Industrial anthrax

Serological evidence for human exposure to Bacillus cereus biovar anthracis in the villages around Taï National Park, Côte d'Ivoire

Bacillus cereus biovar anthracis (Bcbva) is an untypical anthrax-causing pathogen responsible for high wildlife mortality in Taï National Park (TNP), Côte d’Ivoire. However, nothing is known about its effect on the rural population living in the region bordering TNP. Contact to bushmeat is a known risk factor for exposure to a variety of zoonotic pathogens, but no human infections with Bcbva were noted so far. Therefore, we performed a retrospective seroprevalence analysis with sera from 1,386 study volunteers. We used assays which detect antibodies against the protective antigen PA, which is synthesized by both Bcbva and classic B. anthracis, and against the recently described antigen pXO2-60, a 35-kDa protein only produced by Bcbva. We found a high seroprevalence (22.37%) of antibodies against PA, and approximately half of those sera (10.46%) were also positive for the Bcbva-specific antigen pXO2-60. All sera negative for PA were also negative for antibodies against pXO2-60, confirming specificity and suitability of the PA/pXO2-60 combined serological assay. The fact that a large fraction of sera was positive for PA but negative for pXO2-60 can most likely be explained by lower immunogenicity of pXO2-60, but exposure to classic B. anthracis cannot be excluded. As only Bcbva has been detected in the TNP area so far, exposure to Bcbva can be suspected from the presence of antibodies against PA alone. In a questionnaire, most study participants reported contact to bushmeat and livestock carcasses. Unfortunately, risk factor analysis indicated that neither animal contacts, sex, age, nor country of origin were significant predictors of Bcbva seroprevalence. Nevertheless, our study added to an assessment of the distribution of Bcbva and its impact on the human population, and our data can serve to raise awareness of anthrax in the affected regions.

Anthrax is a zoonotic disease transmitted from animals to humans and normally caused by B. anthracis mainly in savanna regions. However, untypical bacteria named Bacillus cereus biovar anthracis (Bcbva) were detected in a variety of wild animals in the rain forest region of the Taï National Park (TNP) in Côte d’Ivoire. No anthrax infections in humans living in the region around TNP were reported until now. Therefore, we assessed exposure to the pathogen by analysis of sera from human volunteers for the presence of antibodies against the protective antigen (PA), which is produced by B. anthracis and Bcbva, and against the Bcbva-specific protein pXO2-60. We found antibodies against PA in more than 20% of sera from humans living in the TNP region, and around 10% possessed also antibodies against pXO2-60, confirming exposure to Bcbva. As only Bcbva, but not classic B. anthracis was found in TNP, we assume that the majority of humans had contact with Bcbva and that pXO2-60 is less immunogenic than PA. Although most people reported animal contacts, there was no statistically significant correlation with the presence of antibodies against Bcbva. Nevertheless, our study confirmed that Bcbva represents a danger for humans living in the affected area.

Pathways to zoonotic spillover

Zoonotic spillover, which is the transmission of a pathogen from a vertebrate animal to a human, presents a global public health burden but is a poorly understood phenomenon. Zoonotic spillover requires several factors to align, including the ecological, epidemiological and behavioural determinants of pathogen exposure, and the within-human factors that affect susceptibility to infection. In this Opinion article, we propose a synthetic framework for animal-to-human transmission that integrates the relevant mechanisms. This framework reveals that all zoonotic pathogens must overcome a hierarchical series of barriers to cause spillover infections in humans. Understanding how these barriers are functionally and quantitatively linked, and how they interact in space and time, will substantially improve our ability to predict or prevent spillover events. This work provides a foundation for transdisciplinary investigation of spillover and synthetic theory on zoonotic transmission.

Animal Models for the Pathogenesis, Treatment, and Prevention of Infection by Bacillus anthracis

This article reviews the characteristics of the major animal models utilized for studies on Bacillus anthracis and highlights their contributions to understanding the pathogenesis and host responses to anthrax and its treatment and prevention. Advantages and drawbacks associated with each model, to include the major models (murine, guinea pig, rabbit, nonhuman primate, and rat), and other less frequently utilized models, are discussed. Although the three principal forms of anthrax are addressed, the main focus of this review is on models for inhalational anthrax. The selection of an animal model for study is often not straightforward and is dependent on the specific aims of the research or test. No single animal species provides complete equivalence to humans; however, each species, when used appropriately, can contribute to a more complete understanding of anthrax and its etiologic agent.

B. anthracis in a wool-processing factory: seroprevalence and occupational risk

In a Belgian wool-processing factory, living anthrax spores were found in raw goat hair and air dust, but confirmed anthrax cases had never been reported. Anthrax vaccines are not licensed nor recommended in Belgium. We conducted a B. anthracis seroprevalence study to investigate risk factors associated with positive serology and advise on protective measures. Overall 12·1% (8/66) employees were seropositive; 30% of persons processing raw goat hair and 20% of persons sorting raw goat hair were seropositive compared to 3% in less exposed jobs [adjusted prevalence ratio (aPR) 44·4, P=0·001; aPR 14·5, P=0·016, respectively). The number of masks used per day was protective (aPR 0·3, P=0·015). Results suggest a dose-response association for those processing raw goat hair. Host-related factors probably played a role as antibody response varied from person to person within an exposure group. Workers exposed to raw goat hair should be offered higher protection against anthrax and have access to anthrax vaccines.

Inhalation anthrax: dose response and risk analysis

The notion that inhalation of a single Bacillus anthracis spore is fatal has become entrenched nearly to the point of urban legend, in part because of incomplete articulation of the scientific basis for microbial risk assessment, particularly dose-response assessment. Risk analysis (ie, risk assessment, risk communication, risk management) necessitates transparency: distinguishing scientific facts, hypotheses, judgments, biases in interpretations, and potential misinformation. The difficulty in achieving transparency for biothreat risk is magnified by misinformation and poor characterization of both dose-response relationships and the driving mechanisms that cause susceptibility or resistance to disease progression. Regrettably, this entrenchment unnecessarily restricts preparedness planning to a single response scenario: decontaminate until no spores are detectable in air, water, or on surfaces-essentially forcing a zero-tolerance policy inconsistent with the biology of anthrax. We present evidence about inhalation anthrax dose-response relationships, including reports from multiple studies documenting exposures insufficient to cause inhalation anthrax in laboratory animals and humans. The emphasis of the article is clarification about what is known from objective scientific evidence for doses of anthrax spores associated with survival and mortality. From this knowledge base, we discuss the need for future applications of more formal risk analysis processes to guide development of alternative non-zero criteria or standards based on science to inform preparedness planning and other risk management activities.

US Food and Drug Administration Approval of Ciprofloxacin Hydrochloride for Management of Postexposure Inhalational Anthrax

In August 2000, the US Food and Drug Administration (FDA) approved ciprofloxacin hydrochloride (Cipro; Bayer) for management of postexposure inhalational anthrax. This was the first antimicrobial drug approved by the FDA for use in treating an infection due to a biological agent used intentionally. The terrorist attacks of 2001 involving anthrax underscore the imperative that safe and effective drugs to manage such infections be readily available in the United States. The approval of ciprofloxacin hydrochloride, which was made on the basis of a surrogate human marker of efficacy, made extensive use of data from an animal model of disease. This represents a new direction in the development of efficacy data in support of drug approval and facilitates the availability of those drugs for which there is an urgent need. This article presents the scientific data and regulatory mechanism that supported the approval of ciprofloxacin hydrochloride for management of postexposure of inhalational anthrax.

Epidemiologic response to anthrax outbreaks: field investigations, 1950-2001

We used unpublished reports, published manuscripts, and communication with investigators to identify and summarize 49 anthrax-related epidemiologic field investigations conducted by the Centers for Disease Control and Prevention from 1950 to August 2001. Of 41 investigations in which Bacillus anthracis caused human or animal disease, 24 were in agricultural settings, 11 in textile mills, and 6 in other settings. Among the other investigations, two focused on building decontamination, one was a response to bioterrorism threats, and five involved other causes. Knowledge gained in these investigations helped guide the public health response to the October 2001 intentional release of B. anthracis, especially by addressing the management of anthrax threats, prevention of occupational anthrax, use of antibiotic prophylaxis in exposed persons, use of vaccination, spread of B. anthracis spores in aerosols, clinical diagnostic and laboratory confirmation methods, techniques for environmental sampling of exposed surfaces, and methods for decontaminating buildings.

An epidemic of inhalation anthrax, the first in the twentieth century: I. Clinical features. 1960

Acute respiratory tract infections are the most common illnesses in all individuals, regardless of age or gender. Epidemiologic surveys and community-based studies conducted since the beginning of the 20th century have determined the rates of illness and the pathogens involved in such infections. These studies have shown that rhinoviruses cause the great majority of these respiratory illnesses, and their findings have examined the means of transmission of respiratory illness. More recently, advances in diagnostic techniques have enabled more complete identification of the viruses involved in respiratory infections, which has aided in the ability to direct specific therapeutic agents at the causative pathogens.

Radiological changes in inhalation anthrax. A report of radiological and pathological correlation in two cases

The radiological changes in two cases of inhalation anthrax are correlated with pathological findings. The earliest radiological sign was widening of the mediastinum, followed by prominent lung markings with peribronchial infiltration due to pulmonary oedema and haemorrhage. Associated pleural effusions are common, and non-specific super-imposed pulmonary infiltration may also be present. Inhalation anthrax must be considered in any case of mediastinal widening in a patient coming in contact with imported animal products or with livestock in endemic areas.