Showing papers by "An Martel published in 2017"
TL;DR: It is shown that arrival of this chytrid is associated with rapid population collapse without any sign of recovery, largely due to lack of increased resistance in the surviving salamanders and a demographic shift that prevents compensation for mortality.
Abstract: The recent arrival of Batrachochytrium salamandrivorans in Europe was followed by rapid expansion of its geographical distribution and host range, confirming the unprecedented threat that this chytrid fungus poses to western Palaearctic amphibians. Mitigating this hazard requires a thorough understanding of the pathogen's disease ecology that is driving the extinction process. Here, we monitored infection, disease and host population dynamics in a Belgian fire salamander (Salamandra salamandra) population for two years immediately after the first signs of infection. We show that arrival of this chytrid is associated with rapid population collapse without any sign of recovery, largely due to lack of increased resistance in the surviving salamanders and a demographic shift that prevents compensation for mortality. The pathogen adopts a dual transmission strategy, with environmentally resistant non-motile spores in addition to the motile spores identified in its sister species B. dendrobatidis. The fungus retains its virulence not only in water and soil, but also in anurans and less susceptible urodelan species that function as infection reservoirs. The combined characteristics of the disease ecology suggest that further expansion of this fungus will behave as a 'perfect storm' that is able to rapidly extirpate highly susceptible salamander populations across Europe.
165 citations
TL;DR: The results show that, despite commonalities that promote infection, specific gene-family radiations contribute to distinct infection strategies, and underscores the urgent need to halt the advance of pathogenic chytrids and prevent incipient loss of biodiversity.
Abstract: To understand the evolutionary pathways that lead to emerging infections of vertebrates, here we explore the genomic innovations that allow free-living chytrid fungi to adapt to and colonize amphibian hosts. Sequencing and comparing the genomes of two pathogenic species of Batrachochytrium to those of close saprophytic relatives reveals that pathogenicity is associated with remarkable expansions of protease and cell wall gene families, while divergent infection strategies are linked to radiations of lineage-specific gene families. By comparing the host-pathogen response to infection for both pathogens, we illuminate the traits that underpin a strikingly different immune response within a shared host species. Our results show that, despite commonalities that promote infection, specific gene-family radiations contribute to distinct infection strategies. The breadth and evolutionary novelty of candidate virulence factors that we discover underscores the urgent need to halt the advance of pathogenic chytrids and prevent incipient loss of biodiversity.
72 citations
TL;DR: Support is provided for the hypothesis that these chytrid fungi may be endemic to Asia and that species within this region may act as a disease reservoir.
Abstract: The amphibian chytrid fungi, Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal), pose a major threat to amphibian biodiversity. Recent evidence suggests Southeast Asia as a potential cradle for both fungi, which likely resulted in widespread host-pathogen co-existence. We sampled 583 salamanders from 8 species across Vietnam in 55 locations for Bsal and Bd, determined scaled mass index as a proxy for fitness and collected environmental data. Bsal was found within 14 of the 55 habitats (2 of which it was detected in 2013), in 5 salamandrid species, with a prevalence of 2.92%. The globalized pandemic lineage of Bd was found within one pond on one species with a prevalence of 0.69%. Combined with a complete lack of correlation between infection and individual body condition and absence of indication of associated disease, this suggests low level pathogen endemism and Bsal and Bd co-existence with Vietnamese salamandrid populations. Bsal was more widespread than Bd, and occurs at temperatures higher than tolerated by the type strain, suggesting a wider thermal niche than currently known. Therefore, this study provides support for the hypothesis that these chytrid fungi may be endemic to Asia and that species within this region may act as a disease reservoir.
65 citations
TL;DR: It is shown that Bsal is present on wild small-webbed fire-bellied toads from Vietnam and on representatives of the same species that have recently been imported in Germany, suggesting that the installment of measures to mitigate the Bsal threat through the amphibian trade should not be limited to urodeles, but should equally take anurans into account.
Abstract: Pathogen pollution has caused dramatic losses of amphibian diversity on a global scale The recently emerged chytrid fungus Batrachochytrium salamandrivorans (Bsal) has been hypothesized to have its origin in Asian urodelan populations, from which it may have been introduced to Europe through the trade in live urodelans We here show that Bsal is present on wild small-webbed fire-bellied toads (Bombina microdeladigitora) from Vietnam and on representatives of the same species that have recently been imported in Germany This finding suggests that the installment of measures to mitigate the Bsal threat through the amphibian trade should not be limited to urodeles, but should equally take anurans into account
58 citations
TL;DR: It is found that a complementary shrub layer exploits the higher light availability in particular tree species combinations, which leads to similar light levels at the forest floor in all species combinations in the authors' plots.
Abstract: Light is a key resource for plant growth and is of particular importance in forest ecosystems, because of the strong vertical structure leading to successive light interception from canopy to forest floor. Tree species differ in the quantity and heterogeneity of light they transmit. We expect decreases in both the quantity and spatial heterogeneity of light transmittance in mixed stands relative to monocultures, due to complementarity effects and niche filling. We tested the degree to which tree species identity and diversity affected, via differences in tree and shrub cover, the spatiotemporal variation in light availability before, during, and after leaf expansion. Plots with different combinations of three tree species with contrasting light transmittance were selected to obtain a diversity gradient from monocultures to three species mixtures. Light transmittance to the forest floor was measured with hemispherical photography. Increased tree diversity led to increased canopy packing and decreased spatial light heterogeneity at the forest floor in all of the time periods. During leaf expansion, light transmittance did differ between the different tree species and timing of leaf expansion might thus be an important source of variation in light regimes for understory plant species. Although light transmittance at the canopy level after leaf expansion was not measured directly, it most likely differed between tree species and decreased in mixtures due to canopy packing. A complementary shrub layer led, however, to similar light levels at the forest floor in all species combinations in our plots. Synthesis. We find that a complementary shrub layer exploits the higher light availability in particular tree species combinations. Resources at the forest floor are thus ultimately determined by the combined effect of the tree and shrub layer. Mixing species led to less heterogeneity in the amount of light, reducing abiotic niche variability.
53 citations
TL;DR: The authors argue for the responsible and sustainable keeping of reptile and amphibian pets by private persons, based on scientific evidence and on the authors' own expertise (veterinary medicine, captive husbandry, conservation biology).
Abstract: The keeping of exotic pets is currently under debate and governments of several countries are increasingly exploring the regulation, or even the banning, of exotic pet keeping. Major concerns are issues of public health and safety, animal welfare and biodiversity conservation. The keeping of reptiles and amphibians in captivity encompasses all the potential issues identified with keeping exotic pets, and many of those relating to traditional domestic pets. Within the context of risks posed by pets in general, the authors argue for the responsible and sustainable keeping of reptile and amphibian pets by private persons, based on scientific evidence and on the authors' own expertise (veterinary medicine, captive husbandry, conservation biology).
51 citations
TL;DR: It is concluded that bacterial inhibition capabilities change among bacterial strains, Batrachochytrium genotypes and temperatures, and a comprehensive understanding of bacterial inhibitory function is needed to better predict the role of bacterial symbionts in amphibian disease ecology.
Abstract: Symbiotic bacteria may dampen the impacts of infectious diseases on hosts by inhibiting pathogen growth. However, our understanding of the generality of pathogen inhibition by different bacterial taxa across pathogen genotypes and environmental conditions is limited. Bacterial inhibitory properties are of particular interest for the amphibian-killing fungal pathogens (Batrachochytrium dendrobatidis [Bd] and B. salamandrivorans [Bsal]), for which probiotic applications as conservation strategies have been proposed. We quantified the inhibition strength of five putatively Bd-inhibitory bacteria isolated from woodland salamander skin against six Batrachochytrium genotypes at two temperatures (12 and 18 °C). We selected six genotypes from across the Batrachochytrium phylogeny: Bsal, Bd-Brazil and four genotypes of the Bd Global Panzootic Lineage (GPL1: JEL647, JEL404; GPL2: SRS810, JEL423). We performed 96-well plate challenge assays in a full factorial design. We detected a Batrachochytrium genotype by temperature interaction on bacterial inhibition score for all bacteria, indicating that bacteria vary in ability to inhibit Batrachochytrium depending on pathogen genotype and temperature. Acinetobacter rhizosphaerae moderately inhibited Bsal at both temperatures (μ = 46 – 53%), but not any Bd genotypes. Chryseobacterium sp. inhibited three Batrachochytrium genotypes at both temperatures (μ = 5 – 71%). Pseudomonas sp. strain 1 inhibited all Batrachochytrium genotypes at 12 °C and four Batrachochytrium genotypes at 18 °C (μ = 5 – 100%). Pseudomonas sp. strain 2 and Stenotrophomonas sp. moderately to strongly inhibited all six Batrachochytrium genotypes at both temperatures (μ = 57 – 100%). All bacteria consistently inhibited Bsal. Using cluster analysis of inhibition scores, we found that more closely related Batrachochytrium genotypes grouped together, suggesting that bacterial inhibition strength may be predictable based on Batrachochytrium relatedness. We conclude that bacterial inhibition capabilities change among bacterial strains, Batrachochytrium genotypes and temperatures. A comprehensive understanding of bacterial inhibitory function, across pathogen genotypes and temperatures, is needed to better predict the role of bacterial symbionts in amphibian disease ecology. For targeted conservation applications, we recommend using bacterial strains identified as strongly inhibitory as they are most likely to produce broad-spectrum antimicrobial agents at a range of temperatures.
49 citations
TL;DR: It is shown that antimicrobial peptides co secreted with frog toxins enhance intoxication of a snake predator by permeabilizing oral cell layers.
Abstract: Animals using toxic peptides and proteins for predation or defense typically depend on specialized morphological structures, like fangs, spines, or a stinger, for effective intoxication. Here we show that amphibian poisons instead incorporate their own molecular system for toxin delivery to attacking predators. Skin-secreted peptides, generally considered part of the amphibian immune system, permeabilize oral epithelial tissue and enable fast access of cosecreted toxins to the predator's bloodstream and organs. This absorption-enhancing system exists in at least three distantly related frog lineages and is likely to be a widespread adaptation, determining the outcome of predator-prey encounters in hundreds of species.
47 citations
TL;DR: It is found little evidence that pre-existing chytrid emergence was associated with ranavirus and the emergence of ranavirosis, and co-infection dynamics have been largely overlooked in an amphibian assemblage in Serra da Estrela.
Abstract: Emerging diseases have been increasingly associated with population declines, with co-infections exhibiting many types of interactions. The chytrid fungus (Batrachochytrium dendrobatidis) and ranaviruses have extraordinarily broad host ranges, however co-infection dynamics have been largely overlooked. We investigated the pattern of co-occurrence of these two pathogens in an amphibian assemblage in Serra da Estrela (Portugal). The detection of chytridiomycosis in Portugal was linked to population declines of midwife-toads (Alytes obstetricans). The asynchronous and subsequent emergence of a second pathogen - ranavirus - caused episodes of lethal ranavirosis. Chytrid effects were limited to high altitudes and a single host, while ranavirus was highly pathogenic across multiple hosts, life-stages and altitudinal range. This new strain (Portuguese newt and toad ranavirus - member of the CMTV clade) caused annual mass die-offs, similar in host range and rapidity of declines to other locations in Iberia affected by CMTV-like ranaviruses. However, ranavirus was not always associated with disease, mortality and declines, contrasting with previous reports on Iberian CMTV-like ranavirosis. We found little evidence that pre-existing chytrid emergence was associated with ranavirus and the emergence of ranavirosis. Despite the lack of cumulative or amplified effects, ranavirus drove declines of host assemblages and changed host community composition and structure, posing a grave threat to all amphibian populations.
45 citations
TL;DR: It is shown that even in a situation with a clear cost incurred by endemic Bd, population sizes remain largely stable, but as higher temperatures increase infection probability, changing environmental conditions could unbalance the current fragile host–pathogen equilibrium.
Abstract: Unravelling the multiple interacting drivers of host-pathogen coexistence is crucial in understanding how an apparently stable state of endemism may shift towards an epidemic and lead to biodiversity loss Here, we investigate the apparent coexistence of the global amphibian pathogen Batrachochytrium dendrobatidis (Bd) with Bombina variegata populations in The Netherlands over a 7-year period We used a multi-season mark-recapture dataset and assessed potential drivers of coexistence (individual condition, environmental mediation and demographic compensation) at the individual and population levels We show that even in a situation with a clear cost incurred by endemic Bd, population sizes remain largely stable Current environmental conditions and an over-dispersed pathogen load probably stabilize disease dynamics, but as higher temperatures increase infection probability, changing environmental conditions, for example a climate-change-driven rise in temperature, could unbalance the current fragile host-pathogen equilibrium Understanding the proximate mechanisms of such environmental mediation and of site-specific differences in infection dynamics can provide vital information for mitigation actions
37 citations
TL;DR: Within the TREEWEB platform, overstorey-understorey diversity relationships were mainly characterised by tree species identity effects, and no clear effects of tree species diversity and forest fragmentation on understorey composition and diversity were found.
Abstract: Background & aim : In general, biodiversity has positive effects on ecosystem functioning. In forests, understorey vegetation is influenced by both the composition and species richness of the overstorey through species-specific effects on environmental conditions at the forest floor. Forest fragmentation is also known to influence understorey vegetation composition and richness. However, the combined effects of tree species diversity and forest fragmentation have not been studied yet. With the TREEWEB research platform, consisting of 53 forest plots along a tree species diversity and forest fragmentation gradient, we aim to unravel the combined effects of tree species diversity, tree species identity and forest fragmentation on the understorey composition and diversity.
Methods : The TREEWEB platform includes forest plots of three tree species richness levels, containing all possible species combinations of Quercus robur, Quercus rubra and Fagus sylvatica. Complete dilution is avoided in the design, allowing separation between tree species identity and diversity effects. Vegetation surveys were conducted in all plots to investigate the species richness, species diversity, compositional turnover and cover of the herb layer as well as the shrub layer cover.
Key results : Within the TREEWEB platform, overstorey-understorey diversity relationships were mainly characterised by tree species identity effects. No clear effects of tree species diversity and forest fragmentation on understorey composition and diversity were found.
Conclusion : Tree species identity effects were most important in explaining the observed patterns in the understorey vegetation. Further in-depth research will allow us to disentangle which mechanisms underlie these patterns and whether effects of fragmentation are more pronounced at higher trophic levels.
TL;DR: For Bsal, enzymatic breakdown of hydrogen peroxide by catalases and specific morphological features, were identified as fungal factors altering susceptibility to several of the disinfectants tested, which recommend 1% Virkon S®, 4% sodium hypochlorite and 70% ethanol for disinfecting equipment in the field, lab or captive setting, with a minimal contact time of 1 minute for the latter disinfectants.
Abstract: The recently emerged chytrid fungus Batrachochytrium salamandrivorans (Bsal) causes European salamander declines. Proper hygiene protocols including disinfection procedures are crucial to prevent disease transmission. Here, the efficacy of chemical disinfectants in killing Bsal was evaluated. At all tested conditions, Biocidal®, Chloramine-T®, Dettol medical®, Disolol®, ethanol, F10®, Hibiscrub®, potassium permanganate, Safe4®, sodium hypochlorite, and Virkon S®, were effective at killing Bsal. Concentrations of 5% sodium chloride or lower, 0.01% peracetic acid and 0.001-1% copper sulphate were inactive against Bsal. None of the conditions tested for hydrogen peroxide affected Bsal viability, while it did kill Batrachochytrium dendrobatidis (Bd). For Bsal, enzymatic breakdown of hydrogen peroxide by catalases and specific morphological features (clustering of sporangia, development of new sporangia within the original sporangium), were identified as fungal factors altering susceptibility to several of the disinfectants tested. Based on the in vitro results we recommend 1% Virkon S®, 4% sodium hypochlorite and 70% ethanol for disinfecting equipment in the field, lab or captive setting, with a minimal contact time of 5 minutes for 1% Virkon S® and 1 minute for the latter disinfectants. These conditions not only efficiently target Bsal, but also Bd and Ranavirus.
TL;DR: It is suggested that concurrent administration of drugs with FBs contaminated feed might alter the pharmacokinetic characteristics of CYP1A4 substrate drugs and MDR1 substrates, such as enrofloxacin.
TL;DR: Acquired antimicrobial resistance is widespread among Belgian B. hyodysenteriae isolates and the emergence of multi-resistant clonal complexes can pose a threat to swine industry.
TL;DR: Two challenge studies were conducted using a recently isolated M. gallisepticum strain belonging to the wildtype population with regard to its tiamulin and tetracycline minimum inhibitory concentration, showing a significant reduction of the severity of clinical respiratory disease post treatment and a significant reduced of the M.gallisepticums numbers in the respiratory tract.
TL;DR: Six nanobodies with a broad specificity were obtained, that recognize strains belonging to the two most relevant species, Campylobacter jejuni and Campylabacter coli, that may be useful to develop a strategy for preserving chickens from Campyobacter colonization.
Abstract: Campylobacter infections are among the most prevalent foodborne infections in humans, resulting in a massive disease burden worldwide. Broilers have been identified as the major source of campylobacteriosis and reducing Campylobacter loads in the broiler caeca has been proposed as an effective measure to decrease the number of infections in humans. Failure of current methods to control Campylobacter in broilers stresses the urgency to develop novel mitigation measures. We obtained six nanobodies with a broad specificity, that recognize strains belonging to the two most relevant species, Campylobacter jejuni and Campylobacter coli. The target of the nanobodies was identified as the major outer membrane protein, a porin that contributes to bacterial virulence and viability. Multimerization of the nanobodies led to agglutination of C. jejuni cells, which may affect colonization in the chicken gut. These Campylobacter-specific nanobodies may be useful to develop a strategy for preserving chickens from Campylobacter colonization.
TL;DR: Bromeliad phytotelmata may act as environmental refuges from Batrachochytrium dendrobatidis, which contribute to protecting associated amphibian communities against chytridiomycosis-driven amphibian declines that threaten the nearby riparian communities.
Abstract: The fungal pathogen Batrachochytrium dendrobatidis (Bd) drives declines and extinctions in amphibian communities. However, not all regions and species are equally affected. Here, we show that association with amphibian aquatic habitat types (bromeliad phytotelmata versus stream) across Central America results in the odds of being threatened by Bd being five times higher in stream microhabitats. This differential threat of Bd was supported in our study by a significantly lower prevalence of Bd in bromeliad-associated amphibian species compared to riparian species in Honduran cloud forests. Evidence that the bromeliad environment is less favorable for Bd transmission is exemplified by significantly less suitable physicochemical conditions and higher abundance of Bd-ingesting micro-eukaryotes present in bromeliad water. These factors may inhibit aquatic Bd zoospore survival and the development of an environmental reservoir of the pathogen. Bromeliad phytotelmata thus may act as environmental refuges from Bd, which contribute to protecting associated amphibian communities against chytridiomycosis-driven amphibian declines that threaten the nearby riparian communities.
TL;DR: It is concluded that two determinants of pathogen infection dynamics, body condition and pathogen occurrence, vary along an urbanization gradient, potentially mediating the impact of urbanization on avian health.
Abstract: Urbanization strongly affects biodiversity, altering natural communities and often leading to a reduced species richness. Yet, despite its increasingly recognized importance, how urbanization impacts on the health of individual animals, wildlife populations and on disease ecology remains poorly understood. To test whether, and how, urbanization-driven ecosystem alterations influence pathogen dynamics and avian health, we use house sparrows (Passer domesticus) and Yersinia spp. (pathogenic for passerines) as a case study. Sparrows are granivorous urban exploiters, whose western European populations have declined over the past decades, especially in highly urbanized areas. We sampled 329 house sparrows originating from 36 populations along an urbanization gradient across Flanders (Belgium), and used isolation combined with 'matrix-assisted laser desorption ionization- time of flight mass spectrometry' (MALDI-TOF MS) and PCR methods for detecting the presence of different Yersinia species. Yersinia spp. were recovered from 57.43% of the sampled house sparrows, of which 4.06%, 53.30% and 69.54% were identified as Y. pseudotuberculosis, Y. enterocolitica and other Yersinia species, respectively. Presence of Yersinia was related to the degree of urbanization, average daily temperatures and the community of granivorous birds present at sparrow capture locations. Body condition of suburban house sparrows was found to be higher compared to urban and rural house sparrows, but no relationships between sparrows' body condition and presence of Yersinia spp. were found. We conclude that two determinants of pathogen infection dynamics, body condition and pathogen occurrence, vary along an urbanization gradient, potentially mediating the impact of urbanization on avian health.
TL;DR: The correlation between local IgA production and protection induced by a weakly haemolytic B. hyodysenteriae strain provides leads for future vaccine development against swine dysentery.
Abstract: Swine dysentery caused by Brachyspira hyodysenteriae, results in substantial economic losses in swine producing countries worldwide. Although a number of different vaccine approaches have been explored with regard to this disease, they show limitations and none of them have reached the market. We here determine the vaccine potential of a weakly haemolytic B. hyodysenteriae strain. The virulence of this strain was assessed in experimental infection trials and its protection against swine dysentery was quantified in a vaccination-challenge experiment using a seeder infection model. Systemic IgG production and local IgA production were monitored in serum and faeces respectively. Across all trials, pigs that were colonized by virulent, strongly haemolytic B. hyodysenteriae strains consistently developed swine dysentery, in contrast to none of the pigs colonized by the weakly haemolytic B. hyodysenteriae vaccine strain. In the seeder vaccination trial nearly all immunised animals developed swine dysentery on subsequent challenge with a virulent strain, but the speed of spread of swine dysentery and faecal score were significantly reduced in animals immunised with the weakly haemolytic strain compared to sham-immunised animals. The IgA response of immunised animals upon challenge with a virulent B. hyodysenteriae strain significantly correlated to a later onset of disease. The correlation between local IgA production and protection induced by a weakly haemolytic B. hyodysenteriae strain provides leads for future vaccine development against swine dysentery.
TL;DR: In this article, a severe skin disease has affected free-ranging, endangered Lesser Antillean iguanas (Iguana delicatissima) on the French Caribbean island of Saint Barthelemy and identified Devriesea agamarum as the causative agent.
Abstract: Infectious diseases affecting wildlife are drivers of global biodiversity loss. Here we report a bacterial threat to endangered wild reptiles. Since April 2011, a severe skin disease has affected free-ranging, endangered Lesser Antillean iguanas (Iguana delicatissima) on the French Caribbean island of Saint Barthelemy and we identified Devriesea agamarum as the causative agent. The presence of this bacterium was also demonstrated in healthy lizards (anoles) co-inhabiting the island. All isolates from the iguanas corresponded to a single AFLP genotype that until now has exclusively been associated with infections in lizard species in captivity. The clonal relatedness of the isolates and recent emergence of the disease suggest recent arrival of a virulent D. agamarum clone on the island. The presence of healthy but infected lizards suggests the presence of asymptomatic reservoir hosts. This is the first description of a bacterial disease that poses a conservation threat towards free-ranging squamates.
TL;DR: The realized trophic strategies, i.e. generalist at the population and specialist at the individual level, were highly consistent geographically and the two populations exploited the different arrays of prey found in their environments similarly.
Abstract: The study of trophic ecology of terrestrial salamanders is central for a better understanding of their adaptability and dispersal, in particular in Mediterranean ecosystems where their feeding activity is reduced because of prolonged arid periods. Terrestrial salamanders are generalist predators that feed on a large array of invertebrate prey groups, however, there are few studies comparing the feeding strategy and the trophic specialization at the individual level in conspecific populations of salamanders living in different habitats. In this study, two populations of the Sardinian endemic salamander Speleomantes imperialis were sampled in areas characterized by different climate, vegetation and geological substrate. Dietary habits, obtained by stomach flushing, and physiological condition, assessed through a body condition index, were analysed and compared between populations. The two populations displayed different diets on the basis of the taxonomic composition of prey categories, but both of them behaved as generalist predators and shared a similar body condition index. Moreover, in both populations the indices of individual trophic specialization were significantly different from null models assuming a random prey distribution among predators. Therefore, the two populations were largely composed by individually specialized salamanders. Overall, these findings are in good agreement with other studies on the trophic ecology of top predators and in particular of terrestrial salamanders. The realized trophic strategies, i.e. generalist at the population and specialist at the individual level, were highly consistent geographically and the two populations exploited the different arrays of prey found in their environments similarly.
TL;DR: In this paper, the authors evaluated the effect of the Fusarium mycotoxins deoxynivalenol ( DON) and fumonisins (FBs) on the stress response in broiler chickens, using corticosterone in plasma as a biomarker.
TL;DR: It is concluded that brown rats are frequent carriers for various Yersinia spp.
Abstract: Brown rats (Rattus norvegicus) have been identified as potential carriers of Yersinia enterocolitica and Y. pseudotuberculosis, the etiological agents of yersiniosis, the third most reported bacterial zoonosis in Europe. Enteropathogenic Yersinia spp. are most often isolated from rats during yersiniosis cases in animals and humans, and from rats inhabiting farms and slaughterhouses. Information is however lacking regarding the extent to which rats act as carriers of these Yersinia spp.. In 2013, 1088 brown rats across Flanders, Belgium, were tested for the presence of Yersinia species by isolation method. Identification was performed using MALDI-TOF MS, PCR on chromosomal- and plasmid-borne virulence genes, biotyping and serotyping. Yersinia spp. were isolated from 38.4% of the rats. Of these, 53.4% were designated Y. enterocolitica, 0.7% Y. pseudotuberculosis and 49.0% other Yersinia species. Two Y. enterocolitica possessing the virF-, ail- and ystA-gene were isolated. Additionally, the ystB-gene was identified in 94.1% of the other Y. enterocolitica isolates, suggestive for biotype 1A. Three of these latter isolates simultaneously possessed the ail-virulence gene. Significantly more Y. enterocolitica were isolated during winter and spring compared to summer. Based on our findings we can conclude that brown rats are frequent carriers for various Yersinia spp., including Y. pseudotuberculosis and (human pathogenic) Y. enterocolitica which are more often isolated during winter and spring.
TL;DR: It is hypothesized that Salmonella Enteritidis downregulates flagellar gene expression in the oviduct and consequently prevents aflagellin-induced inflammatory response, thereby increasing its ovidUCT colonization efficiency.
Abstract: Egg borne Salmonella Enteritidis is still a major cause of human food poisoning. Eggs can become internally contaminated following colonization of the hen’s oviduct. In this paper we aimed to analyze the role of flagella of Salmonella Enteritidis in colonization of the hen’s oviduct. Using a transposon library screen we showed that mutants lacking functional flagella are significantly more efficient in colonizing the hen’s oviduct in vivo. A micro-array analysis proved that transcription of a number of flagellar genes is down-regulated inside chicken oviduct cells. Flagella contain flagellin, a pathogen associated molecular pattern known to bind to Toll-like receptor 5, activating a pro-inflammatory cascade. In vitro tests using primary oviduct cells showed that flagellin is not involved in invasion. Using a ligated loop model, a diminished inflammatory reaction was seen in the oviduct resulting from injection of an aflagellated mutant compared to the wild-type. It is hypothesized that Salmonella Enteritidis downregulates flagellar gene expression in the oviduct and consequently prevents a flagellin-induced inflammatory response, thereby increasing its oviduct colonization efficiency.
TL;DR: There is evidence that GHPV is not only present in countries known for extensive waterfowl production, but disease outbreaks also occur in countries with less extensive goose production.
Abstract: Goose hemorrhagic polyomavirus (GHPV) is the causative agent of hemorrhagic nephritis enteritis of geese (HNEG), one of the major diseases of domestic geese in Europe. This case report describes a persistent outbreak of a GHPV infection on a Belgian goose farm. Clinical symptoms, necropsy lesions, and histopathologic lesions observed were compatible with previous reports of HNEG outbreaks. PCR analysis confirmed the diagnosis of GHPV. To our knowledge, this is the first report of an outbreak of a GHPV infection on a Belgian goose farm. This is evidence that GHPV is not only present in countries known for extensive waterfowl production, but disease outbreaks also occur in countries with less extensive goose production.
TL;DR: The findings suggest the presence of passerine-adapted Salmonella strains in free-ranging tit populations with host pathogen co-existence, and the impact on health and reproduction a larger number of samples have to be analyzed.
Abstract: Endemic infections with the common avian pathogen Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella Typhimurium) may incur a significant cost on the host population. In this study, we determined the potential of endemic Salmonella infections to reduce the reproductive success of blue (Cyanistes caeruleus) and great (Parus major) tits by correlating eggshell infection with reproductive parameters. The fifth egg of each clutch was collected from nest boxes in 19 deciduous forest fragments. Out of the 101 sampled eggs, 7 Salmonella Typhimurium isolates were recovered. The low bacterial prevalence was reflected by a similarly low serological prevalence in the fledglings. In this study with a relatively small sample size, presence of Salmonella did not affect reproductive parameters (egg volume, clutch size, number of nestlings and number of fledglings), nor the health status of the fledglings. However, in order to clarify the impact on health and reproduction a larger number of samples have to be analyzed. Phage typing showed that the isolates belonged to the definitive phage types (DT) 193 and 99, and multi-locus variable number tandem repeat analysis (MLVA) demonstrated a high similarity among the tit isolates, but distinction to human isolates. These findings suggest the presence of passerine-adapted Salmonella strains in free-ranging tit populations with host pathogen co-existence.
TL;DR: Oropharyngeal swab samples were collected from 438 live racing pigeons (Columba livia), with and without signs of respiratory disease, that were housed in 220 lofts in 3 provinces in the western part of the Netherlands to identify Mycoplasma species and pigeon herpesvirus-1 (PHV-1) from the samples.
Abstract: Oropharyngeal swab samples were collected from 438 live racing pigeons (Columba livia), with and without signs of respiratory disease, that were housed in 220 lofts in 3 provinces in the western part of the Netherlands. Polymerase chain reaction (PCR) was used to identify Mycoplasma species and pigeon herpesvirus-1 (PHV-1) from the samples. In 8.6% of the pigeon lofts tested, signs of respiratory disease were present in pigeons at sampling, and in 30.9% of the sampled pigeon lofts, respiratory signs were observed in pigeons during the 6-month period immediately before sampling. A total of 39.8% of tested pigeons (54.5% of tested lofts) were positive for Mycoplasma species, and 30.6% of tested pigeons (48.6% of tested lofts) were positive for PHV-1. In 15.8% of the tested pigeons (26.8% of tested pigeon lofts), coinfection by Mycoplasma species and PHV-1 was identified. The number of pigeon lofts having pigeons coinfected by Mycoplasma species and PHV-1 was higher than that where only one of the infections was identified. Neither the presence of Mycoplasma species, PHV-1, nor the co-occurrence of both infections was significantly associated with signs of respiratory disease.
TL;DR: The findings show a low prevalence of Batrachochytrium dendrobatidis in a population of a high elevation Bolitoglossa species in Nicaragua in an environmental context where pathogen driven declines would be expected to occur.
Abstract: Amphibians are the most threatened terrestrial vertebrates on the planet and are iconic in the global biodiversity crisis. Their global decline caused by the fungal agent Batrachochytrium dendrobatidis (Bd) is well known. Declines of Mesoamerican salamanders of the family Plethodontidae, mainly affecting high elevation species, have equally been attributed to Bd. Here we report the prevalence of Bd in a population of a high elevation Bolitoglossa species in Nicaragua, since its description in 1999 until 2011 in the absence of any obvious population declines. Our findings show a low prevalence in an environmental context where pathogen driven declines would be expected to occur.