Spatiotemporal epidemiology of livestock anthrax in Kazakhstan and analysis of potential contributing factors from 2015 to 2024

Abstract

Anthrax remains a persistent transboundary zoonotic disease in the Republic of Kazakhstan despite long-term vaccination programs and established veterinary surveillance. This study aimed to analyze spatial and temporal patterns of anthrax outbreaks in livestock and humans and to describe their relation to environmental, climatic, and immunoprophylactic factors. Retrospective data on anthrax outbreaks in cattle, small ruminants, and humans recorded between 2015 and 2024 were analyzed using descriptive temporal trend analysis and thematic spatial mapping at the regional level. Climatic parameters, including temperature, precipitation, and soil moisture, were evaluated in relation to outbreak dynamics. Serological monitoring of cattle was conducted using the indirect hemagglutination assay to assess serological response, and non-parametric statistical methods were applied to compare regions and time periods. A total of 33 anthrax outbreaks were registered, with 93.4% occurring in cattle. Outbreaks showed pronounced seasonality, peaking in summer and early autumn, and were concentrated in historically endemic regions. Despite reported vaccination coverage exceeding 97% in several regions, outbreaks persisted, suggesting the influence of multiple factors, including environmental persistence of Bacillus anthracis spores and variability in vaccination practices, animal coverage, or environmental persistence of Bacillus anthracis spores. Serological analysis revealed regional heterogeneity in antibody levels. Human cases were temporally associated with livestock outbreaks and were primarily linked to unauthorized slaughter and handling of infected animals. These findings underscore the need for integrated risk-based surveillance combining climatic monitoring, spatial analysis, and targeted vaccination to support anthrax prevention strategies in endemic areas.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-026-58630-8.

Introduction

Anthrax caused by Bacillus anthracis (B. anthracis) remains an important zoonotic disease with substantial veterinary, public health, and economic significance worldwide, particularly in regions where livestock production represents a major component of agricultural activity¹. In Kazakhstan, anthrax persists in historically endemic regions and continues to be periodically reported among livestock and humans despite ongoing preventive measures^2,3. The persistence of the disease is largely associated with the remarkable environmental resistance of B. anthracis spores, which can survive in soil for decades and contribute to the long-term maintenance of environmental reservoirs of infection^1,4,5.

The epidemiology of anthrax is characterized by pronounced spatial and temporal heterogeneity influenced by multiple environmental and ecological factors, including climatic conditions, soil characteristics, vegetation cover, and land use patterns^2,3,5,6. Previous studies conducted in Kazakhstan and other endemic regions have demonstrated that specific environmental conditions, particularly humus-rich alkaline soils and steppe ecosystems, may support prolonged spore persistence and recurrent outbreak occurrence^1,5. In addition, ecological niche modeling studies have identified geographic areas potentially suitable for the maintenance and circulation of different B. anthracis lineages⁶. However, despite considerable progress in understanding the environmental suitability of anthrax, the mechanisms underlying long-term persistence and periodic re-emergence of outbreaks remain incompletely understood.

Continuous epidemiological surveillance and spatial analysis are therefore essential for improving outbreak prediction and supporting targeted veterinary and public health interventions^2,3. Geographic zoning based on outbreak frequency and recurrence risk has been proposed as a practical tool for identifying high-risk territories and optimizing preventive measures in endemic regions^2,3,7–9. This approach is particularly relevant for Kazakhstan because of its large territory and diverse environmental and climatic conditions, which may contribute to regional variability in anthrax occurrence^1,2. Although the current epidemiological situation in Kazakhstan is generally considered relatively stable, sporadic outbreaks continue to occur in different parts of the country, indicating the continued presence of environmental and epidemiological factors favorable for disease persistence^3,10.

In addition to environmental factors, livestock management practices, vaccination coverage, and population awareness may also influence the dynamics of anthrax outbreaks and the effectiveness of control measures^11,12. Nevertheless, most previous studies have focused primarily on ecological suitability modeling or regional outbreak descriptions, whereas integrated analyses combining epidemiological, climatic, and serological data remain limited.

Therefore, the present study aimed to provide a structured descriptive analysis of anthrax outbreaks in Kazakhstan from 2015 to 2024, focusing on spatial and temporal patterns as well as potential environmental, climatic, and immunoprophylactic factors associated with disease persistence and recurrence.

Materials and methods

Study area

The study was conducted across the entire territory of the Republic of Kazakhstan, encompassing a wide range of climatic, landscape, and agro-ecological zones, including steppe, semi-desert, desert, mountainous, and river floodplain areas. The country is characterized by a sharply continental climate with pronounced seasonal and interannual variability in temperature and precipitation. These environmental conditions are relevant to the persistence and reactivation of soil-borne pathogens, including B. anthracis (Fig. 1).

Fig. 1.

Map of study area.

Map of the Republic of Kazakhstan illustrating administrative divisions and geographic context of the study area used for spatial analysis of anthrax outbreaks during the study period (2015–2024).

Data sources

Epidemiological data on anthrax outbreaks among domestic animals for the period 2015–2024 were obtained from the veterinary surveillance system of the Republic of Kazakhstan, including reports from regional veterinary services and the National Reference Center for Veterinary Medicine. Outbreak records contained information on the year and month of occurrence, administrative unit (region and district), affected animal species, number of cases, and implemented control measures. Anthrax cases included in this study were based on official veterinary reports and were considered laboratory-confirmed according to national diagnostic standards. However, detailed information on specific diagnostic methods was not available in the dataset.

Climatic data, including monthly mean air temperature and total precipitation, were obtained from datasets provided by the National Hydrometeorological Service of Kazakhstan. Climatic parameters were extracted for the month of outbreak occurrence as well as for preceding months relevant to outbreak development.

Information on vaccination coverage, emergency vaccination campaigns, and disinfection measures was obtained from official veterinary reports and regulatory documentation.

Data processing and classification

Anthrax outbreaks were aggregated by year, season, region, and animal species. Seasons were defined as spring (March–May), summer (June–August), autumn (September–November), and winter (December–February). Regions were categorized based on their geographical location (northern, southern, western, eastern, and central Kazakhstan) and dominant landscape characteristics.

Livestock data were stratified by species, including cattle, small ruminants (sheep and goats), horses, and other susceptible species. The proportion of outbreaks by species and region was calculated for the evaluation of host-specific and territorial vulnerability.

An outbreak was defined as a laboratory-confirmed occurrence of anthrax within a herd, regardless of the number of affected animals.

Spatio-temporal analysis

The spatial distribution of anthrax outbreaks was examined at the regional and district levels to identify areas of persistent or recurrent epidemiological activity. The proportion of administrative regions affected during the study period was calculated, and districts with repeated outbreaks were considered potential permanent enzootic foci.

Temporal dynamics were evaluated using annual and monthly trend assessments to characterize interannual variability and seasonal patterns of anthrax occurrence. Time-series approaches were applied to identify periods of increased epidemiological intensity.

Climatic drivers analysis

To examine associations between climatic conditions and anthrax epidemiological activity, outbreak occurrence was compared with deviations of temperature and precipitation from long-term climatic norms. Particular attention was given to prolonged periods of elevated temperatures, drought conditions, and subsequent episodes of increased precipitation, which are considered relevant to Bacillus anthracis spore persistence and potential activation.

Climatic anomalies were defined as deviations of temperature and precipitation from long-term average values based on national meteorological data.

Descriptive comparative analysis was used to evaluate climatic anomalies during years with increased outbreak frequency, with the 2023 epidemic season included as a representative case of climate-associated activation patterns.

Risk factors assessment

Risk factors were evaluated using an integrated approach combining epidemiological, environmental, and management-related variables. The assessment considered the presence of historically documented or unidentified anthrax burial sites, landscape characteristics such as lowlands, floodplains, and foothill zones, soil properties associated with long-term spore persistence, seasonal livestock movement and grazing practices, as well as vaccination coverage and post-vaccination immunity levels.

Serological monitoring

Serological monitoring data were analyzed to evaluate antibody responses across regions and animal species, allowing assessment of preventive measure effectiveness and identification of areas with lower antibody levels. Antibodies were detected using the indirect hemagglutination assay (IHA). Sera were tested with partially purified antigen coated on tanned sheep erythrocytes, following the method described by Buchanan et al.¹³. Prior to testing, sera were heat-inactivated at 56 °C for 30 min and absorbed with sheep erythrocytes to reduce non-specific reactions.

Statistical analysis

Spatial patterns were interpreted using thematic mapping techniques to illustrate regional distribution and intensity of outbreaks. Climatic and epidemiological data were integrated to support qualitative assessment of climate–disease interactions.

The purpose of the antibody titer analysis was to evaluate differences across animals, time points, and geographic regions. Data normality was assessed using the Shapiro–Wilk test, which indicated that the distributions of titers deviated from normality¹⁴. Therefore, non-parametric methods were applied. Differences in titers across days within each animal group were tested using the Kruskal–Wallis test, a non-parametric alternative to Two-way ANOVA, allowing comparison of multiple independent samples without assuming normality¹⁵. Differences in titers across geographic regions were assessed using the Kruskal–Wallis test, which is appropriate for more than two groups with non-normal distributions. Differences between animal species (bovine vs. ovine) were also tested with the Kruskal–Wallis test, equivalent to the Mann–Whitney U test for two-group comparisons. Following significant Kruskal–Wallis results, pairwise Wilcoxon with Bonferroni correction were performed to identify specific differences between regions and between days within each animal group, controlling for multiple comparisons¹⁶. All analyses were conducted in R (version ≥ 4.4) using the rstatix, tidyverse, and emmeans packages, with statistical significance considered at p < 0.05 after adjustment.

This study employed a retrospective descriptive analysis of surveillance, climatic, and serological data to characterize spatiotemporal patterns of anthrax occurrence in Kazakhstan. The analyses were exploratory and intended to identify trends and potential relationships rather than infer causality. No mechanistic, predictive, or multivariable modeling was performed.

Ethical considerations

Human ethics

This study used only aggregated, anonymized human anthrax surveillance data obtained from official reports of the Ministry of Health of the Republic of Kazakhstan. No identifiable personal data were accessed.

The Local Ethics Committee of Kazakh Scientific Research Veterinary Institute reviewed the study design and confirmed that the research was exempt from formal ethical approval due to the use of secondary, de-identified data. All procedures complied with national regulations and the principles of the Declaration of Helsinki. Informed consent was not required, and the requirement was formally waived by the Local Ethics Committee of Kazakh scientific research veterinary institute.

Animal ethics

No procedures or sampling were performed specifically for this research. Serum samples originated from routine state veterinary surveillance activities conducted under official authorization from the Committee for Veterinary Control and Supervision of the Ministry of Agriculture of the Republic of Kazakhstan.

The study protocol was reviewed by the Local Ethics Committee of the Kazakh Scientific Research Veterinary Institute (KazSRVI), which determined that the research was exempt from separate animal ethics approval because it involved routine surveillance activities conducted under national veterinary legislation.

Blood collection was performed by licensed veterinary professionals. Animals were humanely restrained using standard veterinary handling techniques designed to minimize stress and discomfort. No anesthesia or euthanasia procedures were performed for serum collection. All activities complied with national veterinary regulations and internationally accepted principles of animal welfare (IACUC-equivalent standards).

Results

Overall epidemiological situation (2015–2024)

During the study period from 2015 to 2024, anthrax outbreaks among domestic animals were recorded in Kazakhstan with notable regularity. A total of 33 epidemiological outbreaks were officially registered during the ten-year period. Anthrax cases were detected in 13 out of 17 administrative regions, accounting for 76.5% of the country’s territory, indicating widespread geographical distribution (Fig. 2).

Fig. 2.

Geographic distribution of registered anthrax outbreaks in Kazakhstan, 2015–2024.

The map shows the spatial distribution of 33 officially registered anthrax outbreaks among domestic animals across administrative regions of the Republic of Kazakhstan during the study period. Red circles represent officially registered laboratory-confirmed anthrax outbreaks. Circle size reflects the relative number of outbreaks recorded within affected regions during 2015–2024.

During the study period from 2015 to 2024, a total of 33 anthrax outbreaks among cattle were officially registered in Kazakhstan (Fig. 2). Outbreaks were reported in 13 out of 17 administrative regions, indicating a broad geographic distribution of the disease. The highest number of outbreaks was recorded in the Jambyl region (10 outbreaks), followed by Kostanay (4 outbreaks), Turkestan (3 outbreaks), and Karaganda (3 outbreaks). West Kazakhstan, East Kazakhstan, Aktobe, and Akmola regions each reported two outbreaks during the study period. Single outbreaks were documented in the Abay, Almaty, North Kazakhstan, Atyrau, and Pavlodar regions. No anthrax outbreaks among cattle were reported in the Mangystau, Zhetysu, and Kyzylorda regions throughout the entire observation period.

Temporal dynamics

Interannual analysis demonstrated pronounced variability in outbreak frequency. Anthrax outbreaks were recorded almost annually, with the exception of 2017 and 2020, when no cases were reported. The highest number of outbreaks occurred in 2023 ¹⁶ and 2016 (5 outbreaks). Lower activity was observed in 2015, 2018, and 2019, with one to two outbreaks per year.

Seasonal distribution showed a strong concentration of cases during the warm period of the year. Of the total outbreaks, 75.8% (25/33) were registered between June and September. Summer months accounted for 57.6% of outbreaks, while 36.3% occurred in autumn. Only 6.1% of cases were recorded in spring, and no outbreaks were registered during winter months. The seasonal and species distribution of anthrax cases is presented in Fig. 3, which illustrates the incidence of animal anthrax from 2015 to 2024 by season. The highest number of cases occurred during the summer months.

Fig. 3.

Distribution of anthrax cases in livestock in Kazakhstan during 2015–2024: monthly and seasonal dynamics of outbreaks.

The figure shows the monthly distribution of officially registered anthrax outbreaks among livestock in Kazakhstan during the study period. Bars indicate the number of outbreaks recorded in each month, while seasons are grouped as winter (December–February), spring (March–May), summer (June–August), and autumn (September–November). The dashed line represents the overall monthly trend. Seasonal proportions of outbreaks are indicated for each season.

Spatial distribution

Anthrax outbreaks were detected across all major climatic and geographical zones of Kazakhstan, including northern, southern, western, eastern, and central regions. The highest number of outbreaks (n = 10) was recorded in the Jambyl (southern) region, followed by Kostanay (northern, n = 4), Turkestan (southern, n = 3), and Karaganda (central, n = 3). Several regions experienced repeated outbreaks in different years, although in most cases outbreaks occurred in different districts within the same region (Fig. 2).

Repeated outbreaks in the same districts were identified in Talas and Zhualy districts of Jambyl region and Denisov district of Kostanay region. In this study, repeated outbreaks refer to anthrax outbreaks reported in the same administrative district during different years. Such districts were considered potential persistent enzootic areas, indicating long-term environmental maintenance of anthrax risk. (Fig. 2).

Host species structure

Analysis of affected animal species revealed a clear predominance of anthrax cases among cattle, which accounted for 78.3% (112 cases) of all recorded animal infections. In this study, a case is defined as a laboratory-confirmed occurrence of anthrax within a herd, regardless of the total number of affected animals. Horses represented 17.5% (25 cases), while small ruminants accounted for 4.2% (6 cases). These results indicate that cattle accounted for the majority of reported anthrax cases during the study period. However, the present data do not allow determination of whether this pattern reflects biological susceptibility, differences in exposure, livestock management practices, vaccination coverage, or other epidemiological factors. (Fig. 4).

Fig. 4.

Distribution of anthrax cases in livestock in Kazakhstan during 2015–2024: proportion of cases by animal species.

The figure shows the proportion of reported anthrax cases among livestock by animal species during the study period. Percentages represent the share of total reported animal cases attributed to cattle, horses, and small ruminants.

The distribution analysis makes it possible to identify the most vulnerable animal species and assess the epizootic situation, which is important for planning preventive measures, vaccination and veterinary supervision.

As noted above, anthrax in Kazakhstan shows pronounced seasonality, with most animal cases occurring between June and September. This pattern is likely driven by warmer conditions following wet periods, which increase livestock exposure to contaminated soil. High-risk zones are more common in southern regions due to intensive farming, highlighting the need for enhanced surveillance and vaccination during warmer months.

Climatic conditions during outbreak periods

Given the significance of climatic factors in the activation of anthrax foci, this study analyzed official data from the National Hydrometeorological Service for the period from June to September 2023 (Supplementary Materials). It was established that during this timeframe, multiple anthrax outbreaks among livestock were registered across several regions of the Republic of Kazakhstan, with the highest concentration of epidemiological foci observed in the Jambyl and Kostanay regions (Fig. 2).

A comparative analysis of outbreak timing relative to climatic indicators revealed that periods of heightened anthrax epidemiological activity were associated with prolonged air temperature anomalies exceeding long-term averages, coupled with a reduction in precipitation, which was followed by episodes of intense rainfall. During the 2023 epidemiological season, elevated temperatures were observed from April to July across most of the study area; conversely, in August, precipitation levels exceeded long-term norms by 1.3 to 2.7 times. Similar climatic patterns were consistently recorded in outbreak regions, including foothill zones, river floodplains, and lowland territories.

Climatic associations were evaluated qualitatively based on observed temporal patterns and were not formally quantified using statistical modeling. Therefore, these observations should be interpreted cautiously, as temperature and precipitation may influence anthrax occurrence indirectly through soil conditions, vegetation dynamics, and livestock exposure patterns that were not explicitly analyzed in this study.

Vaccination coverage and post-vaccination immunity

Serum samples were collected immediately before immunization, then until 31 and 90 days after immunization.

Antibody titers differed across time points in both bovine and ovine groups. Kruskal–Wallis tests revealed significant differences between days (bovine: χ²(2) = 646, p < 0.001; ovine: χ²(2) = 713, p < 0.001). Pairwise Wilcoxon rank-sum tests (equivalent to Mann–Whitney U tests) with Bonferroni correction confirmed that all time points differed significantly from each other in both animal groups (all adjusted p-values < 0.001).

Analysis of geographic heterogeneity demonstrated significant differences in antibody titers across regions at 31 days post-immunization (dpi) (χ²(5) = 43.2, p < 0.001), indicating a regional effect on antibody levels. Post-hoc pairwise Wilcoxon rank-sum tests with Bonferroni correction identified specific regional differences. Although some comparisons were not statistically significant after adjustment, several pairs of regions showed significant differences (Table 1). Significant differences between animal species were also observed (χ²(1) = 30.9, p < 0.001), with bovine titers being higher than ovine titers.

Table 1.

Post-hoc pairwise comparisons of antibody titers between regions (31 dpi).

Region 1	Region 2	p-value	p.adj
Akmola Region	East Kazakhstan Region	0.078	1.00
	Karaganda Region	0.758	1.00
	Kostanay Region	0.034	0.446
	West Kazakhstan Region	0.008	0.114
	Jambyl Region	0.018	0.266
East Kazakhstan Region	Karaganda Region	0.034	0.453
	Kostanay Region	0.674	1.00
	West Kazakhstan Region	< 0.001	< 0.001
	Jambyl Region	< 0.001	< 0.001
Karaganda Region	Kostanay Region	0.008	0.126
	West Kazakhstan Region	0.011	0.166
	Jambyl Region	0.026	0.392
Kostanay Region	West Kazakhstan Region	< 0.001	< 0.001
	Jambyl Region	< 0.001	< 0.001
West Kazakhstan Region	Jambyl Region	0.744	1.00

Table 1 summarizes the results of post-hoc pairwise Wilcoxon rank-sum tests with Bonferroni correction performed to compare post-vaccination antibody titers between geographic regions. For each regional pair, unadjusted p-values and Bonferroni-adjusted p-values (p. adj) are presented. Statistically significant differences after correction (p. adj < 0.05) indicate regional heterogeneity in antibody titers, while non-significant adjusted p-values reflect comparable post-vaccination antibody responses between regions.

Longitudinal antibody responses were assessed in cattle and sheep across multiple regions (Figs. 5, 6, 7). Figure 5 presents the distribution of individual antibody titers measured at 0, 31, and 90 days post-immunization by region and animal species. Figure 6 shows the density distribution of antibody titers at day 90. Figure 7 presents changes in mean antibody titers from day 0 to day 90 across regions and animal species.

Fig. 5.

Distribution of individual antibody titers across regions.

Fig. 6.

Density distribution of antibody titers on day 90.

Fig. 7.

Longitudinal changes in mean antibody titers from day 0 to day 90.

Individual post-vaccination antibody titers measured by indirect hemagglutination assay (IHA) in cattle and sheep across regions at 0, 31, and 90 days post-immunization. Each point represents an individual serum sample, and boxplots indicate median values and interquartile ranges.

Density plots showing the distribution of post-vaccination antibody titers in cattle and sheep across regions at 90 days post-immunization. The plots illustrate variability in antibody responses within animal species and regions.

Dumbbell plots showing mean post-vaccination antibody titers measured at 0 and 90 days post-immunization across regions for cattle and sheep. Lines connect mean values within each region and animal species.

Analysis of official vaccination records showed that annual vaccination plans for susceptible livestock were largely fulfilled. Vaccination coverage exceeded 97% in most years. Emergency vaccination campaigns were implemented in all registered epidemiological foci.

Serological monitoring of 926 serum samples collected from vaccinated animals in six regions demonstrated that 93.4% of animals demonstrated antibody titers within the range observed in the majority of vaccinated animals in this study. Relatively lower antibody titers compared with the study population distribution were observed in 3.1% of animals, while 3.5% of samples showed absence of detectable antibodies. Comparable immune responses were observed following vaccination with vaccines produced by different manufacturers.

The serological findings are presented descriptively and were not directly linked to outbreak occurrence or protective thresholds within this study.

Human cases associated with animal outbreaks

Several animal outbreaks were accompanied by human anthrax cases, primarily associated with slaughtering, processing, or handling of infected animals or contaminated meat. Human cases were recorded in multiple regions during years of heightened epidemiological activity, notably in 2016, 2023, and 2024.

Human anthrax cases were reported concurrently with livestock outbreaks during the study period. According to data from the RSE REM of the National Center for Public Health, 127 human cases of anthrax were recorded between 2014 and 2023 within actively functioning soil foci (soil foci are areas contaminated with Bacillus anthracis spores, where the pathogen can persist in the environment for long periods and serve as a source of recurrent anthrax outbreaks) (Fig. 8). For visualization purposes, the infection rate was multiplied by a factor of 10, as plotting it on the same scale as the absolute number of cases would otherwise render its dynamics visually indistinguishable due to substantial differences in magnitude (Fig. 8).

Fig. 8.

Regional and national temporal dynamics of livestock anthrax cases and infection rates in Kazakhstan (2014–2023).

Blue bars indicate the annual number of registered anthrax cases in livestock for each administrative region (upper panels) and nationwide (lower panel). The red line represents the infection rate, which was multiplied by a factor of 10 to improve visual comparability with absolute case counts due to differences in scale. Years without reported cases are shown as zero values.

Discussion

These instances highlight the crucial zoonotic potential of anthrax and the direct public health implications of livestock outbreaks, particularly when appropriate biosecurity measures are not rigorously followed¹⁷. This underscores the necessity for comprehensive public health campaigns focusing on safe handling practices for animal products and heightened awareness regarding the risks of contact with potentially infected livestock¹⁸. Furthermore, the sustained presence of anthrax in Kazakhstan, particularly in regions like Jambyl and Kostanay, suggests the existence of persistent environmental reservoirs or enzootic cycles that continue to pose a risk to both animal and human populations¹⁹.

These findings should be interpreted as descriptive observations that generate hypotheses rather than evidence of causal relationships. The integration of epidemiological, climatic, and serological data provides a combined perspective, although these components were not analyzed within a unified quantitative framework.

The continued incidence of outbreaks despite high vaccination coverage may reflect multiple factors, including variability in vaccination practices and environmental persistence of B. anthracis. The observed regional variation in antibody titers may also reflect differences in exposure intensity rather than solely vaccination-induced immune response. In anthrax-endemic systems, areas with higher environmental contamination may exhibit both increased seroprevalence and elevated outbreak risk. However, the present study did not formally assess the relationship between serological indicators and outbreak occurrence, and this should be addressed in future analyses.

In addition, ecological and socioeconomic factors, such as specific soil properties and human activities, may contribute to disease transmission dynamics, influencing the establishment of new foci and the re-emergence of anthrax from dormant spores²⁰. It should be noted that anthrax vaccination does not confer sterilizing immunity and may be influenced by factors such as vaccination timing, booster intervals, and cold chain integrity. According to official veterinary reports, vaccination coverage in livestock populations in Kazakhstan is generally high (> 97%), and a live anthrax vaccine based on strain 55-VNIIVViM is commonly used. This complexity necessitates an integrated approach, moving beyond vaccination to incorporate detailed spatial epidemiology and ecological modeling to identify and mitigate environmental risk factors⁸. This comprehensive strategy should include advanced molecular epidemiological techniques to trace infection sources and understand transmission pathways more precisely². Moreover, the discrepancies observed between high reported vaccination coverage and the continued occurrence of outbreaks could indicate issues with vaccine efficacy under field conditions, improper vaccine handling, or incomplete coverage of the susceptible animal population^21,22. Alternatively, these discrepancies may highlight the challenge of accurately capturing all livestock movements and the potential for a proportion of the unvaccinated population to serve as a reservoir for B. anthracis²³. This necessitates further investigation into vaccine administration protocols, supply chain integrity, and the actual proportion of immune animals within at-risk populations. Therefore, understanding the underlying reasons for these apparent disparities is critical for optimizing vaccination strategies and achieving effective disease control, potentially through targeted interventions based on fine-scale epidemiological data¹. Additionally, socio-economic factors such as farming practices and market chains can influence disease spread, making community engagement and farmer education critical components of a robust control program, particularly in regions where passive serological surveillance and outbreak-only vaccination are common¹¹. Furthermore, issues related to vaccine batch quality and variations in cold chain maintenance could contribute to insufficient immunity, as observed in other endemic regions²⁴. Such challenges emphasize the need for rigorous post-vaccination monitoring, including regular serological surveys to confirm antibody presence levels across diverse geographic and livestock management contexts.

In addition, the observed epidemiological patterns may be explained by established transmission pathways of B. anthracis. These include ingestion of spores during grazing on contaminated pastures, exposure to infected carcass sites, vector-mediated transmission (e.g., insects), and livestock management practices that influence contact with contaminated environments. However, these pathways were not explicitly quantified in the present study and are discussed here to provide biological context for the observed patterns.

In addition, the available data do not allow distinction between vaccine efficacy and real-world effectiveness, nor do they account for temporal alignment between vaccination and outbreak occurrence.

As a rule, anthrax-endemic zones are located in lowland and foothill landscapes. These areas are characterized by high thermal energy supply and humus content, which may facilitate the vegetation of the anthrax pathogen and, consequently, the stabilization of soil foci. It should be noted that the anthrax pathogen persists longest in chernozems and other humus-rich soils with an alkaline or neutral reaction and significant moisture levels.

Anthrax is a highly dangerous zoonotic infection caused by the bacterium B. anthracis. It is characterized by high fatality rates and is recorded annually among both the population and livestock. The primary epidemiological and epidemiological risks are associated with direct contact with infected animals, consumption of contaminated meat and animal products, processing of infected raw materials, and the long-term persistence of pathogen spores in the soil.

This study has several limitations that should be considered when interpreting the findings. First, the human component was based on aggregated national surveillance data, which did not allow for individual-level analysis or assessment of potential reporting biases. Second, the retrospective design and reliance on officially registered cases may underestimate the true incidence of anthrax, particularly in regions with informal livestock production systems. Third, serological monitoring was conducted in selected regions and may not fully represent the epidemiological situation across the entire territory of Kazakhstan. In addition, environmental and spatial analyses were performed at regional scales and may not capture fine-scale microenvironmental variability affecting B. anthracis spore persistence. Despite these limitations, the integrated analytical approach provides valuable insights into spatial patterns and risk factors associated with livestock anthrax in Kazakhstan.

The ecological design of this study limits the ability to establish causal links between climatic factors, immune response, and outbreak occurrence. The use of officially reported surveillance data may be subject to underreporting and reporting bias, particularly in remote or small-scale livestock systems. In addition, the study relies on officially reported cases, and detailed information on diagnostic confirmation methods was not available, which may introduce potential misclassification bias, particularly in distinguishing B. anthracis from closely related species.

Based on the analysis and comprehensive assessment of the anthrax epidemiological situation in Kazakhstan, a conceptual framework of cascade risk formation was developed. This scheme reflects the stepwise development of the epidemiological process from the soil reservoir to the spatial spread of the infection (Fig. 9). The framework is based on the stratification of seven key risk factors grouped into three hierarchical levels.

Fig. 9.

A systematization scheme of epidemiological safety threats, visualizing the interrelationship between the seven identified risk factors. This figure represents a conceptual framework rather than a quantitative model.

The proposed conceptual framework illustrates a three-level system of increasing epidemiological risk. The first level (Soil Reservoir Zone) reflects the latent persistence of Bacillus anthracis in natural foci and historically contaminated soils, where long-term survival of spores is ensured by soil infectivity, high resistance of spores, and territorial confinement of the pathogen. The second level (Activation Factors Zone) describes the mechanisms triggering the reactivation of soil foci, including climatic and environmental drivers such as extreme temperature fluctuations, floods, droughts, and soil disturbance, as well as the presence of unaccounted or destroyed livestock burial sites that facilitate the upward movement of spores to the surface. The third level (Spread Vector Zone) represents the realization of epidemiological risk through biological and anthropogenic vectors, including domestic and wild animal movement, grazing pressure, and human economic activity, which may facilitate the transmission of infection beyond the enzootic zone and contribute to regional spread. This hierarchical structure suggests that effective control of anthrax outbreaks should not rely solely on monitoring animal movement, but may also require systematic surveillance and management of underlying soil reservoirs and activation factors. These factors are discussed in a general context, as no detailed quantitative assessment of soil and environmental variation across regions was performed in this study.

Future studies should aim to quantitatively assess the relationship between serological indicators, climatic variables, and outbreak occurrence using integrated analytical approaches.

Conclusion

The identification of these underlying factors is important for the development of more effective control and prevention strategies⁴. Such strategies should include improved surveillance systems, targeted interventions in high-risk areas, and enhanced community engagement to promote biosecurity and early reporting of suspected cases. Addressing socio-economic barriers, including the informal nature of household livestock establishments and potential underreporting due to economic incentives, may contribute to improving disease surveillance and control efforts²⁵. Strengthening collaboration between veterinary and public health sectors represents an essential component of a holistic “One Health” approach to managing and mitigating anthrax risks^9,26. This integrated approach can benefit from advanced spatial analysis and molecular techniques to help identify environmental drivers and characterize bacterial strains, thereby refining risk assessments and supporting more evidence-based allocation of resources for control^17,27. Lifting indicators of veterinary measures’ effectiveness may enhance epidemiological surveillance efficiency in historically affected territories in Kazakhstan and potentially reduce the risk of epidemic complications⁹. The observed spatial distribution of anthrax cases, particularly in central regions, suggests the possible presence of a persistent environmental reservoir or enzootic cycle influenced by ecological factors and human activities¹⁷. Further research into soil characteristics, including pH levels and calcium content, may improve understanding of the environmental persistence of Bacillus anthracis spores and their role in anthrax re-emergence²⁸.

Author contributions

MY, VS and AN (Ainur Nurpeisova): conceptualization, Data curation, Project administration, Supervision, Writing—original draft, Writing—review & editing. AK, АА (Akmaral Adambayeva), АА (Altynay Arysbekova), KB, NK, RA, NA (Natalya Akhmanova), ZT: investigation, Methodology, Writing—original draft. RN (Raikhan Nissanova), ZA and AN: investigation, Methodology, Writing—review & editing. HY, NR (Nurkuisa Rametov) ZZ and AN: formal analysis. AN and MK: project administration, Supervision.

Funding

This work was carried out within the framework of the Scientific Research Program IRN BR28712975 “Scientific support of veterinary safety: development of new diagnostic tools and therapeutic and preventive drugs against infectious diseases of animals and birds” (2025–2027), funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan.

Data availability

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Declarations

Competing interests

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.