Botulinum toxins are the most deadly toxins known. Because botulinum toxin is so lethal and easy to manufacture and weaponize, it represents a credible threat as a biological warfare agent. When used in this manner, exposure is likely to occur following inhalation of aerosolized toxin or ingestion of food contaminated with the toxin or its microbial spores. Iraq admitted to active research on the offensive use of botulinum toxins and to weaponizing and deploying more than 100 munitions with botulinum toxin in 1995.

All 7 subtypes (A-G) of botulinum toxin act in similar ways. The toxin produces similar effects whether ingested, inhaled, or via a wound. The time course and severity of illness vary with route of exposure and dose received. Symptom onset is slower after inhalation exposure.

Signs and symptoms

Symptoms may occur hours to several days after exposure. Initial signs and symptoms include blurred vision, dilated pupils, difficulty swallowing, difficulty speaking, an altered voice, and muscle weakness. After 24-48 hours, muscle weakness and paralysis may cause the person to be unable to breathe. Varying degrees of muscular weakness may occur.

Diagnosis

Paralysis may indicate the presence of this exposure. Laboratory tests generally are not helpful. Infection by inhalation can be diagnosed from nasal swabs up to 24 hours after exposure.

Treatment

The most serious complication is respiratory failure. With attention to symptoms and help breathing, sometimes with a ventilator, death occurs in fewer than 5% of cases. For confirmed exposures, an antitoxin is available from the CDC. This antitoxin has all of the disadvantages of horse serum products, including the risks for shock and serum sickness. Skin testing is performed first by injecting a small amount of the antitoxin into the skin and then monitoring the person for 20 minutes.

Prevention

A toxoid (inactivated toxin that produces immunity) has been used in volunteers and occupationally at-risk workers. It is available through the CDC. It was used to immunize US military troops during the Persian Gulf War. The current schedule for immunization is at 0, 2, and 12 weeks with an annual booster.