Environmental persistence of foot-and-mouth disease virus applied to endemic regions

Foot-and-Mouth Disease

Foot-and-mouth disease (FMD) is a viral infection of livestock that is an important determinant of global trade in animal products. The disease causes a highly contagious vesicular syndrome of cloven-hoofed animals. Successful control of FMD is dependent upon early detection and recognition of the clinical signs, followed by appropriate notification and response of responsible government entities. Awareness of the clinical signs of FMD amongst producers and veterinary practitioners is therefore the key in protecting US agriculture from the catastrophic impacts of an FMD outbreak. This review summarizes key clinical and epidemiologic features of FMD from a US perspective.

Arthropod-Borne Viruses of Human and Animal Importance: Overwintering in Temperate Regions of Europe during an Era of Climate Change

The past three decades have seen an increasing number of emerging arthropod-borne viruses in temperate regions This process is ongoing, driven by human activities such as inter-continental travel, combined with the parallel emergence of invasive arthropods and an underlying change in climate that can increase the risk of virus transmission and persistence. In addition, natural events such as bird migration can introduce viruses to new regions. Despite the apparent regularity of virus emergence, arthropod-borne viruses circulating in temperate regions face the challenge of the late autumn and winter months where the arthropod vector is inactive. Viruses therefore need mechanisms to overwinter or they will fail to establish in temperate zones. Prolonged survival of arthropod-borne viruses within the environment, outside of both vertebrate host and arthropod vector, is not thought to occur and therefore is unlikely to contribute to overwintering in temperate zones. One potential mechanism is continued infection of a vertebrate host. However, infection is generally acute, with the host either dying or producing an effective immune response that rapidly clears the virus. There are few exceptions to this, although prolonged infection associated with orbiviruses such as bluetongue virus occurs in certain mammals, and viraemic vertebrate hosts therefore can, in certain circumstances, provide a route for long-term viral persistence in the absence of active vectors. Alternatively, a virus can persist in the arthropod vector as a mechanism for overwintering. However, this is entirely dependent on the ecology of the vector itself and can be influenced by changes in the climate during the winter months. This review considers the mechanisms for virus overwintering in several key arthropod vectors in temperate areas. We also consider how this will be influenced in a warming climate.

Phylodynamic analysis of foot-and-mouth disease virus evolution in Mar Chiquita, Argentina

Foot-and-mouth disease is a highly contagious disease affecting cloven-hoofed animals, resulting in considerable economic losses. Its causal agent is foot-and-mouth disease virus (FMDV), a picornavirus. Due to its error-prone replication and rapid evolution, the transmission and evolutionary dynamics of FMDV can be studied using genomic epidemiological approaches. To analyze FMDV evolution and identify possible transmission routes in an Argentinean region, field samples that tested positive for FMDV by PCR were obtained from 21 farms located in the Mar Chiquita district. Whole FMDV genome sequences were obtained by PCR amplification in seven fragments and sequencing using the Sanger technique. The genome sequences obtained from these samples were then analyzed using phylogenetic, phylogeographic, and evolutionary approaches. Three local transmission clusters were detected among the sampled viruses. The dataset was analyzed using Bayesian phylodynamic methods with appropriate coalescent and relaxed molecular clock models. The estimated mean viral evolutionary rate was 1.17 × 10- 2 substitutions/site/year. No significant differences in the rate of viral evolution were observed between farms with vaccinated animals and those with unvaccinated animals. The most recent common ancestor of the sampled sequences was dated to approximately one month before the first reported case in the outbreak. Virus transmission started in the south of the district and later dispersed to the west, and finally arrived in the east. Different transmission routes among the studied herds, such as non-replicating vectors and close contact contagion (i.e., aerosols), may be responsible for viral spread.

Molecular Epidemiology of Foot-and-Mouth Disease Viruses in the Emirate of Abu Dhabi, United Arab Emirates

Foot-and-mouth disease (FMD) is an endemic disease in the United Arab Emirates (UAE) in both wild and domestic animals. Despite this, no systematic FMD outbreak investigation accompanied by molecular characterisation of FMD viruses (FMDVs) in small ruminants or cattle has been performed, and only a single report that describes sequences for FMDVs in wildlife from the Emirate has been published. In this study, FMD outbreaks that occurred in 2021 in five animal farms and one animal market in the Emirate of Abu Dhabi were investigated. Cases involved sheep, goats, and cattle, as well as Arabian oryx (Oryx leucoryx). Twelve samples were positive for FMDV via RT-qPCR, and four samples (Arabian oryx n = 1, goat n = 2, and sheep n = 1) were successfully genotyped using VP1 nucleotide sequencing. These sequences shared 88~98% identity and were classified within the serotype O, Middle East-South Asia topotype (O/ME-SA). Phylogenetic analysis revealed that the Arabian oryx isolate (UAE/2/2021) belonged to the PanAsia-2 lineage, the ANT-10 sublineage, and was closely related to the FMDVs recently detected in neighbouring countries. The FMDV isolates from goats (UAE/10/2021 and UAE/11/2021) and from sheep (UAE/14/2021) formed a monophyletic cluster within the SA-2018 lineage that contained viruses from Bangladesh, India, and Sri Lanka. This is the first study describing the circulation of the FMDV O/ME-SA/SA-2018 sublineage in the UAE. These data shed light on the epidemiology of FMD in the UAE and motivate further systematic epidemiological studies and genomic sequencing to enhance the ongoing national animal health FMD control plan.

Seasonal dynamics of the wild rodent faecal virome

Viral discovery studies in wild animals often rely on cross-sectional surveys at a single time point. As a result, our understanding of the temporal stability of wild animal viromes remains poorly resolved. While studies of single host-virus systems indicate that host and environmental factors influence seasonal virus transmission dynamics, comparable insights for whole viral communities in multiple hosts are lacking. Utilizing noninvasive faecal samples from a long-term wild rodent study, we characterized viral communities of three common European rodent species (Apodemus sylvaticus, A. flavicollis and Myodes glareolus) living in temperate woodland over a single year. Our findings indicate that a substantial fraction of the rodent virome is seasonally transient and associated with vertebrate or bacteria hosts. Further analyses of one of the most common virus families, Picornaviridae, show pronounced temporal changes in viral richness and evenness, which were associated with concurrent and up to ~3-month lags in host density, ambient temperature, rainfall and humidity, suggesting complex feedbacks from the host and environmental factors on virus transmission and shedding in seasonal habitats. Overall, this study emphasizes the importance of understanding the seasonal dynamics of wild animal viromes in order to better predict and mitigate zoonotic risks.

Patterns of foot-and-mouth disease virus detection in environmental samples in an endemic setting

Foot-and-Mouth Disease virus (FMDV) is endemic in several regions and is a virus that can persist in the environment dependent on pH, relative humidity (RH), temperature, and matrix (i.e., soil, water, or air). Our previously published analysis of available viral persistence data showed that persistence is likely affected by interactions between RH, temperature, and matrix. Understanding these relationships will aid efforts to eliminate FMD, which has significant impacts on economies and food security. In Cameroon, West Africa, the livestock system consists of mobile (transhumant), transboundary trade and sedentary herds. Studying this system can provide information about the patterns of environmental detection of FMDV RNA that may influence approaches to virus elimination on premises during an outbreak. To improve our understanding of these patterns, we collected samples from individuals, vehicles, and along cattle pathways at three sedentary herds beginning on day one of owner-reported outbreaks, ending by day 30, and tested for the presence of FMD viral RNA using rRT-PCR. Our analysis suggests that detection decreases in soil surface samples with increased distance from herd and time from the first report of disease. Whereas time but not distance decreases detection in air samples. Interaction of RH and temperature suggests increased detection at high temperatures (>24°C) and RH (>75%), providing us with new information about the patterns of FMD viral RNA detection in and around cattle herds that could help to inform targeted virus elimination strategies, such as location and application of disinfectants.

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.

Epidemiology of foot-and-mouth disease outbreaks in Thailand from 2011 to 2018

Foot-and-mouth disease (FMD) is one of the most important animal diseases hindering livestock production in Thailand. In this study, a temporal and spatial analysis at the subdistrict level was performed on FMD outbreak reports in Thailand from 2011 to 2018. Risk factors associated with FMD outbreaks were furthermore investigated using generalized estimating equations. The results showed that the incidence of FMD outbreaks was the highest in 2016 and was affected by season, with a peak in FMD outbreaks occurring in the rainy-winter season, during October to December. FMD outbreaks were mostly distributed in small clusters within a few subdistricts. Some high-risk areas with repeated outbreaks were detected in the central regions. Risk factors, including the increase of subdistrict's size of the dairy population, beef population or pig population, the low percentage of forest area, subdistricts in the provinces adjacent to Malaysia, the presence of a livestock market and the occurrence of an FMD outbreak in a neighbouring subdistrict in the previous month significantly increased the odds of having an FMD outbreak. The increase in proximity to the nearest subdistrict with an FMD outbreak in the previous month decreased the odds of having FMD outbreaks. This study helped to identify high-risk areas and periods of FMD outbreaks in Thailand. Together with the identified risk factors, its results can be used to optimize the FMD control programme in Thailand and in other countries having a similar livestock industry and FMD situation.

A model exploration of carrier and movement transmission as potential explanatory causes for the persistence of foot-and-mouth disease in endemic regions

Foot-and-mouth disease (FMD) is a virulent and economically important disease of livestock, still endemic in many areas of Asia and sub-Saharan Africa. Transmission from persistently infected livestock, also known as carriers, has been proposed as a mechanism to support the persistence of FMD in endemic regions. However, whether carrier livestock can infect susceptible animals is controversial; recovered virus is infectious and there are claims of field transmission, but it remains undemonstrated experimentally. Alternate hypotheses for persistence include the movement of livestock within and between regions, and fomite contamination of the environment. Using a stochastic compartmental ordinary differential equation (ODE) model, we investigate the minimum rates of carrier transmission necessary to contribute to the maintenance of FMD in a region, and compare this to the alternate mechanism of persistence through cattle shipments. We find that carrier transmission can theoretically support persistence even at transmission rates much lower than the highest realistic rates previously proposed, and that the parameters with the most effect on the feasibility of carrier-mediated persistence are the average duration of both the carrier phase and natural immunity. However, shipment-mediated persistence remains a viable alternate mechanism for persistence without carrier transmission.

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

Foot-and-mouth disease (FMD) is a severe infectious disease in animal, which affects regional economies and food security of many countries. A total of 109 FMD outbreaks in China (from 2010 to 2019) were assessed. To investigate whether the FMD outbreaks were significantly aggregated in China, spatio-temporal cluster analysis was performed. A MaxEnt model was established to identify high risk areas for FMD in China and to identify relevant risk factors. As a result, both the FMD serotype A and O had one cluster each. Roads density, isothermality, UV-B seasonality and railways density were identified as important factors that affect the occurrence of FMD serotype A. The minimum temperature of the coldest month contributed most to FMD serotype O outbreak, followed by railways density and markets distribution. This study may provide useful information for decision makers for the tailoring of a risk-based surveillance of FMD in China.

Foot-and-Mouth Disease Space-Time Clusters and Risk Factors in Cattle and Buffalo in Bangladesh

Foot-and-mouth disease (FMD) is highly endemic in Bangladesh. Using passive surveillance data (case records from all 64 districts of Bangladesh, 2014–2017) and district domestic ruminant population estimates, we calculated FMD cumulative incidence per 10,000 animals at risk per district, conducted cluster (Moran’s spatial autocorrelation and scan statistics) and hotspot analysis (local indicator of spatial association statistic), created predictive maps and identified risk factors using a geographically weighted regression model. A total of 548,817 FMD cases in cattle and buffalo were reported during the four-year study period. The highest proportion (31.5%) of cases were reported during the post-monsoon season, and from Chattogram (29.2%) division. Five space-time clusters, 9 local clusters, and 14 hotspots were identified. Overall, higher cumulative incidences of FMD were consistently predicted in eastern parts of Bangladesh. The precipitation in the pre-monsoon season (p = 0.0008) was positively associated with FMD in Bangladesh. Results suggest climate plays an important role in the epidemiology of FMD in Bangladesh, and high risk zones exist. In a resource limited-setting, hotspots and clusters should be prioritized for vaccination coverage, and surveillance for FMD should be targeted in eastern areas of Bangladesh and during the post-monsoon season.