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Movement in the French Pacific: recent situation and prospects.

"Population movements in the French Pacific territories (French Polynesia, New Caledonia, Wallis and Futuna) are discussed. The local government of French Polynesia and the French authorities have tried since the beginning of the 1980s to prevent migration to Tahiti by retaining the population on the outer islands and by encouraging return migration.... The purpose of this paper is not to describe in detail the population movements in the French territories, but to review recent changes in the course of these movements, examine the impact of policy measures, and discuss the prospects for the next ten or twenty years."

Demography↗

Reductions in the mitochondrial DNA diversity of coral reef fish provide evidence of population bottlenecks resulting from Holocene sea-level change.

This study investigated the influence of reproductive strategy (benthic or pelagic eggs) and habitat preferences (lagoon or outer slope) on both diversity and genetic differentiation using a set of populations of seven coral reef fish species over different geographic scales within French Polynesia. We hypothesized that a Holocene sea-level decrease contributed to severe reduction of population size for species inhabiting lagoons and a subsequent decrease of genetic diversity. Conversely, we proposed that species inhabiting stable environments, such as the outer slope, should demonstrate higher genetic diversity but also more structured populations because they have potentially reached a migration-genetic drift equilibrium. Sequences of the 5' end of the mitochondrial DNA (mtDNA) control region were compared among populations sampled in five isolated islands within two archipelagos of French Polynesia. For all the species, no significant divergences among populations were found. Significant differences in mtDNA diversity between lagoonal and outer-slope species were demonstrated both for haplotype diversity and sequence divergence but none were found between species with different egg types. Pairwise mismatch distributions suggested rapid population growth for all the seven species involved in this study, but they revealed different distributions, depending on the habitat preference of the species. Although several scenarios can explain the observed patterns, the hypothesis of population size reduction events relative to Holocene sea-level regression and its consequence on French Polynesia coral reefs is the most parsimonious. Outer-slope species have undergone a probable weak and/or old bottleneck (outer reefs persisted during low sea level, leading to reef area reductions), whereas lagoonal species suffered a strong and/or recent bottleneck since Holocene sea-level regression resulted in the drying out of all the atolls that are maximum 70 meters deep. Since present sea level was reached between 5000 and 6000 years ago, different demographic events (bottlenecks or founder events) have lead to the actual populations of lagoons in French Polynesia.

Animals↗

Phylogeography of marine mutualists: parallel patterns of genetic structure between obligate goby and shrimp partners.

The survival of many organisms depends on interspecific, mutualistic interactions. Hence, it is important to assess the phylogeography of multiple mutualistic species simultaneously to gain insight into how their metapopulations persist, spread and recover from disturbance. Consequently, we sequenced mitochondrial DNA (cytochrome b) from a gobiid fish (Ctenogobiops feroculus) and its mutualistic partner, an alpheid snapping shrimp (Alpheus djeddensis). These obligate mutualists are common in shallow coral reef lagoons, and we collected individuals from 11 Indo-Pacific islands that were likely exposed to different disturbance histories due to sea level fluctuations associated with glaciation events [geological studies indicate that eastern oceanic islands (Cook Islands, French Polynesia) were more disturbed than western continental plate islands that have deeper, more extensive lagoons (Okinawa, Fiji)]. Both phylogenetic and population genetic analyses indicated that gobies from Okinawa and Fiji were genetically distinct both from each other and those in the Cook Islands and French Polynesia. Shrimp, by contrast, grouped into two distinct genetic groups that showed no geographic structure. Restricting the analysis to one clade of shrimp, which contained two-thirds of the individuals, showed that these shrimp had very similar phylogeographical structure to the gobies. Mismatch distributions demonstrated that both gobies and shrimp experienced a recent, rapid population expansion into French Polynesia. Finally, nucleotide and haplotype diversities per sample location were significantly correlated between mutualists and tended to be higher on western continental than eastern oceanic islands. Our results suggest that these mutualists recovered from a major disturbance by colonizing South Pacific islands in synchrony.

Animals↗

Review of solutions for 3D hydrodynamic modeling applied to aquaculture in South Pacific atoll lagoons.

A workshop organized in French Polynesia in November 2004 allowed reviewing the current methods to model the three-dimensional hydrodynamic circulation in semi-enclosed atoll lagoons for aquaculture applications. Mollusk (e.g. pearl oyster, clam) aquaculture is a major source of income for South Pacific countries such as French Polynesia or Cook Islands. This aquaculture now requires a better understanding of circulation patterns to improve the spatial use of the lagoons, especially to define the best area to set larvae collectors. The pelagic larval duration of the relevant species (<20 days) and the size of the semi-closed lagoons (few hundreds of km2) drive the specifications of the model in terms of the spatial and temporal scale. It is considered that, in contrast with fish, mollusk larvae movements are limited and that their cycle occurs completely in the lagoon, without an oceanic stage. Atolls where aquaculture is productive are generally well-bounded, or semi-closed, without significant large and deep openings to the ocean. Nevertheless part of the lagoon circulation is driven by oceanic water inputs through the rim, ocean swells, tides and winds. Therefore, boundary conditions of the lagoon system are defined by the spatial structure of a very shallow rim (exposition and number of hoas), the deep ocean swell climate, tides and wind regimes. To obtain a realistic 3D numerical model of lagoon circulation with adequate forcing, it is thus necessary to connect in an interdisciplinary way a variety of methods (models, remote sensing and in situ data collection) to accurately represent the different components of the lagoon system and its specific boundary conditions. We review here the current methods and tools used to address these different components for a hypothetical atoll of the Tuamotu Archipelago (French Polynesia), representative of the semi-closed lagoons of the South Pacific Ocean. We hope this paper will serve as a guide for similar studies elsewhere and we provide guidelines in terms of costs for all the different stages involved.

Animals↗

Prediction of the fate of radioactive material in the South Pacific Ocean using a global high-resolution ocean model.

We investigate the release of radioactive contaminants from Moruroa Atoll in a global high-resolution off-line model. The spread of tracer is studied in a series of simulations with varying release depths and time-scales, and into ocean velocity fields corresponding to long-term annual mean, seasonal, and interannually varying scenarios. In the instantaneous surface release scenarios we find that the incorporation of a seasonal cycle greatly influences tracer advection, with maximum concentrations still found within the French Polynesia region after 10 years. In contrast, the maximum trace is located in the southeast Pacific when long-term annual mean fields are used. This emphasizes the importance of the seasonal cycle in models of pollution dispersion on large scales. We further find that during an El Niño/Southern Oscillation (ENSO) event reduced currents in the region of Moruroa Atoll result in increased concentrations of radioactive material in French Polynesia, as direct flushing from the source is reduced. In terms of the sensitivity to tracer release time-rates, we find that a gradual input results in maximum concentrations in the near vicinity of French Polynesia. This contrasts the instantaneous-release scenarios, which see maximum concentrations and tracer spread across much of the South Pacific Ocean. For example, in as little as seven years radioactive contamination can reach the east coast of Australia diluted by only a factor of 1,000 of the initial concentration. A comparison of results is made with previous studies. Overall, we find much higher concentrations of radionuclides in the South Pacific than has previously been predicted using coarser-resolution models.

Forecasting↗

Implementation of chemoprophylaxis of leprosy in the Southern Marquesas with a single dose of 25 mg per kg rifampin.

Between 1967 and 1987 in the Southern Marquesas, a remote archipelago in French Polynesia, the detection rate of leprosy was 48.9 per 100,000 when it was 8.6 per 100,000 for French Polynesia as a whole. In 1988, a program of chemoprophylaxis of leprosy with a single dose of 25 mg/kg rifampin was implemented, and 2751 persons (98.7% of the population) were treated in the Southern Marquesas. In addition, 678 South Marquesans and 2466 members of their families living in the Northern Marquesas and in the Society Archipelago, received the same chemoprophylaxis. Among 2676 persons studied in the Southern Marquesas (97.4% of the treated population), 130 had elevated IgM anti-phenolic glycolipid-I antibodies by ELISA without any evidence of leprosy. The onset of a skin lesion of borderline leprosy in a boy 3 months after chemoprophylaxis raises the question of the nature of such a skin lesion and, indirectly, of the effectiveness of the chemoprophylaxis.

Antibodies, Bacterial↗

Distribution of HBsAg subtypes in the world.

HBsAg subtyping was performed in 5,337 sera from chronic carriers who originated from 54 different countries of the 5 continents. Nine subtypes were defined: ayw1, ayw2, ayw3, ayw4, ayr, adw2, adw4, adr q- and adr q+. The repartition of these subtypes, according to the country of origin of the carriers, enhances the previous results and supplies new data: ayw1 is prevalent only in Vietnam (51%); ayw2 in Mediterranean countries (73%); ayw3 in Greece and Yugoslavia (54%) along with ayw2 (41%); ayw4 in West Africa (82%) and Central Africa (42%) along with ayw2; ayr was only found in Vietnam (3.4%); adw2 is prevalent in North and Central Europe (70%), East and South Africa (95%), India (55%), along with ayw3 (35%) in northern South American (74%), and in the Antilles (82%); adw4 is widespread in French Polynesia (45%)--with a 100% frequency in the Marquesas archipelago--as well as in Argentina (42%); adr q--was found only in Ocean: French Polynesia (34%) with a 69% frequency in the Australes, New Caledonia (3 out of 3 HBsAg carriers); adr q+ is the prevalent subtype in South-East Asia if we exclude Vietnam (61%). These results show that a precise geographical distribution of HBsAg subtypes needs more than 'four main subtypes' generally used. Enlarging from 4 subtypes to 9 is a requirement for valuable epidemiologic studies, as well as for the specification of anti-HBs antibodies produced by hybrids or induced by synthetic peptide. The geographical distribution of these 9 HBsAg subtypes and the serological relationship between some determinants suggest a genetic recombination of viral DNA.

Africa↗

[Nursing practice in the context of geographic isolation: implications for training].

A survey on the characteristics of the unique working context of nursing practice in remote areas of French Polynesia and semi-remote areas of northern Quebec demonstrates the importance of a specific training to best prepare the professionals who find themselves in this type of setting. Twenty professionals were interviewed: six nurses practicing in isolated stations in French Polynesia (Tuamotu Archipelago, Marquesas Islands and Austral Islands), six nurses practicing in semi-remote areas within northern Quebec (namely among the Algonquins, the Crees and the Attikameks), four officials of the French Polynesian Health Directorate and four training programme designers from Quebec who were encountered during an expedition to Montreal, Mistissini and Trois-Rivieres. The authors identified ten characteristics which were then regrouped into two categories for both of the practice contexts: first, those inherently linked to professional practice in an isolated context (including the characteristics of nursing practice, the working conditions, the community's health problems, their forms of socio-professional relations, their way of life, and their perception and responses to isolation); and second, those pertaining to the social and natural environment, the economic conditions and the community's cultural specificities. All of the results strongly demonstrate that the specificities of the skills utilised by these nurses are indeed very different than those which they received in their initial preparatory training. If a training programme specific to nursing practice in isolated settings seems essential for these nurses, their individual predisposition to practice in such a complex environment and the acknowledgement of their professional competencies are equally to be considered within the perspective of human resources management.

Adult↗

Transport of radionuclides from the Mururoa and Fangataufa atolls through the marine environment.

A dispersion of radionuclides (3H, 90Sr, 137Cs, 239Pu) potentially released from the Mururoa and Fangataufa atolls through the South Pacific Ocean has been studied by means of computer models. The models used consisted of three differently structured compartmental models for the regional field and a hydrodynamic world ocean model for the far-field simulations. The outcome of regional modelling is predicted activity concentrations with time in different regions of French Polynesia (over up to 10,000 years for plutonium). The far-field model simulates large-scale dispersion in the South Pacific Ocean over periods of up to 50 years. The overall result suggests that there will not be radioactive contamination of any radiological interest at inhabited sites in French Polynesia or anywhere else in the ocean at present or in the future.

Models, Chemical↗

Detection and characterization of Wolbachia infections in Wuchereria bancrofti (Spirurida: Onchocercidae) var. pacifica and Aedes (Stegomyia) polynesiensis (Diptera: Culicidae).

Despite control programs based on mass drug administration (MDA) of microfilaricidal compounds, Bancroftian lymphatic filariasis remains a problem in French Polynesia. For an alternative strategy to MDA, we investigated the potential role of Wolbachia to control filarial transmission. Wolbachia are intracellular alpha-proteobacteria endosymbionts that infect a broad range of insects and nematodes. These bacteria have a suspected role in the pathogenesis of filariasis. They also may be useful in mosquito control through cytoplasmic incompatibility. To detect and characterize these bacteria in the filarial and mosquito-vectors in French Polynesia, a survey was conducted on field-collected mosquitoes and microfilariae from infected people. Samples were analyzed by a polymerase chain reaction and gene sequencing. The results indicate that these bacteria are widespread. Sequence analysis of the wsp and ftsZ genes positioned the Aedes polynesiensis Wolbachia in cluster A and Wuchereria bancrofti var. pacifica Wolbachia in cluster D. The implications for possible improved treatment and vector control are discussed.

Aedes↗

Longitudinal study on relapses of leprosy in Polynesian multibacillary patients on dapsone monotherapy between 1946 and 1970.

Between 1946 and 1970, 295 new leprosy patients were detected in French Polynesia, of whom 145 were multibacillary. Of these 145, put on dapsone monotherapy, 131 reached bacteriological negativity in a period of time ranging from 2 to 12 years (average 4.72 years) and were followed-up for a period of time ranging from 19 to 43 years (median follow-up period after bacteriological negativity; 18 years). Among the 131 patients, 36 relapses were detected, the first one 4 years after bacteriological negativity and the last one 26 years after. The crude relapse rate was 27.5%, the risk of relapse was 1.39 per 100 patient years and the cumulative relapse probability, calculated using the lifetable method, reached 0.38 +/- 11 by year 31 of the study. From these findings one may assume that, at least in French Polynesia, one-third to one-half of multibacillary patients put on dapsone monotherapy would relapse if still present 36 years after bacteriological negativity. Such results re-emphasize the need for leprosy patients to be treated with multidrug therapy as recommended by WHO.

Dapsone↗

Effect of two successive annual treatments with single doses of ivermectin on microfilaraemia due to Wuchereria bancrofti var. pacifica.

Between 1986 and 1988 a single-blind, dose-ranging study was carried out in French Polynesia to determine the efficacy and tolerability of single 50, 100, 150 and 200 micrograms/kg doses of ivermectin in Wuchereria bancrofti carriers. Forty male microfilariae (mf) carriers between 18 and 50 years of age, in whom mf density was greater than or equal to 20 mf/ml, were treated twice at a one-year interval. Twelve months after the second treatment, in carriers who were given a dose greater than or equal to 100 micrograms/kg, mean mf density was 4-7% of the initial pretreatment mf density. Therefore, several successive annual treatments with single doses greater than or equal to 100 micrograms/kg of ivermectin should result in reducing mf densities to a very low level. Nevertheless, at 9 months after the second treatment, residual parasitaemia ranged from 1 to 2182 mf/ml (median 85) in 30 patients. Finally, in patients with pretreatment mf counts less than or equal to 150 mf/ml, mean mf density was 2.8 and 8.9 mf/ml, respectively, during the 2 six-month periods following treatment, while in patients with pretreatment mf densities greater than 150 mf/ml (median 1500) it was 92.3 and 334.1 mf/ml during the same periods. These results suggest that, when implementing filariasis control programmes, the best strategy might be administration of several treatments with a single dose of ivermectin every 6 months to the entire population, at least in French Polynesia. Afterwards, when mf densities had been reduced to a relatively low level (100-150 mf/ml), annual treatments could be considered.

Adolescent↗