Infection In Wild Boar Research Articles

Monitoring SARS-CoV-2 infection in urban and peri-urban wildlife species from Catalonia (Spain)

BackgroundHuman activities including deforestation, urbanization, and wildlife exploitation increase the risk of transmission of zoonotic diseases. Urban and peri-urban wildlife species often flourish in human-altered environments, with their survival and behavior heavily influenced by human-generated food and waste. In Catalonia, Spain, and other Mediterranean regions, species of rodents, including the house mouse (Mus musculus), black rat (Rattus rattus), Norway rat (Rattus norvegicus), as well as wild boar (Sus scrofa) are common in urban and peri-urban areas. These species host numerous infectious agents, including coronaviruses (CoVs), posing potential human health risks. During the coronavirus disease 2019 (COVID-19) pandemic, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evolved to infect previously non-susceptible species, with variants capable of infecting rodents, emphasizing their importance in surveillance studies.MethodsThe present study assessed SARS-CoV-2 presence and/or exposure in 232 rodents, 313 wild boar, and 37 Vietnamese Pot-bellied pigs in Catalonia during the pandemic period (2020–2023).ResultsAll the animals tested for acute SARS-CoV-2 infection (232 rodents and 29 wild boar) were negative. For SARS-CoV-2 exposure, 3 out of 313 (0.96%) wild boar tested positive by ELISA, while the remaining 32 rodents, 310 wild boar, and 37 Vietnamese Pot-bellied pigs were all negative. Cross-reactivity with other CoVs was predicted for ELISA-positive samples, as the 3 wild boar tested negative by the virus neutralization assay, considered as the gold standard technique.ConclusionsThe absence of SARS-CoV-2 exposure or acute infection in wild boar and rodent species supports their negligible role in viral spread or transmission during the COVID-19 pandemic in Catalonia. However, their proximity to humans and the ongoing genetic evolution of SARS-CoV-2 underline the need for continued monitoring. Surveillance of SARS-CoV-2 infection in animal species can contribute to design measures to control the emergence of new animal reservoirs or intermediate hosts that could facilitate viral spillover events.

The occurrence of Leptospira spp. serogroup Pomona infections in wild boars

Leptospirosis is a worldwide zoonosis caused by different pathogenic serovars of the genus Leptospira, with very complex aetiology and epidemiology. Recent publications suggest that wild boar (Sus scrofa) has an important role in the epizootiology of leptospirosis, representing a potential source of infection. Wild boar populations in urban environments are increasing, posing not only agricultural and ecosystem concerns, but also a public health concern. The aim of this study was to assess the prevalence, temporal patterns and risk factors of Pomona infection in wild boars from areas with pronounced human activity. A total of 159 wild boar serum samples were collected within a health monitoring project in Medvednica Nature Park over a period of six hunting seasons (2012–2016; 2018) and 25.2% samples tested positive. Seropositivity against seven different serogroups was observed, with the highest number of positive reactions to the serogroup Pomona. Annual variation in Pomona reactivity was also detected, and positive reactions were five times more common in females than in males. In most of studies, adults had a higher seroprevalence than younger categories; however, in this study,seroprevalence against Pomona was higher in piglets and subadults. The results indicate that wild boar has the potential of maintaining serovars from the serogroup Pomona in certain natural foci. Due to the expansion of wild boar populations and their intrusion into urban areas, they should be considered a potentially important source of infection for humans and domestic animals.

Helminth infection in wild boars in Primorye, Russia

Wild boars have a worldwide distribution and also have major economic, veterinary, and medical importance. Due to a small amount of data on the parasitic fauna of wild boars in the Russian Far East, especially in Prymorye territory, a post-mortem parasitic examination of 20 wild boars was provided. The general prevalence was 25%, and a total of six helminth species, including one larva stage, were found. The most prevalent helminth species were Gnathostoma doloresi (25%) and Metastrongylus elongatus (20%). Followed by Trichuris suis and Ascaris suum (15%). The lowest prevalence was registered for Cysticercus tenuicollis (the larvae stage of T. hydatigena). Parasites were found in each region, with the highest prevalence registered in the Chuguevskii region. Totally 100% of adult boars were positive for helminth infections, instead of 60% of young specimens. Some helminthes found (G. doloresi, T. suis, A. suum) have zoonotic potential and can be involved in the circulation of human parasitic diseases, especially in rural areas. Further research work on parasitic infections in wild boars in Prymorye is necessary due to the high prevalence of helminthes in wild boars.

Risk factors associated with Coxiella burnetii in wild boars: A study in South Korea

Coxiella burnetii is a Gram-negative bacterium that causes the zoonotic disease Q fever. Wild boars serve as reservoirs for C. burnetii. This study aimed to identify the risk factors associated with C. burnetii infection in wild boars. We analyzed the data from 975 wild boar samples collected from June to November 2021 in South Korea. We utilized the indirect ELISA to detect antibodies against C. burnetii. A sample optical density to positive-control optical density value exceeding 50% was classified as positive. We gathered data on the forestation, terrain, weather, agriculture, and animal density of the region where the samples were collected. Continuous variables were categorized into tertiles. We performed a univariate logistic regression analysis and included variables with a p-value < 0.2 in the final multivariable logistic regression model. In our multivariable logistic regression analysis to identify risk factors for C. burnetii infection in wild boars, we used a forward selection method to enter variables based on the order of their significance. We performed the final multivariable logistic regression analyses using either continuous variables or variables categorized into tertiles. The prevalence of C. burnetii was 14.6% (n=142). Locations with the highest maximum wind speeds (3.92–8.24 m/s) showed a 59% increase in infection odds compared to locations with the lowest speeds (1.45–3.25 m/s)(p=0.044). For each 1 m/s increase in maximum wind speed, infection odds increased by 24.1% (p=0.037). Regions with the highest percentage of paddy fields per area (8.3–45%) showed a 76% increase in infection odds compared to regions with the lowest percentage (0–1.5%)(p=0.011). For each 1% increase in the proportion of paddy fields per area, infection odds increased by 3.3% (p=0.003). High maximum wind speed and a high percentage of paddy field were identified as significant risk factors for C. burnetii infection in wild boars.

Analysis of effective spatial range of oral vaccination against classical swine fever for wild boar

Classical swine fever (CSF) re-emerged in Gifu Prefecture, central Japan, in September 2018 and is currently widespread in wild boar populations. Due to its widespread in wild boars, an oral mass vaccination strategy was initiated in March 2019, employing a commercial bait vaccine that is a live attenuated vaccine. To enhance the effectiveness of oral vaccination, it is crucial to determine the vaccine’s effective spatial range. This understanding is essential for devising a comprehensive vaccination strategy, which should also include a preliminary investigation of wild boar habitats before vaccination. This study aimed to estimate the effective range of oral vaccination for wild boars against CSF by analyzing the geographical relationship between immune wild boars and vaccination points within the vaccination areas in Gifu Prefecture. This study utilized oral vaccination data from April 2021 to March 2022. The prevalence of CSF infections in wild boars remained below 5% in this period, suggesting limited disease transmission and immune wild boars were considered to be induced by the effect of vaccination. Two vaccination campaigns were conducted during this period, with almost 2000 vaccination points each. To investigate the factors associated with the intensity (i.e., density) of immune wild boar, the nearest distances to a vaccination point and to a susceptible wild boar were evaluated as explanatory variables. The Rhohat procedure and point process model were utilized to analyze the relationship between the intensity of immune wild boars and the explanatory variables. The point process model revealed a significant decrease in the intensity of immune wild boars when the distance from the nearest vaccination point exceeded 500 m, indicating that the effective spatial range of bait vaccination is within 500 m of the vaccination point. Although the distance to the nearest susceptible animal did not show significance in the model, Rhohat plots indicated that the intensity of immune wild boars decreased at distances greater than 1200 m from the nearest susceptible wild boar. This finding highlights the importance of investigating susceptible wild boar populations within a range of at least 1200 m from a vaccination point before implementation. The present study revealed the effective range of oral vaccination for wild boars against CSF and indicated the importance of investigating susceptible wild boar habitats around vaccination points before the implementation of vaccination. These findings may help improve the effectiveness of oral vaccinations.

Accelerometer-based detection of African swine fever infection in wild boar.

Infectious wildlife diseases that circulate at the interface with domestic animals pose significant threats worldwide and require early detection and warning. Although animal tracking technologies are used to discern behavioural changes, they are rarely used to monitor wildlife diseases. Common disease-induced behavioural changes include reduced activity and lethargy ('sickness behaviour'). Here, we investigated whether accelerometer sensors could detect the onset of African swine fever (ASF), a viral infection that induces high mortality in suids for which no vaccine is currently available. Taking advantage of an experiment designed to test an oral ASF vaccine, we equipped 12 wild boars with an accelerometer tag and quantified how ASF affects their activity pattern and behavioural fingerprint, using overall dynamic body acceleration. Wild boars showed a daily reduction in activity of 10-20% from the healthy to the viremia phase. Using change point statistics and comparing healthy individuals living in semi-free and free-ranging conditions, we show how the onset of disease-induced sickness can be detected and how such early detection could work in natural settings. Timely detection of infection in animals is crucial for disease surveillance and control, and accelerometer technology on sentinel animals provides a viable complementary tool to existing disease management approaches.

Seroprevalence of Brucella Infection in Wild Boars (Sus scrofa) of Bavaria, Germany, 2019 to 2021 and Associated Genome Analysis of Five B. suis Biovar 2 Isolates

Brucella species are highly pathogenic zoonotic agents and are found in vertebrates all over the world. To date, Germany is officially declared free from brucellosis and continuous surveillance is currently limited to farm ruminants. However, porcine brucellosis, mostly caused by B. suis biovar 2, is still found in wild boars and hares. In the present study, a three-year monitoring program was conducted focusing on the wild boar population in the state of Bavaria. Serologic screening of 11,956 animals and a direct pathogen detection approach, including a subset of 681 tissue samples, was carried out. The serologic incidence was 17.9%, which is in approximate accordance with previously published results from various European countries. Applying comparative whole genome analysis, five isolated B. suis biovar 2 strains from Bavaria could be assigned to three known European genetic lineages. One isolate was closely related to another strain recovered in Germany in 2006. Concluding, porcine brucellosis is endemic in Bavaria and the wild boar population represents a reservoir for genetically distinct B. suis biovar 2 strains. However, the transmission risk of swine brucellosis to humans and farm animals is still regarded as minor due to low zoonotic potential, awareness, and biosafety measures.

Serological survey of Peaton virus among wild boars (Sus scrofa) in Ehime Prefecture, Japan.

Peaton virus (PEAV) is a type of arthropod-borne virus similar to Akabane virus (AKAV), belonging to the genus Orthobunyavirus. AKAV infection is common in cattle, but previous reports have suggested that pigs may play a role in transmission cycle. In addition, antibodies against AKAV were detected in wild boars (Sus scrofa). By contrast, PEAV could infect cattle and pigs, but it remains unknown whether PEAV infects wild boars. This study aimed to reveal the possibility of PEAV infection in wild boars by conducting a serological survey. Consequently, the seropositive rate of PEAV was 26.5% in 264 free-living wild boars in Ehime Prefecture, Japan. This is the first study to report the detection of antibodies against PEAV in wild boars.

Epidemiology of Trichinella infection in wild boar from Spain and its impact on human health during the period 2006-2019.

Trichinellosis is a notifiable zoonotic disease caused by parasitic nematode larvae belonging to the genus Trichinella. Domestic pig and wild boar are important hosts within the natural cycle of T. spiralis, the last one being an animal whose populations have experienced an important growth. Therefore, this paper studies the prevalence of Trichinella infection in wild boar in Spain, as well as its relation with hunting and its impact on public health during the period 2006–2019. For this purpose, different sources of information were consulted and analyzed depending on the autonomous communities of Spain and years. During the fourteen years of study, the number of wild boars hunted and the number of cases of Trichinella infection in them increased (from 172 cases in 2006 to 421 in 2019), although prevalence values remained low as the number of animals analyzed also increased. On the other hand, trichinellosis in humans tended to decrease (from a peak of 107 cases in 2007 to 11 cases in 2019). Nevertheless, the numbers of both wild boars and humans infected with Trichinella in Spain are among the highest in Europe, and this emphasizes the importance of food safety, sanitary controls of game meat and citizen awareness campaigns, which prevent the spread of Trichinella through the human population.

Genetic characterization of hepatitis E virus from wild boar in China.

Hepatitis E virus (HEV), the causative agent of hepatitis E (HE), is classified into four major genotypes (1-4), with wild boar being the main natural reservoir for genotypes 3 and 4. However, little is known about the prevalence of HEV infection in wild boars in China. In this study, RT-nested PCR and RT-quantitative PCR were used to detect the HEV RNA in tissue samples taken from 331 free-ranging wild boars collected between 2018 and 2020 from 24 regions across China, and the partial ORF2 genes or complete genomes of the positive samples were sequenced. Furthermore, antibodies against HEV in 216 serum samples from wild boars were tested by ELISA. As a result, HEV RNA was detected in nine out of 331 liver samples of wild boars (2.72%), which were distributed in eight regions. Genetic and evolutionary analysis of partial ORF2 sequences indicated that the HEV strains identified in this study share 83.9%-100% nucleotide sequence identity and belong to subtypes 4d (n=6), 4g (n=2), and 4h (n=1), and similar phylogeny was obtained using the complete genome sequences of seven wild boar HEV strains. Additionally, the HEV viral loads were higher in the liver than in other tissues and blood. Moreover, 61 out of 216 sera (28.2%) from wild boars tested positive for anti-HEV antibodies. To our knowledge, this is the first study to report the epidemiological situations of HEV infections in free-ranging wild boars in China, and the obtained data are valuable for prevention and control of HE.

Identification of candidate genes associated with bacterial and viral infections in wild boars hunted in Tuscany (Italy)

Wild boar (Sus scrofa L.) is one of the large mammals most spread worldwide, highly adaptable, and its population rapidly increased in many areas in Europe, including Italy, where Tuscany is considered particularly suitable for wild boar. Wild boars are potential hosts for different etiological agents, such as Brucella spp., Leptospira spp. and Pseudorabies virus and they can contribute to maintain and/or to disseminate some bacterial or viral pathogens to humans and domestic animals, above all-in free-range farms. In order to identify hypothetical genomic regions associated with these infection diseases, 96 samples of wild boars hunted in Tuscany during the 2018–2019 and 2019–2020 hunting seasons were considered. Diagnosis was achieved by serological tests and 42 Pseudorabies, 31 Leptospira and 15 Brucella positive animals were identified. All animals were genotyped with Geneseek Genomic Profiler Porcine HD (70 k) and a genome-wide scan was then performed. Significant markers were highlighted for Pseudorabies (two SNPs), Brucella (seven SNPs), and Leptospira (four SNPs) and they were located within, or nearby, 29 annotated genes on chromosome 6, 9, 12, 13, 14 and 18. Eight genes are implicated in viral (SEC14L1, JMJD6, SRSF2, TMPRSS2, MX1, MX2) or bacterial (COL8A1, SPIRE1) infections, seven genes (MFSD11, METTL23, CTTNBP2, BACE2, IMPA2, MPPE1 and GNAL) are involved in mental disorders and one gene (MGAT5B) is related to the Golgi complex. Results presented here provide interesting starting points for future research, validation studies and fine mapping of candidate genes involved in bacterial and viral infections in wild boar.

The Role of the Wild Boar Spreading African Swine Fever Virus in Asia: Another Underestimated Problem

African swine fever (ASF) is a highly lethal infectious disease in naive populations of domestic pigs and wild boar. In Asia, from the first outbreak in August 2018 until the end of November 2021, ASF has been reported in 16 Asian countries. The ASF virus (ASFV) circulation in domestic pigs is considered the main problem in Asia. On the other hand, there are very few reports of ASF in wild boar in this region. However, considering the high wild boar density within the same area of smallholder domestic pig farms in Asia, the occurrence of ASFV infection in wild boar may be underestimated. The role of the wild boar in other ASF epidemiological scenarios, such as Europe, is a key for the maintenance and transmission of the disease. Hence, we performed a preliminary study estimating the extent of ASFV infection in the Asian wild boar population. The potential risk area of ASF-infected wild boar was calculated based on the habitat suitability for wild boar, the kernel density of ASF notification in smallholder farms and wild boar, and the ASFV transmission rate of wild boar. As a result of the analysis, high-, medium-, and low-risk areas were identified throughout Southeast and East Asia. The highest risk area was detected in China, followed by Myanmar, Far East Russia, Thailand, Vietnam, Laos, Cambodia, and the Philippines. Additionally, another risk area was detected from northeastern China to the Korean Peninsula, including Far East Russia. This study shows hot spots where a high risk of infection in wild boar is most likely to occur, helping to control ASF.

Phylogeny and spatiotemporal dynamics of hepatitis E virus infections in wild boar and deer from six areas of Germany during 2013-2017.

The hepatitis E virus (HEV) can cause acute and chronic hepatitis in humans. Infections with the zoonotic HEV genotype 3, which can be transmitted from infected wild boar and deer to humans, are increasingly detected in Europe. To investigate the spatiotemporal HEV infection dynamics in wild animal populations, a study involving 3572 samples of wild boar and three deer species from six different geographic areas in Germany over a 4-year period was conducted. The HEV-specific antibody detection rates increased between 2013-2014 and 2016-2017 in wild boar from 9.5% to 22.8%, and decreased in deer from 1.1% to 0.2%. At the same time, HEV-RNA detection rates increased in wild boar from 2.8% to 13.3% and in deer from 0.7% to 4.2%. Marked differences were recorded between the investigated areas, with constantly high detection rates in one area and new HEV introductions followed by increasing detection rates in others. Molecular typing identified HEV subtypes 3c, 3f, 3i and a putative new subtype related to Italian wild boar strains. In areas, where sufficient numbers of positive samples were available for further analysis, a specific subtype dominated over the whole observation period. Phylogenetic analysis confirmed the close relationship between strains from the same area and identified closely related human strains from Germany. The results suggest that the HEV infection dynamics in wild animals is dependent on the particular geographical area where area-specific dominant strains circulate over a long period. The virus can spread from wild boar, which represent the main wild animal reservoir, to deer, and generally from wild animals to humans.

Seropositive Wild Boars Suggesting the Occurrence of a Wild Cycle of Trichinella spp. in Brazil.

Simple SummaryTrichinellosis is an important zoonotic disease with worldwide distribution and two types of cycles: the domestic cycle and the wild cycle, and spillover between them can occur occasionally. There are several cases of human and animal infection by Trichinella spp. in South America, but Brazil is considered free of the domestic cycle, even though there is unpublished serological evidence of Trichinella spp. in wild boars. This study investigates Trichinella spp. infection in wild boars and wild carnivores in Brazil by serological and artificial digestion tests. We tested 136 samples: 121 from wild boars and 15 from wild carnivores, the latter only by artificial digestion. No larvae were found in the artificial digestion tests, but 6.1% (95% CI 3.0–12.0) of the wild boars were positive in iELISA. These results suggest the occurrence of a Trichinella spp. wild cycle related to wild boars in Brazil, but further analyses should be performed to confirm the presence of the parasite.Trichinella is a zoonotic nematode traditionally detected worldwide in both domestic and wild animals. In South America, along with the occurrence of this parasite in domestic pigs and wild boars, there are reports of infection in wild carnivores. Brazil is considered free of the domestic cycle of Trichinella, but there is unpublished serological evidence of infection in wild boars, which changed the Brazilian status in OIE regarding the disease after an official communication. We investigated Trichinella spp. infection in wild boars and wild carnivores in the Southeastern region of Brazil. A total of 136 samples were tested, 121 from wild boars and 15 from wild carnivores. Artificial enzymatic digestion (AED) tests were performed on muscle samples from 37 wild boars and 15 wild carnivores, and 115 serum samples from wild boars were tested by iELISA. Seven serum samples from wild boars tested positive (7/115 = 6.1%, 95% CI 3.0–12.0), but no larvae were found in the AED. There was no significant difference between sex, age, and location of the samples. The serological results suggest that a wild cycle of Trichinella spp. may occur in Brazil, but further analyses should be performed to confirm the presence of the parasite.

Detection of Hepatitis E Virus Infections in Wild Boars in Southwest Germany Using a Stepwise Laboratory Diagnostic Approach

Hepatitis E virus (HEV) is the main cause of enterically transmitted hepatitis in humans worldwide. Among HEV, genotypes 3 and 4 are considered zoonotic agents associated with domestic pigs and wild boars, showing an increasing trend in Europe. The aim of this study is to contribute data on the prevalence of HEV in wild boars in Southwest Germany and to present a time and cost-effective two-step laboratory diagnostic approach for serological monitoring of blood samples. This method uses enzyme-linked immunosorbent assay (ELISA), followed by testing for HEV RNA by reverse transcription real-time PCR (RT-qPCR). A total of 2295 blood samples were collected in 234 municipalities in 12 counties in the period from 2016 to 2020. There was an overall seroprevalence of 10.8%, ranging from 3.6% to 17.5% per county and 7.5% to 14% per year. Retesting of these blood samples for HEV RNA revealed 15.7% viremic wild boars originating from 30 municipalities in 11 counties. Viremic wild boars were found in seven regional clusters, including 84% of the animals that tested positive for HEV. Seropositive animals &lt;1 year of age were significantly more likely to be viremic than those &gt;1 year. Further characterization of HEV RNA resulted in the identification of genotype 3. Altogether, serological monitoring of the blood samples, complemented by successive and targeted investigations into the presence of HEV RNA based on blood samples, provide reliable information on the seroprevalence and virus load in wild boars, which proved to be a relevant and persistent sylvatic reservoir for HEV.

In search of hepatitis E virus infection in wild boar and cattle from Argentina

Notas sobre Mamíferos Sudamericanos es una revista de la Sociedad Argentina para el Estudio de los Mamíferos (SAREM). Publica información acotada donde se describen nuevas localidades de registro, datos sobre comportamiento y aspectos ecológicos de mamíferos neotropicales.

How do genetic relatedness and spatial proximity shape African swine fever infections in wild boar?

The importance of social and spatial structuring of wildlife populations for disease spread, though widely recognized, is still poorly understood in many host-pathogen systems. In particular, system-specific kin relationships among hosts can create contact heterogeneities and differential disease transmission rates. Here, we investigate how distance-dependent infection risk is influenced by genetic relatedness in a novel host-pathogen system: wild boar (Sus scrofa) and African swine fever (ASF). We hypothesized that infection risk would correlate positively with proximity and relatedness to ASF-infected individuals but expected those relationships to weaken with the distance between individuals due to decay in contact rates and genetic similarity. We genotyped 323 wild boar samples (243 ASF-negative and 80 ASF-positive) collected in north-eastern Poland in 2014-2016 and modelled the effects of geographic distance, genetic relatedness and ASF virus transmission mode (direct or carcass-based) on the probability of ASF infection. Infection risk was positively associated with spatial proximity and genetic relatedness to infected individuals with generally stronger effect of distance. In the high-contact zone (0-2km), infection risk was shaped by the presence of infected individuals rather than by relatedness to them. In the medium-contact zone (2-5km), infection risk decreased but was still associated with relatedness and paired infections were more frequent among relatives. At farther distances, infection risk further declined with relatedness and proximity to positive individuals, and was 60% lower among un-related individuals in the no-contact zone (33% in10-20km) compared among relatives in the high-contact zone (93% in 0-2km). Transmission mode influenced the relationship between proximity or relatedness and infection risk. Our results indicate that the presence of nearby infected individuals is most important for shaping ASF infection rates through carcass-based transmission, while relatedness plays an important role in shaping transmission rates between live animals.

First report of Eimeria sp. from Eurasian wild boar (Sus scrofa) in Iran

In Iran, wild boar is distributed throughout the country, except the Central Desert. One of the important habitats of this animal is the northern mountainous area. They may pass infected faeces in these areas, which can lead to zoonotic disease, though information about parasitic infections in wild boar is rare in Iran and further study is necessary. In February 2019, a wild boar carcass was submitted to the Veterinary Parasitology Department of the Science and Research University of Tehran by the Department of Environment of Mazandaran province in order to study its parasitic infections. Faeces and the gastrointestinal tract were separated and their contents were tested using two flotation methods (Willis and Clayton-Lane), and the samples were referred to the Parasitology Laboratory of Urmia University for further study. The sample was infected with Eimeria protozoa; Eimeria porci and Eimeria neodebliecki were diagnosed based on the size and morphology factors of the isolated oocysts. This is the first report of wild boar infection by Eimeria sp. protozoa in Iran.

A serological survey of porcine reproductive and respiratory syndrome virus in wild boar in Gifu Prefecture, Japan.

Porcine reproductive and respiratory syndrome (PRRS) is an infectious swine disease caused by the PRRS virus (PRRSV) that results in economic loss to the pig-rearing industry. To study PRRSV infection in wild boars and pigs, we conducted a serological survey in Gifu Prefecture, Japan, from 2020 to 2021. Three out of 453 (0.7%) wild boar sera were positive for PRRSV antibodies in a commercial ELISA. However, given that PRRSV RNA was not detected in these three wild boars and the specificity and sensitivity of the test kit, these are considered as false positives. Although seropositive pigs were found in multiple pig farms in the study area, the role of wild boars as a source of PRRS to pig farms appeared to be minimal.

Mycobacterium microti at the Environment and Wildlife Interface.

An unexpected high presence of Mycobacterium microti in wild boar in Northern Italy (Garda Lake) has been reported since 2003, but the factors contributing to the maintenance of this pathogen are still unclear. In this study, we investigated the presence of M. microti in wild rodents and in water and soil samples collected at wild boar aggregation areas, such as watering holes, with the aim of clarifying their role in M. microti transmission. In total, 8 out of 120 captured animals tested positive for the Mycobacterium tuberculosis complex (MTBC) as assessed by real-time PCR, and six samples were confirmed to be M. microti. A strain with a genetic profile similar to those previously isolated in wild boars in the same area was isolated from one sample. Of the 20 water and 19 mud samples, 3 and 1, respectively, tested positive for the presence of MTBC, and spacer oligotype SB0118 (vole type) was detected in one sample. Our study suggests that wild rodents, in particular Apodemus sylvaticus, Microtus sp. and Apodemus flavicollis, play roles in the maintenance of M. microti infections in wild boar through ingestion or by contact with either infected excreta or a contaminated environment, such as at animal aggregation sites.