Botulinum toxin A

Prepared by: Michael J. Huerkamp, DVM, Diplomate ACLAM
Date: August 30, 2002

Agent: Botulinum toxin A

Botulinum toxin in solution is colorless, odorless, and, as far as is known, tasteless. It is readily inactivated by heat. Botulinum toxin is derived from the genus of anaerobic bacteria named Clostridia. Seven antigenic types of botulinum toxin exist, designated from A through G. Botulism is typically a foodborne illness, but botulinum toxin(s) could be used as biological weapons and local injections (Botox) are used are used medically for cosmetic effect. All forms of botulism result from absorption of botulinum toxin into the circulation from either ingestion, inhalation or a wound. Botulinum toxin does not penetrate intact skin. Botulinum intoxication causes difficulty swallowing, speaking difficulties, stuttering, blurred or double vision, drooping eyelids, loss of head control and weakness followed by life-threatening paralysis usually occurring 12 to 72 hours after exposure.

Potential Hazard: Rabbits given botulinum toxin are adminstered low doses (1.6 ng/kg) topically on surgically-exposed nerves and generally represent no greater hazard than encountering a human treated cosmetically with a Botox injection. The amount of toxin given to an animal is sufficient to alter a nerve or group of nerves, but generally is not a lethal dose for the animal. Consequently, even if the entire dose is excreted into the cage, it is not likely to represent an amount sufficient to intoxicate a human. However, to avoid exposure to any toxin, animal care and research personnel should wear protective outerwear and gloves and practice good hygienic practices such as washing hands after handling affected animals, their bedding, or any animal that dies unexpectedly.

Recommended Precautions: The CDC, under the auspices of the Patriot Act of 2002 (select agents list), dictates that animals given Botulinum toxin(s) be isolated under animal biosafety level 2 conditions. When handling animals given botulinum toxin, or their bedding or cages, always wear gloves, lab coat/gown and surgical-type mask. Soiled cage pan liners from rabbits given botulinum toxin should be bagged and discarded in the waste stream designated for landfill. Cages and cage racks may be washed in the mechanical cagewasher at 180oF.

Persons who believe they have been exposed to botulinum toxin should seek medical attention. There is no protective vaccine, but effective treatment with antitoxin can be given early in the course of exposure.

References:  JAMA. 2001;285:1059-1070
                      MMWR 2001 Oct 19;50(41):893-897.