Snake Bite Diagnosis

Any snakebite needs emergency medicine and evaluation. Identification of fang or bite marks is done, even if the snake is nonvenomous, to determine local trauma or tissue damage at the site of the bite. Identification of the snake type by description or picture, along with the circumstances of the bite and the surrounding environment usually provides the health care professional a working diagnosis.

For example, a snakebite occurring in dry west Texas is likely a rattlesnake bite, while a snakebite in a swampy area of the U.S. is likely a water moccasin, and Tiger snakes (body has bands of colors) are found mainly in Australia and its costal islands. A zookeeper or private snake owner/collector who is bitten will likely know the exact type of snake that caused the bite or toxic spray (spitting cobras).

Diagnostic tests and tools
At present there is only one commercial diagnostic test available that makes it possible to confirm the type of snake venom present in the body of an envenomed patient. This test uses antibodies to recognize specific types of venom produced by different species of snakes.

Other diagnostic tests that use similar approaches are being used experimentally, but there is a need in some regions and countries for commercial tests that can be used to better inform the proper selection of antivenoms to treat patients.
There are however simple tests and diagnostic tools (algorithms or checklists) that can be used to confirm the presence of important clinical signs of snakebite envenoming which indicate the need for early antivenom treatment and, in some cases, can help differentiate the most likely genus or species of snake responsible for the bite.

Spontaneous haemorrhage due to envenoming by some snake species is an SNAKEBITE DIAGNOSTIC TEST_WHO2important clinical indication for antivenom. Diagnosis is aided by a test known as the 20 Minute Whole Blood Clotting Test (20WBCT). A clean, dry glass bottle or vial into which 1-2 millilitres of venous blood is added, is allowed to stand at room temperature for 20 minutes, and is then inverted and the presence or absence of a complete clot is recorded.
Where a blood is present, the test result is negative, whereas if no clot forms and the blood remains liquid, the test result is positive, indicating presence of a coagulopathy and the need for antivenom treatment. Where this test is used it is essential that it be appropriately standardized using uniform glassware, sample volume and temperature, and validated for accuracy using serial donor samples prior to routine use.


Diagnostic tools also have considerable potential to better inform the surveillance of snakebite envenoming by enabling retrospective identification in pathology samples of venom immunotypes from various species of snakes. This can improve the reporting of snakebite envenoming and assist in determining optimal antivenom needs for regions.