Matthieu Bastien

Massive infection of seabird ticks with bacterial species related to Coxiella burnetii.

ABSTRACT Seabird ticks are known reservoirs of bacterial pathogens of medical importance; however, ticks parasitizing tropical seabirds have received less attention than their counterparts from temperate and subpolar regions. Recently, Rickettsia africae was described to infect seabird ticks of the western Indian Ocean and New Caledonia, constituting the only available data on bacterial pathogens associated with tropical seabird tick species. Here, we combined a pyrosequencing-based approach with a classical molecular analysis targeting bacteria of potential medical importance in order to describe the bacterial community in two tropical seabird ticks, Amblyomma loculosum and Carios (Ornithodoros) capensis. We also investigated the patterns of prevalence and host specificity within the biogeographical context of the western Indian Ocean islands. The bacterial community of the two tick species was characterized by a strong dominance of Coxiella and Rickettsia. Our data support a strict Coxiella-host tick specificity, a pattern resembling the one found for Rickettsia spp. in the same two seabird tick species. Both the high prevalence and stringent host tick specificity suggest that these bacteria may be tick symbionts with probable vertical transmission. Detailed studies of the pathogenicity of these bacteria will now be required to determine whether horizontal transmission can occur and to clarify their status as potential human pathogens. More generally, our results show that the combination of next generation sequencing with targeted detection/genotyping approaches proves to be efficient in poorly investigated fields where research can be considered to be starting from scratch.

Rickettsia spp. in seabird ticks from western Indian Ocean islands, 2011-2012.

We found a diversity of Rickettsia spp. in seabird ticks from 6 tropical islands. The bacteria showed strong host specificity and sequence similarity with strains in other regions. Seabird ticks may be key reservoirs for pathogenic Rickettsia spp., and bird hosts may have a role in dispersing ticks and tick-associated infectious agents over large distances.

Influenza A Virus on Oceanic Islands: Host and Viral Diversity in Seabirds in the Western Indian Ocean

Ducks and seabirds are natural hosts for influenza A viruses (IAV). On oceanic islands, the ecology of IAV could be affected by the relative diversity, abundance and density of seabirds and ducks. Seabirds are the most abundant and widespread avifauna in the Western Indian Ocean and, in this region, oceanic islands represent major breeding sites for a large diversity of potential IAV host species. Based on serological assays, we assessed the host range of IAV and the virus subtype diversity in terns of the islands of the Western Indian Ocean. We further investigated the spatial variation in virus transmission patterns between islands and identified the origin of circulating viruses using a molecular approach. Our findings indicate that terns represent a major host for IAV on oceanic islands, not only for seabird-related virus subtypes such as H16, but also for those commonly isolated in wild and domestic ducks (H3, H6, H9, H12 subtypes). We also identified strong species-associated variation in virus exposure that may be associated to differences in the ecology and behaviour of terns. We discuss the role of tern migrations in the spread of viruses to and between oceanic islands, in particular for the H2 and H9 IAV subtypes.

Absence of coronaviruses, paramyxoviruses, and influenza A viruses in seabirds in the southwestern Indian Ocean.

Abstract We investigated circulation of coronaviruses, paramyxoviruses, and influenza A viruses in eight seabird species of the southwestern Indian Ocean. Viruses were not detected by real-time polymerase chain reactions in the 338 tested cloacal swab samples, supporting that they did not circulate in the studied colonies at the time of sampling.

The role of seabirds of the Iles Eparses as reservoirs and disseminators of parasites and pathogens

Abstract The role of birds as reservoirs and disseminators of parasites and pathogens has received much attention over the past several years due to their high vagility. Seabirds are particularly interesting hosts in this respect. In addition to incredible long-distance movements during migration, foraging and prospecting, these birds are long-lived, site faithful and breed in dense aggregations in specific colony locations. These different characteristics can favor both the local maintenance and large-scale dissemination of parasites and pathogens. The Iles Eparses provide breeding and feeding grounds for more than 3 million breeding pairs of seabirds including at least 13 species. Breeding colonies on these islands are relatively undisturbed by human activities and represent natural metapopulations in which seabird population dynamics, movement and dispersal can be studied in relation to that of circulating parasites and pathogens. In this review, we summarize previous knowledge and recently-acquired data on the parasites and pathogens found in association with seabirds of the Iles Eparses. These studies have revealed the presence of a rich diversity of infectious agents (viruses, bacteria and parasites) carried by the birds and/or their local ectoparasites (ticks and louse flies). Many of these agents are widespread and found in other ecosystems confirming a role for seabirds in their large scale dissemination and maintenance. The heterogeneous distribution of parasites and infectious agents among islands and seabird species suggests that relatively independent metacommunities of interacting species may exist within the western Indian Ocean. In this context, we discuss how the patterns and determinants of seabird movements may alter parasite and pathogen circulation. We conclude by outlining key aspects for future research given the baseline data now available and current concerns in eco-epidemiology and biodiversity conservation.

Haemoproteus iwa in Great Frigatebirds (Fregata minor) in the Islands of the Western Indian Ocean

Blood parasites of the sub-genus Haemoproteus have been reported in seabirds, in particular in species in the Suliformes order. These parasites are transmitted by hippoboscid flies of the genus Olfersia; strong specificity has been suggested between the vector and its vertebrate host. We investigated the prevalence of Haemoproteus infection in Suliformes and hippoboscid flies in two oceanic islands of the Western Indian Ocean: Europa and Tromelin. In total, 209 blood samples were collected from great frigatebirds (Fregata minor), masked boobies (Sula dactylatra) and red-footed boobies (Sula sula). Forty-one hippoboscid flies were also collected from birds. Seventeen frigatebirds and one fly collected on Europa tested positive for the presence of Haemoproteus parasites by polymerase chain reaction. Phylogenetic analyses based on partial sequences of the Cytochrome b gene showed that parasites were closely related to Haemoproteus iwa reported from frigatebirds in the Pacific Ocean and in the Caribbean. Plasmodium was also detected in a frigatebird on Europa; however, its placement on the phylogenetic tree could not be resolved. We provide strong support for transmission of blood parasites in seabirds in the Western Indian Ocean and suggest that migrations between the Pacific and the Indian oceans could favor the large-scale distribution of Haemoproteus iwa in frigatebird populations.

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.

Avian cholera outbreaks threaten seabird species on Amsterdam Island

Infectious diseases may be particularly critical for the conservation of endangered species. A striking example is the recurrent outbreaks that have been occurring in seabirds on Amsterdam Island for the past 30 years, threatening populations of three Endangered seabird species and of the endemic, Critically Endangered Amsterdam albatross Diomedea amsterdamensis. The bacteria Pasteurella multocida (avian cholera causative agent), and to a lesser extent Erysipelothrix rhusiopathiae (erysipelas causative agent), were both suspected to be responsible for these epidemics. Despite this critical situation, demographic trends were not available for these threatened populations, and the occurrence and characterization of potential causative agents of epizootics remain poorly known. The aims of the current study were to (i) provide an update of population trends for four threatened seabird species monitored on Amsterdam Island, (ii) assess the occurrence of P. multocida, and E. rhusiopathiae in live birds from five species, (iii) search for other infectious agents in these samples and, (iv) isolate and genotype the causative agent(s) of epizooties from dead birds. Our study shows that the demographic situation has worsened substantially in three seabird species during the past decade, with extremely low reproductive success and declining populations for Indian yellow-nosed albatrosses Thalassarche carteri, sooty albatrosses Phoebetria fusca, and northern rockhopper penguins Eudyptes moseleyi. Pasteurella multocida or E. rhusiopathiae were detected by PCR in live birds of all five investigated species, while results were negative for eight additional infectious agents. A single strain of P. multocida was repeatedly cultured from dead birds, while no E. rhusiopathiae could be isolated. These results highlight the significance of P. multocida in this particular eco-epidemiological system as the main agent responsible for epizootics. The study stresses the urgent need to implement mitigation measures to alter the course of avian cholera outbreaks threatening the persistence of seabird populations on Amsterdam Island.