Microscopic Aquatic Predators Strongly Affect Infection Dynamics of a Globally Emerged Pathogen

Research on emerging infectious wildlife diseases has placed particular emphasis on host-derived barriers to infection and disease. This focus neglects important extrinsic determinants of the host/pathogen dynamic, where all barriers to infection should be considered when ascertaining the determinants of infectivity and pathogenicity of wildlife pathogens [1–3]. Those pathogens with free-living stages, such as fungi causing catastrophic wildlife declines on a global scale [4], must confront lengthy exposure to environmental barriers before contact with an uninfected host [5–8]. Hostile environmental conditions therefore have the ability to decrease the density of infectious particles, reducing the force of infection and ameliorating the impact as well as the probability of establishing an infection [9]. Here we show that, in nature, the risk of infection and infectious burden of amphibians infected by the chytrid fungus Batrachochytrium dendrobatidis (Bd) have a significant, site-specific component, and that these correlate with the microfauna present at a site. Experimental infections show that aquatic microfauna can rapidly lower the abundance and density of infectious stages by consuming Bd zoospores, resulting in a significantly reduced probability of infection in anuran tadpoles. Our findings offer new perspectives for explaining the divergent impacts of Bd infection in amphibian assemblages and contribute to our understanding of ecosystem resilience to colonization by novel pathogens

An emerging viral pathogen truncates population age structure in a European amphibian and may reduce population viability

Infectious diseases can alter the demography of their host populations, reducing their viability even in the absence of mass mortality. Amphibians are the most threatened group of vertebrates globally, and emerging infectious diseases play a large role in their continued population declines. Viruses belonging to the genus Ranavirus are responsible for one of the deadliest and most widespread of these diseases. To date, no work has used individual level data to investigate how ranaviruses affect population demographic structure. We used skeletochronology and morphology to evaluate the impact of ranaviruses on the age structure of populations of the European common frog (Rana temporaria) in the UK. We compared ecologically similar populations that differed most notably in their historical presence or absence of ranavirosis (the acute syndrome caused by ranavirus infection). Our results suggest that ranavirosis may truncate the age structure of R. temporaria populations. One potential explanation for such a shift might be increased adult mortality and subsequent shifts in the life history of younger age classes that increase reproductive output earlier in life. Additionally, we constructed population projection models which indicated that such increased adult mortality could heighten the vulnerability of frog populations to stochastic environmental challenges

Recent Asian origin of chytrid fungi causing global amphibian declines

Globalized infectious diseases are causing species declines worldwide, but their source often remains elusive. We used whole-genome sequencing to solve the spatiotemporal origins of the most devastating panzootic to date, caused by the fungus Batrachochytrium dendrobatidis, a proximate driver of global amphibian declines. We traced the source of B. dendrobatidis to the Korean peninsula, where one lineage, BdASIA-1, exhibits the genetic hallmarks of an ancestral population that seeded the panzootic. We date the emergence of this pathogen to the early 20th century, coinciding with the global expansion of commercial trade in amphibians, and we show that intercontinental transmission is ongoing. Our findings point to East Asia as a geographic hotspot for B. dendrobatidis biodiversity and the original source of these lineages that now parasitize amphibians worldwide

Chytrid fungi and global amphibian declines

Discovering that chytrid fungi cause chytridiomycosis in amphibians represented a paradigm shift in our understanding of how emerging infectious diseases contribute to global patterns of biodiversity loss. In this Review we describe how the use of multidisciplinary biological approaches has been essential to pinpointing the origins of amphibian-parasitizing chytrid fungi, including Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans, as well as to timing their emergence, tracking their cycles of expansion and identifying the core mechanisms that underpin their pathogenicity. We discuss the development of the experimental methods and bioinformatics toolkits that have provided a fuller understanding of batrachochytrid biology and informed policy and control measure

Persistence of the emerging pathogen Batrachochytrium dendrobatidis outside the amphibian host greatly increases the probability of host extinction

Pathogens do not normally drive their hosts to extinction; however, Batrachochytrium dendrobatidis, which causes amphibian chytridiomycosis, has been able to do so. Theory predicts that extinction can be caused by long-lived or saprobic free-living stages. The hypothesis that such a stage occurs in B. dendrobatidis is supported by the recent discovery of an apparently encysted form of the pathogen. To investigate the effect of a free-living stage of B. dendrobatidis on host population dynamics, a mathematical model was developed to describe the introduction of chytridiomycosis into a breeding population of Bufo bufo, parametrized from laboratory infection and transmission experiments. The model predicted that the longer that B. dendrobatidis was able to persist in water, either due to an increased zoospore lifespan or saprobic reproduction, the more likely it was that it could cause local B. bufo extinction (defined as decrease below a threshold level). Establishment of endemic B. dendrobatidis infection in B. bufo, with severe host population depression, was also possible, in agreement with field observations. Although this model is able to predict clear trends, more precise predictions will only be possible when the life history of B. dendrobatidis, including free-living stages of the life cycle, is better understood

Principer för planering av vägar för vindkraftsområde

Det här examensarbetet handlar om iståndsättning av befintliga och planering av nya vägar till en vindkraftspark. Storbötesområdet i Pensala är ett exempel. Där kommer att byggas 32 vindmöllor utspridda på en yta av ca 2000 ha. Uppdragsgivare är Prokon Wind Energi Finland. Målet är att slå fast principer vid dimensionering av vägar, vilka skall uppfylla alla tekniska krav. Detta vill säga krav som ställs beträffande vägens bärighet samt formen på vertikala och horisontala kurvor. De här egenskaperna har en avgörande betydelse vid transport av tunga och långa laster. Vidare omfattar arbetet några förslag till hurudana jord och bärighetsprov man bör ta vid planering av vägar. Den teoretiska delen av arbetet grundar sig på InfraRYL, RT kort samt olika broschyrer gällande utbyggnad och transport av vindkraftverk. Några fackmän inom transportoch byggbranschen bidrar via intervjuer med sin sakkunskap. I den empiriska delen behandlas okulär besiktning av terräng, jordprovstest vid Novias laboratorium och olika mätningar på området. Som resultat av detta arbete görs ett utkast till situationsplan för Storbötesområdet, längdprofil och skärning till en vald vägsträcka, vägkort samt entreprenadprogram. _________________________________Tämä opinnäytetyö käsittelee tuulimyllyalueelle johtavien vanhojen teiden kunnostamista sekä uusien suunnittelemista. Storböte niminen alue Pensalassa on yksi tuulivoimahanke. Sinne on tarkoitus rakentaa 32 tuulimyllyä. Toimeksiantaja on Prokon Wind Energi Finland. Aikomus on selvittää periaatteet, joiden mukaan teiden mitat lasketaan täyttäen kaikki tekniset vaatimukset. Asetetut vaatimukset koskevat ensisijassa teiden kantavuutta sekä mutkien muotoa. Nämä ominaisuudet ovat olennaisia raskaiden ja pitkien kuormien kuljettamisessa. Työhön sisältyy myös ehdotus siihen, mitkä maanäytteet pitää ottaa ja mitkä kantavuuskokeet pitää suorittaa teiden suunnittelemisen yhteydessä. Teoreettinen osa perustuu InfraRYL hyn, Rt kortistoon sekä esitteisiin koskien tuulivoimalan perustamista ja myllyjen kuljettamista. Rakennus ja kuljetusalan asiantuntijat antavat mielipiteitään eri asiaan kuuluvien ongelmien ratkaisemisesta. Empiirisessä osassa on käsitelty maaston silmämääräinen tarkastus, Novian laboratoriossa maanäytteistä tehdyt analyysit ja erilaisia mittaustöitä hankkeen alueella. Tuloksena on tehty asemapiirros Storböte-alueelta, pitkittäisprofiili ja leikkaus valitulta tieosuudelta sekä urakoitsijan ohjelma.This thesis work is about putting existing roads in order and planning new ones for a windmill farm. Storböte in Pensala is such a farm. Thirtytwo windmills are to be built there in an area of 2000 hectares. The work is done on behalf of Prokon Wind Energi Finland. The purpose of this work is to compose a manual of how to build these roads so that all demands are fulfilled, because the heavy turbines and the tall rotor blades make great demands on the transportation. To make a stable road you need to take soil samples and run some tests. This work includes suggestions and explanations of some methods. The theoretical part is based on InfraRYL, RT cards and brochures on transporting windmills and building wind farms. Professionals in the transportation and construction industry have also contributed with their special knowledge. The empirical part consists of visual inspections of the terrain, soil sample testing at Novia laboratory and various measurements in the field. The result of this work is a final site plan for Storböte area, a cross section of a road and a longitudinal profile of a chosen section. There are also short technical description cards of those roads and one example of a tender management program

Genetic and demographic vulnerability of adder populations : Results of a genetic study in mainland Britain

Genetic factors are often overlooked in conservation planning, despite their importance in small isolated populations. We used mitochondrial and microsatellite markers to investigate population genetics of the adder (Vipera berus) in southern Britain, where numbers are declining. We found no evidence for loss of heterozygosity in any of the populations studied. Genetic diversity was comparable across sites, in line with published levels for mainland Europe. However, further analysis revealed a striking level of relatedness. Genetic networks constructed from inferred first degree relationships suggested a high proportion of individuals to be related at a level equivalent to that of half-siblings, with rare inferred full-sib dyads. These patterns of relatedness can be attributed to the high philopatry and low vagility of adders, which creates high local relatedness, in combination with the polyandrous breeding system in the adder, which may offset the risk of inbreeding in closed populations. We suggest that reliance on standard genetic indicators of inbreeding and diversity may underestimate demographic and genetic factors that make adder populations vulnerable to extirpation. We stress the importance of an integrated genetic and demographic approach in the conservation of adders, and other taxa of similar ecology