The Film Archives
Published on Aug 12, 2016
The virulent Ames strain, which was used in the 2001 anthrax attacks in the United States, has received the most news coverage of any anthrax outbreak. The Ames strain contains two virulence plasmids, which separately encode for a three-protein toxin, called anthrax toxin, and a polyglutamic acid capsule. Nonetheless, the Vollum strain, developed but never used as a biological weapon during the Second World War, is much more dangerous. The Vollum (also incorrectly referred to as Vellum) strain was isolated in 1935 from a cow in Oxfordshire. This same strain was used during the Gruinard bioweapons trials. A variation of Vollum known as “Vollum 1B” was used during the 1960s in the US and UK bioweapon programs. Vollum 1B is widely believed to have been isolated from William A. Boyles, a 46-year-old scientist at the U.S. Army Biological Warfare Laboratories at Camp (later Fort) Detrick, Maryland, (precursor to USAMRIID), who died in 1951 after being accidentally infected with the Vollum strain. The Sterne strain, named after the Trieste-born immunologist Max Sterne, is an attenuated strain used as a vaccine, which contains only the anthrax toxin virulence plasmid and not the polyglutamic acid capsule expressing plasmid.
Anthrax spores can survive for very long periods of time in the environment after release. Chemical methods for cleaning anthrax-contaminated sites or materials may use oxidizing agents such as peroxides, ethylene oxide, Sandia Foam, chlorine dioxide (used in the Hart Senate Office Building), peracetic acid, ozone gas, hypochlorous acid, sodium persulfate, and liquid bleach products containing sodium hypochlorite. Nonoxidizing agents shown to be effective for anthrax decontamination include methyl bromide, formaldehyde, and metam sodium. These agents destroy bacterial spores. All of the aforementioned anthrax decontamination technologies have been demonstrated to be effective in laboratory tests conducted by the US EPA or others. A bleach solution for treating hard surfaces has been approved by the EPA.
Chlorine dioxide has emerged as the preferred biocide against anthrax-contaminated sites, having been employed in the treatment of numerous government buildings over the past decade. Its chief drawback is the need for in situ processes to have the reactant on demand.
To speed the process, trace amounts of a nontoxic catalyst composed of iron and tetroamido macrocyclic ligands are combined with sodium carbonate and bicarbonate and converted into a spray. The spray formula is applied to an infested area and is followed by another spray containing tert-butyl hydroperoxide.
Using the catalyst method, a complete destruction of all anthrax spores can be achieved in under 30 minutes. A standard catalyst-free spray destroys fewer than half the spores in the same amount of time.
Cleanups at a Senate office building, several contaminated postal facilities, and other US government and private office buildings showed decontamination to be possible, but it is time-consuming and costly. Clearing the Senate office building of anthrax spores cost $27 million, according to the Government Accountability Office. Cleaning the Brentwood postal facility in Washington cost $130 million and took 26 months. Since then, newer and less costly methods have been developed.
Cleanup of anthrax-contaminated areas on ranches and in the wild is much more problematic. Carcasses may be burned, though it often takes up to three days to burn a large carcass and this is not feasible in areas with little wood. Carcasses may also be buried, though the burying of large animals deeply enough to prevent resurfacing of spores requires much manpower and expensive tools. Carcasses have been soaked in formaldehyde to kill spores, though this has environmental contamination issues. Block burning of vegetation in large areas enclosing an anthrax outbreak has been tried; this, while environmentally destructive, causes healthy animals to move away from an area with carcasses in search of fresh grass. Some wildlife workers have experimented with covering fresh anthrax carcasses with shadecloth and heavy objects. This prevents some scavengers from opening the carcasses, thus allowing the putrefactive bacteria within the carcass to kill the vegetative B. anthracis cells and preventing sporulation. This method also has drawbacks, as scavengers such as hyenas are capable of infiltrating almost any exclosure.
The experimental site at Gruinard Island is said to have been decontaminated with a mixture of formaldehyde and seawater by the Ministry of Defence. It is not clear whether similar treatments had been applied to US test sites.
Global Climate Change