Leaderless foot-and-mouth disease virus serotype O did not cause clinical disease and failed to establish a persistent infection in cattle.

The foot-and-mouth disease virus (FMDV) Leader proteinase Lpro inhibits host mRNA translation and blocks the interferon response which promotes viral survival. Lpro is not required for viral replication in vitro but serotype A FMDV lacking Lpro has been shown to be attenuated in cattle and pigs. However, it is not known, whether leaderless viruses can cause persistent infection in vivo after simulated natural infection and whether the attenuated phenotype is the same in other serotypes. We have generated an FMDV O/FRA/1/2001 variant lacking most of the Lpro coding region (ΔLb). Cattle were inoculated intranasopharyngeally and observed for 35 days to determine if O FRA/1/2001 ΔLb is attenuated during the acute phase of infection and whether it can maintain a persistent infection in the upper respiratory tract. We found that although this leaderless virus can replicate in vitro in different cell lines, it is unable to establish an acute infection with vesicular lesions and viral shedding nor is it able to persistently infect bovine pharyngeal tissues.

[Proceedings of the International Symposium of the World Association of Veterinary Laboratory Diagnosticians, 2023]. / Compte-rendu du Symposium international de la Société mondiale des Laboratoires vétérinaires de diagnostic, 2023.

The International Symposium of the World Association of Veterinary Laboratory Diagnosticians (ISWAVLD) is the unmissable biannual meeting of all diagnostic veterinary laboratories including biologists, veterinarians and other scientists involved in laboratory diagnostics. It took place at the Lyon Convention Centre (29 June-1 July 2023). It was a pleasant and enriching moment, which allowed participants to discover and/or discuss new diagnostic methods and the epidemiology of animal diseases, around all themes involving veterinarians (animal health, but also environmental and human health, and food safety).

Development of a primary cell model derived from porcine dorsal soft palate for foot-and-mouth disease virus research and diagnosis.

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed animals that has a significant socio-economic impact. One concern associated with this disease is the ability of its etiological agent, the FMD virus (FMDV), to persist in its hosts through underlying mechanisms that remain to be elucidated. While persistence has been described in cattle and small ruminants, it is unlikely to occur in pigs. One of the factors limiting the progress in understanding FMDV persistence and, in particular, differential persistence is the lack of suitable in vitro models. A primary bovine cell model derived from the dorsal soft palate, which is the primary site of replication and persistence of FMDV in cattle, has been developed, and it seemed relevant to develop a similar porcine model. Cells from two sites of FMDV replication in pigs, namely, the dorsal soft palate and the oropharyngeal tonsils, were isolated and cultured. The epithelial character of the cells from the dorsal soft palate was then assessed by immunofluorescence. The FMDV-sensitivity of these cells was assessed after monolayer infection with FMDV O/FRA/1/2001 Clone 2.2. These cells were also grown in multilayers at the air-liquid interface to mimic a stratified epithelium susceptible to FMDV infection. Consistent with what has been shown in vivo in pigs, our study showed no evidence of persistence of FMDV in either the monolayer or multilayer model, with no infectious virus detected 28 days after infection. The development of such a model opens up new possibilities for the study and diagnosis of FMDV in porcine cells.

Foot and mouth disease virus: transmission, pathogenesis, diagnosis and surveillance / Le virus de la fièvre aphteuse : transmission, pathogenèse, diagnostic et surveillance

Foot-and-mouth disease (FMD) is one of the most contagious viral animal diseases. It is an old disease which still poses a permanent threat of re-emergence for free zones. Foot-and-Mouth Disease Virus (FMDV), a Picornavirus belonging to genus Aphthovirus affects domestic and wild artiodactyls. FMD has a considerable socio-economic impact on agricultural production and trade in endemic regions, but also when incursions occur into FMD free areas, as in Europe in 2001. FMDV is historically one of the most studied viruses. Due to its high genetic and antigenic variability, the absence of cross-immunity between its seven serotypes, its ability to survive in the environment, its high contagiousness, its wide range of hosts and its particular biology, FMDV remains of major interest in animal health and the subject of many research projects. This review presents different aspects of FMDV infection, ranging from basic biology to diagnosis, surveillance and control.

La fièvre aphteuse (FA) est l'une des maladies virales animales les plus contagieuses. Bien que très ancienne, la FA reste toujours d'actualité et représente une menace permanente de réémergence pour les pays indemnes. Le virus de la FA ou FMDV (pour foot-and-mouth disease virus), de la famille Picornaviridae, genre Aphthovirus, affecte les artiodactyles domestiques comme sauvages (principalement bovins, ovins, caprins, porcins, camélidés et cervidés). La fièvre aphteuse a un impact socio-économique considérable sur la production et le commerce agricoles en zone d'enzootie mais également en cas d'incursion dans une zone précédemment indemne comme ce fut le cas en 2001 en Europe. Le virus de la FA est historiquement l'un des virus les plus étudiés. Par sa grande variabilité génétique et antigénique, l'absence d'immunité croisée entre ses sept sérotypes, sa capacité de survie dans l'environnement, sa grande contagiosité, son large spectre d'hôtes ainsi que sa biologie particulière, ce virus reste d'intérêt majeur en santé animale et l'objet de nombreux travaux de recherche. Cette revue vise à présenter différents aspects de l'infection par le virus de la fièvre aphteuse et ses problématiques actuelles, de la biologie fondamentale au diagnostic en passant par la surveillance et les moyens de lutte.

Identification of diffusion routes of O/EA-3 topotype of foot-and-mouth disease virus in Africa and Western Asia between 1974 and 2019 - a phylogeographic analysis.

Foot-and-mouth disease (FMD) affects the livestock industry and socioeconomic sustainability of many African countries. The success of FMD control programs in Africa depends largely on understanding the dynamics of FMD virus (FMDV) spread. In light of the recent outbreaks of FMD that affected the North-Western African countries in 2018 and 2019, we investigated the evolutionary phylodynamics of the causative serotype O viral strains all belonging to the East-Africa 3 topotype (O/EA-3). We analyzed a total of 489 sequences encoding the FMDV VP1 genome region generated from samples collected from 25 African and Western Asian countries between 1974 and 2019. Using Bayesian evolutionary models on genomic and epidemiological data, we inferred the routes of introduction and migration of the FMDV O/EA-3 topotype at the inter-regional scale. We inferred a mean substitution rate of 6.64 × 10-3  nt/site/year and we predicted that the most recent common ancestor for our panel of samples circulated between February 1967 and November 1973 in Yemen, likely reflecting the epidemiological situation in under sampled cattle-exporting East African countries. Our study also reinforces the role previously described of Sudan and South Sudan as a frequent source of FMDVs spread. In particular, we identified two transboundary routes of O/EA-3 diffusion: the first from Sudan to North-East Africa, and from the latter into Israel and Palestine AT; a second from Sudan to Nigeria, Cameroon, and from there to further into West and North-West Africa. This study highlights the necessity to reinforce surveillance at an inter-regional scale in Africa and Western Asia, in particular along the identified migration routes for the implementation of efficient control measures in the fight against FMD.

Molecular characterization of encephalomyocarditis virus strains isolated from an African elephant and rats in a French zoo.

In November 2013, a fatal encephalomyocarditis virus (EMCV) case in a captive African elephant (Loxodonta africana) occurred at the Réserve Africaine de Sigean, a zoo in the south of France. Here we report the molecular characterization of the EMCV strains isolated from samples collected from the dead elephant and from 3 rats (Rattus rattus) captured in the zoo at the same time. The EMCV infection was confirmed by reverse-transcription real-time PCR (RT-rtPCR) and genome sequencing. Complete genome sequencing and sequence alignment indicated that the elephant's EMCV strain was 98.1-99.9% identical to the rat EMCV isolates at the nucleotide sequence level. Phylogenetic analysis of the ORF, P1, VP1, and 3D sequences revealed that the elephant and rat strains clustered into lineage A of the EMCV 1 group. To our knowledge, molecular characterization of EMCV in France and Europe has not been reported previously in a captive elephant. The full genome analyses of EMCV isolated from an elephant and rats in the same outbreak emphasizes the role of rodents in EMCV introduction and circulation in zoos.

Inter-laboratory comparison of 2 ELISA kits used for foot-and-mouth disease virus nonstructural protein serology.

Serologic assays used to detect antibodies to nonstructural proteins (NSPs) of foot-and-mouth disease virus (FMDV) are used for disease surveillance in endemic countries, and are essential to providing evidence for freedom of the disease with or without vaccination and to recover the free status of a country after an outbreak. In a 5-site inter-laboratory study, we compared the performance of 2 commercial NSP ELISA kits (ID Screen FMD NSP ELISA single day [short] and overnight protocols, ID.Vet; PrioCHECK FMDV NS antibody ELISA, Thermo Fisher Scientific). The overall concordance between the PrioCHECK and ID Screen test was 93.8% (95% CI: 92.0-95.2%) and 94.8% (95% CI: 93.1-96.1%) for the overnight and short ID Screen incubation protocols, respectively. Our results indicate that the assays (including the 2 different formats of the ID Screen test) can be used interchangeably in post-outbreak serosurveillance.

Bovine Organospecific Microvascular Endothelial Cell Lines as New and Relevant In Vitro Models to Study Viral Infections.

Microvascular endothelial cells constitute potential targets for exogenous microorganisms, in particular for vector-borne pathogens. Their phenotypic and functional variations according to the organs they are coming from provide an explanation of the organ selectivity expressed in vivo by pathogens. In order to make available relevant tools for in vitro studies of infection mechanisms, our aim was to immortalize bovine organospecific endothelial cells but also to assess their permissivity to viral infection. Using transfection with SV40 large T antigen, six bovine microvascular endothelial cell lines from various organs and one macrovascular cell line from an umbilical cord were established. They display their own panel of endothelial progenitor/mature markers, as assessed by flow cytometry and RT-qPCR, as well as the typical angiogenesis capacity. Using both Bluetongue and foot-and-mouth disease viruses, we demonstrate that some cell lines are preferentially infected. In addition, they can be transfected and are able to express viral proteins such as BTV8-NS3. Such microvascular endothelial cell lines bring innovative tools for in vitro studies of infection by viruses or bacteria, allowing for the study of host-pathogen interaction mechanisms with the actual in vivo target cells. They are also suitable for applications linked to microvascularization, such as anti-angiogenic and anti-tumor research, growing fields in veterinary medicine.

The antibody response induced FMDV vaccines in sheep correlates with early transcriptomic responses in blood.

Foot and mouth disease (FMD) is a highly contagious viral disease with high economic impact, representing a major threat for cloven-hooved mammals worldwide. Vaccines based on adjuvanted inactivated virus (iFMDV) induce effective protective immunity implicating antibody (Ab) responses. To reduce the biosafety constraints of the manufacturing process, a non-replicative human adenovirus type 5 vector encoding FMDV antigens (Ad5-FMDV) has been developed. Here we compared the immunogenicity of iFMDV and Ad5-FMDV with and without the ISA206VG emulsion-type adjuvant in sheep. Contrasted Ab responses were obtained: iFMDV induced the highest Ab levels, Ad5-FMDV the lowest ones, and ISA206VG increased the Ad5-FMDV-induced Ab responses to protective levels. Each vaccine generated heterogeneous Ab responses, with high and low responders, the latter being considered as obstacles to vaccine effectiveness. A transcriptomic study on total blood responses at 24 h post-vaccination revealed several blood gene module activities correlating with long-term Ab responses. Downmodulation of T cell modules' activities correlated with high responses to iFMDV and to Ad5-FMDV+ISA206VG vaccines as also found in other systems vaccinology studies in humans and sheep. The impact of cell cycle activity depended on the vaccine types, as it positively correlated with higher responses to iFMDV but negatively to non-adjuvanted Ad5-FMDV. Finally an elevated B cell activity at 24 h correlated with high Ab responses to the Ad5-FMDV+ISA206VG vaccine. This study provides insights into the early mechanisms driving the Ab response induced by different vaccine regimens including Ad5 vectors and points to T cell modules as early biomarker candidates of different vaccine-type efficacy across species.

Model of persistent foot-and-mouth disease virus infection in multilayered cells derived from bovine dorsal soft palate.

Foot-and-mouth disease virus (FMDV) causes a highly contagious vesicular disease in livestock, with serious consequences for international trade. The virus persists in the nasopharynx of cattle and this slows down the process to obtain an FMDV-free status after an outbreak. To study biological mechanisms, or to identify molecules that can be targeted to diagnose or interfere with persistence, we developed a model of persistent FMDV infection in bovine dorsal soft palate (DSP). Primary DSP cells were isolated after commercial slaughter and were cultured in multilayers at the air-liquid interface. After 5 weeks of culture without further passage, the cells were infected with FMDV strain O/FRA/1/2001. Approximately, 20% of cells still had a polygonal morphology and displayed tight junctions as in stratified squamous epithelia. Subsets of cells expressed cytokeratin and most or all cells expressed vimentin. In contrast to monolayers in medium, multilayers in air demonstrated only a limited cytopathic effect. Integrin αV ß6 expression was observed in mono- but not in multilayers. FMDV antigen, FMDV RNA and live virus were detected from day 1 to 28, with peaks at day 1 and 2. The proportion of infected cells was highest at 24 hr (3% and 36% of cells at an MOI of 0.01 and 1, respectively). At day 28 after infection, at a time when animals that still harbour FMDV are considered carriers, FMDV antigen was detected in 0.2%-2.1% of cells, in all layers, and live virus was isolated from supernatants of 6/8 cultures. On the consensus level, the viral genome did not change within the first 24 hr after infection. Only a few minor single nucleotide variants were detected, giving no indication of the presence of a viral quasispecies. The air-liquid interface model of DSP brings new possibilities to investigate FMDV persistence in a controlled manner.

Seroprevalence and molecular characterization of foot-and-mouth disease virus in Chad.

This study aimed at determining the seroprevalence of foot-and-mouth disease (FMD) in domestic ruminants and at characterizing the virus strains circulating in four areas of Chad (East Batha, West Batha, Wadi Fira and West Ennedi). The study was carried out between October and November 2016. A total of 1,520 sera samples (928 cattle, 216 goats, 254 sheep and 122 dromedaries) were collected randomly for FMD serological analyses. Nine epithelial tissue samples were also collected from cattle showing clinical signs, for FMDV isolation and characterization. Serological results showed an overall NSP seroprevalence of 40% (375/928) in cattle in our sample (95% CrI [19-63]). However, seroprevalences of 84% (27/32), 78% (35/45) and 84% (21/25) were estimated in cattle over 5 years of age in East Batha, West Batha and Wadi Fira, respectively. In cattle under 1 year of age, 67% (18/27) seroprevalence was estimated in Wadi Fira, 64% (14/22) in East Batha and 59% (13/22) in West Batha. It was found that the high seroprevalences have been obtained in areas where pastures are shared by several different herds but also in farms where two to three species (bovine, caprine and ovine) are raised together. ELISA PrioCHECK® FMDV types O and A and in-house solid phase competition ELISA serotyping results showed that the four O, A, SAT1 and SAT2 serotypes have circulated in Chad in 2016. However, the type SAT2 dominated with an overall seroprevalence of 43% (29/67) and was present in the four areas investigated. The phylogenetic analyses of the VP1 coding sequence allowed determining the serotype SAT2 topotype VII, close to viral strains found in Cameroon in 2015 with a similarity of 98.60%.

Acute death associated with Citrobacter freundii infection in an African elephant (Loxodonta africana).

A 21-year-old male African elephant (Loxodonta africana) died suddenly with no previous medical history. Grossly, there were severe multifocal epicardial and endocardial hemorrhages of the atria and ventricles, hydropericardium, multifocal pleural hemorrhages, and severe pulmonary congestion and edema. Histologically, there was fibrinoid vasculitis and thrombosis in the heart and lung and myocardial necrosis. Citrobacter freundii was isolated in abundance in pure culture from liver and heart samples. Low levels of multiples types of elephant endotheliotropic herpesvirus (EEHV-6, EEHV-2B, and EEHV-3A) were detected in spleen samples, but not in heart samples. The levels of EEHV DNA found were much lower than those usually associated with acute EEHV hemorrhagic disease, and many other genomic loci that would normally be found in such cases were evidently below the level of detection. Therefore, these findings are unlikely to indicate lethal EEHV disease. Polymerase chain reaction for encephalomyocarditis virus (EMCV) and toxicology for oleander (Nerium oleander) were negative. Stress, resulting from recent transport, and antimicrobial therapy may have contributed to the death of this animal.

Establishment of persistent foot-and-mouth disease virus (FMDV) infection in MDBK cells.

In addition to acute infection and disease, foot-and-mouth disease virus (FMDV) can cause persistent infection in ruminants. Such "carrier" animals represent a potential risk for FMDV transmission to susceptible animals. However, the mechanisms and the factors that determine FMDV persistence remain unknown. We describe here the establishment of FMDV type O persistent infection in a bovine epithelial cell line (Madin-Darby bovine kidney; MDBK). Preliminary experiments to assess the permissivity of MDBK cells to FMDV O infection revealed an unusual pattern of infection: after the initial phase of acute cell lysis, new monolayers formed within 48-72 h post-infection. We found that some cells survived cytolytic infection and subsequently regrew, thereby demonstrating that this bovine cell line can be persistently infected with FMDV type O. Further evidence that MDBK cells were persistently infected with FMDV includes: (i) detection of viral RNA in cells as well as in cell culture supernatants, (ii) detection of viral antigens in the cells by immunofluorescence analysis, and (iii) production of infectious viral particles for up to 36 cell passages. Furthermore, preliminary sequence analysis of persistent virus revealed a single nucleotide substitution within the VP1 coding region, resulting in the V50A amino acid substitution. This bovine model of FMDV persistence holds promise for the investigation of the viral and cellular molecular determinants that promote FMDV persistence.

FATAL ENCEPHALOMYOCARDITIS VIRUS INFECTION IN AN AFRICAN SAVANNA ELEPHANT (LOXODONTA AFRICANA) IN A FRENCH ZOO.

A fatal case of encephalomyocarditis virus (EMCV) involving an African elephant ( Loxodonta africana ) occurred in November 2013 at the Réserve Africaine de Sigean, France. An adult female was found dead without any preliminary symptoms. Gross pathologic changes consisted of petechiae and hemorrhages on mucosae and internal organs, abundant transudate in the abdominal and pericardial cavities, and myocarditis. Histopathologic examination showed extensive degeneration and necrosis of ventricular cardiomyocytes with concurrent lymphoplasmocytic and eosinophilic infiltrate. An EMCV was isolated from several organs and considered the causative agent of the myocarditis. The same strain of virus was also isolated in rodents captured on zoo premises and considered to be the reservoir of the virus. To the authors' knowledge, this is the first EMCV case in a captive African elephant in Europe.

Novel bluetongue virus in goats, Corsica, France, 2014.

During 2000-2013, 4 genotypes of bluetongue virus (BTV) were detected in Corsica, France. At the end of 2013, a compulsory BTV-1 vaccination campaign was initiated among domestic ruminants; biological samples from goats were tested as part of a corresponding monitoring program. A BTV strain with nucleotide sequences suggestive of a novel serotype was detected.

First isolation and molecular characterization of foot-and-mouth disease virus in Benin.

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed animals. It is one of the most economically devastating diseases affecting livestock animals. In West Africa, where constant circulation of FMD virus (FMDV) is assumed, very few studies on the characterization of circulating strains have been published. This study describes the first isolation and characterization of FMDV in Benin. FMDV was isolated from 42 samples. Antigen Capture Elisa (Ag-ELISA) and VP1 coding sequence analysis revealed 33 strains of serotype O and 9 strains of serotype A. Phylogenetic analysis of the VP1 sequence revealed two different groups of type O isolates and one group of A isolates. VP1 sequence comparison with the sequences available in the GenBank database revealed a close relationship of the Benin isolates with topotype O of West Africa and with African topotype A of genotype VI. Knowledge of the recent strains circulating in Benin should contribute to better selection of vaccine strains and enable the updating of molecular epidemiology data available for West Africa in general.