Evidence of exposure of laughing doves (Spilopelia senegalensis) to West Nile and Usutu viruses in southern Tunisian oases.

It has previously been suggested that southern Tunisian oases may be suitable areas for the circulation of flaviviruses. In order to anticipate and prevent possible epidemiological spread of flaviviruses in humans and domestic animals, the ecology of their transmission in the oasis system needs to be better understood. Thus, the aim of this study was to assess the seroprevalence of anti-flavivirus antibodies in the laughing dove (Spilopelia senegalensis), an abundant resident bird in Tunisian oases. Anti-flavivirus antibodies were detected in 17% of sampled doves. Ten per cent of the total tested doves were West Nile virus (WNV) seropositive and 4% were Usutu virus (USUV) seropositive, which provides the first evidence of USUV circulation in Tunisian birds. We also found that the occurrence probability of anti-flavivirus antibodies in dove plasma increased with decreasing distance to coast, suggesting that doves inhabiting coastal oases were more exposed to flaviviruses compared with those inhabiting inland oases. We also found significantly higher antibody occurrence probability in adult doves compared with young doves, which underlines the effect of exposure time. Overall, our results suggest that the laughing dove may be used for WNV and USUV surveillance in southern Tunisia. They also stress the need for investigations combining data on birds and mosquitoes to better understand the ecological factors governing the circulation of flaviviruses in this area.

Serological evidence for the circulation of flaviviruses in seabird populations of the western Indian Ocean.

Birds play a central role in the epidemiology of several flaviviruses of concern for public and veterinary health. Seabirds represent the most abundant and widespread avifauna in the western Indian Ocean and may play an important role as host reservoirs and spreaders of arthropod-borne pathogens such as flaviviruses. We report the results of a serological investigation based on blood samples collected from nine seabird species from seven islands in the Indian Ocean. Using a commercial competitive enzyme-linked immunosorbent assay directed against the prototypic West Nile flavivirus, antibodies against flaviviruses were detected in the serum of 47 of the 855 seabirds tested. They were detected in bird samples from three islands and from four bird species. Seroneutralization tests on adults and chicks suggested that great frigatebirds (Fregata minor) from Europa were infected by West Nile virus during their non-breeding period, and that Usutu virus probably circulated within bird colonies on Tromelin and on Juan de Nova. Real-time polymerase chain reactions performed on bird blood samples did not yield positive results precluding the genetic characterization of flavivirus using RNA sequencing. Our findings stress the need to further investigate flavivirus infections in arthropod vectors present in seabird colonies.

Maternal antibody persistence: a neglected life-history trait with implications from albatross conservation to comparative immunology.

The evolution of different life-history strategies has been suggested as a major force constraining physiological mechanisms such as immunity. In some long-lived oviparous species, a prolonged persistence of maternal antibodies in offspring could thus be expected in order to protect them over their long growth period. Here, using an intergenerational vaccination design, we show that specific maternal antibodies can display an estimated half-life of 25 days post-hatching in the nestlings of a long-lived bird. This temporal persistence is much longer than previously known for birds and it suggests specific properties in the regulation of IgY immunoglobulin catabolism in such a species. We also show that maternal antibodies in the considered procellariiform species are functional as late as 20 days of age. Using a modelling approach, we highlight that the potential impact of such effects on population viability could be important, notably when using vaccination for conservation. These results have broad implications, from comparative immunology to evolutionary eco-epidemiology and conservation biology.

Variable exposure and immunological response to Lyme disease Borrelia among North Atlantic seabird species.

Colonial seabirds often breed in large aggregations. These individuals can be exposed to parasitism by the tick Ixodes uriae, but little is known about the circulation of pathogens carried by this ectoparasite, including Lyme disease Borrelia. Here we investigated the prevalence of antibodies (Ab) against Borrelia burgdorferi sensu lato in seabird species sampled at eight locations across the North Atlantic. Using enzyme-linked immunosorbent assay tests, we found that the prevalence of anti-Borrelia Ab in adult seabirds was 39.6% on average (over 444 individuals), but that it varied among colonies and species. Common guillemots showed higher seroprevalence (77.1%+/-5.9) than black-legged kittiwakes (18.6%+/-6.7) and Atlantic puffins (22.6%+/-6.3). Immunoblot-banding patterns of positive individuals, reflecting the variability of Borrelia antigens against which Ab were produced, also differed among locations and species, and did not tightly match the prevalence of Borrelia phylogroups previously identified in ticks collected from the same host individuals. These results represent the first report of the widespread prevalence of Ab against Borrelia within an assemblage of seabird species and demonstrate that Borrelia is an integrated aspect in the interaction between seabirds and ticks. More detailed studies on the dynamics of Borrelia within and among seabird species at different spatial scales will now be required to better understand the implications of this interaction for seabird ecology and the epidemiology of Lyme disease.

Food availability affects the maternal transfer of androgens and antibodies into eggs of a colonial seabird.

Mothers can improve the quality of their offspring by increasing the level of certain components in their eggs. To examine whether or not mothers increase deposition of such components in eggs as a function of food availability, we food-supplemented black-legged kittiwake females (Rissa tridactyla) before and during egg laying and compared deposition of androgens and antibodies into eggs of first and experimentally induced replacement clutches. Food-supplemented females transferred lower amounts of androgens and antibodies into eggs of induced replacement clutches than did non-food-supplemented mothers, whereas first clutches presented no differences between treatments. Our results suggest that when females are in lower condition, they transfer more androgens and antibodies into eggs to facilitate chick development despite potential long-term costs for juveniles. Females in prime condition may avoid these potential long-term costs because they can provide their chicks with more and higher quality resources.

Analysis of aggregation, a worked example: numbers of ticks on red grouse chicks.

The statistical aggregation of parasites among hosts is often described empirically by the negative binomial (Poisson-gamma) distribution. Alternatively, the Poisson-lognormal model can be used. This has the advantage that it can be fitted as a generalized linear mixed model, thereby quantifying the sources of aggregation in terms of both fixed and random effects. We give a worked example, assigning aggregation in the distribution of sheep ticks Ixodes ricinus on red grouse Lagopus lagopus scoticus chicks to temporal (year), spatial (altitude and location), brood and individual effects. Apparent aggregation among random individuals in random broods fell 8-fold when spatial and temporal effects had been accounted for.

Induced maternal response to the Lyme disease spirochaete Borrelia burgdorferi sensu lato in a colonial seabird, the kittiwake Rissa tridactyla.

Mothers are predicted to invest in their offspring depending on the quality of their mate, their opportunity to invest in future reproduction and the characteristics of the habitat in which their offspring will be born. Recent studies have suggested a transfer of maternal immunity to offspring as an induced response to the local presence of parasites in the environment, but evidence has been indirect. Here, we show the presence of antibodies against the Lyme disease agent Borrelia burgdorferi sensu lato, a spirochaete transmitted by the seabird tick Ixodes uriae, in the eggs of kittiwakes Rissa tridactyla. We report higher prevalence of antibodies against Borrelia in eggs from breeding areas with higher prevalence and abundance of ticks. Further, high repeatabilities of antibody-positive eggs within clutches and between first and replacement clutches show that, within a breeding season, females differ consistently with respect to the expression of this induced maternal response. Our results suggest that mothers can alter investment in their young depending on local conditions. Such maternal effects clearly have implications for the ecology and evolution of host-parasite interactions.

Ecological biogeography of southern ocean islands: the importance of considering spatial issues.

Understanding patterns of among-island variation in species richness has long been an important question in ecology and biogeography. However, despite the clear spatial nature of the data used for such investigations, the spatial distribution of the different sampled locations is rarely explicitly considered, which may be critical for statistical and biological reasons. In a recent study, Chown et al. (1998) investigated the relationships between species richness of different indigenous and introduced taxonomic groups and a variety of variables characterizing Southern Ocean islands, and here, we use these data to address spatial issues. As predicted, we found spatial autocorrelation in species richness for terrestrial taxa with high dispersal ability or for terrestrial taxa that had time to disperse locally (introduced land birds and indigenous taxa) but not for taxa that had low opportunity to disperse to nearby islands (introduced plants, insects, and mammals), which suggests that colonization from nearby islands has played an important role in shaping present-day patterns of among-island variation in species richness. Interestingly, in several cases, the estimated effect of variables changed when spatial covariance was incorporated. Moreover, the absence of autocorrelation of some variables allowed us to confirm some important results of Chown et al. (1998), notably those involving the potential impact of human presence on the biodiversity of these islands. Overall, our results illustrate the importance of considering spatial structures in ecological studies. This is notably the case when dispersal processes can be expected to explain some of the observed patterns.

Dispersal and distribution of the tick Ixodes uriae within and among seabird host populations: the need for a population genetic approach.

The aim of this study was to characterize the spatial distribution of the tick Ixodes uriae within and among populations of its seabird hosts and to consider the potential insight that could be gained by a population genetic approach to the issue of dispersal of this tick. Analyses of data collected around the Avalon Peninsula, Newfoundland, indicated that both the prevalence and mean abundance of ticks varied significantly among sample locations. Whereas ticks were found on all 4 host species examined (Rissa tridactyla, Uria aalge, Alca torda, Fratercula arctica), infestation prevalence and mean abundance differed among the species. On R. tridactyla, ticks were significantly aggregated at the among-nest scale and nestling infestation was spatially autocorrelated. Conversely, ticks were not aggregated among chicks within nests. These results enabled us to make a priori predictions regarding tick dispersal and host specificity and suggest there may be spatial structure of Ixodes uriae populations at both macro- and microgeographic scales. Investigating the population genetic structure of ticks within and among populations of hosts with different breeding biologies should provide direct insight into the metapopulation dynamics of such a spatially structured system.

Higher temporal variability of forest breeding bird communities in fragmented landscapes.

Understanding the relationship between animal community dynamics and landscape structure has become a priority for biodiversity conservation. In particular, predicting the effects of habitat destruction that confine species to networks of small patches is an important prerequisite to conservation plan development. Theoretical models that predict the occurrence of species in fragmented landscapes, and relationships between stability and diversity do exist. However, reliable empirical investigations of the dynamics of biodiversity have been prevented by differences in species detection probabilities among landscapes. Using long-term data sampled at a large spatial scale in conjunction with a capture-recapture approach, we developed estimates of parameters of community changes over a 22-year period for forest breeding birds in selected areas of the eastern United States. We show that forest fragmentation was associated not only with a reduced number of forest bird species, but also with increased temporal variability in the number of species. This higher temporal variability was associated with higher local extinction and turnover rates. These results have major conservation implications. Moreover, the approach used provides a practical tool for the study of the dynamics of biodiversity.

Genetics of host-parasite interactions.

The evolution of host susceptibility or resistance to parasites has important consequences for the evolution of parasite virulence, host sexual selection, population dynamics of both host and parasite populations, and programs of biological control. The general observation of a fraction of Individuals within a population that is not parasitized, and/or the variability in parasite intensity among hosts, may reflect several phenomena acting at different levels of ecological organization. Yet, host-parasite coevolution requires host susceptibility and parasite virulence to be genetically variable. In spite of evolutionary and epidemiological implications of genetic heterogeneities in host-parasite systems, evidence concerning natural populations is still scarce. Here, we wish to emphasize why we need a better knowledge of the genetics of host-parasite interaction in natural populations and to review the evidence concerning the heritability of host susceptibility or resistance to parasites in natural populations of animals.