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[Human diseases transmitted by Culicidae in southwest Indian Ocean islands].

South-West Indian Ocean islands were inhabited at the beginning and free from all kind of vector. In Madagascar, Mayotte, Moheli and Anjouan, malaria vectors were carried by the first settlements. According to epidemics, the anopheles arrived in 1867 in Mauritius, 1869 in La Reunion and 1920 in Grande Comore. Rodrigues, Saint-Brandon and the Seychelles are still free from malaria vectors in the coastal part of Madagascarcar and in Comores archipelago, malaria is stable with a permanent transmission. Unstable malaria is seasonaly transmitted in the high territories of Madagascar; it was the same in Mauritius and Reunion island before the eradication campaign. Lymphatic filariasis is quoted in Madagascar, but Comores archipelago is an area with high transmission. The incidence of the disease is moderate in La Reunion and Mauritius and very low in Chagos and Seychelles archipelagos. There is no transmission in Rodrigues and St Brandon. Epidemics of dengue were described during the second part of the XIXth century in Mauritius and La Reunion, then in 1943 in Mayotte. But the disease was controlled in the fifties by the antimalaria campaign. A new epidemy appeared in Seychelles by the end of 1976 and then in Reunion and Mauritius next year. An isolated outbreak was described in Grande Comore only in 1994.

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Population structure of Anopheles arabiensis on La Réunion island, Indian Ocean.

Anopheles arabiensis, together with Anopheles gambiae sensu stricto, are the most important vectors of human malaria in sub-Saharan Africa. The malaria situation keeps worsening, with 1 to 3 million deaths a year, and alternative strategies are needed to decrease malaria transmission intensity. In this paper, we studied the population structure of An. arabiensis from three sample sites on the remote Indian Ocean island of La Réunion. Our results showed strong genetic structuring between An. arabiensis populations on La Réunion, indicating the presence of barriers to gene flow. Reasons for such a high genetic differentiation are discussed, including the role of intensive control measures that have maintained reduced effective population size as well as a putative genetic adaptation to the environment. This strong structuring situation on the island represents an ideal framework for the prospect of genetic-based control trials.

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Novel chikungunya virus variant in travelers returning from Indian Ocean islands.

Chikungunya virus (CHIKV) emerged in Indian Ocean islands in 2005 and is causing an ongoing outbreak that involves >260,000 patients, including travelers returning home from these islands. We investigated cases in 4 patients returning from Mayotte and Reunion Islands with CHIKV infection and a nurse infected in metropolitan France after direct contact with the blood of a traveler. Four patients had tenosynovitis and pain at wrist pressure, and 1 had life-threatening manifestations. Four CHIKV strains were isolated, including 1 from the patient with the autochthonous case. The complete genomic sequence identified a new CHIKV variant emerging from the East/ central African evolutionary lineage. Aedes albopictus, the implicated vector of CHIKV in Indian Ocean islands, has dispersed worldwide in recent decades. High viral loads in patients returning from Indian Ocean islands to countries where Ae. albopictus is prevalent may be a source of epidemics.

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South West Indian Ocean islands tomato begomovirus populations represent a new major monopartite begomovirus group.

Biological and molecular properties of Tomato leaf curl Madagascar virus isolates from Morondova and Toliary (ToLCMGV-[Tol], -[Mor]), Tomato leaf curl Mayotte virus isolates from Dembeni and Kahani (ToLCYTV-[Dem], -[Kah]) and a Tomato yellow leaf curl virus isolate from Reunion (TYLCV-Mld[RE]) were determined. Full-length DNA components of the five isolates from Madagascar, Mayotte and Reunion were cloned and sequenced and, with the exception of ToLCMGV-[Tol], were shown to be both infectious in tomato and transmissible by Bemisia tabaci. Sequence analysis revealed that these viruses had genome organizations of monopartite begomoviruses and that both ToLCMGV and ToLCYTV belong to the African begomoviruses but represent a distinct monophyletic group that we have tentatively named the South West islands of the Indian Ocean (SWIO). All of the SWIO isolates examined were apparently complex recombinants. None of the sequences within the recombinant regions closely resembled that of any known non-SWIO begomovirus, suggesting an isolation of these virus populations.

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Seroepidemiology, viral isolation, and molecular characterization of human T cell leukemia/lymphoma virus type I from La Réunion Island, Indian Ocean.

Data indicate the presence in the Seychelles Islands of a high level of human T cell leukemia/lymphoma virus type I (HTLV-I) endemicity as well as the presence of tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM). We present here the results of an hospital survey performed since 1988 in La Réunion Island, located in the Indian Ocean southeast of the Seychelles archipelago, aimed at evaluating HTLV-I endemicity, detecting HTLV-I-associated diseases, and characterizing viral isolates. Seven individuals were found to have HTLV-I-specific antibodies in their sera. These include 3 of 257 patients from St. Pierre Hospital, 1 of them exhibiting a typical clinical feature of TSP/HAM (the first described case in this region), 1 blood donor of 3900, and 3 relatives. A further nine individuals exhibiting only "gag-encoded proteins" by Western blot (p19 and/or p24 bands) were found negative by polymerase chain reaction using LTR, pol, and tax HTLV-I specific primers. A long-term T cell line, designated Mel.J, exhibiting T cell activation markers (CD4+, CD25+, HLA-DR+), and producing HTLV-I antigens and viral particles, was established from one of the HTLV-I,-seropositive patients. The sequence of a 522-bp fragment corresponding to the carboxy terminus of gp46 and the majority of gp21 were determined for five HTLV-I-seropositive individuals, including the TSP/HAM patient. Alignment and phylogenetic comparison of these five nucleotide sequences with all the 53 other available HTLV-I env sequences demonstrated that the virus from La Réunion Island belongs to the group of the HTLV-I cosmopolitan subtype and is not related to the Melanesian HTLV-I variants.

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Re-emergence of Anopheles funestus and its possible effect on malaria transmission on Mayotte Island, Indian Ocean.

Malaria constitutes a major public health problem on Mayotte Island, with the major vector being Anopheles gambiae s.s. The seeming disappearance of An. funestus, the 2nd vector on the island, was observed 15 years ago. Now, the presence of An. funestus during the biting collections performed in November and December 2004 confirms the re-emergence of this vector, which plays an important role in malaria transmission with An. gambiae.

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Prevalence and secular trends in obesity in Pacific and Indian Ocean island populations.

Surveys conducted in 10 Pacific island populations and in the multiethnic populations of Mauritius and Rodrigues in the Indian Ocean have provided data on the prevalence of obesity, potential etiological factors and medical hazards associated with obesity. The results indicate that the prevalence of obesity (by body mass index (BMI) in some of these populations is among the highest in the world. Obesity related to degree of modernization is more common in urban than in rural locations and tends to be found more often in women. In two populations where longitudinal data were available, there were dramatic increases in prevalence over relatively short time periods. Obesity contributed to the risk of non-insulin-dependent diabetes mellitus (NIDDM) and was associated with other risk factors for cardiovascular disease (CVD) in all populations, but no relationship could be found with total mortality in three ethnic groups for whom data were available. A genetic susceptibility to obesity combined with social pressures that favor high energy intakes and reduced physical activity are believed to be important in these populations. The challenge for the future lies in developing culturally appropriate programs for preventing obesity and thus reducing associated morbidity, while continuing to research its behavioral and genetic determinants.

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Population structure of Aedes albopictus from La Réunion Island (Indian Ocean) with respect to susceptibility to a dengue virus.

Ten F1 Aedes albopictus samples collected from Réunion Island in the Indian Ocean were tested for oral susceptibility to dengue 2 virus and 20 were analysed for genetic polymorphism by starch gel electrophoresis. Data from infection rates defined two distinct geographical areas: east coast vs. west coast. Genetic differentiation was found to be dependent on ecological factors and the biological characteristics of Ae. albopictus. These results have implications for the vector ecology and pattern of migration, and have importance in the understanding of dengue transmission.

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Immigration, species radiation and extinction in a highly diverse songbird lineage: white-eyes on Indian Ocean islands.

Molecular phylogenetic hypotheses of species-rich lineages in regions where geological history can be reliably inferred may provide insights into the scale of processes driving diversification. Here we sample all extant or recently extinct white-eye (Zosterops) taxa of the southwest Indian Ocean, combined with samples from all principal continental lineages. Results support a high dispersal capability, with at least two independent continental sources for white-eyes of the region. An early (within 1.8 million years ago) expansion into the Indian Ocean may have originated either from Asia or Africa; the three resulting lineages show a disparate distribution consistent with considerable extinction following their arrival. Africa is supported as the origin of a later expansion into the region (within 1.2 million years ago). On two islands, a pair of Zosterops species derived from independent immigrations into the Indian Ocean co-occur or may have formerly co-occurred, providing strong support for their origin by double-island colonization rather than within-island (sympatric or microallopatric) speciation. On Mauritius and La Réunion, phylogenetic placement of sympatric white-eyes allow us to rule out a scenario in which independent within-island speciation occurred on both islands; one of the species pairs must have arisen by double colonization, while the other pair is likely to have arisen by the same mechanism. Long-distance immigration therefore appears to be responsible for much of the region's white-eye diversity. Independent immigrations into the region have resulted in lineages with mutually exclusive distributions and it seems likely that competition with congeneric species, rather than arrival frequency, may limit present-day diversity.

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[Rickettsia africae, the agent of African tick-bite fever: an emerging pathogen in the West Indies and Reunion Island (Indian Ocean)].

Rickettsia africae is the agent of African tick bite fever, an emerging disease transmitted by Amblyomma ticks in sub-Saharan Africa. In 1998, we reported the first documented case of R. africae in the New World, in a patient who had returned from Guadeloupe. In order to confirm the presence of R. africae in the West Indies, entomologic surveys were conducted from 1999 to 2003 to collect Amblyomma, which are considered as potential vectors and reservoirs of the bacteria. Ticks were used as epidemiological tools to detect R. africae by molecular tools and/or cultivate the bacteria in shell-vial cell culture. This paper summarizes the results obtained in the West Indies. R. africae was detected and isolated for the first time in Guadeloupe, and then detected by molecular tools in Martinique and St-Kitts and Nevis. These last results confirm our first hypotheses--that is R. africae is prevalent on all the Caribbean islands where A. variegatum ticks have been introduced from Africa in the 18th and 19th centuries. We also present the results of a study conducted on the Reunion Island, a French island in the Indian Ocean. For the first time there, R. africae was detected in A. variegatum ticks, which were probably introduced from the African mainland or Madagascar with the human colonization during the 17th century Thus, clinicians should be aware that patient presenting in the West Indies or on Reunion Island (or after a trip over there) with fever, eschar (often multiple), regional lymphadenopathy and a rash, might be infected by R. africae.

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Patterns of alcohol consumption in the Seychelles Islands (Indian Ocean).

Self-reported drinking habits were examined in a random sample of 1067 persons aged 25-64 years in the Seychelles, a country in epidemiological transition where consumption of home-brewed, mostly unregistered beverages has been traditionally high. Alcohol consumption was calculated from respondents reporting at least one drink per week ('regular drinkers'). Among men, 51.1% were regular drinkers and had average intake of 112.1 ml alcohol a day. Among women, 5.9% were regular drinkers and had 49.7 ml alcohol a day. Frequency of drinking, but not amount per drinker, was slightly less in the 25-34-year than older-age categories. Home-brews (mostly palm toddy and fermented sugar cane juice) were consumed by 52% of regular drinkers and accounted for 54% of the total alcohol intake reported by all regular drinkers. Based on the reported consumption by regular drinkers only, the average annual alcohol consumption amounted respectively to 20.7 litres and 1.2 litres per man and woman aged 25-64 years, or, using extrapolation, 13.2 litres and 0.8 litres per man and woman respectively of the total population. These values may underestimate the true figures by half, since reported beer consumption accounted for 53% of beer sales. Socio-economic status was associated strongly and inversely with home-brew consumption, but slightly and positively with consumption of commercially marketed beverages. Alcohol intake was associated with smoking, high-density lipoprotein cholesterol, carbohydrate-deficient transferrin and blood pressure, but not with age and body mass index. In conclusion, these data show high alcohol consumption in the Seychelles with an important gender difference, a large proportion of alcohol derived from home-brews, and opposite tendencies for the relationships between socio-economic status and home-made or commercially marketed beverages.

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[Historical epidemiology of bancroftian filariasis in southwest islands of the Indian Ocean].

Bancroftian filariasis arose in the South-West Indian Ocean Islands with human settlements. During the XIXe century, most of the islands were infected but the prevalence and clinical features of the disease were different from an Island to an other. The vectors are Cx. quinquefasciatus, An. gambiae, An. arabiensis, An. funestus. Even if Culex are proven vectors most of the transmission is due to anophelines. The introduction of the parasite was followed by an explosion of the diseases with dramatic clinical features. But since the beginning of the century the disease retreats. Whatever this is due to malaria vector control and specifies chemoprophylaxis or is linked to the rise of life standard is still a subject of debate.

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