FIP 2009: Anthrax bioterrorism: prevention and treatment
In the event of anthrax spores being used in bioterrorism, the principal management strategies include immunisation of key personnel (eg, emergency workers, healthcare workers, military personnel) where there is risk of anthrax exposure, said Tom Waytes, Emergent BioSolutions, Michigan, during the 69th World Congress of Pharmacy and Pharmaceutical Sciences.
Antibiotics should be given to those developing symptoms of anthrax infection. If exposure to anthrax occurs, but before symptoms develop, a course of antibiotics immunisation should be given.
The rationale for this strategy is based on an understanding of anthrax infection. Anthrax spores must enter the body through a cut, abrasion or open wound (cutaneous anthrax), ingestion or inhalation. Inhalational anthrax, which was the focus of Dr Waytes’s presentation, has a mortality rate of 90 per cent, the highest of all three types of infection. Once inside the body, the spores germinate into bacteria, then multiply and release toxins.
He explained that early symptoms of inhalational anthrax often resemble those of common upper respiratory disease, but the later release of toxins leads to fever, haemorrhage, respiratory disease and shock, after which death may follow within hours or days.
Antibiotics are not effective against either spores or toxins. However, spores can exist in the lungs for 100 days before germination.
Dr Waytes reminded participants of the events in the US in 2001, when letters containing spores were posted. These attacks resulted in 22 cases of anthrax, of which 11 were inhalational and 11 were cutaneous. Five people died. Based on the anticipated exposure to spores, a 60-day course of antibiotics (ciprofloxacin, doxycycline or amoxicillin) was recommended for 10,300 people.
“Surprisingly, overall adherence was only about 44 per cent, which turned out to be because people thought the antibiotic side effects were worse than the risk of anthrax infection,” he said.
Nevertheless, given the potential viability of spores for more than 100 days and the known ineffectiveness of antibiotics against dormant spores, people who took the initial treatment were offered an additional 40-day course of antibiotic with an option to receive three injections of anthrax vaccine. “No one on antibiotics, with or without the vaccine, developed anthrax,” he said.
The anthrax vaccine approved by the US Food and Drug Administration is BioThrax injection (anthrax vaccine adsorbed), which should be given intramuscularly at 0, one, six, 12 and 18 months, with annual boosters.
More than 8.9 million doses have been administered to 2.2 million people, mostly those in high risk areas, such as Afghanistan, and safety has been confirmed in more than 25 scientific studies. A US Centres for Disease Control and Prevention study due to be published may allow for reduced doses, he added.
According to Dr Waytes the 2001 attacks could have been far worse if some of the letters had not been marked with warnings, and antibiotic-resistant spores and better dissemination methods had been used. “Exposure could be larger and more widespread in the future. We must be prepared for future attacks,” he warned.
Preparation means ensuring adequate numbers of immunised military personnel, police and healthcare workers, as well as developing immunisation plans, and providing well trained and equipped medical teams able to diagnose and provide post-exposure prophylaxis and treatment.
Adequate stockpiles of antibiotics and vaccines with clear cut distribution strategies should also be in place, he concluded.
Citation: The Salvadore URI: 10980661
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