Sunday, 27 November 2016

New pathogen causes anthrax like disease

A new report has detected a species of Bacillus, genetically distinct to the bacterium that causes anthrax, which causes a similar disease in chimpanzees, gorillas and other animals in Africa.
The newly described bacterium is of significance in terms of environment, ecology and animal health. There is also the possibility that the organism could cause harm to people. The scientists behind the discovery are calling for increased surveillance.
Anthrax is a disease caused by the bacterium Bacillus anthracis, specifically by the spores of the organism. The areas most commonly affected are Africa and southern Asia. The disease is can occur via one of four ways: skin, inhalation, intestinal and injection. The effect of the disease can appear as quickly as one day or up to two months following infection. Many scientists regard anthrax as among the world's major neglected zoonotic diseases.
The main symptoms are blisters forming on the skin that ulcerate and form black centers. This is accompanied by fever, chest pain, and shortness of breath, together with nausea, vomiting and abdominal pain. The disease is confirmed through antibody testing. Treatment is by antibiotics and sometimes antitoxin.
Detection of the bacterium is difficult because of its similarity with two other species of Bacillus: Bacillus thuringiensis and Bacillus cereus (they each are members of the B. cereus group). These are also spore-formers (a means for some bacteria to remain dormant under extreme or unfavorable environmental conditions), found in soil.
The ability of Bacillus species to cause disease relates to virulence factors. Some of these factors are encoded on fragments of genetic material that are exchanged between bacteria called plasmids. With the anthrax causing bacterium - B. anthracis – this organism has two plasmids that are responsible for virulence. These are called pXO1 and pXO2.
The newly characterized organism in Africa that causes ‘anthrax-like’ symptoms is a type of B. cereus. This has been examined at the Robert Koch Institute in Berlin. The organism was isolated from a diseased chimpanzee in Ivory Coast. Typically most B. cereus isolates are non pathogenic. However, some strains can cause food poisoning, due to production of toxins.
Interestingly, the B. cereus bacterium was found to contain the pXO1 and pXO2 'anthrax' plasmids. However it was genetically close to other types of B. cereus and not to B. anthracis. The researchers, led by Dr. Fabian Leendertz,, think the bacterium ‘acquired’ its particular disease causing properties. Moreover, due to its genetic difference the scientists have described the organism as a new species: 'B. cereus biovar (bv) anthracis'.
Further research has tracked down four other isolates of the bacterium, taken from a goat, gorillas, a chimpanzee and an elephant in Cameroon, the Central African Republic, and the Democratic Republic of Congo respectively. Each animal was diseased and died from the disease.
These additional isolates also shared the virulence plasmids pXO1 and pXO2. The evidence points to these organisms sharing a common ancestor, and one different to B. anthracis. The organisms each possessed a mutation in a specific gene; however, the four bacteria possessed different physiological properties.
The implications are potentially significant and could cause significant harm for wildlife. The researchers are calling for increased surveillance and testing. A risk to humans cannot be ruled out. With this, the U.S. Centers for Disease Control and Prevention (CDC) is proposing the addition of Bacillus cereus Biovar anthracis to the list of select agents and toxins as a Tier 1 select agent. This means it would be regarded as a potential bio-terrorism threat. According to Outbreak News Today, the CDC has said: "We are taking this action to regulate this agent that is similar to B. anthracis to prevent its misuse, which could cause a biological threat to public health and/or national security."
The new organism is described in the journal PLOS Neglected Tropical Diseases. The research paper is headed “Bacillus cereus Biovar Anthracis Causing Anthrax in Sub-Saharan Africa—Chromosomal Monophyly and Broad Geographic Distribution.”

Posted by Dr. Tim Sandle

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