WASHINGTON– Recent isolated cases of anthrax in Minnesota and elsewhere, along with the disease’s relative ease of transmission from animals or plants to humans, should heighten U.S. physicians’ awareness of anthrax’s symptoms and treatments, warned Dr. Jason K. Blackburn.
“[Anthrax] is something that our international partners deal with on an annual basis [as] we can see the disease reemerging, or at least increasing, in annual reports on humans in a number of countries,” explained Dr. Blackburn of the University of Florida in Gainesville, at a meeting on biodefense and emerging diseases sponsored by the American Society for Microbiology. “Here in the United States, we’re seeing it shift from a livestock disease [to] a wildlife disease, where we have these populations that we can’t reach with vaccines, and where surveillance is very logistically challenging.”
(c) Janice Haney Carr/CDC
Under a very high magnification of 31,207X, this scanning electron micrograph depicted spores from the Sterne strain of Bacillus anthracis bacteria.
Environmental factors can drive higher incidences of anthrax cases. Temperature, precipitation, and vegetation indices are key variables that facilitate anthrax transmission and spread of the disease. Geographically, lowland areas also have higher prevalences of the disease.
For example, Dr. Blackburn and his colleagues used predictive models to quantify the theory that anthrax case rates increase during years that have wet springs followed by hot, dry summers in the region of western Texas.
Using these data would allow scientists and health care providers to predict which years would have an increased risk for anthrax cases in humans, Dr. Blackburn said, and could help hospitals and clinics effectively prepare to treat a higher influx of these cases and prevent possible outbreaks.
Although relatively large numbers of human anthrax cases persist in parts of world – particularly in Africa and central Asia – cases in the United States have been primarily relegated to livestock.
However, during the last decade, there has been a noticeable shift in cases from livestock to wildlife, particularly in western Texas and Montana, where local populations of elk, bison, and white-tailed deer have been affected. The newfound prevalence in wildlife species, along with continued presence in domestic animals such as cattle and sheep, mean that transmission to humans could become even easier.
“Human cases are usually driven by direct human interaction with mammalian hosts,” said Dr. Blackburn, citing farms and meat factories as prime examples of where the Bacillus anthracis organism would easily spread. In addition, Dr. Blackburn specifically noted a scenario in which flies can transmit the disease from sheep to humans, and have also been found to carry anthrax from carcasses to wildlife and vegetation.
From 2010 to 2012, anthrax cases in Europe, particularly Georgia and Turkey, increased, compared with numbers over a similar time frame between 2000 and 2009. While case reporting can be partly attributed to this increase, Dr. Blackburn indicated that it was most likely evidence of an associative trend between livestock and human anthrax cases.
Dr. Blackburn did not report any disclosures.