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Recurrent Anthrax Outbreaks in Humans, Livestock, and Wildlife in the Same Locality, Kenya, 2014–2017
Abstract.Epidemiologic data indicate a global distribution of anthrax outbreaks associated with certain ecosystems that promote survival and viability of Bacillus anthracis spores. Here, we characterized three anthrax outbreaks involving humans, livestock, and wildlife that occurred in the same locality in Kenya between 2014 and 2017. Clinical and epidemiologic data on the outbreaks were collected using active case finding and review of human, livestock, and wildlife health records. Information on temporal and spatial distribution of prior outbreaks in the area was collected using participatory epidemiology. The 2014–2017 outbreaks in Nakuru West subcounty affected 15 of 71 people who had contact with infected cattle (attack rate = 21.1%), including seven with gastrointestinal, six with cutaneous, and two with oropharyngeal forms of the disease. Two (13.3%) gastrointestinal human anthrax cases died. No human cases were associated with infected wildlife. Of the 54 cattle owned in 11 households affected, 20 died (attack rate = 37%). The 2015 outbreak resulted in death of 10.5% of the affected herbivorous wildlife at Lake Nakuru National Park, including 745 of 4,500 African buffaloes (species-specific mortality rate = 17%) and three of 18 endangered white rhinos (species-specific mortality rate = 16%). The species mortality rate ranged from 1% to 5% for the other affected wildlife species. Participatory epidemiology identified prior outbreaks between 1973 and 2011 in the same area. The frequency and severity of outbreaks in this area suggests that it is an anthrax hotspot ideal for investigating risk factors associated with long-term survival of anthrax spores and outbreak occurrence.
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Modeling the Ecological Niche of Bacillus anthracis to Map Anthrax Risk in Kyrgyzstan
AbstractAnthrax, caused by the environmental bacterium Bacillus anthracis, is an important zoonosis nearly worldwide. In Central Asia, anthrax represents a major veterinary and public health concern. In the Republic of Kyrgyzstan, ongoing anthrax outbreaks have been reported in humans associated with handling infected livestock and contaminated animal by-products such as meat or hides. The current anthrax situation has prompted calls for improved insights into the epidemiology, ecology, and spatial distribution of the disease in Kyrgyzstan to better inform control and surveillance. Disease control for both humans and livestock relies on annual livestock vaccination ahead of outbreaks. Toward this, we used a historic database of livestock anthrax reported from 1932 to 2006 mapped at high resolution to develop an ecological niche model–based prediction of B. anthracis across Kyrgyzstan and identified spatial clusters of livestock anthrax using a cluster morphology statistic. We also defined the seasonality of outbreaks in livestock. Cattle were the most frequently reported across the time period, with the greatest number of cases in late summer months. Our niche models defined four areas as suitable to support pathogen persistence, the plateaus near Talas and Bishkek, the valleys of western Kyrgyzstan along the Fergana Valley, and the low-lying areas along the shore of Lake Isyk-Kul. These areas should be considered “at risk” for livestock anthrax and subsequent human cases. Areas defined by the niche models can be used to prioritize anthrax surveillance and inform efforts to target livestock vaccination campaigns.
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Human Anthrax Transmission at the Urban–Rural Interface, Georgia
More LessAbstractHuman anthrax has increased dramatically in Georgia and was recently linked to the sale of meat in an urban market. We assessed epidemiological trends and risk factors for human anthrax at the urban–rural interface. We reviewed epidemiologic records (2000–2012) that included the place of residence (classified as urban, peri-urban, or rural), age, gender, and self-reported source of infection (handling or processing animal by-products and slaughtering or butchering livestock). To estimate risk, we used a negative binomial regression. The average incidence per 1 million population in peri-urban areas (24.5 cases) was > 2-fold higher compared with rural areas and > 3-fold higher compared with urban area. Risk from handling or purchasing meat was nearly 2-fold higher in urban areas and > 4-fold higher in peri-urban areas compared with rural area. Our findings suggest a high risk of anthrax in urban and peri-urban areas likely as a result of spillover from contaminated meat and animal by-products. Consumers should be warned to purchase meat only from licensed merchants.
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Anthrax Outbreaks in Bangladesh, 2009–2010
Abstract.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.
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Modeling the Geographic Distribution of Bacillus anthracis, the Causative Agent of Anthrax Disease, for the Contiguous United States using Predictive Ecologic Niche Modeling
More LessThe 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.
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Cutaneous Anthrax in the Artibonite Valley of Haiti: 1992–2002
More LessMore cutaneous anthrax cases were noted at Hospital Albert Schweitzer (HAS) in the Artibonite Valley of Haiti. We examine the incidence of anthrax in the Artibonite between 1992 and 2002, describe the clinical presentation of cutaneous anthrax, and determine risk factors for anthrax. In 1992 HAS reported 1 case of anthrax for an incidence of 4 cases per million persons/year. In 2002, there were 20 cases of anthrax for an incidence of 72 cases per million persons/year. This is a 17-fold increase (P = 0.0002). Causes of death from anthrax included asphyxiation from edema of the neck with tracheal compression and concurrent gastrointestinal anthrax. Butchering cattle that had died of illness was identified as a risk factor. The incidence of human anthrax has increased in the Artibonite Valley and is a cause of significant mortality. Control of anthrax in humans depends on improved animal vaccination programs.
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RISK FACTORS FOR HUMAN ANTHRAX AMONG CONTACTS OF ANTHRAX-INFECTED LIVESTOCK IN KAZAKHSTAN
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.
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