Biological Health Hazard – New Pathogen | Anthrax-like infection (Bacillus cereus): Africa
BACILLUS CEREUS, ANTHRAX-LIKE INFECTION – AFRICA: WILDLIFE, LIVESTOCK
Published Date: 2016-09-08 23:16:00
Subject: PRO/AH/EDR> Bacillus cereus, anthrax-like infection – Africa: wildlife, livestock
Archive Number: 20160908.4475451
Date: Thu 8 Sep 2016
Source: IFL Science [edited]
New Pathogen Discovered in Africa Causes Anthrax-Like Disease
Caused by a bacterium, anthrax is a life-threatening deadly disease. While rare, people can contract the disease if they come into contact with infected animals, people or contaminated animal products. But anthrax is only one species in a group of bacteria, and now researchers have identified a brand new pathogen causing an anthrax-like disease in Central Africa that infects both domestic and wild animals, including our closest evolutionary relatives.
The bacterium responsible for anthrax is known as _Bacillus anthracis_, and is closely related to another less threatening and more widespread species known as _Bacillus cereus_. Commonly found in the ground and soil around the world, most of the time _B. cereus_ is harmless, but it now seems that one particular strain in Africa has developed a more sinister ability.
After sampling goats in a remote Congolese village, researchers from the Robert Koch Institute in Berlin isolated a bacterium found in an animal that was dying. Not long after, they also sampled the remains of a chimpanzee, gorilla, and forest elephant found dead in the forests of Cameroon, Central African Republic, and Côte d’Ivoire.
From these, they identified a novel strain of the _B. cereus_ bacteria, but one that has seemingly evolved a similar lifestyle to _B. anthracis_ independently. The researchers have called the new strain “_B. cereus_ biovar anthracis”, as it seemingly displays a mixture of features from both bacteria. They reported the findings in the journal PLOS Neglected Tropical Diseases.
The main factor that makes _B. anthracis_ so virulent and deadly when contracted is the genes encoded on 2 small plasmids within the bacteria, known as pXO1 and pXO2. The researchers found that the new _B. cereus_ biovar anthracis strain also has these 2 plasmids, presumably also conferring the virulence displayed, but that it has seemingly acquired them on its own. Yet while there are many subgroups within _B. anthracis_ indicating multiple ancestors, there is only one within _B. cereus_ biovar anthracis, suggesting a singular ancestry.
The researchers suspect that the newly identified pathogen may be more widespread, potentially throughout the African continent, though it is potentially restricted to the more humid and warm regions of the tropics. This, postulate the authors, could be down to the strain’s ability to produce spores under very specific climatic conditions, although obviously at the time of writing this is mainly speculation as more research needs to be undertaken as to the exact biology of the pathogen.
They warn, however, that due to the presence of the disease in both chimpanzees and gorillas, as well as in livestock, coupled with its apparent deadly nature, that more surveillance should be carried out in the region in order to assess its impact not only on threatened wildlife species, but also the local people living in the region.
[Byline: Josh Davis]
Date: Thu 8 Sep 2016
Source: PLOS Neglected Tropical Diseases [edited]
Antonation KS, Grützmacher K, Dupke S, Mabon P, Zimmermann F, Lankester F, et al. (2016). _Bacillus cereus_ Biovar Anthracis Causing Anthrax in Sub-Saharan Africa — Chromosomal Monophyly and Broad Geographic Distribution. PLoS Negl Trop Dis 10(9): e0004923. doi:10.1371/journal.pntd.0004923
Through full genome analyses of 4 atypical _Bacillus cereus_ isolates, designated _B. cereus_ biovar anthracis, we describe a distinct clade within the _B. cereus_ group that presents with anthrax-like disease, carrying virulence plasmids similar to those of classic _Bacillus anthracis_. We have isolated members of this clade from different mammals (wild chimpanzees, gorillas, an elephant and goats) in West and Central Africa (Côte d’Ivoire, Cameroon, Central African Republic and Democratic Republic of Congo). The isolates shared several phenotypic features of both _B. anthracis_ and _B. cereus_, but differed amongst each other in motility and their resistance or sensitivity to penicillin. They all possessed the same mutation in the regulator gene plcR, different from the one found in _B. anthracis_, and in addition, carry genes which enable them to produce a 2nd capsule composed of hyaluronic acid. Our findings show the existence of a discrete clade of the _B. cereus_ group capable of causing anthrax-like disease, found in areas of high biodiversity, which are possibly also the origin of the worldwide distributed _B. anthracis_. Establishing the impact of these pathogenic bacteria on threatened wildlife species will require systematic investigation. Furthermore, the consumption of wildlife found dead by the local population and presence in a domestic animal reveal potential sources of exposure to humans.
Anthrax has historically been attributed to a single cluster within the _Bacillus cereus_ complex denoted as _B. anthracis_. Here, we demonstrate the existence of a distinct clade of _B. cereus_ isolates causing anthrax-like disease in a range of wild and domestic mammals in tropical Africa. These strains, designated _B. cereus_ biovar anthracis, combine bacteriological and molecular features of _B. cereus_ and _B. anthracis_. Many questions about the epidemiology, biology and impact of this cluster of anthrax causing _B. cereus_ still remain open. On the technical side it will be important to adapt diagnostic methods for the detection of such atypical _B. cereus_ strains-through the inclusion of molecular tools for the detection of the _B. anthracis_ virulence plasmids that appear to be the prerequisite to cause disease. Through reliable detection of a broad range of _B. cereus_ group isolates causing anthrax-like disease it will be possible to assess the distribution and diversity of these pathogens and their impact on public health and wildlife populations.
[This paper raises an important question: How often in the past have simplistic sorting of _Bacillus_ colonies from a dead animal led to a pathogenic _B. cereus_ being dismissed because it wasn’t “_B. anthracis_”? To get around this traditional act, if it clinically looks like “anthrax” do a quick plasmid DNA check. We have carried reports of anthrax-like _B. cereus_ being found in the US and Italy; see list of posts below. We must now add the Congo, and its African neighbouring states, and look forward more such reports. Never a dull moment! – Mod.MHJ
A HealthMap/ProMED-mail map can be accessed at: http://healthmap.org/promed/p/6075.]
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