 metres. Head is short, triangular shaped and distinct from narrow neck. Eyes are large in size, golden yellow, cat-like, with vertically elliptical pupils. Dorsal scales are keeled except for the first dorsal scale row.

Habitat: Often found among small bush vegetation in plain and hill terrain up to about 1000 metres. Occasionally enters dwellings in search of prey and often found in urban areas including Bangkok.

Habits: Arboreal and mainly nocturnal, often seen at dusk or early morning.

Prey: Feeds mainly on rodents, lizards, birds and tree frogs.

Venom

General: Venom Neurotoxins	Probably not present
General: Venom Myotoxins	Unknown
General: Venom Procoagulants	Unknown
General: Venom Anticoagulants	Unknown
General: Venom Haemorrhagins	Unknown
General: Venom Nephrotoxins	Unknown
General: Venom Cardiotoxins	Probably not present
General: Venom Necrotoxins	Unknown
General: Venom Other	Unknown

Clinical Effects

General: Dangerousness	Unknown, but potentially lethal envenoming, though unlikely, cannot be excluded
General: Rate of Envenoming	Unknown but likely to be moderate
General: Untreated Lethality Rate	Unknown but lethal potential cannot be excluded
General: Local Effects	Local pain & swelling
General: Local Necrosis	Does not occur, based on current clinical evidence
General: General Systemic Effects	Does not occur, based on current clinical evidence
General: Neurotoxic Paralysis	Unlikely to occur
General: Myotoxicity	Not likely to occur
General: Coagulopathy & Haemorrhages	No reports of coagulopathy, though related species can cause bleeding problems
General: Renal Damage	Does not occur, based on current clinical evidence
General: Cardiotoxicity	Unlikely to occur
General: Other	Does not occur, based on current clinical evidence

First Aid

Description:

First aid for bites by Viperid snakes likely to cause significant local injury at the bite site.

Details

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

Treatment Summary: Bites by this species are not recorded, but might cause moderate, possibly major local & systemic effects, including coagulopathy/bleeding. Urgently assess & admit all cases. Antivenom therapy is probably the key treatment, especially for coagulopathy.

Key Diagnostic Features: Local pain, swelling, blistering, necrosis + coagulopathy, bleeding

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.

Antivenoms

1. Antivenom Code: SAsTRC01

Antivenom Name: Green Pit Viper Antivenin

Manufacturer: Science Division, Thai Red Cross Society

Phone: ++66-2-252-0161 (up to 0164)

Address: Queen Saovabha Memorial Institute

1871 Rama IV Road

Pathumwan

Bangkok 10330

Country: Thailand

Source: Clinical Toxinology Resources