Environmental determinants influencing anthrax distribution in Queen Elizabeth Protected Area, Western Uganda

One Health intervention for elimination of anthrax in an endemic district of Odisha: A baseline and endline study

Background

This study was to compare a baseline and endline survey which were conducted to assess the changes in knowledge, attitude and practices about anthrax disease among the communities after One Health intervention for the elimination of human anthrax in an endemic district of Odisha.

Methods

A total of 2670 respondents were interviewed during the baseline and 2511 for the endline survey using a structured questionnaire by multi-stage sampling method. Descriptive statistics were used and logistic regression was performed to estimate the relationship between the variables and knowledge of anthrax.

Results

Out of the total participants in the study, males were about 76.25% in baseline and 72.08% in endline and about half of the total respondents were illiterate. Majority of the respondents had reported agriculture as their main occupation during both surveys. More than 50% of the respondents had livestock in their houses and farming was the main purpose for keeping them in both surveys. Around 20.26% of respondents knew about anthrax in baseline which raised to 53.64% after One Health intervention. Almost 21.29% of livestock owners had vaccinated their animals against anthrax disease throughout baseline, which increased to 66.5% during the endline survey.

Conclusion

This study highlights a significant surge in both knowledge and practices related to anthrax within the community after the implementation of intervention packages based on the One Health approach. The outcome of our study signified the importance of One Health interventions to address the health challenges related to zoonotic diseases in tribal communities. The data could be useful for local Governments to incorporate such an approach in their health policy to eliminate human anthrax.

Mapping high probability area for the Bacillus anthracis occurrence in wildlife protected area, South Omo, Ethiopia

Anthrax is a zoonotic disease caused by a spore-forming gram-positive bacterium, Bacillus anthracis. Increased anthropogenic factors inside wildlife-protected areas may worsen the spillover of the disease at the interface. Consequently, environmental suitability prediction for B. anthracis spore survival to locate a high-risk area is urgent. Here, we identified a potentially suitable habitat and a high-risk area for appropriate control measures. Our result revealed that a relatively largest segment of Omo National Park, about 23.7% (1,218 square kilometers) of the total area; 36.6% (711 square kilometers) of Mago National Park, and 29.4% (489 square kilometers) of Tama wildlife Reserve predicted as a high-risk area for the anthrax occurrence in the current situation. Therefore, the findings of this study provide the priority area to focus on and allocate resources for effective surveillance, prevention, and control of anthrax before it causes devastating effects on wildlife.

Modelling climate change impacts on the spatial distribution of anthrax in Zimbabwe

BACKGROUND

In Zimbabwe, anthrax is endemic with outbreaks being reported almost annually in livestock, wildlife, and humans over the past 40 years. Accurate modelling of its spatial distribution is key in formulating effective control strategies. In this study, an Ensemble Species Distribution Model was used to model the current and future distribution of anthrax occurrence in Zimbabwe.

METHODS

Bioclimatic variables derived from the Beijing Climate Centre Climate System Model were used to model the disease. Collinearity testing was conducted on the 19 bioclimatic variables and elevation to remove redundancy. Variables that had no collinearity were used for anthrax habitat suitability modelling. Two future climate change scenarios for different Representative Concentration Pathways (RCP), RCP4.5 and RCP8.5 were used. Model evaluation was done using true skill, Kappa statistics and receiver operating characteristics.

RESULTS

The results showed that under current bioclimatic conditions, eastern and western districts of Zimbabwe were modelled as highly suitable, central districts moderately suitable and southern parts marginally suitable for anthrax occurrence. Future predictions demonstrated that the suitable (8%) and highly suitable (7%) areas for anthrax occurrence would increase under RCP4.5 scenario. In contrast, a respective decrease (11%) and marginal increase (0.6%) of suitable and highly suitable areas for anthrax occurrence were predicted under the RCP8.5 scenario. The percentage contribution of the predictors varied for the different scenarios; Bio6 and Bio18 for the current scenario, Bio2, Bio4 and Bio9 for the RCP4.5 and Bio3 and Bio15 for the RCP8.5 scenarios.

CONCLUSIONS

The study revealed that areas currently suitable for anthrax should be targeted for surveillance and prevention. The predicted future anthrax distribution can be used to guide and prioritise surveillance and control activities and optimise allocation of limited resources. In the marginally to moderately suitable areas, effective disease surveillance systems and awareness need to be put in place for early detection of outbreaks. Targeted vaccinations and other control measures including collaborative 'One Health' strategies need to be implemented in the predicted highly suitable areas. In the southern part where a high decrease in suitability was predicted, continued monitoring would be necessary to detect incursions early.

Investigation of human anthrax outbreak in Koraput district of Odisha, India

BACKGROUND

Anthrax is a zoonotic infection resulting from the bacteria Bacillus anthracis. Humans contract cutaneous anthrax by coming into contact, and gastrointestinal (GI) anthrax by consumption of infected animals or animal products. An outbreak investigation was conducted to confirm the occurrence of the anthrax outbreak, comprehend its extent, understand the epidemiological characteristics, identify the outbreak's cause, and propose control measures.

METHODS

A descriptive epidemiology was carried out for this outbreak investigation. We defined a suspected human cutaneous anthrax case as appearance of skin lesions and symptoms (itching/redness/swelling) and a suspected case of GI anthrax as appearance of diarrhoea/abdominal pain/vomiting in a resident of Koraput district after being associated with slaughtering and/or consumption of carcass during 5th April to 15th May 2023. The etiological hypothesis was formulated using descriptive epidemiological methods. Laboratory confirmation was performed by real-time polymerase chain reaction (RT-PCR). Statistical analyses were conducted using SPSS 25.

RESULTS

A total of 47 clinically suspected anthrax cases were identified during the outbreak in five villages of Koraput district in Odisha. The epidemic curve indicated multiple point-source exposures starting from 13th April 2023. About 10 cases were identified by RT-PCR testing as confirmed cases of anthrax. No death was recorded in this outbreak investigation.

CONCLUSIONS

Based on a thorough examination of epidemiological survey results and laboratory findings, we conclude that the outbreak was of human cutaneous and GI anthrax. Exposures from handling dead animals were associated with cutaneous anthrax, whereas eating uncooked meat of dead sheep was associated with gastrointestinal anthrax.

The potential distribution of Bacillus anthracis suitability across Uganda using INLA

To reduce the veterinary, public health, environmental, and economic burden associated with anthrax outbreaks, it is vital to identify the spatial distribution of areas suitable for Bacillus anthracis, the causative agent of the disease. Bayesian approaches have previously been applied to estimate uncertainty around detected areas of B. anthracis suitability. However, conventional simulation-based techniques are often computationally demanding. To solve this computational problem, we use Integrated Nested Laplace Approximation (INLA) which can adjust for spatially structured random effects, to predict the suitability of B. anthracis across Uganda. We apply a Generalized Additive Model (GAM) within the INLA Bayesian framework to quantify the relationships between B. anthracis occurrence and the environment. We consolidate a national database of wildlife, livestock, and human anthrax case records across Uganda built across multiple sectors bridging human and animal partners using a One Health approach. The INLA framework successfully identified known areas of species suitability in Uganda, as well as suggested unknown hotspots across Northern, Eastern, and Central Uganda, which have not been previously identified by other niche models. The major risk factors for B. anthracis suitability were proximity to water bodies (0-0.3 km), increasing soil calcium (between 10 and 25 cmolc/kg), and elevation of 140-190 m. The sensitivity of the final model against the withheld evaluation dataset was 90% (181 out of 202 = 89.6%; rounded up to 90%). The prediction maps generated using this model can guide future anthrax prevention and surveillance plans by the relevant stakeholders in Uganda.

A Retrospective Study on the Epidemiology of Anthrax Among Livestock from 2011 to 2020 in Awi Administrative Zone, Amhara Region, Northwest Ethiopia

Background

In Ethiopia, anthrax is the second most important zoonotic disease, next to rabies. Data quantifying occurrence and distribution of animal anthrax in Awi administrative zone of Amhara region, Ethiopia, are limited. Thus, this study was conducted to describe the distribution of animal anthrax between 2011 and 2020 in Awi zone.

Methods

This study used secondary data of animal anthrax that occurred in the Awi zone and reported to the Regional and National Veterinary Authority between 2011 and 2020.

Results

A total of 1262 cases of anthrax in animals and 324 animals that died due to anthrax were reported. The highest number of anthrax cases were reported in 2012 (n = 671), sharing 48.9% of the 10-year animal anthrax reported. However, the highest number of animal death due to anthrax (n = 104) was reported in 2014. The overall case fatality rate of anthrax was 25.67% (n = 324). The highest animal anthrax cases (n = 984; 77.97%) and deaths (n = 259; 79.94%) were recorded in Bovine. The highest cases of anthrax were registered in May (n = 313), while no anthrax case was reported during December. The highest and lowest number of animal death due to anthrax were reported during July (n = 64) and January (n = 6), respectively. The highest number of anthrax cases was reported in the hot-dry season (n = 479; 37.96%) whereas the lowest was reported during the cold-dry season (n = 30; 2.38%).

Conclusion

The current study revealed a considerable number of animal anthrax cases and deaths in Awi zone every year. Hence, it is necessary for practicing prevention strategies including immunization programs before the peak season of anthrax outbreaks.

Modelling the ecological niche of naturally occurring anthrax at global and circumpolar extents using an ensemble modelling framework

Bacillus anthracis, the causative agent of anthrax, is a spore-forming bacterium that primarily affects herbivorous livestock, wildlife and humans exposed to direct contact with infected animal carcasses or products. To date, there are a limited number of studies that have delineated the potential global distribution of anthrax, despite the importance of the disease from both an economic and public health standpoint. This study compiled occurrence data (n = 874) of confirmed human and animal cases from 1954 to 2021 in 94 countries. Using an ensemble ecological niche model framework, we developed updated maps of the global predicted ecological suitability of anthrax to measure relative risk at multiple scales of analysis, including a model for circumpolar regions. Additionally, we produced maps quantifying the disease transmission risk associated with anthrax to cattle, sheep and goat populations. Environmental suitability for B. anthracis globally is concentred throughout Eurasia, sub-Saharan Africa, the Americas, Southeast Asia, Australia and Oceania. Suitable environments for B. anthracis at the circumpolar scale extend above the Arctic Circle into portions of Russia, Canada, Alaska and northern Scandinavia. Environmental factors driving B. anthracis suitability globally include vegetation, land surface temperature, soil characteristics, primary climate conditions and topography. At the circumpolar scale, suitability is influenced by soil factors, topography and the derived climate characteristics. The greatest risk to livestock is concentrated within the Indian subcontinent, Australia, Anatolia, the Caucasus region, Central Asia, the European Union, Argentina, Uruguay, China, the United States, Canada and East Africa. This study expands on previous work by providing enhanced knowledge of the potential spatial distribution of anthrax in the Southern Hemisphere, sub-Saharan Africa, Asia and circumpolar regions of the Northern Hemisphere. We conclude that these updated maps will provide pertinent information to guide disease control programs, inform policymakers and raise awareness at the global level to lessen morbidity and mortality among animals and humans located in environmentally suitable areas.

Ecological Niche Model of Bacillus cereus Group Isolates Containing a Homologue of the pXO1 Anthrax Toxin Genes Infecting Metalworkers in the United States

While Bacillus cereus typically causes opportunistic infections in humans, within the last three decades, severe and fatal infections caused by isolates of the B. cereus group harboring anthrax toxin genes have been reported in the United States. From 1994 to 2020, seven cases of anthrax-like illness resulting from these isolates have been identified. With one exception, the cases have occurred in the Gulf States region of the United States among metalworkers. We aimed to develop an ecological niche model (ENM) to estimate a spatial area conducive to the survival of these organisms based on the presence of known human infections and environmental variables. The estimated ecological niche for B. cereus was modeled with the maximum entropy algorithm (Maxent). Environmental variables contributing most to the model were soil characteristics (cation exchange capacity, carbon content, soil pH), temperature, enhanced vegetation index (EVI), and land surface temperature (LST). Much of the suitable environments were located throughout the Gulf Coast Plain, Texas Backland Prairies, East Central Texas Plains, Edwards Plateau, Cross Timbers, Mississippi Alluvial Plain, and Central Great Plains. These findings may provide additional guidance to narrow potential risk areas to efficiently communicate messages to metalworkers and potentially identify individuals who may benefit from the anthrax vaccine.

Isolation and identification of avirulent strains of Bacillus anthracis from environmental samples in Central Java, Indonesia

Background and Aim: Anthrax is a non-contagious infectious disease caused by Bacillus anthracis. The bacteria form spores that are resistant to extreme conditions and can contaminate the environment for decades. This study aimed to detect and characterize B. anthracis found in endemic areas of anthrax in Yogyakarta and Central Java province, Indonesia. Materials and Methods: Soil samples were collected from Gunungkidul regency, Yogyakarta province (n=315) and Boyolali regency, Central Java province (n=100). Additional soil samples (n=10) and straw samples (n=5) were obtained from Pati regency, Central Java province. The isolation and identification of B. anthracis were performed using conventional methods: Morphology of bacteria colony in solid media, Gram staining, capsule staining, spores staining, and motility test. Isolates were further identified using polymerase chain reaction (PCR) against Ba813, lef (pXO1), and capC (pXO2) gene. An avirulent vaccine strain of B. anthracis (strain 34F2) was used as a control. Results: Only four samples grew on blood agar with a ground-glass appearance, white-gray colony (Gunungkidul and avirulent strain) or yellowish (Boyolali and Pati). All were Gram-positive, presented chains, square-ended rods, spores, and were then identified as B. anthracis. Boyolali, Pati, and avirulent strain isolates had slightly different characteristics, including the growth of non-mucoid in the bicarbonate agar medium, and their uncapsulated form. The PCR showed two Gunungkidul isolates which amplified three genes, including Ba813, lef, and capC. Contrarily, the other isolates did not amplify the capC gene. Conclusion: Gunungkidul isolates were identified as virulent strains of B. anthracis while Boyolali and Pati isolates were proposed as avirulent strains. This is the first report of isolation and identification of avirulent strains of B. anthracis in Central Java, Indonesia.

An Estimate of Global Anthrax Prevalence in Livestock: A Meta-analysis

Background and Aim:

Anthrax, caused by the soil-borne spore-forming bacteria called Bacillus anthracis, is a zoonotic disease that persists worldwide in livestock and wildlife and infects humans. It is a great hazard to livestock; henceforth, evaluating the global concerns about the disease occurrence in livestock is essential. This study was conducted to estimate the global prevalence of anthrax and predict high-risk regions, which could be an input to veterinarians to take necessary steps to control and avoid the disease.

Materials and Methods:

A literature review was performed using online databases, namely, PubMed, Google Scholar, Scopus, Biomed Central, and Science Direct, to extract relevant publications worldwide between 1992 and 2020.</AQ9> Initially, 174 articles were selected, and after scrutinizing, 24 articles reporting the prevalence of anthrax were found to be adequate for the final meta-analysis. The statistical study was accompanied by employing fixed effects and random effects models using R.

Results:

The pooled prevalence of anthrax globally was 28% (95% confidence interval, 26-30%) from 2452 samples through the fixed effects model. Continent-wise subgroup analysis through the random effects model revealed that the pooled prevalence of anthrax was highest in Africa (29%) and least in North America (21%).

Conclusion:

In these publications, anthrax causes economic loss to farmers and, thus, to the world. Hence, controlling anthrax infections in high-risk regions are essential by implementing appropriate control measures to decrease the effect of the disease, thereby reducing economic loss.