Anthrax

During August 2009–October 2010, a multidisciplinary team investigated 14 outbreaks of animal and human anthrax in Bangladesh to identify the etiology, pathway of transmission, and social, behavioral, and cultural factors that led to these outbreaks. The team identified 140 animal cases of anthrax and 273 human cases of cutaneous anthrax. Ninety one percent of persons in whom cutaneous anthrax developed had history of butchering sick animals, handling raw meat, contact with animal skin, or were present at slaughtering sites. Each year, Bacillus anthracis of identical genotypes were isolated from animal and human cases. Inadequate livestock vaccination coverage, lack of awareness of the risk of anthrax transmission from animal to humans, social norms and poverty contributed to these outbreaks. Addressing these challenges and adopting a joint animal and human health approach could contribute to detecting and preventing such outbreaks in the future.

The ecology and distribution of Bacillus anthracis is poorly understood despite continued anthrax outbreaks in wildlife and livestock throughout the United States. Little work is available to define the potential environments that may lead to prolonged spore survival and subsequent outbreaks. This study used the genetic algorithm for rule-set prediction modeling system to model the ecological niche for B. anthracis in the contiguous United States using wildlife and livestock outbreaks and several environmental variables. The modeled niche is defined by a narrow range of normalized difference vegetation index, precipitation, and elevation, with the geographic distribution heavily concentrated in a narrow corridor from southwest Texas northward into the Dakotas and Minnesota. Because disease control programs rely on vaccination and carcass disposal, and vaccination in wildlife remains untenable, understanding the distribution of B. anthracis plays an important role in efforts to prevent/eradicate the disease. Likewise, these results potentially aid in differentiating endemic/natural outbreaks from industrial-contamination related outbreaks or bioterrorist attacks.

A retrospective cohort analysis was conducted in Kazakhstan to define modifiable risk factors during seven outbreaks of human anthrax. Fifty-three cases and 255 non-ill persons with an epidemiologic link to an infected animal were enrolled. Cases were 58% male and had a median age of 35 years (range = 5–71). Nearly all cases had cutaneous disease (96%). Two patients (4%) were diagnosed with gastrointestinal disease. Although all cases had some contact with an infected animal other than consumption, in multivariable analysis the act of butchering an animal (relative risk [RR] = 3.6, 95% confidence interval [CI] = 1.5–9.6) and the presence of visible cuts on the hands were associated with anthrax (RR = 3.0, 95% CI = 0.9–9.6). Contact with infected livestock, in particular butchering, is associated with developing anthrax. The risk may be exacerbated by the presence of cuts on the hands at the time of contact with the animal or animal products.