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Recurrent wound botulism among users of injected heroin in California has become a growing concern, with 17 cases documented over a 14-year period.

According to Duc Vugia, MD, and colleagues at the California Department of Public Health, the burgeoning epidemic of wound botulism among injection drug users -- most of whom used so-called black tar heroin -- is concerning because it suggests that exposure does not confer protective immunity to the bacterial culprits.

Therefore, both clinicians and injection drug users "should be aware of the potential for wound botulism to recur with continued injection drug use to allow for timely diagnosis and early administration of botulinum antitoxin and appropriate supportive care," Vugia and co-authors wrote online in Clinical Infectious Diseases.

Botulism, an acute neurologic illness characterized by cranial nerve palsies and descending flaccid paralysis, is caused by botulinum neurotoxin produced by various Clostridia species.

Wound botulism occurs when a wound is contaminated with C. botulinum and the neurotoxin is produced in the injury. Early reports of the condition involved gross trauma, but almost all recent cases, including the California cases, involve subcutaneous injection of heroin -- so-called "skin-popping."

Early administration of the botulinum antitoxin shortens hospital stays and reduces the risk of respiratory failure, researchers at the University of California Davis Medical Center in Sacramento reported last year.

The California Department of Public Health reported the first documented case of recurrent wound botulism in 1997, Vugia and colleagues noted, and another 16 cases have been reported since, including three people with two recurrent episodes.

California makes up approximately three-quarters of the reported wound botulism cases in the U.S., they pointed out.

All of the California patients were 32 to 61 years old, 94% were male, and all reported using heroin; with 88% injecting black tar heroin, a crudely refined form of the drug that is often contaminated with Clostridia species.

In general, the clinical presentation did not differ significantly between episodes, the researchers found, with the most common signs being a visible wound, speech difficulty, double vision, respiratory difficulty, and trouble swallowing.

On the other hand, patients tended to seek care earlier during the recurrent episode, Vugia and colleagues reported -- a median of three days with a range from one to 20 in the first case and a median of two days, with a range of one to 10 in the second.

In all but one episode, patients got antitoxin within a day of seeking care. Patients were treated with antibiotics and the infected wounds were debrided.

Among the 17 wound botulism patients, 10 required mechanical ventilation during the first episode, and four needed ventilatory support for every episode, Vugia and co-authors reported.

The investigators provided details for two of the recurrent cases -- a woman first treated in 1995 with three episodes within 20 months and a man who had two episodes over a four-year period.

The 17 documented cases in the report probably represent "only a portion of all recurrent cases," Vugia and colleagues stressed, noting that not all injection drug users seek care, ER doctors may not recognize wound botulism, and that laboratory tests may not be sensitive enough to catch the pathogen.

Doctors should be aware of the limited sensitivity of lab tests and "base their diagnosis on clinical assessment when the test is negative," the team argued.

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