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Venomous snake bites are a risk to equids residing in certain areas of North America. Pre-exposure Western diamondback rattlesnake (Crotalus atrox) vaccination may be recommended for those animals residing in or traveling to geographical areas where exposure risk to venomous snakes justifies vaccine usage.

Vaccinating for rattlesnake envenomation should only be done in collaboration with your veterinarian.


One conditionally licensed inactivated (Crotalus atrox Toxoid) vaccine exists for use in healthy horses 4 months of age or older (per manufacturer) as an aid in the reduction of morbidity and mortality due to envenomation with Crotalus atrox toxin.

The vaccine label claims possible protection against the venoms of the Western rattlesnake (including the prairie, Great Basin, Northern and Southern Pacific varieties), sidewinder, timber rattlesnake, massasauga, and the copperhead. Partial protection may be obtained against Eastern diamondback rattlesnake venom. This vaccine does not provide protection against venom from the water moccasin (cottonmouth), Mojave rattlesnake or coral snake. 

This product license is conditional. Efficacy and potency test studies in progress.

Vaccination Schedule: 

Use in healthy horses 4 months of age or older. Do not vaccinate within 21 days of slaughter. Administration should be performed under the supervision of a licensed veterinarian. 

Adult horses: Administer a primary series of three doses at one-month intervals. Booster doses are recommended at 6-month intervals. The recommended vaccination site is the pectoral muscles, although this site is not generally recommended for most vaccines. 

Pregnant mares: Manufacturer information claims the product is safe for use in pregnant mares, however this information does not appear on the product label. It is recommended veterinarians contact the manufacturer with questions regarding use in pregnant mares. 

Foals (4 months of age and older per manufacturer): Administer a primary series of three doses at one-month intervals. Booster doses are recommended at 6-month intervals. There is no specific information available regarding the vaccination of foals less than 4 months of age. 

**Occasionally, swelling may occur at the injection site. Such swellings typically resolve in a few days without intervention but may occasionally require treatment. Rarely, anaphylactic or other adverse systemic reactions may occur. If adverse systemic reactions occur, appropriate therapy with epinephrine or other anti-anaphylactic drugs should be instituted immediately.

Revised – 2021