Spatial distribution and risk areas of foot and mouth disease in mainland China

Spatiotemporal pattern and suitable areas analysis of equine influenza in global scale (2005-2022)

Equine influenza (EI) is a severe infectious disease that causes huge economic losses to the horse industry. Spatial epidemiology technology can explore the spatiotemporal distribution characteristics and occurrence risks of infectious diseases, it has played an important role in the prevention and control of major infectious diseases in humans and animals. For the first time, this study conducted a systematic analysis of the spatiotemporal distribution of EI using SaTScan software and investigated the important environmental variables and suitable areas for EI occurrence using the Maxent model. A total of 517 occurrences of EI from 2005 to 2022 were evaluated, and 14 significant spatiotemporal clusters were identified. Furthermore, a Maxent model was successfully established with high prediction accuracy (AUC = 0.920 ± 0.008). The results indicated that annual average ultraviolet radiation, horse density, and precipitation of the coldest quarter were the three most important environmental variables affecting EI occurrence. The suitable areas for EI occurrence are widely distributed across all continents, especially in Asia (India, Mongolia, and China) and the Americas (Brazil, Uruguay, USA, and Mexico). In the future, these suitable areas will expand and move eastward. The largest expansion is predicted under SSP126 scenarios, while the opposite trend will be observed under SSP585 scenarios. This study presents the spatial epidemiological characteristics of EI for the first time. The results could provide valuable scientific insights that can effectively inform prevention and control strategies in regions at risk of EI worldwide.

Epidemiological characterization and risk assessment of rabbit haemorrhagic disease virus 2 (RHDV2/b/GI.2) in the world

A novel variant of rabbit haemorrhagic disease virus, designated RHDV2/b/GI.2, was first discovered in France in 2010. Subsequently, RHDV2 rapidly spread to Africa, North America, Australia, and Asia. RHDV2 outbreaks have resulted in significant economic losses in the global rabbit industry and disrupted the balance of natural ecosystems. Our study investigated the seasonal characteristics of RHDV2 outbreaks using seasonal indices. RHDV2 is prone to causing significant outbreaks within domestic and wild rabbit populations during the spring season and is more likely to induce outbreaks within wild rabbit populations during late autumn in the Southern Hemisphere. Furthermore, based on outbreak data for domestic and wild rabbits and environmental variables, our study established two MaxEnt models to explore the relationship between RHDV2 outbreaks and the environmental factors and conducted outbreak risk predictions for RHDV2 in global domestic and wild rabbit populations. Both models demonstrated good predictive performance, with AUC values of 0.960 and 0.974, respectively. Road density, isothermality, and population density were identified as important variables in the outbreak of RHDV2 in domestic rabbits, while road density, normalized difference vegetation index, and mean annual solar radiation were considered key variables in the outbreak of RHDV2 in wild rabbits. The environmental factors associated with RHDV2 outbreaks identified in our study and the outbreak risk prediction maps generated in our study will aid in the formulation of appropriate RHDV2 control measures to reduce the risk of morbidity in domestic and wild rabbits.

Spatio-temporal analysis and risk modeling of foot-and-mouth disease outbreaks in China

FMD is an acute contagious disease that poses a significant threat to the health and safety of cloven-hoofed animals in Asia, Europe, and Africa. The impact of FMD exhibits geographical disparities within different regions of China. The present investigation undertook an exhaustive analysis of documented occurrences of bovine FMD in China, spanning the temporal range from 2011 to 2020. The overarching objective was to elucidate the temporal and spatial dynamics underpinning these outbreaks. Acknowledging the pivotal role of global factors in FMD outbreaks, advanced machine learning techniques were harnessed to formulate an optimal prediction model by integrating comprehensive meteorological data pertinent to global FMD. Random Forest algorithm was employed with top three contributing factors including Isothermality(bio3), Annual average temperature(bio1) and Minimum temperature in the coldest month(bio6), all relevant to temperature. By encompassing both local and global factors, our study provides a comprehensive framework for understanding and predicting FMD outbreaks. Furthermore, we conducted a phylogenetic analysis to trace the origin of Foot-and-mouth disease virus (FMDV), pinpointing India as the country posing the greatest potential hazard by leveraging the spatio-temporal attributes of the collected data. Based on this finding, a quantitative risk model was developed for the legal importation of live cattle from India to China. The model estimated an average probability of 0.002254% for FMDV-infected cattle imported from India to China. TA sensitivity analysis identified two critical nodes within the model: he possibility of false negative clinical examination in infected cattle at destination (P5) and he possibility of false negative clinical examination in infected cattle at source(P3). This comprehensive approach offers a thorough evaluation of FMD landscape within China, considering both domestic and global perspectives, thereby augmenting the efficacy of early warning mechanisms.

Epidemiological and genetic characteristics of foot-and-mouth disease virus in China from 2010 to 2022

Foot-and-mouth disease virus (FMDV) is a highly contagious picornavirus that can infect cloven-hoofed animals of significant agricultural importance. In China, foot-and-mouth disease (FMD) epidemics occur annually, resulting in localized outbreaks or sporadic epidemics that cause significant economic losses. This study summarized 123 cases of FMD reported in China between 2010 and 2022, using data from the official website of the Chinese Center for Animal Disease Control and Prevention. The epidemic situation and genetic characteristics of FMDV in China were studied through phylogenetic analysis, amino acid variation analysis of antigenic epitopes, and genetic recombination analysis. The findings provide important references for predicting the FMDV epidemic situation in China, developing vaccines, and effectively preventing and controlling FMD.

Socioeconomic and environmental determinants of foot and mouth disease incidence: an ecological, cross-sectional study across Iran using spatial modeling

Foot-and-mouth disease (FMD) is a highly contagious animal disease caused by a ribonucleic acid (RNA) virus, with significant economic costs and uneven distribution across Asia, Africa, and South America. While spatial analysis and modeling of FMD are still in their early stages, this research aimed to identify socio-environmental determinants of FMD incidence in Iran at the provincial level by studying 135 outbreaks reported between March 21, 2017, and March 21, 2018. We obtained 46 potential socio-environmental determinants and selected four variables, including percentage of population, precipitation in January, percentage of sheep, and percentage of goats, to be used in spatial regression models to estimate variation in spatial heterogeneity. In our analysis, we employed global models, namely ordinary least squares (OLS), spatial error model (SEM), and spatial lag model (SLM), as well as local models, including geographically weighted regression (GWR) and multiscale geographically weighted regression (MGWR). The MGWR model yielded the highest adjusted [Formula: see text] of 90%, outperforming the other local and global models. Using local models to map the effects of environmental determinants (such as the percentage of sheep and precipitation) on the spatial variability of FMD incidence provides decision-makers with helpful information for targeted interventions. Our findings advocate for multiscale and multidisciplinary policies to reduce FMD incidence.

The prevalence of foot-and-mouth disease in Asia

Foot-and-mouth disease (FMD) is listed among the highly contagious diseases in animals and is endemic throughout the Asian continent. The disease is caused by the Foot-and-mouth disease virus (FMDV) and affects a wide variety of domesticated animals as well as wild ungulates. Clinically, the disease is described as a vesicular lesion on the tongue, muzzle, lips, gum, dental pad, interdigital cleft, coronary band, and heel of the foot. Sometimes these lesions give rise to lameness. Mastitis is also caused due to teat lesions. A biochemical test reveals that during FMD infection, there are elevated levels of interleukin-1 (IL-1), tumor necrosis factor-alpha, interferon-gamma (IFN-γ), interleukin-6, serum amyloid A protein, lactoferrin, mannose-binding lectin, and monocytes chemo-attractant protein-1 in the serum of infected animals. There is no specific treatment for FMD although some antivirals are given as prophylaxis and antibiotics are given to prevent secondary bacterial infection. This review presents comprehensive data on the prevalence of FMD and serotypes of FMDV that are attributable to the cause of FMD from a regional point of view. It also explains the worldwide dynamics of the seven serotypes of FMD and tries to identify epidemiological clusters of FMD in various geographical areas. Furthermore, the pathology associated with the foot and mouth disease virus along with the pathophysiology is discussed. The continent-wide prevalence and diversity patterns of FMD suggest that there is a need for stringent policies and legislation implementation regarding research and development aimed at manufacturing strain-specific vaccination, infection prevention, and control of the disease.

DEC-205 receptor targeted poly(lactic-co-glycolic acid) nanoparticles containing Eucommia ulmoides polysaccharide enhances the immune response of foot-and-mouth disease vaccine in mice

Nanoparticles targeting the DEC-205 receptor were found to induce antigen-specific protective immune response. When the delivery system carries both antigens and immunomodulators, it can maximize the expected therapeutic effect of the drug and induce effective humoral and cellular immune responses to antigens.In this study, we encapsulated the Eucommia ulmoides Oliv. polysaccharides (EUPS) into PLGA nanoparticles (NPs) and conjugated it with anti-CD205 monoclonal Ab (MAb) to produce a DEC-205 receptor targeted PLGA nanoparticles (anti-DEC-205-EUPS-PLGA NPs). The physicochemical characteristics and adjuvant activity of the above NPs were evaluated in vitro and in vivo. In the in vitro setting, 200 μg·mL^-1 anti-DEC-205-EUPS-PLGA could improve the proliferation of DCs and promote their antigen up-take activity. In the in vivo setting, anti-DEC-205-EUPS-PLGA NPs remarkably controlled the release of drug and antigen to induce sustained immune responses and up-regulated the levels of FMDV-specific IgG antibodies, promoted the cytotoxic activity of CTLs and NK cells, and improved the proliferation of splenocytes. Moreover, the anti-DEC-205-EUPS-PLGA NPs facilitated the maturation of DCs. The above data indicated that anti-DEC-205-EUPS-PLGA NPs employed as an targeted adjuvant induced the humoral and cellular immune activity by promoting the maturation of DCs. These findings may provide a new insight onto the development of vaccine adjuvants.

A scoping review of foot-and-mouth disease risk, based on spatial and spatio-temporal analysis of outbreaks in endemic settings

Foot-and-mouth disease (FMD) is one of the most important transboundary animal diseases affecting livestock and wildlife species worldwide. Sustained viral circulation, as evidenced by serological surveys and the recurrence of outbreaks, suggests endemic transmission cycles in some parts of Africa, Asia and the Middle East. This is the result of a complex process in which multiple serotypes, multi-host interactions and numerous socio-epidemiological factors converge to facilitate disease introduction, survival and spread. Spatial and spatio-temporal analyses have been increasingly used to explore the burden of the disease by identifying high-risk areas, analysing temporal trends and exploring the factors that contribute to the outbreaks. We systematically retrieved spatial and spatial-temporal studies on FMD outbreaks to summarize variations on their methodological approaches and identify the epidemiological factors associated with the outbreaks in endemic contexts. Fifty-one studies were included in the final review. A high proportion of papers described and visualized the outbreaks (72.5%) and 49.0% used one or more approaches to study their spatial, temporal and spatio-temporal aggregation. The epidemiological aspects commonly linked to FMD risk are broadly categorizable into themes such as (a) animal demographics and interactions, (b) spatial accessibility, (c) trade, (d) socio-economic and (e) environmental factors. The consistency of these themes across studies underlines the different pathways in which the virus is sustained in endemic areas, with the potential to exploit them to design tailored evidence based-control programmes for the local needs. There was limited data linking the socio-economics of communities and modelled FMD outbreaks, leaving a gap in the current knowledge. A thorough analysis of FMD outbreaks requires a systemic view as multiple epidemiological factors contribute to viral circulation and may improve the accuracy of disease mapping. Future studies should explore the links between socio-economic and epidemiological factors as a foundation for translating the identified opportunities into interventions to improve the outcomes of FMD surveillance and control initiatives in endemic contexts.

Climate Change Influences the Spread of African Swine Fever Virus

Climate change is an inevitable and urgent issue in the current world. African swine fever virus (ASFV) is a re-emerging viral animal disease. This study investigates the quantitative association between climate change and the potential spread of ASFV to a global extent. ASFV in wild boar outbreak locations recorded from 1 January 2019 to 29 July 2022 were sampled and investigated using the ecological distribution tool, the Maxent model, with WorldClim bioclimatic data as the predictor variables. The future impacts of climate change on ASFV distribution based on the model were scoped with Representative Concentration Pathways (RCP 2.6, 4.5, 6.0, and 8.5) scenarios of Coupled Model Intercomparison Project 5 (CMIP5) bioclimatic data for 2050 and 2070. The results show that precipitation of the driest month (Bio14) was the highest contributor, and annual mean temperature (Bio1) was obtained as the highest permutation importance variable on the spread of ASFV. Based on the analyzed scenarios, we found that the future climate is favourable for ASFV disease; only quantitative ratios are different and directly associated with climate change. The current study could be a reference material for wildlife health management, climate change issues, and World Health Organization sustainability goal 13: climate action.

A Naked-Eye Visual Reverse Transcription Loop-Mediated Isothermal Amplification with Sharp Color Changes for Potential Pen-Side Test of Foot-and-Mouth Disease Virus

Visual loop-mediated isothermal amplification (LAMP) is qualified to be applied in the field to detect pathogens due to its simplicity, rapidity and cost saving. However, the color changes in currently reported visual reverse transcription LAMP (RT-LAMP) for foot-and-mouth disease virus (FMDV) detection are not so obvious to the naked eye, so interpretation of results is troublesome. In this study, a new naked-eye visual RT-LAMP to detect all seven distinct serotypes of FMDV was established based on the 3D genes by using pH-sensitive neutral red as the indicator, rendering a sharp contrast of color changes between the negative (light orange) and the positive (pink). Analytical sensitivity tests showed that the detection limit of the visual RT-LAMP was 10⁴ copies/µL while those were 10³ and 10⁴ copies/µL for the RT-qPCR and conventional RT-PCR methods, respectively. Specificity tests proved that the established visual RT-LAMP assay had no cross-reactivity with other common livestock viruses. Furthermore, the analysis of 59 clinical samples showed 98.31% and 100% concordance with the RT-qPCR and the RT-PCR, respectively. The pan-serotypic FMD visual RT-LAMP assay could be suitable for a pen-side test of all seven serotypes of FMDV because the results could be easily distinguished by the naked eye without the requirement of complicated instruments and professional technicians. Hence, the novel method may have a promising prospect in field tests which exert an important role in monitoring, preventing, and controlling FMD, especially in regions with no PCR or qPCR instrument available.

Subdistrict-Level Reproductive Number for Foot and Mouth Disease in Cattle in Northern Thailand

Foot and mouth disease (FMD) is an important contagious transboundary disease that causes a significant economic loss for several countries. The FMD virus (FMDV) can spread very rapidly by direct and indirect transmission among susceptible animals. The complexity and magnitude of FMDV transmission at the initial stages of the epidemic can be expressed by the basic reproductive number (R ₀), and furthermore, control strategies can be assessed by the estimation of the effective reproductive number. In this study, we aimed to describe FMD outbreaks among smallholder cattle farms by subdistricts in the northern Thailand and compute the effective reproductive number for outbreaks caused by FMDV serotype O and overall serotypes, including serotype O, serotype A, and unidentified serotype, at the subdistrict level (R _sd ) using an epidemic doubling time method. Field data of FMD outbreaks during 2015-2017 that affected 94 subdistricts in northern Thailand were assessed to estimate the R _sd . Results showed that 63.38% (90/142) of the FMD outbreak episodes in cattle were caused by FMDV serotype O. The average doubling time and the R _sd estimated of the outbreaks caused by FMDV serotype O and overall serotype were 2.80 and 4.67 months, and 1.06 and 1.04, respectively. Our results indicated that transmission of FMD in cattle at the subdistrict level in northern Thailand was not controlled (R _sd > 1), which indicates the endemicity of the disease in the region. Although control measures are in place, the results from this study highlighted the need for enhancing FMD monitoring and control strategies in northern Thailand.

Unpacking the myth between increased government initiatives and reduced selling of dead live stocks in China: An approach towards exploring hidden danger of zoonotic diseases

Prohibiting the unsafe sale of livestock that have died in production and harmlessly disposing of them are key measures to control and prevent outbreaks of zoonotic diseases and exert a great significance for maintaining meat-derived food and public health safety. However, under the strict implementation of governmental initiatives, some farmers still choose to sell dead livestock unsafely in developing countries such as China, Brazil, Mexico, and Kenya, which have become an important hidden danger in preventing and controlling zoonotic diseases. Based on data from 496 pig farmers in Hebei, Henan, and Hubei, China, the Double Hurdle Model was employed to explore the impact of governmental initiatives on the willingness and proportion of dead pigs sold unsafely by farmers. Besides, based on the heterogeneity of organization participation and breeding scale, the impact of governmental initiatives on different scale farmers' unsafely selling behaviors is also discussed. The results showed that the harmless disposal subsidy significantly reduces farmers' willingness to unsafely sell dead pigs (SW, RC = −0.0666, and SE = 0.0261). Still, the impact on the proportion is weak (SP, RC = −0.0502, and SE = 0.0474). Though the effect of supervision punishment is greatly weakened (SW, RC =−0.0381, and SE = 0.0324; SP, RC = −0.0204 and SE = 0.0263), it can significantly enhance the effect of harmless disposal subsidy by creating a good law-abiding environment (SW, RC = −0.1370, and SE = 0.0374; SP, RC = −0.0820, and SE = 0.0431). Governmental initiatives have an undue impact on the unsafe sale of dead livestock by farmers participating in cooperatives. The effects of these measures on different scale farmers' unsafe sale of dead pigs are highly heterogeneous. In addition, the study also found that food and public health safety risk perceptions are important endogenous drivers for curbing farmers selling dead pigs. This research can also provide important inspiration for other countries. The government should raise farmers' risk perception level of food and public safety, optimize governmental initiatives, play the key role of cooperative organization, increase the proportion of dead pigs harmlessly disposed of, and finally eliminate new hidden dangers in the prevention and control of zoonotic diseases.

Modeling the current distribution suitability and future dynamics of Culicoides imicola under climate change scenarios

BACKGROUND

African horse sickness, a transboundary and non-contagious arboviral infectious disease of equids, has spread without any warning from sub-Saharan Africa towards the Southeast Asian countries in 2020. It is imperative to predict the global distribution of Culicoides imicola (C. imicola), which was the main vector of African horse sickness virus.

METHODS

The occurrence records of C. imicola were mainly obtained from the published literature and the Global Biodiversity Information Facility database. The maximum entropy algorithm was used to model the current distribution suitability and future dynamics of C. imicola under climate change scenarios.

RESULTS

The modeling results showed that the currently suitable habitats for C. imicola were distributed in most of the southern part areas of America, southwestern Europe, most of Africa, the coastal areas of the Middle East, almost all regions of South Asia, southern China, a few countries in Southeast Asia, and the whole Australia. Our model also revealed the important environmental variables on the distribution of C. imicola were temperature seasonality, precipitation of coldest quarter, and mean temperature of wettest quarter. Representative Concentration Pathways (RCPs) is an assumption of possible greenhouse gases emissions in the future. Under future climate change scenarios, the area of habitat suitability increased and decreased with time, and RCP 8.5 in the 2070s gave the worst prediction. Moreover, the habitat suitability of C. imicola will likely expand to higher latitudes. The prediction of this study is of strategic significance for vector surveillance and the prevention of vector-borne diseases.