Outbreak of Swine Erysipelas in a Semi-Intensive Wild Boar Farm in Spain

First Serologic Survey of Erysipelothrix rhusiopathiae in Wild Boars Hunted for Private Consumption in Portugal

Erysipelothrix rhusiopathiae is a relevant zoonotic infectious agent causing swine erysipelas (SE) in wild boar. In Portugal, there is no information on its occurrence. For this reason, this study aims to perform a first serosurvey of SE in hunted wild boars in Portugal. During the 2019/2020 hunting season, 111 sera from hunted wild boar were collected and analysed serologically in the laboratory with a commercial ELISA kit. No animals were eviscerated and examined after the hunt. The hunters took it all for private consumption. The results identified 18 animals that were exposed to SE, corresponding to a seroprevalence of 16.2% (95% CI: 19.9-24.4%). No statistical significance was observed on the effect of gender and age on seropositivity. However, wild boar hunted in Pinhel County, had five times more likely to be seropositivity (p-value < 0.05; OD = 5.4). Apart from its potential debilitating capacity and chronicity in the wild boar population, SE is also a very serious occupational zoonosis. Thus, the result of this first serosurvey in Portugal should raise awareness and alert competent national veterinary authorities and those involved in the hunting sector, especially hunters who directly handle these carcasses. Further studies should be conducted to better understand the role of wild boar as a reservoir and spillover of this disease to other animals and humans.

Influence of Anthropic Environmental-Related Factors on Erysipelas in Wild Boar

Erysipelothrix rhusiopathiae (ER) is an old but still emerging zoonotic infection that is not yet completely understood. ER infects a wide range of species and wild boar is of significant interest because of their similarities to pigs, a known ER reservoir. Moreover, the increase of its densities and the limited data available about ER in this species should be considered. The need is to investigate whether wild boar could represent a risk of erysipelas at the wildlife-domestic-human interface. Here, 1067 sera and 149 tonsils of wild boar from five hunting districts in Northwest Italy were tested using ELISA and bacteriological culture, respectively. Using generalized linear models, we evaluated host and environmental factors influencing ER spread and dynamics. We found an ER seroprevalence of 69.4% among wild boar. Increased human density and pig farm density lead to an increase of ER seropositivity highlighting its association with anthropic environmental-related factors. The high ER percentage of isolation (34.2%) found in healthy wild boar suggests that this species can serve as a healthy carrier. This fact, together with the high seroprevalence, supports a role of wild boar as an ER reservoir. Potential zoonotic and economic risks should be considered in light of these data.

Potential risk factors of swine erysipelas outbreak in Northeast Mainland China

Swine erysipelas is a common infectious disease that affects the pig-breeding industry. The purpose of this study was to elucidate the risk factors and their role in the prevalence of swine erysipelas so that one may be able to better prevent and control the swine erysipelas outbreaks in Northeast China. Using spatial clusters, the study area was divided into two parts: South Central Mainland China (hot spots) and Northeast Mainland China (potential outbreak areas). We investigated a total of 31 environmental factors and used the lasso regression and k-fold cross-validation methods to determine the main factors involved. Seven risk factors were determined to have a major impact on swine erysipelas. Multiple logistic regression was used to examine the contribution of these seven risk factors to the outbreak from 2008 to 2018, in the two research regions. In South Central Mainland China, where swine erysipelas was most prevalent, the extreme maximum temperature [OR = 1.143 (95%CI: 1.032-1.342)], total precipitation [OR = 2.298 (95%CI: 1.410-5.112)] and precipitation ≥0.1 mm [OR = 2.396 (95%CI: 1.329-5.941)] exhibited positive effects. The maximum wind speed [OR = 0.550 (95%CI: 0.303-0.775)] and concentration of O3-8H-90 per [OR = 0.876 (95%CI: 0.747-0.980)] exhibited negative effects. Summer was the main season for the erysipelas epidemic in South Central Mainland China. In Northeast China, only the total precipitation [OR = 1.048 (95%CI: 0.900-0.989)] was positively correlated with the prevalence of swine erysipelas, whereas the other factors were not significant. There was no obvious seasonal feature for the epidemic. Through the comparison and analysis of risk factors between the two research regions, more attention should be given to the impacts of high temperature and precipitation on the swine erysipelas epidemic in Northeast China.

Comparative genome analysis of Erysipelothrix rhusiopathiae isolated from domestic pigs and wild boars suggests host adaptation and selective pressure from the use of antibiotics

The disease erysipelas caused by Erysipelothrix rhusiopathiae (ER) is a major concern in pig production. In the present study the genomes of ER from pigs (n=87), wild boars (n=71) and other sources (n=85) were compared in terms of whole-genome SNP variation, accessory genome content and the presence of genetic antibiotic resistance determinants. The aim was to investigate if genetic features among ER were associated with isolate origin in order to better estimate the risk of transmission of porcine-adapted strains from wild boars to free-range pigs and to increase our understanding of the evolution of ER. Pigs and wild boars carried isolates representing all ER clades, but clade one only occurred in healthy wild boars and healthy pigs. Several accessory genes or gene variants were found to be significantly associated with the pig and wild boar hosts, with genes predicted to encode cell wall-associated or extracellular proteins overrepresented. Gene variants associated with serovar determination and capsule production in serovars known to be pathogenic for pigs were found to be significantly associated with pigs as hosts. In total, 30 % of investigated pig isolates but only 6 % of wild boar isolates carried resistance genes, most commonly tetM (tetracycline) and lsa(E) together with lnu(B) (lincosamides, pleuromutilin and streptogramin A). The incidence of variably present genes including resistance determinants was weakly linked to phylogeny, indicating that host adaptation in ER has evolved multiple times in diverse lineages mediated by recombination and the acquisition of mobile genetic elements. The presented results support the occurrence of host-adapted ER strains, but they do not indicate frequent transmission between wild boars and domestic pigs. This article contains data hosted by Microreact.

Meteorological Factors and Swine Erysipelas Transmission in Southern China

Swine erysipelas (SE) is one of the best-known and most serious diseases that affect domestic pigs, which is caused by Erysipelothrix rhusiopathiae. It is endemic in Nanning and has been circulating for decades, causing considerable economic losses. The aim of this study was to investigate the effect of meteorological-related variations on the epidemiology of swine erysipelas in Nanning City, a subtropical city of China. Data on monthly counts of reported swine erysipelas and climate data in Nanning are provided by the authorities over the period from 2006 to 2015. Cross-correlation analysis was applied to identify the lag effects of meteorological variables. A zero-inflated negative binomial (ZINB) regression model was used to evaluate the independent contribution of meteorological factors to SE transmission. After controlling seasonality, autocorrelation and lag effects, the results of the model indicated that Southern Oscillation Index (SOI) has a positive effect on SE transmission. Moreover, there is a positive correlation between monthly mean maximum temperature and relative humidity at 0-1 month lag and the number of cases. Furthermore, there is a positive association between the number of SE incidences and precipitation, with a lagged effect of 2 months. In contrast, monthly mean wind velocity negatively correlated with SE of the current month. These findings indicate that meteorological variables may play a significant role in SE transmission in southern China. Finally, more public health actions should be taken to prevent and control the increase of SE disease with consideration of local weather variations.

Outbreaks of antimicrobial resistant Salmonella Choleraesuis in wild boars piglets from central-western Spain

Salmonella enterica serovar Choleraesuis is the aetiological agent of swine paratyphoid being a highly invasive zoonotic pathogen. Wild boar natural populations are experiencing a demographical expansion as well as some farms are breeding this species to release for hunting with management sometimes identical to that of domestic pigs, including supplementation, grouping, and antibiotic treatments. This situation increases the chance of contact between wild boars and livestock, and potentially induces stress, with different sanitary consequences. The present work aims to describe the clinical features of recent outbreaks caused by S. Choleraesuis in wild boar from central-western Spain, as well as the antimicrobial resistance and phylogenetic relationships of isolates involved. 28 strains of S. Choleraesuis were isolated from 28 different wild boars belonging to 10 different game states located in central western Spain and submitted to the Clinical Veterinary Hospital (CVH) of the University of Extremadura. Samples were taken from different organs and cultured according to the ISO 6579:2002 procedure. Suspicious colonies were identified by PCR and antimicrobial resistance was evaluated by disc diffusion susceptibility test and the presence of the main resistance genes as well as 18 plasmid replicons frequently found among the Enterobacteriaceae was verified by PCR. Pulsed field gel electrophoresis was applied to determine the genetic relationship between isolates. The outbreaks under study were characterized by high mortality (35%-84%) and a septicaemic presentation. S. Choleraesuis was isolated from all the wild boars analysed, and 26 of the 28 isolates presented resistance to at least one antibiotic. The predominant resistances found were against sulphonamide, streptomycin, tetracycline, and doxicicline and sul1, strA-strB, and tetA were the most prevalent resistance genes among isolates. 10 strains carried FIIA, FIB+H/1 or FIIA+H/1 plasmids. PFGE classified the isolates into four different profiles, grouped into two clusters. This results show that prevention against S. Choleraesuis must be considered in the sanitary programs of the wild boar breeders.

Suidae and Tayassuidae

The Suidae and Tayassuidae live on all continents except Antarctica. True wild boars were indigenous to Europe and Asia and are the ancestors to the domestic pig; with whom they share the same scientific name Sus scrofa. Wild boars have been introduced to the Americas and many islands. Because of the close genetic relationship, in many areas they have interbred with domestic pigs and formed considerable populations of feral suids that represent wild boar and feral pig crosses. Wild suid populations are relatively hardy and most disease research has been focused on their potential as a reservoir for diseases of concern for commercial pig production. The Togian Island babirusa, pygmy hog, Visayan warty pig, Javan warty pig, and Chacoan peccary are endangered. For all species, hunting, habitat loss, and hybridization are important threats to conservation.

Isolation of Aeromonas hydrophila in the respiratory tract of wild boar: pathologic implications

Aeromonas hydrophila has been repeatedly reported as an animal pathogen. This study describes a case of a wild boar piglet in Spain with severe purulent pneumonia caused by A. hydrophila. To confirm the presence of A. hydrophila in the respiratory tract of wild boars from the same region, lung samples from 34 adult hunted animals and nasal samples from 12 live animals were collected and cultured in selective medium. Lung lesions were studied in hunted wild boars to determine the presence of A. hydrophila and to assess its role as a possible respiratory pathogen in wild boars. A. hydrophila was isolated in 10.87% of the animals studied (8.82% of the dead animals and 16% of the live animals). However, its presence in the lungs of adults could not be correlated with the lesions found. Thus, the role of A. hydrophila as a respiratory pathogen is likely to be influenced by other factors, such as age, immunologic status, or coinfection with other pathogens. As a zoonotic pathogen, the presence of A. hydrophila in wild boars may pose a potential risk to people who consume their flesh.

Fatal outbreak of systemic pasteurellosis in a wild boar (Sus scrofa) population from southwest Spain

Pasteurella multocida is a common pathogen of swine that causes specific diseases with great economic impact. However, the importance of this pathogen in wild boar is still unknown. In the current work, an outbreak of systemic pasteurellosis in wild boar with a high mortality rate is described. A total of 23 wild boar of all ages were found dead over a 5-day period on a game estate in southwest Spain (11.11% mortality). Three animals were necropsied and showed subcutaneous edema, a generalized congestion, and fibrin deposits in the peritoneal cavity. Hemorrhages, general congestion, and intravascular thrombosis were microscopically observed. Pasteurella multocida type B was isolated from all of the studied organs. Outbreaks of systemic pasteurellosis have been described in domestic pigs from Asia and Australia, but not to date in Europe. This outbreak suggests that systemic pasteurellosis affecting wild boar populations may be an important cause of mortality.

Fatal infection due to Haemophilus parasuis in a young wild boar (Sus scrofa)

Haemophilus parasuis is a recognized pathogen in domestic pigs; the pathogen has been also isolated from healthy wild boar (Sus scrofa). In the current report, a case of fatal H. parasuis infection in a wild boar piglet from central Spain is described. The affected animal presented severe pneumonic lesions, inflammation in tarsal joints with presence of fibrinous deposits, and epidural hemorrhage in the atlanto-occipital joint. Pure growth of H. parasuis was obtained from lungs and tarsal joints. The current case illustrates the susceptibility of wild boar to this agent. The gross pathology results were similar to that described in domestic pigs, but there were no fibrinous deposits on serosal surfaces.

Zoonoses: a potential obstacle to the growing wildlife industry of Namibia

Zoonoses, which account for approximately 75% of emerging human infectious diseases worldwide, pose a re-emerging threat to public health. With an ever-increasing interrelationship between humans, livestock and wildlife species, the threat to human health will rise to unprecedented levels. Wildlife species contribute to the majority of emerging diseases; therefore, there is an urgent need to define control systems of zoonoses of wildlife origin but very little information exists. In this review, we examine prevalent zoonotic infections reported in Namibia between 1990 and 2009 and assess their potential impact on the growing wildlife industry. A wide spectrum of zoonotic diseases was confirmed in both livestock and wildlife species, with rabies and anthrax cases being over-represented and also showing the widest species distribution. Whilst vaccination and ante-mortem inspection against these diseases may curb infected livestock species from entering the human food chain, such practices are difficult to implement in free-ranging wildlife species. In this context, there is a need to improve existing control measures and/or develop novel and better interventional strategies to reduce the threat of this re-emerging global problem. This review provides the basis for initiating a multidisciplinary evidence-based approach to control zoonoses in countries with thriving wildlife and game farming.

Seroprevalence evolution of selected pathogens in Iberian wild boar

A total of 1279 Eurasian wild boar (Sus scrofa) sera were collected from 2000 to 2011 in the Iberian Peninsula to reveal time changes in serum antibody prevalences against selected infectious agents (porcine circovirus type 2, PCV2; porcine reproductive and respiratory syndrome virus, PRRSV; hepatitis E virus, HEV; and Erysipelothrix rhusiopathiae) and to identify putative individual or population factors driving such changes. Overall seroprevalences were 48%, 26%, 2% and 15% for PCV2, HEV, PRRSV and E. rhusiopathiae, respectively. The global observed prevalence of antibodies against PCV2 and HEV remained stable during the study period, while the global mean antibody seroprevalence against E. rhusiopathiae declined. The mean increment in prevalence was always lower for open than for fenced sites. This study evidenced for the first time that wild boar from the Iberian Peninsula have widespread contact with E. rhusiopathiae, and confirmed high prevalences of antibodies against PCV2 and HEV. Maintained high prevalences of transmissible agents in wild boar suggest that epidemiological drivers such as aggregation and high density are still acting. This will most probably also affect the transmission rates of other disease agents and should be taken into account regarding disease control at the wildlife-livestock interface.