Maternal Antibody Transfer in Yellow-legged Gulls

International audienc

Interpreting ELISA analyses from wild animal samples: some recurrent issues and solutions

Many studies in disease and ecological immunology rely on the use of assays that quantify the amount of specific antibodies (immunoglobulin) in samples. Enzyme‐linked immunosorbent assays (ELISAs) are increasingly used in ecology due to their availability for a broad array of antigens and the limited amount of sampling material they require. Two recurrent methodological issues are nevertheless faced by researchers: (1) the limited availability of immunological assays and reagents developed for non‐model species, and (2) the statistical determination of the cut‐off threshold used to distinguish individual samples that are likely to have or not to have antibodies against a specific antigen. Here, we outline two solutions to deal with these issues. First, we show that implementing two assays with differing detection methods can help validate the use of reagents, such as antibodies, in species different from their intended target. We illustrate this by comparing the quantification of specific vaccinal antibodies against Newcastle disease virus (NDV) using two ELISA approaches in four seabird species (Cory's shearwater, European shag, European storm petrel and Southern rockhopper penguin). Second, we provide a simple way to determine from the distribution of ELISA values whether the assayed samples are likely to be made of a single group of individuals (likely negative) or of two groups of individuals (negative and positive). We illustrate the use of this approach with two independent datasets: NDV antibody levels following vaccination and anti‐Borrelia antibody levels following natural exposure. The practical implementation of these methodological approaches could provide a way to efficiently apply ELISAs and other immune‐based assays to address questions in the growing fields of ecological immunology and disease ecology

Seabirds and the circulation of Lyme borreliosis bacteria in the North Pacific

Seabirds act as natural reservoirs to Lyme borreliosis spirochetes and may play a significant role in the global circulation of these pathogens. While Borrelia burgdorferi sensu lato (Bbsl) has been shown to occur in ticks collected from certain locations in the North Pacific, little is known about interspecific differences in exposure within the seabird communities of this region. We examined the prevalence of anti-Bbsl antibodies in 805 individuals of nine seabird species breeding across the North Pacific. Seroprevalence varied strongly among species and locations. Murres (Uria spp.) showed the highest antibody prevalence and may play a major role in facilitating Bbsl circulation at a worldwide scale. Other species showed little or no signs of exposure, despite being present in multispecific colonies with seropositive birds. Complex dynamics may be operating in this wide scale, natural hostparasite system, possibly mediated by the host immune system and host specialization of the tick vector

Contacts and foot and mouth disease transmission from wild to domestic bovines in Africa

Wildlife is a maintenance host for several significant livestock diseases. Interspecific pathogen transmission may occur in complex socio-ecological systems at wild-domestic interfaces that have so far been seldom studied. We investigated the relationship between the dynamics of foot and mouth disease (FMD) in vaccinated and unvaccinated cattle populations with respect to frequency of contacts with African buffalo at different buffalo-cattle interfaces. A total of 36 GPS collars were deployed on African buffalo (Syncerus caffer) and cattle (Bos taurus, Bos indicus) to assess contact patterns at the periphery of 3 protected areas in Zimbabwe. Simultaneously, a longitudinal survey of 300 cattle with five repeated sampling sessions on known individuals during 16 months was undertaken. Immunological assays (ELISAs), that allowed tracking the production of antibodies following infection or vaccination, were used to assess serological transitions (i.e., incidence and reversion) in the surveyed cattle. Variation in rates of serological transitions across seasons, sites and as a function of the frequency of contact with buffalo was analyzed using generalized linear mixed models. The incidence in the cattle populations of FMD antibodies produced following infection varied among sites and as a function of contact rates with African buffalo. The incidence was higher for sites with higher contact rates between the two species. The serological incidence was also related to seasons, being higher during the dry or rainy seasons depending on sites. The reversion rate pattern was the opposite of this incidence rate pattern. Vaccination seemed partly efficient at the individual level, but it did not prevent the diffusion of FMD viruses from the wild reservoir host to the domestic cattle population. Furthermore, antibodies were detected in areas where cattle had not been vaccinated, suggesting that the virus may have spread without being detected in domestic populations. Access to resources shared by buffalo and livestock, particularly water and grazing areas during the dry season, could partly explain the observed patterns of FMD transmission. We discuss how insights on ecological processes leading to wildlife-livestock contacts may provide some innovative solutions to improve FMD management, including surveillance, prevention or control of buffalo-borne outbreaks, by adopting strategies targeting risky areas and periods. (Résumé d'auteur

Mixture models for distance sampling detection functions

Funding: EPSRC DTGWe present a new class of models for the detection function in distance sampling surveys of wildlife populations, based on finite mixtures of simple parametric key functions such as the half-normal. The models share many of the features of the widely-used “key function plus series adjustment” (K+A) formulation: they are flexible, produce plausible shapes with a small number of parameters, allow incorporation of covariates in addition to distance and can be fitted using maximum likelihood. One important advantage over the K+A approach is that the mixtures are automatically monotonic non-increasing and non-negative, so constrained optimization is not required to ensure distance sampling assumptions are honoured. We compare the mixture formulation to the K+A approach using simulations to evaluate its applicability in a wide set of challenging situations. We also re-analyze four previously problematic real-world case studies. We find mixtures outperform K+A methods in many cases, particularly spiked line transect data (i.e., where detectability drops rapidly at small distances) and larger sample sizes. We recommend that current standard model selection methods for distance sampling detection functions are extended to include mixture models in the candidate set.Publisher PDFPeer reviewe

Climate change in the Arctic: Testing the poleward expansion of ticks and tick‐borne diseases

Climate change is most strongly felt in the polar regions of the world, with significant impacts on the species that live there. The arrival of parasites and pathogens from more temperate areas may become a significant problem for these populations, but current observations of parasite presence often lack a historical reference of prior absence. Observations in the high Arctic of the seabird tick Ixodes uriae suggested that this species expanded poleward in the last two decades in relation to climate change. As this tick can have a direct impact on the breeding success of its seabird hosts and vectors several pathogens, including Lyme disease spirochaetes, understanding its invasion dynamics is essential for predicting its impact on polar seabird populations. Here, we use population genetic data and host serology to test the hypothesis that I. uriae recently expanded into Svalbard. Both black-legged kittiwakes (Rissa tridactyla) and thick-billed murres (Uria lomvia) were sampled for ticks and blood in Kongsfjorden, Spitsbergen. Ticks were genotyped using microsatellite markers and population genetic analyses were performed using data from 14 reference populations from across the tick's northern distribution. In contrast to predictions, the Spitsbergen population showed high genetic diversity and significant differentiation from reference populations, suggesting long-term isolation. Host serology also demonstrated a high exposure rate to Lyme disease spirochaetes (Bbsl). Targeted PCR and sequencing confirmed the presence of Borrelia garinii in a Spitsbergen tick, demonstrating the presence of Lyme disease bacteria in the high Arctic for the first time. Taken together, results contradict the notion that I. uriae has recently expanded into the high Arctic. Rather, this tick has likely been present for some time, maintaining relatively high population sizes and an endemic transmission cycle of Bbsl. Close future observations of population infestation/infection rates will now be necessary to relate epidemiological changes to ongoing climate modifications

Similar at-sea behaviour but different habitat use between failed and successful breeding albatrosses

Breeding failure is expected to induce behavioural changes in central place foragers. Indeed, after a failed reproductive attempt, breeding individuals are relieved from having to return to their breeding site for reproductive duties and thus are less constrained than successful breeders in their movements during the remainder of the breeding season. Accordingly, they are expected to adjust their behaviour, travelling longer in distance and/or time to reach foraging grounds. They are also expected to use different foraging areas to decrease local intra-specific competition with successful breeders. We compared the at-sea behaviour and habitat use of successful and failed Indian yellow-nosed albatrosses nesting in Amsterdam Island, Southern Indian Ocean, during 2 chick-rearing seasons. Failed breeders exhibited the same at-sea foraging behaviour, travelling as far and as long as successful breeders. They also spent the same amount of time on their nest between at-sea trips. Nevertheless, habitat models revealed partial spatial segregation of failed breeders, which used specific foraging areas characterized by deeper and colder waters in addition to the areas they shared with successful breeders. Our study shows the importance of combining a range of analytical methods (spatial analysis, behavioural inferences with advanced movement models and habitat models) to infer the at-sea behaviour and habitat use of seabirds. It also stresses the importance of considering individual breeding status when aiming to understand the spatial distribution of individuals, especially when this information may have conservation implications

Infestation of small seabirds by Ornithodoros maritimus ticks : Effects on chick body condition, reproduction and associated infectious agents

Funding This Project was partially funded by the Govern Balear (Acciones Especiales, AAEE031/2017) and the Spanish Ministry of Innovation and Universities (RESET, ref: CGL2017-85210-P). ASA was funded by the Spanish Ministry of Innovation and Universities Innovation and Universities, the Agencia Estatal de Investigación and the European Social Found (RYC-2017- 22796). Data accessibility Data will be available via the Spanish National Research Council data repository. Sanz-Aguilar, A., Payo-Payo, A., Igual, J. M., Rotger, A., Viñas Torres, M., Picorelli, V., 2019. Storm petrel data sets. https://doi.org/10.20350/digitalCSIC/. Declaration of Competing Interest The authors declare no conflicts of interest. Acknowledgements We thank Esteban Cardona, Oliver Martínez, Raül Luna, Toni Avila, Esther López Marín, Miquel Mas, Enric Real y Santiago de la Vega for their help and support on the colony monitoring. Balearic Islands Government, Sant Josep City Hall, COFIB and Fundación Balearia for their logistic support. Ethical statement This study was authorized by the Reserves des Vedrà es Vedranell i els illots de Ponent, Balearic Government. All aspects of the study were performed according to guidelines established for the ethical treatment of animals and complied with current Spanish regulations. The collection of ticks was authorized by the Balearic Government (Reference: CAP 21/2018).Peer reviewedPostprin