Snakebite is a global health crisis. Even though this is a neglected tropical disease, many parts of the USA fall into tropical or sub-tropical climate zones.

You don’t have to be in a rainforest to be in a tropical climate. 1/3 of the world’s population lives in one! Many venomous snakes thrive in tropical and subtropical climates. Where are you on the map? Does this tropical disease effect your area?

USA Snakebites

In humans, there are roughly 5,000 - 10,000 pit viper (cottonmouths, copperheads, and rattlesnakes) snakebites annually. Fortunately, few are fatal. The exact number of pets bitten is unknown, but the ASPCA claims bites range from 100,000 - 300,000, with an estimated mortality rate ranging from 1% up to 30%.

Snakebites are medical emergencies that require prompt treatment. Antivenom works best within the first six hours, but can still provide benefit when there are ongoing venom effects. Due to the time-sensitive nature, several snakebite victims or pet owners may become frustrated if human and/or veterinary medical professionals postpone immediate antivenom administration in order to draw blood for labwork. So the question becomes, why are labs so important and what do they even show?

Why is labwork important?

Antivenom is the only effective treatment to neutralize venom, which in turn stops progression of the direct venom effects. Those effects most often include swelling, bruising, and pain, but can also include bleeding, low platelets, low blood pressure, vomiting, and diarrhea, among others. It’s important to establish a baseline with bloodwork in order to determine when control is achieved with antivenom. Snakes are able to meter their venom (control the amount injected). This is why any suspected or confirmed bite needs to be monitored in a emergency setting for a minimum of eight hours. Snakebites are dynamic and can develop over time. Something that initally seems unimpressive with local findings (the immediate area around the fang scratch/bite), can end up developing into a significant envenomation. Comparing the initial labwork to labs drawn following antivenom are one of the factors that can assist medical professionals determine if additional antivenom is indicated.

How Do You Test For Venom?

Blood drawn for labs that assist in confirming a pit viper envenomation differs from diagnostic test such as urine test. The results aren’t going to show a negative or positive result for venom like you would see in a pregnancy test — but it can show the direct venom effects. For example, when veterinarians look at a blood film under the microscope, they look for echinocytes or to count and/or confirm the number of platelets.

Human testing may include:

CBC (complete blood count)
BMP (basic metabolic panel)
PT/INR (prothrombin time/international normalized ratio)
Fibrinogen
CK (creatine kinase)

Veterinary testing may include:

CBC (complete blood count)
Chemisty
PCV/TS (packed cell volume/total protein)
PT/PTT (prothrombin time/activated partial prothromboplastin time
Blood Film

What if labs are normal following a bite?

Results should be used as part of the diagnostic puzzle. All labs may, and often do, return WNL (within normal limits). This does not mean the envenomation was a dry bite or that lab results alone should rule out envenomation. If swelling, bruising, and pain are present following a bite from a pit viper, antivenom should be considered.

Can you tell which snake is responsible?

There is no definitive test to determine the species that caused the envenomation. Anyone can speculate based on lab results, severity of local tissue damage, and systemic effects, but it’s only speculation. Even if the species is known, the decision to treat should be based on symptoms. Any pit viper envenomation has the potential to be mild, moderate, or severe.

Understanding Blood Test & Results for USA Snakebites

Antivenom For Private Keepers