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.

Phylogeography of the weasel (Mustela nivalis) in the western-Palaearctic region: combined effects of glacial events and human movements.

The Iberian, Italian or Balkan peninsulas have been considered as refugia for numerous mammalian species in response to Quaternary climatic fluctuations in Europe. In addition to this 'southerly refugial model', northern refugia have also been described notably for generalist and cold-tolerant species. Here, we investigated the phylogeographic pattern of the weasel (Mustela nivalis) to assess the impact of Quaternary glaciations on the genetic structure, number and location of refugia as well as to determine the impact of human movements on the colonization of Mediterranean islands. We sequenced 1690 bp from the mitochondrial control region and cytochrome b for 88 weasels distributed throughout the western-Palaearctic region, including five Mediterranean islands. Phylogenetic analyses of combined genes produced a clear phylogeographic pattern with two main lineages. The first lineage included all of the western-continental samples (from Spain to Finland) and shows low levels of genetic structure. Demographic analysis highlighted several characteristics of an expanding group, dated approximately at 116 kiloyears (kyr; Riss glaciation). The genetic pattern suggested a northeastern-European origin from which colonization of southwestern Europe took place. The second lineage was divided into five subgroups and indicated a common origin of insular and Moroccan samples from eastern Europe. Eastern-continental weasels did not exhibit signs of sudden expansion, suggesting stable population size during the last ice ages. The time of expansion of Sicilian and Corsican populations was dated around 10 kyr ago, which supports the hypothesis of an early human intervention in the colonization of Mediterranean islands.

Do distantly related parasites rely on the same proximate factors to alter the behaviour of their hosts?

Phylogenetically unrelated parasites often increase the chances of their transmission by inducing similar phenotypic changes in their hosts. However, it is not known whether these convergent strategies rely on the same biochemical precursors. In this paper, we explored such aspects by studying two gammarid species (Gammarus insensibilis and Gammarus pulex; Crustacea: Amphipoda: Gammaridae) serving as intermediate hosts in the life cycle of two distantly related parasites: the trematode, Microphallus papillorobustus and the acanthocephalan, Polymorphus minutus. Both these parasite species are known to manipulate the behaviour of their amphipod hosts, bringing them towards the water surface, where they are preferentially eaten by aquatic birds (definitive hosts). By studying and comparing the brains of infected G. insensibilis and G. pulex with proteomics tools, we have elucidated some of the proximate causes involved in the parasite-induced alterations of host behaviour for each system. Protein identifications suggest that altered physiological compartments in hosts can be similar (e.g. immunoneural connexions) or different (e.g. vision process), and hence specific to the host-parasite association considered. Moreover, proteins required to alter the same physiological compartment can be specific or conversely common in both systems, illustrating in the latter case a molecular convergence in the proximate mechanisms of manipulation.

Hairworm anti-predator strategy: a study of causes and consequences.

One of the most fascinating anti-predator responses displayed by parasites is that of hairworms (Nematomorpha). Following the ingestion of the insect host by fish or frogs, the parasitic worm is able to actively exit both its host and the gut of the predator. Using as a model the hairworm, Paragordius tricuspidatus, (parasitizing the cricket Nemobius sylvestris) and the fish predator Micropterus salmoïdes, we explored, with proteomics tools, the physiological basis of this anti-predator response. By examining the proteome of the parasitic worm, we detected a differential expression of 27 protein spots in those worms able to escape the predator. Peptide Mass Fingerprints of candidate protein spots suggest the existence of an intense muscular activity in escaping worms, which functions in parallel with their distinctive biology. In a second step, we attempted to determine whether the energy expended by worms to escape the predator is traded off against its reproductive potential. Remarkably, the number of offspring produced by worms having escaped a predator was not reduced compared with controls.