Transboundary and Emerging Diseases

African swine fever (ASF) is a highly contagious and lethal viral disease of swine with significant socio-economic impact in the developed and developing world. Since its reintroduction in 2007 in the Republic of Georgia, the disease has spread dramatically thorough Europe and Asia. Among the most affected countries in Europe is Romania, which initially reported the disease in 2017 and in 2018-2019 lost about 1 million pigs. There is no molecular characterization of the virus circulating in Romania during that reported period; therefore, the purpose of this study was to provide an initial molecular characterization using samples collected from two farms affected by ASFV. The causative strain belongs to genotype II, and its closest relatives are the strains circulating in Belgium, Russia, and China.

ObjectivesCorynebacteria of the diphtheriae complex (Cdc) can cause diphtheria in humans and have been reported from companion animals. We aimed to describe animal infection cases caused by Cdc isolates. Methods18 308 animals (dogs, cats, horses and small mammals) with rhinitis, dermatitis, non-healing wounds and otitis were sampled in metropolitan France (August 2019 to August 2021). Data on symptoms, age, breed, and the administrative region of origin were collected. Cultured bacteria were analyzed for tox gene presence, for production of the diphtheria toxin, for antimicrobial susceptibility, and genotyped by multilocus sequence typing. ResultsC. ulcerans was identified in 51 cases, 24 of which were toxigenic. Rhinitis was the most frequent presentation (18/51). Eleven cases (6 cats, 4 dogs, 1 rat) were mono-infections. Large breed dogs, especially German Shepherds (9 of 28 dogs; p < 0.00001) were overrepresented. C. ulcerans isolates were susceptible to all tested antibiotics. tox-positive C. diphtheriae was identified in 2 horses. Last, 11 infections cases (9 dogs, 2 cats; mostly chronic otitis, and 2 sores) had tox-negative C. rouxii, a recently defined species. C. rouxii and C. diphtheriae isolates were susceptible to most antibiotics tested, and almost all of these infections were polymicrobial. ConclusionsMonoinfections with C. ulcerans point towards a primary pathogenic potential to animals. C. ulcerans represents an important zoonotic risk, and C. rouxii may represent a novel zoonotic agent. This case series provides novel clinical and microbiological data on Cdc infections, and underlines the need for management of animals and their human contacts. ImportanceWe report on the occurrence, clinical and microbiological characteristics of infections caused by members of the Corynebacteria of the diphtheriae complex (Cdc) in companion animals. This is the first study based on the systematic analysis of a very large animal cohort (18 308 samples), which provides data on the frequency of Cdc isolates in various types of clinical samples from animals. Awareness of this zoonotic bacterial group remains low among veterinarians and veterinary laboratories, among which it is often considered a commensal bacteria of animals. We suggest that in case of Cdc detection in animals, the veterinary laboratories should be encouraged to send the samples to a reference laboratory for analysis of the presence of the tox gene. This work is relevant to the development of guidelines in case of Cdc infections in animals, and underlines their public health relevance given the zoonotic transmission risk.

Leptospirosis is a zoonosis of great impact on public health since it is considered a notifiable disease occurring mainly in tropical regions with poor sanitation and vulnerable socioeconomic conditions. It is caused by bacteria of the genus Leptospira and phylum Spirochaetes and contamination occurs through direct or indirect contact with the contaminating agent. In addition to taxonomic classification, which is performed through sequencing and the analysis of some marker genes, such as 16S rRNA and secY, they are usually classified based on their antigenic characteristics into serogroups and serovars. This kind of classification is largely applied in epidemiological studies and vaccine development. Despite its importance, few studies have been conducted to understand the evolutionary dynamics of the emergence or change of serology in this genus. In view of this, we applied phylogenetic methods in order to understand the evolutionary processes involving the serology of the genus. To this end, sequences of genes comprising the rfb locus from samples of serogroups Sejroe, Mini, and Hebdomadis (34 samples) were extracted and submitted to the phylogenetic pipeline, resulting in the inference of 75 maximum likelihood trees. Topology tests showed that most of the gene trees are significantly different from the species tree. We could depict the occurrence of lateral gene transfer between L. borgpetersenii and L. kirschneri; and L. interrogans and L. weilli. In this analysis, no evidence was found for the lateral gene transfer between samples of the Hardjo serovar of L. interrogans and L. borgpetersenii. Thus, it is also suggested that the occurrence of horizontal transfer of genes from the rfb locus between distinct species is less frequent than expected.

We report the transmission of SARS-CoV-2 Omicron variant from a COVID-19 symptomatic individual to two domestic rats, one of which developed severe symptoms. Omicron carries several mutations which permit rodent infection. This report demonstrates that pet, and likely wild, rodents could therefore contribute to SARS-CoV-2 spread and evolution.

Porcine reproductive and respiratory syndrome (PRRSV) remains costly for the swine industry. Measures intended to irradicate or reduce the prevalence of PRRSV have limited effectiveness. Vaccination, the primary control strategy for PRRSV, has yet to be thoroughly investigated to ensure an optimal strategy is being implemented. Due to insufficient cross-immunity between strains, it is prudent to administer the most influential vaccine for the most dominant or threatening PRRSV strain in circulation at a given time. With this in mind, we demonstrated the benefits of targeted vaccination using metapopulation-based modeling. By using up-to-date data describing real farms to simulate the effects of variable vaccine efficacy in both a single and a double strain system, we showed that tailoring vaccines to prevalent PRRSV strains reduces infections, but using multiple vaccines may be more effective if strains vary in vaccine response. Therefore, the impact of the strain-specific effectiveness of market vaccines, paired with computational methods that allow tracking the effects on PRRVS dissemination at individual barns.

Two samples positive for the same strain (2103CP) of human astrovirus (HAstV) were identified during an acute gastroenteritis outbreak in Beijing, China. A full genomic analysis showed that for both samples, open reading frame 1a (ORF1a) clustered with HAstV-1, whereas ORF1b and ORF2 clustered with HAstV-5. The recombination site was detected upstream of the region where ORF1a and ORF1b overlapped. Recombinant HAstV-5 strains were reported previously in China in 2013 and 2021. Our results indicate the need for continuous surveillance of the prevalence and evolution of this recombinant HAstV-5 in China.

We describe the first detection in the European Union of the epizootic haemorrhagic disease virus (EHDV). EHDV-8 has been detected in cattle farms in Sardinia and Sicily. The virus has a direct Northern African origin as its genome is identical (>99.9% nucleotide sequence identity) to EHDV-8 strains detected in Tunisia in 2021/2022.

Foodborne diseases (FBD) constitute a significant worldwide concern with both health and socioeconomic repercussions. FBD predominantly manifest with gastrointestinal symptoms. Nevertheless, extraintestinal infections and symptoms caused by foodborne pathogens are increasingly being reported worldwide. Furthermore, FBD caused by drug resistant bacteria causing both intestinal and extra-intestinal FBD (EIFBD) has further exacerbated their burden. This review (i) summarizes the status of intestinal foodborne pathogens, (ii) delineates the drivers, highlights the (iii) genomic evidence, and (iv) global significance of EIFBD. Understanding the transmission routes and genomic evolution of the principal bacteria causing extra-intestinal FBD is of paramount importance to fully assess the burden of FBD globally, especially in under-resourced regions of Asia, Africa, and Latin America. Acknowledging EIFBD as an integral part of FBD is critical to reach sustainable development. Integrated strategies considering the One Health approach are requisite if FBD are to be controlled, plus to ensure food safety and security. Data summaryThe authors confirm that all supporting data, code and protocols have been provided within the article or through supplementary data files. Impact StatementFoodborne diseases (FBD) present a global health challenge, with the significant health impact and economic costs. Commonly, these illnesses manifest as gastrointestinal troubles; however, there is an alarming increase in reports of foodborne pathogens causing infections beyond the intestinal tract. The complexity of managing FBD is worsened as various pathogens exhibit resistance to antibiotics, a concern applicable to both intestinal and extraintestinal infections. This review serves several critical functions: (i) provide a current overview of the pathogens responsible for gastrointestinal FBD, (ii) examine the underlying factors contributing to the proliferation of these diseases, (iii) present insights gleaned from genomic studies, which enhance our understanding of these pathogens. Grasping the mechanisms of pathogen transmission and genetic evolution is essential to accurately evaluate the worldwide impact of FBD. Acknowledging extraintestinal infections as a significant component of FBD is vital for sustainable progress. Combating FBD effectively necessitates a comprehensive "One Health" approach, which integrates the well-being of humans, animals, and the environment. Such a strategy is imperative not only for controlling FBD but also for ensuring the safety and availability of food resources globally.

African swine fever (ASF) represents a global threat with huge economic consequences for the swine industry. Even though direct contact is likely to be the main transmission route from infected to susceptible hosts, recent epidemiological investigations have raised questions regarding the role of hematophagous arthropods, in particular the stable fly (Stomoxys calcitrans). In this study, we developed a mechanistic vector-borne transmission model for ASF virus (ASFV) within an outdoor domestic pig farm in order to assess the relative contribution of stable flies to the spread of the virus. The model was fitted to the ecology of the vector, its blood-feeding behaviour and pig-to-pig transmission dynamic. Model outputs suggested that in a context of low abundance (<5 flies per pig), stable flies would play a minor role in the spread of ASFV, as they are expected to be responsible for around 10% of transmission events. However, with abundances of 20 and 50 stable flies per pig, the vector-borne transmission would likely be responsible for almost 30% and 50% of transmission events, respectively. In these situations, time to reach a pig mortality of 10% would be reduced by around 26% and 40%, respectively. The sensitivity analysis emphasised that the expected relative contribution of stable flies was strongly dependent on the volume of blood they regurgitated and the infectious dose for pigs. This study identified crucial knowledge gaps that need to be filled in order to assess more precisely the potential contribution of stable flies to the spread of ASFV, including a quantitative description of the populations of hematophagous arthropods that could be found in pig farms, a better understanding of blood-feeding behaviours of stable flies, and the quantification of the probability that stable flies partially fed with infectious blood transmits the virus to a susceptible pig during a subsequent blood-feeding attempt.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a pandemic of unprecedented extent. Beside humans, a number of animal species can be infected, however, in some species differing susceptibilities were observed depending on the virus variant. Here, we serologically investigated cats and dogs living in households with human COVID-19 patients. The study was conducted during the transition period from delta as the dominating variant of concern (VOC) to omicron (BA.1/BA.2) to investigate the frequency of virus transmission of both VOCs from infected owners to their pets. The animal sera were tested by surrogate virus neutralization tests (sVNT) using either the original receptor-binding domain (RBD), enabling the detection of antibodies against the delta variant, or an omicron-specific RBD. Of the 290 canine samples, 20 tested positive by sVNT, but there were marked differences between the sampling time, and, related thereto, the virus variants, the dogs had contact to. While in November 2021 infected owners led to 50% seropositive dogs (18/36), only 0.8% (2/254) of animals with household contacts to SARS-CoV-2 between December 2021 and April 2022 tested positive. In all cases, the positive reaction was recorded against the original RBD. For cats, a similar pattern was seen, as in November 2021 38.1% (16/42) tested positive and between December 2021 and March 2022 only 5.0% (10/199). The markedly reduced ratio of seropositive animals during the period of omicron circulation suggests a considerably lower susceptibility of dogs and cats to this VOC. To examine the effect of BA.2, BA.4 and BA.5 omicron subvariants, sera taken in the second and third quarter of 2022 from randomly selected cats were investigated. 2.3% (11/372) tested seropositive and all of them showed a stronger reaction against the original RBD, further supporting the assumption of a lower susceptibility of companion animals to the omicron VOC.

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first reported in Wuhan, China, and rapidly spread worldwide. Previous studies suggested cat could be a potential susceptible animal of SARS-CoV-2. Here, we investigated the infection of SARS-CoV-2 in cats by detecting specific serum antibodies. A cohort of serum samples were collected from cats in Wuhan, including 102 sampled after COVID-19 outbreak, and 39 prior to the outbreak. 15 of 102 (14.7%) cat sera collected after the outbreak were positive for the receptor binding domain (RBD) of SARS-CoV-2 by indirect enzyme linked immunosorbent assay (ELISA). Among the positive samples, 11 had SARS-CoV-2 neutralizing antibodies with a titer ranging from 1/20 to 1/1080. No serological cross-reactivity was detected between the SARS-CoV-2 and type I or II feline infectious peritonitis virus (FIPV). Our data demonstrates that SARS-CoV-2 has infected cat population in Wuhan during the outbreak.

Mycoplasma hyorhinis is an emerging swine pathogen bacterium with high prevalence worldwide. The main lesions caused are arthritis and polyserositis and the clinical manifestation of the disease may result in significant economic losses due to the decreased weight gain and enhanced medical costs. Our aim was to compare two challenge routes to induce M. hyorhinis infection using the same clinical isolate. Five-week-old, Choice hybrid pigs were inoculated on two consecutive days by intravenous route (Group IV-IV) or by intravenous and intraperitoneal route (Group IV-IP). Mock infected animals were used as control (Control Group). After challenge, the clinical signs were recorded for 28 days, after which the animals were euthanized. Gross pathological and histopathological examinations, PCR detection, isolation and genotyping of the re-isolated Mycoplasma sp. and culture of bacteria other than Mycoplasma sp. were carried out. ELISA test was used to detect anti-M. hyorhinis immunoglobulins in the sera of all animals. Pericarditis and polyarthritis were observed in both challenge groups, however the serositis was more severe in Group IV-IV. Statistically significant differences were detected between the challenged groups and the control group regarding the average daily weight gain, pathological scores and ELISA titres. Additionally, histopathological scores in Group IV-IV differed significantly from the scores in the Control Group. All re-isolated strains were the same or a close genetic variant of the original challenge strain. Our results indicate that both challenge routes are suitable for modelling the disease. However, due to the more severe pathological lesions and the more natural-like route of infection in Group IV-IV, the two-dose intravenous challenge is recommended by the authors to induce serositis and arthritis associated with M. hyorhinis infection.

Bluetongue (BT) is a viral midge borne disease primarily affecting ruminants such as sheep, cattle, and goats. In 2023, the Netherlands reported the first case of bluetongue virus serotype 3 (BTV-3), after being BTV free for eleven years. Since May 2024, vaccination with inactivated BT vaccines for serotype 3 was applied in the Netherlands. Nonetheless, in late June/July 2024, BTV-3 re-emerged and spread over large parts of Europe. In October 2024, BTV-12 was identified by follow-up diagnostics after a BTV-3 vaccinated sheep with signs of BT was tested positive for BTV but negative for serotype 3. This marks a significant event, as BTV-12 had never been reported in Europe. Screening of farms in close proximity to the sheep farm and retrospective analysis of previously BTV PCR positive tested clinical suspicions, resulted in nine BTV-12 affected farms in total. The emergence of BTV-12 in the Netherlands raises important questions about the route of introduction of BT in the Netherlands and mechanisms of viral spread of this specific serotype. Possible adaptation of new BTV serotypes to the European climatic and husbandry conditions prompts reconsideration of surveillance, prevention, and control strategies in relation to changing ecological conditions and vector dynamics. The initial findings, respective studies as well as the initial attempts to trace the origin of BTV-12 are described.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can infect many animals, including pets such as dogs and cats. Many studies have documented infection in companion animals by bio-molecular and serological methods. However, only a few have compared seroprevalence in cats and dogs from the general population, and these studies were limited by small sample sizes and collections over short periods. Our goal was to obtain a more accurate evaluation of seroprevalence in companion animals in France and to determine whether cats and dogs differ in their exposure to SARS-CoV-2. For this purpose, we conducted an extensive SARS-CoV-2 cross-sectional serological survey of 2036 cats and 3577 dogs sampled by veterinarians during medical examinations in clinics throughout France. Sampling was carried out from October 2020 through June 2021, a period encompassing the second and third waves of SARS-CoV-2 infections in humans in the country. Using a microsphere immunoassay targeting the receptor binding domain and trimeric spike protein, we found 7.1% seroprevalence in pets. In a subset of 308 seropositive samples, 26.3% had neutralizing antibodies. We found that cats were significantly more likely to test positive than dogs, with seropositivity rates of 9.3% and 5.9% in cats and dogs, respectively. Finally, data for both species showed that seroprevalence was lower in older animals and was not associated with the date of sampling or the sex of the animal. Our results show that cats are significantly more sensitive to SARS-CoV-2 than dogs, in line with experimental studies. Our large sample size provides for a reliable, statistically robust estimate of the frequency of infection of pets from their owners and offers strong support for the notion that cats are more sensitive to SARS-CoV-2 than dogs. Our findings emphasise the importance of a One-Health approach to the SARS-CoV-2 pandemic and raise the question of whether companion animals in close contact with humans should be vaccinated.

Crimean-Congo Haemorrhagic Fever (CCHF) is a tick-borne zoonosis with significant public health implications due to its expanding geographic distribution and potential for severe outcomes in humans. This study represents the first serological survey conducted in mainland France to detect antibodies against the Crimean-Congo Haemorrhagic Fever Virus (CCHFV) in domestic and wild fauna, providing critical insights into the viruss circulation. We analyzed 8,609 cattle sera and 2,182 wildlife sera collected across the French Mediterranean region from 2008 to 2022, using enzyme-linked immunosorbent assays (ELISA) and pseudo-plaque reduction neutralization tests (PPRNT) for antibody detection and confirmation. Seropositivity was detected in both cattle (2.04%) and wildlife (2.25%), with higher rates observed in specific regions such as Pyrenees-Orientales and Hautes-Pyrenees. These findings reveal spatial clusters of CCHFV circulation and suggest the existence of enzootic transmission cycles involving local tick vectors and animal hosts. Our multivariate analysis identified key factors influencing seropositivity, including animal age, habitat characteristics, and potential wildlife interactions. The presence of natural open habitats and coniferous forests was significantly associated with higher seropositivity in cattle, while sex and geographical variability played a role in wildlife seroprevalence. These findings highlight the importance of environmental and anthropogenic factors in shaping the dynamics of CCHFV transmission. This study demonstrates that CCHFV is actively circulating in parts of mainland France, emphasizing the need for enhanced surveillance and integrated approaches to monitor zoonotic pathogens. It also raises questions about the role of additional tick vectors, such as Hyalomma lusitanicum, in the transmission cycle. These results contribute to a better understanding of CCHF epidemiology and offer valuable guidance for public health strategies to mitigate the risks associated with this emerging disease. Author SummaryCrimean-Congo Haemorrhagic Fever (CCHF) is a severe disease spread by ticks that affects humans and animals. Although the disease is largely distributed in parts of Europe, Africa, and Asia, its presence in France has been uncertain. My study investigated whether the virus causing this disease is circulating in southern mainland France by testing blood samples from domestic animals, like cattle, and wild animals, such as deer and wild boars, for signs of previous infection. I found evidence of the virus in several regions, particularly in the Pyrenees-Orientales, Hautes-Pyrenees and Alpes-maritimes, suggesting that the virus is indeed circulating among animals and ticks in some parts of mainland France. By studying where infected animals were found and considering factors such as age, habitat, and environmental conditions, I identified that older animals seem to have been more often exposed to the virus, as well as animals frequenting open environments favorable to ticks. These findings are important because they show that the disease could potentially spread to new areas and affect human populations. My work highlights the need for ongoing monitoring of ticks and animals for CCHFV epidemiological surveillance and the protection of public health.

Evaluating the trade-off hypothesis for the evolution of virulence using empirical data poses significant challenges. The hypothesis suggests that pathogens evolve to maximize transmissibility, but fatality imposes limits as there are diminishing gains in transmissibility. In this study, we analyzed a secondary dataset of influenza virus infections in ferrets (Mustela putorius furo), categorized by Hemagglutinin (HA) and Neuraminidase (NA) subtypes. Subgroups defined by the H7/N9 and H7/N7 combinations exhibited fatality rates of approximately 30% and reached cumulative viral titers close to 7.5 (log10 titer/mL). These levels represent intermediate fatality rates, as the H5/N6 and H5/N1 subgroups had higher fatality rates but reached lower cumulative viral titers. Using cumulative viral titer as a proxy for potential secondary transmissions, the analysis suggests that intermediate fatality rates are associated with higher numbers of secondary transmissions. However, there are significant uncertainties in subgroups with lower or no fatalities. Additionally, subgroups without fatalities showed substantial variability in cumulative viral titers.

Widespread human SARS-CoV-2 infections pose a constant risk for virus transmission to animals. Here, we serologically investigated 1000 cattle samples collected in late 2021 in Germany. Eleven sera tested antibody-positive, indicating that cattle may be occasionally infected by contact to SARS-CoV-2-positive keepers, but there is no indication of further spreading.

Infectious bursal disease viruses (IBDVs) have a profound impact on poultry production worldwide, directly causing mortality rates of up to 100%, and indirectly through their immunosuppressive effects. Since the emergence of the antigenically modified very virulent IBDV (vvIBDV) in Egypt in late 1999, the country has experienced recurrent outbreaks with high mortality rates and typical vvIBDV gross lesions. However, a notable shift occurred in 2023, characterized by a substantial increase in reported subclinical IBDV cases exhibiting atrophied bursa and associated immunosuppression. To assess the field situation, we examined samples from 21 farms in 2023 and 18 farms from 2021 and 2022, all of which experienced IBD outbreaks based on clinical diagnosis. These samples were submitted to our laboratory for confirmatory testing and subsequently subjected to VP2-HVR sequencing. Phylogenetic analysis revealed that all samples collected in 2021 and 2022 clustered with classical virulent strains and very virulent IBDV. In 2023, one sample clustered with the Egyptian vvIBDV, while one sample clustered with classic virulent IBDV, and the remaining 2023 samples clustered with the Chinese novel variant IBDV (nVarIBDV). The alignment of deduced amino acid sequences for VP2 revealed that all Egyptian classic virulent strains were similar to the Winterfield or Leukert strains. In contrast, vvIBDV strains exhibited two out of the three typical residues found in Egyptian antigenically atypical vvIBDV, namely Y220F and G254S, but not A321T, and one sample was identical to the European vvIBDV (emerged in 1989). Meanwhile, all variant strains recognized in the present study exhibited typical residues found in variant IBDV, in addition to the three conserved amino acid residues found only in Chinese variant IBDVs. However, all Egyptian variant strains showed a mutation at position 321 (321V), which represents the most exposed part of the capsid and is known to have a massive impact on IBDV antigenicity, with the exception of one sample that had 318G instead. This report highlights the emergence of a new variant IBDV clustered with the Chinese new variant in Egypt, causing bursa atrophy and spreading subclinically in broiler farms over a wide geographic distance, resulting in massive economic losses due to immunosuppression.

In autumn 2025, an unprecedented mass mortality event was observed among the western migrating subpopulation of Eurasian cranes (Grus grus) in Germany. Systemic infection with highly pathogenic avian influenza virus H5N1, clade 2.3.4.4b, genotype DI.2.1, was identified as the cause of acute death. The gregarious behaviour of cranes at feeding and resting sites likely has contributed to the rapid and massive dissemination of viruses within the crane population.

African Swine Fever virus (ASFv) is a rapidly spreading animal disease with impacts on global economy and food security. Since the first known case of ASFv in Kenya in 1921, the virus has undergone significant evolution resulting in the emergence of 25 distinct genotypes. These genotypes have a wide variety of epidemiological traits, leading to uncertainty about how a genotype or variant of a genotype might spread in a population. Understanding the impacts of different epidemiological traits on the spread of ASFv is important for developing effective surveillance systems and control strategies. We developed a spatial epidemiological model of ASFv transmission in wild pigs, which contributes to ASFv persistence in countries where wild pig populations are widespread. We evaluated the impacts of a realistic set of epidemiological traits including incubation period, infectious period, disease-induced mortality rate, and length of immunity on spatial transmission dynamics under different ecological conditions for the host population (i.e. host density). We analyze effects of these conditions on outbreak metrics using boosted regression models with response variables: peak incidence, rate of spatial spread, seroprevalence and area invaded after one year, and probability that an outbreak will occur. We found that the infectious period of living individuals is the most important predictor at all pig densities for peak incidence and the area affected at one year, followed closely by the incubation period of the virus. We discuss considerations for surveillance and control strategies for different genotypes of ASFv.