Bangladesh anthrax outbreaks are probably caused by contaminated livestock feed.

In Bangladesh from 1 July to 30 September 2010 there were 104 animal cases of anthrax and 607 associated human cases. This investigation was conducted in Sirajganj district in December 2010, on eight farms where animal cases had occurred. Bacillus anthracis was recovered from soil samples and turbinate bones on six farms. Canonical single nucleotide polymorphism (SNP) analysis showed that all the isolates belonged to the major lineage A, sublineage A.Br.001/002 of China and South East Asia while a multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) with 15 VNTRs demonstrated three unique genotypes. The single nucleotide repeat (SNR) analyses showed two SNR types in 97 out of 99 isolates; nevertheless, due to its higher discriminatory power the presence of two isolates with different SNR-type polymorphisms were detected within two MLVA genotypes. The epidemic occurred during the monsoon season, a time of extensive flooding, suggesting that the source was contaminated feed, not grazing, which is supported by the genetic variance.

The Sverdlovsk anthrax outbreak of 1979.

In April and May 1979, an unusual anthrax epidemic occurred in Sverdlovsk, Union of Soviet Socialist Republics. Soviet officials attributed it to consumption of contaminated meat. U.S. agencies attributed it to inhalation of spores accidentally released at a military microbiology facility in the city. Epidemiological data show that most victims worked or lived in a narrow zone extending from the military facility to the southern city limit. Farther south, livestock died of anthrax along the zone's extended axis. The zone paralleled the northerly wind that prevailed shortly before the outbreak. It is concluded that the escape of an aerosol of anthrax pathogen at the military facility caused the outbreak.

Distinguishing between natural and unnatural outbreaks of animal diseases.

An intentional outbreak of disease among livestock, or agricultural crops, will share a number of characteristics with those aimed at humans - unexpected pattern of disease in season or place, possible explosive incidence, unusual pathogen either in itself or of its genetic structure, difficult diagnosis - but there will also be notable differences: human cases, if they occur, will be coincidental and the major impacts will be delayed and of severe economic consequence. An investigative and analytical protocol is proposed for identifying such an event. Unless the nature of the event is self-declaring, such investigations necessitate a very thorough and careful investigation by a dedicated and experienced epidemiologic team. Atthe same time a country should take steps in advance of such an event to be prepared and to save time later, such as determining possible targets, identifying early warning indicators, establishing molecular biologic expertise and reference collections of possible pathogens, and preparing a tactical and forensic response.

Accidental and intentional animal disease outbreaks: assessing the risk and preparing an effective response.

Intentional animal disease outbreaks are infrequent, if not rare, yet they carry the potential for disastrous consequences. Normal but accidental outbreaks are not uncommon and they must be handled efficiently, effectively and economically. And whatever its origin a disease will then follow its usual epidemiology. Therefore, the effectiveness in dealing with the normal, and the practice, experience and confidence gained, will significantly aid a country in how it minimises the cost of an intentional disease outbreak. The response is what determines the financial and economic costs of a disease outbreak. This paper provides an overview of the various threats, targets, and possible government responses, all of which is then expanded upon in detail in the other papers in this issue of the Review.

The statistical analysis of truncated data: application to the Sverdlovsk anthrax outbreak.

An outbreak of anthrax occurred in the city of Sverdlovsk in Russia in the spring of 1979. The outbreak was due to the inhalation of spores that were accidentally released from a military microbiology facility. In response to the outbreak a public health intervention was mounted that included distribution of antibiotics and vaccine. The objective of this paper is to develop and apply statistical methodology to analyse the Sverdlovsk outbreak, and in particular to estimate the incubation period of inhalational anthrax and the number of deaths that may have been prevented by the public health intervention. The data available for analysis from this common source epidemic are the incubation periods of reported deaths. The statistical problem is that incubation periods are truncated because some individuals may have had their deaths prevented by the public health interventions and thus are not included in the data. However, it is not known how many persons received the intervention or how efficacious was the intervention. A likelihood function is formulated that accounts for the effects of truncation. The likelihood is decomposed into a binomial likelihood with unknown sample size and a conditional likelihood for the incubation periods. The methods are extended to allow for a phase-in of the intervention over time. Assuming a lognormal model for the incubation period distribution, the median and mean incubation periods were estimated to be 11.0 and 14.2 days respectively. These estimates are longer than have been previously reported in the literature. The death toll from the Sverdlovsk anthrax outbreak could have been about 14% larger had there not been a public health intervention; however, the confidence intervals are wide (95% CI 0-61%). The sensitivity of the results to model assumptions and the parametric model for the incubation period distribution are investigated. The results are useful for determining how long antibiotic therapy should be continued in suspected anthrax cases and also for estimating the ultimate number of deaths in a new outbreak in the absence of any public health interventions.

What and how do we communicate?

The rapid, inexpensive transmission of words and data, brought about by the internet and cheap computers, is changing the world faster than anything mankind has ever experienced, reaching into nearly every aspect of our lives, public and private, commercial and governmental. We are in an Information Age with an essentially instantaneous availability of large volumes of information and data. Technological pressures have their own momentum. The changes and improvements in data handling and information sharing will take place, however much or little we do in veterinary medicine, whether at the international or national levels. In addition, there are new superpowers emerging in the world. These are the small and medium third world countries that are gradually gaining democracy through political restructuring and involving the civil society in decision making. There are also the marginal pressure groups, once too small and insignificant to be noticed. These are changing the rules by which the way the world is governed and they are doing it now by the internet and banding together to serve their common interests. The rapid provision of accurate information on animal diseases is desirable goal from a public health as well as an economic viewpoint.

Emergency response planning for anthrax outbreaks in bison herds of northern Canada: a balance between policy and science.

Anthrax outbreaks in northern Canada have implications for ongoing recovery efforts for the threatened wood bison and may pose a health risk to humans, other wildlife, and domestic livestock. RWED and WBNP maintain Anthrax Emergency Response Plans (AERPs) for their respective jurisdictions. An AERP is a pre-planned logistical framework for responding effectively and rapidly to an outbreak so as to minimize spread of the disease, reduce environmental load of spores available for future outbreaks, and minimize risk to public health. In this paper, we describe the main components of an AERP and outline areas for future research.

Geographic information system-aided analysis of factors associated with the spatial distribution of Echinococcus multilocularis infections of foxes.

To investigate the influence of environmental factors on the spatial epidemiology of infections with Echinococcus multilocularis, foxes were sampled in a focal endemic region in the Northwest of Brandenburg, Germany, and examined for infection by the parasite. The locations where foxes were obtained were recorded in a geographic information system database. Positions of infected and uninfected foxes were analyzed on the background of geographic vector data of water, settlements, streets, forests, crop, and pasture. Fox positions were allocated to different land-use classes by use of a Landsat Thematic Mapper (TM) satellite image. Infected foxes were more frequently shot near water, in areas of high soil humidity, and on pastures, suggesting that dryness may limit the tenacity of E. multilocularis oncospheres. Thus open landscapes with humid soil seem to be favorable for the life cycle of the parasite. In contrast, infected foxes were significantly underrepresented in forest areas.

Evaluation of the origin of Mycobacterium leprae infections in the wild armadillo, Dasypus novemcinctus.

An enzyme-linked immunosorbent assay (ELISA) using the phenolic glycolipid-1 (PGL-1) antigen of Mycobacterium leprae and cross-reactive antisera specific for human IgM was developed to detect IgM antibodies to M. leprae in the nine-banded armadillo (Dasypus novemcinctus). Statistical definitions for positive and negative interpretations in the ELISA were developed by screening animals recently captured and experimentally inoculated with M. leprae. The ELISA was shown to have high sensitivity and specificity. Modern day armadillos of central Louisiana were observed to have a PGL-1 antibody prevalence rate as high as 20%, and a clinical disease rate as high as 5%. A retrospective serological survey of 182 armadillos taken in the years 1960-1964 and predating the use of armadillos in leprosy research was used to evaluate the 1968 environmental contamination hypothesis for the origin of M. leprae infections in the wild armadillo. Antibodies to the apparently species-specific PGL-1 antigen were detected in 17 of the samples taken in 1960-1964. Absorption with whole M. leprae, M. intracellulare, M. terrae, M. rhodesiae, M. scrofulaceum, M. diernhoferi, M. kansasii, M. phlei, M. avium, BCG, and 2 new armadillo-derived mycobacterial species showed these antibody reactions to be specific for PGL-1. Apparently, M. leprae was enzootic in armadillos as early as 1961, and original infection of these animals could not have occurred in 1968.

Evaluation of alternative strategies to prevent Newcastle disease in Cambodia.

Velogenic viscerotropic Newcastle disease (vvNCD), which is endemic in Cambodia, can be prevented in theory by a combination of biosecurity and immunization of broiler flocks. The relative contribution of appropriate biosecurity and effective vaccination was quantified at the farm level, applying realistic projections for capital investment, fixed and variable production costs and losses following infection. Non-protected broiler flocks generate a loss when the probability of vvNCD infection exceeds 0.4. Applying both biosecurity and effective vaccination would sustain profitability up to a probability of exposure of 1.0. The benefit to cost ratios for alternative strategies were evaluated for a range of probabilities of exposure to vvNCD extending from 0.1 to 1.0. The benefit-to-cost ratio for biosecurity exceeded unity at a risk of exposure exceeding 0.1, and 0.2 for vaccination and the combination of vaccination and biosecurity respectively. A sensitivity analysis demonstrated that the efficiency of protection, feed cost, and financial consequences of infection markedly affected the projected benefit-to-cost ratios associated with alternative methods of prevention.

Evaluation of biosecurity in broiler breeders.

The economic impact of management practices designed to limit the introduction of disease into a parent broiler breeder flock (biosecurity) was evaluated using benefit-cost analysis. Equations were developed to quantify the losses resulting from infection with one of four alternative categories of disease representing incremental levels of pathogenicity. Realistic costs and assumed values relating to the probability of infection were used to evaluate the ameliorative effect of three alternative levels of biosecurity. A microcomputer spreadsheet program was used to confirm that expenditure on protective measures can be justified by both the risk of introducing a disease and the magnitude of losses that may occur following infection.

Satellite imaging as a technique for obtaining disease-related data.

Because of its initial expense, remote sensing imagery has been frequently ignored in studying the epidemiology and ecology of human and animal diseases. However, these digital images have many advantages when the theoretical restrictions and constraints on the data are understood. Remote sensing imagery has the potential significantly to improve the effectiveness and delivery of disease control programmes. As soon as it can be integrated into the operational aspects of programmes, remote sensing imagery will pass from being a data-driven research tool to being need-driven.

Geographical information systems as a tool in epidemiological assessment and wildlife disease management.

Geographical information systems (GIS) facilitate the incorporation of spatial relationships into epidemiological investigations of wildlife diseases. Consisting of data input, management, analysis and presentation components, GIS act as an integrative technology in that a range of very varied data sources can be combined which describe different aspect of the environment of wild animals. The analytical functionality of GIS is still evolving, and ranges from visual to exploratory and modelling methods. Output generated by GIS in map format has the particular advantage of allowing implicit representation of spatial dependence relationships in an intuitive manner. The technology is becoming an essential component of modern disease surveillance systems.

Anthrax and wildlife.

Although livestock anthrax is declining in many parts of the world, with an increasing number of countries probably truly free of the disease, anthrax remains enzootic in many national parks and even in some game ranching areas. These infected areas can present a persistent risk to surrounding livestock, which may otherwise be free of the disease, as well as a public health risk. The authors use as examples the national parks in southern Africa, the Wood Buffalo National Park in northern Alberta, Canada, and the deer ranching counties in south-west Texas, United States of America, to present the range of problems, epidemiology, and control procedures. While many advances have been achieved in the understanding of this disease, research is required into the genotypic grouping of anthrax isolates, improved field diagnostic techniques, and oral vaccines, as well as to provide a better understanding of spore survival in soil and the ecology of the disease under natural conditions.

Prevalence of Toxoplasma gondii antibodies in southern Louisiana swine in 1980 and 1981.

Sera from 1,219 pigs slaughtered in southern Louisiana in 1980 and 1981 were tested, using the indirect hemagglutination test and microtitration system, for Toxoplasma gondii antibodies; 19.19% had titers of greater than or equal to 1:64. Pigs slaughtered in the colder months, November to March, had significantly higher seroprevalences than did pigs slaughtered in the warmer months. Examination of blood samples from 236 sows and gilts on 52 farms revealed a seroprevalence of 24.6%.

Leptospiral and brucellar titers in frozen bovine sera after 20 years of storage.

Generally good agreement was obtained between the rankings of sera titers when originally tested (T1), and those of the same sera 20 years later (T2). At the later time, the majority of samples (88%) were in, or within 1 dilution factor of their classification at T1. Test results for Brucella abortus and Leptospira interrogans var pomona antibodies demonstrated that original titers, in the upper-lower limits of 20 to 50, had decreased over a wide range (20% to 90%), and the later tests show that the greater the original titer, the greater the proportional decrease. Thus, titers of 20,000 at T1 had decreased by 49% to 99% and those of 200,000, by 95% to 99.8%. Variations in T2 test results were noted between some samples which had given identical results at T1. A decrease in titer over time has been demonstrated. An estimate of the expected half-lives of sera of differing initial Leptospira antibody titers is that for each unit increase in log10 of the initial titer, the half-life is reduced by about 50%. The heterogeneity of the immune response is postulated as the reason for this variation.

Prevalence of trichinosis in southern Louisiana swine.

After an outbreak of human trichinosis in Louisiana involving 45 cases and 1 death in 1979 and 1980, a survey of pigs killed in 21 selected small slaughterhouses in southwestern Louisiana was conducted from November 1980 to September 1981. The sera from 1,225 pigs were examined for trichinella antibodies using an enzyme-linked immunosorbent assay (ELISA); 1,223 diaphragms were subjected to peptic digestion and examined for the presence of Trichinella spiralis larvae. One diaphragm (0.08%) was found to contain T spiralis (26 larvae/g of muscle) and 4 of the slaughterhouse sera were positive (0.33% seroprevalence). Pigs in 52 herds throughout the state were also tested for ELISA antibodies. The ELISA-positive pigs were not found among the 267 pigs tested from the 52 herds.

Rabbit mortality survey.

In a survey of mortality in 2224 rabbits of up to 12 weeks of age, drawn from 10 production units, neonatal mortality was important with 111 stillbirths and 175 deaths in the 1st week of life out of a total of 457 deaths in the whole survey. There was a low overall incidence of death from respiratory and enteric disease during the period of study.

Seroepidemiology of Anaplasma marginale in white-tailed deer (Odocoileus virginianus) from Louisiana.

Antibodies to Anaplasma marginale were detected by the indirect fluorescent antibody test (IFA) in six of 331 (2%) serum samples of white-tailed deer (Odocoileus virginianus) from Louisiana. None of the serum samples were positive using the A. marginale modified rapid card agglutination test. Of the six IFA positive sera retested by the complement fixation test four sera gave anticomplementary and two gave seropositive reactions. The low A. marginale reactor rate in this white-tailed deer population was probably a reflection of the lack of cohabitation between cattle and deer and the fact that the primary arthropod vectors in Louisiana are tabanids. The validity of the indirect fluorescent antibody test for A. marginale antibodies in white-tailed deer should be evaluated.

Surveillance for naturally acquired leprosy in a nine-banded armadillo population.

Samples from 77 nine-banded armadillos (Dasypus novemcinctus) inhabiting a 16.7 km portion of the East Atchafalaya River Levee, Point Coupee Parish, Louisiana, were serologically tested and/or histopathologically examined for evidence of naturally acquired leprosy. Five of 67 (7.5%) armadillos tested sero-positive with ELISA test for IGM class antibodies to the phenolic-glycolipid-1 antigen of Mycobacterium leprae. One of 74 (1.3%) was histopathologically positive as determined by presence of acid-fast bacteria in nerves.