Anthrax Control Research Articles

Effects of Experimental Exclusion of Scavengers from Carcasses of Anthrax-Infected Herbivores on Bacillus anthracis Sporulation, Survival, and Distribution

Scavenging of anthrax carcasses has long been hypothesized to play a critical role in the production of the infectious spore stage of Bacillus anthracis after host death, though empirical studies assessing this are lacking. We compared B. anthracis spore production, distribution, and survival at naturally occurring anthrax herbivore carcasses that were either experimentally caged to exclude vertebrate scavengers or left unmanipulated. We found no significant effect of scavengers on soil spore density (P > 0.05). Soil stained with terminally hemorrhaged blood and with nonhemorrhagic fluids exhibited high levels of B. anthracis spore contamination (ranging from 10(3) to 10(8) spores/g), even in the absence of vertebrate scavengers. At most of the carcass sites, we also found that spore density in samples taken from hemorrhagic-fluid-stained soil continued to increase for >4 days after host death. We conclude that scavenging by vertebrates is not a critical factor in the life cycle of B. anthracis and that anthrax control measures relying on deterrence or exclusion of vertebrate scavengers to prevent sporulation are unlikely to be effective.

Mechanisms of NK Cell-Macrophage Bacillus anthracis Crosstalk: A Balance between Stimulation by Spores and Differential Disruption by Toxins

NK cells are important immune effectors for preventing microbial invasion and dissemination, through natural cytotoxicity and cytokine secretion. Bacillus anthracis spores can efficiently drive IFN-γ production by NK cells. The present study provides insights into the mechanisms of cytokine and cellular signaling that underlie the process of NK-cell activation by B. anthracis and the bacterial strategies to subvert and evade this response. Infection with non-toxigenic encapsulated B. anthracis induced recruitment of NK cells and macrophages into the mouse draining lymph node. Production of edema (ET) or lethal (LT) toxin during infection impaired this cellular recruitment. NK cell depletion led to accelerated systemic bacterial dissemination. IFN-γ production by NK cells in response to B. anthracis spores was: i) contact-dependent through RAE-1-NKG2D interaction with macrophages; ii) IL-12, IL-18, and IL-15-dependent, where IL-12 played a key role and regulated both NK cell and macrophage activation; and iii) required IL-18 for only an initial short time window. B. anthracis toxins subverted both NK cell essential functions. ET and LT disrupted IFN-γ production through different mechanisms. LT acted both on macrophages and NK cells, whereas ET mainly affected macrophages and did not alter NK cell capacity of IFN-γ secretion. In contrast, ET and LT inhibited the natural cytotoxicity function of NK cells, both in vitro and in vivo. The subverting action of ET thus led to dissociation in NK cell function and blocked natural cytotoxicity without affecting IFN-γ secretion. The high efficiency of this process stresses the impact that this toxin may exert in anthrax pathogenesis, and highlights a potential usefulness for controlling excessive cytotoxic responses in immunopathological diseases. Our findings therefore exemplify the delicate balance between bacterial stimulation and evasion strategies. This highlights the potential implication of the crosstalk between host innate defences and B. anthracis in initial anthrax control mechanisms.

Ecological Niche Modelling of the Bacillus anthracis A1.a sub-lineage in Kazakhstan

BackgroundBacillus anthracis, the causative agent of anthrax, is a globally distributed zoonotic pathogen that continues to be a veterinary and human health problem in Central Asia. We used a database of anthrax outbreak locations in Kazakhstan and a subset of genotyped isolates to model the geographic distribution and ecological associations of B. anthracis in Kazakhstan. The aims of the study were to test the influence of soil variables on a previous ecological niche based prediction of B. anthracis in Kazakhstan and to determine if a single sub-lineage of B. anthracis occupies a unique ecological niche.ResultsThe addition of soil variables to the previously developed ecological niche model did not appreciably alter the limits of the predicted geographic or ecological distribution of B. anthracis in Kazakhstan. The A1.a experiment predicted the sub-lineage to be present over a larger geographic area than did the outbreak based experiment containing multiple lineages. Within the geographic area predicted to be suitable for B. anthracis by all ten best subset models, the A1.a sub-lineage was associated with a wider range of ecological tolerances than the outbreak-soil experiment. Analysis of rule types showed that logit rules predominate in the outbreak-soil experiment and range rules in the A1.a sub-lineage experiment. Random sub-setting of locality points suggests that models of B. anthracis distribution may be sensitive to sample size.ConclusionsOur analysis supports careful consideration of the taxonomic resolution of data used to create ecological niche models. Further investigations into the environmental affinities of individual lineages and sub-lineages of B. anthracis will be useful in understanding the ecology of the disease at large and small scales. With model based predictions serving as approximations of disease risk, these efforts will improve the efficacy of public health interventions for anthrax prevention and control.

Componentes del paisaje que favorecen la aparición de carbunco en la Pampa Deprimida (provincia de Buenos Aires, Argentina)

The authors studied the landscape components that favour the occurrence of anthrax in the Flooding Pampa grasslands (Buenos Aires province, Argentina). They made spatial locations of anthrax outbreaks diagnosed by registered veterinary laboratories in the study area's zone of influence. As variables for study, they differentiated areas that are flooded for 20% of the time or more from primary and secondary runoff channels. They also identified areas with low-productivity pasture. Logistic regression analysis of farm populations revealed that landscape components favouring the occurrence of anthrax outbreaks are shared runoff channels (odds ratio (OR) = 2.3; confidence interval (CI) = 1.2; 4.7) and > or = 40% low-productivity pasture (OR = 5.4; CI = 3.5; 8.3). Contrary to initial assumptions, susceptibility to flooding was not a significant variable (OR = 1.1; CI = 0.5; 2.1). The authors concluded that the first step in decision-making and ensuring more efficient implementation of future anthrax control and eradication plans was to identify risk variables.

Anthrax in Togo: Spatial Risk in the Savannah Region

During the dry season in northern Togo, herds are led in search of water sources and natural pasture. These areas are often unfamiliar to the herdsmen and can also pose health risks to the herd. Additionally, migrating animals can spread diseases to other herds. The Savannah Region, in northern of Togo, has experienced recurrent anthrax outbreaks between 2007-2009. In this context, a study was undertaken from June-October 2009 regarding the spatial risk of anthrax in the Savannah Region of northern Togo. The principal objective was to identify the location of anthrax outbreaks in relation to the corridors along which animal movements occur, providing guidance about which areas should be avoided for grazing. The methodological approach was based on interviews of 147 people across 5 categories: 25 veterinarians from the public and private sectors, 84 livestock owners and herdsmen, 24 abattoirs, 3 transhumant herdsman originated from other countries, and 11 representatives of the human health sector. Data collection involved interviews using a pre-designed questionnaire. The results showed that: of the 35 animal outbreak sites of 1997-2008 identified during the interviews, 80% were first detected in the hot, humid period from March-June. Furthermore, 91% of the 35 outbreaks sites of 1997-2008 were situated along the actual transhumant corridors used by herdsmen, which differ from the officially designated corridors and are generally poorly marked out. Consequently, it is possible that livestock movements are a factor in the spread of anthrax and that there is a real and important risk posed by grazing contaminated pasture. The identified outbreak sites should be forbidden for grazing within the context of the regional anthrax control program.

Evaluation of the House Fly Musca domestica as a Mechanical Vector for an Anthrax

Anthrax is a disease of human beings and animals caused by the encapsulated, spore-forming, Bacillus anthracis. The potential role of insects in the spread of B. anthracis to humans and domestic animals during an anthrax outbreak has been confirmed by many studies. Among insect vectors, the house fly Musca domestica is considered a potential agent for disease transmission. In this study, laboratory-bred specimens of Musca domestica were infected by feeding on anthrax-infected rabbit carcass or anthrax contaminated blood, and the presence of anthrax spores in their spots (faeces and vomitus) was microbiologically monitored. It was also evaluated if the anthrax spores were able to germinate and replicate in the gut content of insects. These results confirmed the role of insects in spreading anthrax infection. This role, although not major, given the huge size of fly populations often associated with anthrax epidemics in domestic animals, cannot be neglected from an epidemiological point of view and suggest that fly control should be considered as part of anthrax control programs.

An alternative approach to combination vaccines: intradermal administration of isolated components for control of anthrax, botulism, plague and staphylococcal toxic shock

BackgroundCombination vaccines reduce the total number of injections required for each component administered separately and generally provide the same level of disease protection. Yet, physical, chemical, and biological interactions between vaccine components are often detrimental to vaccine safety or efficacy.MethodsAs a possible alternative to combination vaccines, we used specially designed microneedles to inject rhesus macaques with four separate recombinant protein vaccines for anthrax, botulism, plague and staphylococcal toxic shock next to each other just below the surface of the skin, thus avoiding potentially incompatible vaccine mixtures.ResultsThe intradermally-administered vaccines retained potent antibody responses and were well- tolerated by rhesus macaques. Based on tracking of the adjuvant, the vaccines were transported from the dermis to draining lymph nodes by antigen-presenting cells. Vaccinated primates were completely protected from an otherwise lethal aerosol challenge by Bacillus anthracis spores, botulinum neurotoxin A, or staphylococcal enterotoxin B.ConclusionOur results demonstrated that the physical separation of vaccines both in the syringe and at the site of administration did not adversely affect the biological activity of each component.The vaccination method we describe may be scalable to include a greater number of antigens, while avoiding the physical and chemical incompatibilities encountered by combining multiple vaccines together in one product.

Private and Public Economic Incentives for the Control of Animal Diseases: The Case of Anthrax in Livestock

This study examined the roles of the public and private sectors as economic components of anthrax control with direct reference to the 2005 anthrax outbreak in livestock in North Dakota. Anthrax is an endemic disease in North Dakota, which often causes disease outbreaks in livestock, leading to economic losses to the livestock industry. The economic incentives and interests behind public and private control of an anthrax outbreak are investigated. Anthrax management is most effective with the participation of public and private firms. As anthrax is an infectious disease, its control also brings positive economic externalities, which are not accounted for in a producer's decision to protect animals. Therefore, public programs designed to control the disease must be implemented. The government can change producer response to anthrax by setting up policies and incentives that encourage their participation. However, these interventions must encourage compliance and not discourage producers from actively taking part in anthrax management. Producers have economy-based interests and personal reasons for controlling anthrax in their farms. The main reason behind government intervention is to provide assurance to the public who consume livestock products. Another reason is to assist producers and veterinarians, and to achieve biosecurity and biosafety objectives. The contribution of each animal healthcare partner in making anthrax management a success in North Dakota is discussed.

A Review of Management Practices for the Control of Anthrax in Animals: The 2005 Anthrax Epizootic in North Dakota – Case Study

Outbreaks of anthrax have diverse consequences on society. Establishing the appropriate control strategies is very important and crucial in reducing the socio-economic impact of the disease. Control measures are aimed at breaking the cycle of infection, and their implementation must be adhered to rigorously. The objectives of this paper were: (i) to review the control strategies currently used in management of anthrax in animals and (ii) to describe management strategies used by producers in North Dakota during the 2005 anthrax outbreak in livestock. Anthrax control strategies were divided in to strategies that apply before, during, and after an anthrax outbreak. This paper also highlights the problems or constraints faced by North Dakota producers in controlling anthrax during the outbreak of 2005.

Carbunco bacteridiano en animales y seres humanos en Mongolia

Anthrax is endemic throughout Mongolia, except in the semi-desert and desert areas of the south. The prevalence of anthrax in Mongolia had drastically decreased since the 1950s due to the use of anthrax antiserum and vaccines, but the privatisation of the animal husbandry sector and changes in the structures of the veterinary and medical delivery systems in Mongolia over the last decade have resulted in challenges for disease control. Animal and human anthrax has become an increasing problem since the mid-1990s. Human cutaneous anthrax is common in Mongolia as a result of exposure to infected animals. In this paper, the authors identify potential causes forthe increase of anthrax in Mongolia. The current prevention efforts may not be adequate. Anthrax surveillance and control must be intensified, particularly in areas of high prevalence.

Cutaneous Anthrax in the Artibonite Valley of Haiti: 1992–2002

More 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.

Opinión del sector ganadero sobre el rol de las vacunas en el control y eradicación de las enfermedades del ganadero en Argentina

Research by a number of international organisations indicates that world demand for red meat protein is set to increase significantly in the coming years. However, faced with the risk of infectious animal diseases and zoonoses--factors that could limit the growth of this production sector--the fight against livestock diseases must continue, especially against those that affect food safety or pose a threat to human life. The use of vaccination to prevent infectious animal diseases is of key importance, not only because it helps to control and effectively eradicate infectious livestock diseases, but also because it makes it possible to introduce new technologies for intensive or semi-intensive production, to protect the environment, to care for animal welfare and to guarantee the safety of animal-derived foodstuffs. As part of their professional culture, livestock producers have come to fully appreciate the advantages of using vaccination to prevent disease rather than curative measures, which are more costly to implement and in some cases not very effective. The control of anthrax and rabies by means of effective vaccines was a factor in the widespread development of livestock in Argentina and other parts of Latin America. Recent results in the control and eradication of foot and mouth disease have made producers even more convinced of the merits of this technology. Animal disease prevention has proven to be highly conducive to the production of healthy foodstuffs. It is the responsibility of international organisations to draw up appropriate regulations to protect trade, supply safe and healthy products and prevent the application of unjustified non-tariff measures.

Anthrax in Wabessa village in the Dessie Zuria district of Ethiopia

In 2002 an investigation of sudden death in a goat in Wabessa village in the Dessie Zuria district of Ethiopia was undertaken using fresh blood brought to the Kombolcha Regional Veterinary Laboratory. The sample was examined using standard bacteriological techniques and animal pathogenicity tests were also performed. The laboratory investigation revealed Bacillus anthracis as the cause of sudden death. Information gathered from stockowners in the same village revealed other similar recent cases and deaths, both in animals and humans, with farmers clearly describing the clinical signs and necropsy findings of anthrax. The disease occurs annually in this area in May and June, and in the 2002 outbreak mortality rates of 7.7%, 32.7% and 47.1% were observed in cattle, goats and donkeys, respectively. This study indicates that the community of this particular village neither knows of, nor practises, any of the conventional methods for anthrax control. The cutaneous form of the disease in humans and the environmental contamination associated with the practise of opening cadavers are briefly described and the findings are discussed with reference to the epidemiology of anthrax in both Ethiopia and elsewhere. Control strategies are also recommended.

The story of anthrax from antiquity to the present: a biological weapon of nature and humans

Anthrax is a disease of extraordinary interest. A condition affecting animals and humans identifiable clinically as anthrax occurred in both biblical times and during the classical period. The discovery of the etiologic agent parallels the history of modern bacteriology, whereas the control of anthrax previews the modern interest in occupational pulmonary medicine. The current wave of terrorism has brought renewed interest in this zoonosis, and anthrax has three presentations in humans.

Control of zoonoses in Cyprus.

The excellent results achieved in the control of animal diseases in Cyprus have allowed the Veterinary Services to take a leading role in the elimination, surveillance and investigation of important zoonoses. The programmes for the control of echinococcosis, brucellosis, bovine tuberculosis, anthrax and taeniasis, and the measures taken to prevent the importation of rabies are described. Public awareness of the risks posed by the presence of zoonoses and the efficient and effective intersectoral co-operation achieved between the veterinary, medical, public health and other Government services and non-governmental organisations are considered to be the key to the successful control of zoonoses in Cyprus.

World Health Organization activities on anthrax surveillance and control.

The achievements of a World Health Organization Anthrax Working Group, established in 1990, have been the production of two editions of guidelines on anthrax surveillance and control and the formulation of templates to assist countries in the construction of their surveillance and control programmes. The latter was made possible by the active participation of the Department of Animal Production and Health, Ministry of Agriculture, Food and Fisheries, Zambia and the Livestock Development Programme, Mongu, Western Province, Zambia in a model country programme designed by the Working Group for the purpose. This paper elaborates on these achievements, particularly the lessons learned from the experience of Western Province, Zambia.

Surveillance and control of anthrax and rabies in wild herbivores and carnivores in Namibia

Anthrax has been studied intensively in Etosha National Park, Namibia since 1966; in addition, since 1975, mortality due to rabies and all other causes has been recorded, totalling 6,190 deaths. Standard diagnostic procedures demonstrated that at least 811 deaths (13%) were due to anthrax and 115 deaths (2%) were caused by rabies. Of the total number of deaths due to anthrax, 97% occurred in zebra (Equus burchelli), elephant (Loxodonta africana), wildebeest (Connochaetes taurinus) and springbok (Antidorcas marsupialis) while 96% of rabies deaths occurred in kudu (Tragelaphus strepsiceros), jackal (Canis mesomelas), bat-eared fox (Otocyon megalotis) and lion (Panthera leo). Anthrax deaths were highest in the rainy season for zebra, wildebeest and springbok, while elephant mortality peaked during dry seasons. No statistical relationship existed between seasonal rainfall and overall incidence of either anthrax or rabies. Control of anthrax is limited to prophylactic inoculation when rare or endangered species are threatened. Incineration of anthrax carcasses and chemical disinfection of drinking water are not feasible at Etosha. Rabies control consists of the destruction of rabid animals and incineration of their carcasses when possible.

Mechanical transmission of Bacillus anthracis by stable flies (Stomoxys calcitrans) and mosquitoes (Aedes aegypti and Aedes taeniorhynchus).

We evaluated the potential of stable flies, Stomoxys calcitrans, and two species of mosquitoes, Aedes aegypti and Aedes taeniorhynchus, to transmit Bacillus anthracis Vollum 1B mechanically. After probing on Hartley guinea pigs with a bacteremia of ca. 10(8.6) CFU of B. anthracis per ml of blood, individual or pools of two to four stable flies or mosquitoes were allowed to continue feeding on either uninfected guinea pigs or A/J mice. All three insect species transmitted lethal anthrax infections to both guinea pigs and mice. Both stable flies and mosquitoes transmitted anthrax, even when they were held at room temperature for 4 h after exposure to the bacteremic guinea pig before being allowed to continue feeding on the susceptible animals. This study confirms that blood-feeding insects can mechanically transmit anthrax and supports recent anecdotal reports of fly-bite-associated cutaneous human anthrax. The potential for flies to mechanically transmit anthrax suggests that fly control should be considered as part of a program for control of epizootic anthrax.

A brief review of anthrax in domestic animals

Summary Although there exists in the U.K. a high degree of control of industrial and agricultural anthrax in man and anthrax in animals originating either from animal products or from materials contaminated by contact with them, total control of anthrax in this country seems unlikely to follow until the disease is eliminated from livestock in the enzootic areas abroad. This view rests on the probability that any contamination of agricultural land by anthrax spores is unlikely to be permanent in Britain.

CONTROL OF ANTHRAX: Suggestions based on Survey of Imported Hides

CONTROL OF ANTHRAX: Suggestions based on Survey of Imported Hides