Two families of exocomets in the ß Pictoris system.

The young planetary system surrounding the star ß Pictoris harbours active minor bodies. These asteroids and comets produce a large amount of dust and gas through collisions and evaporation, as happened early in the history of our Solar System. Spectroscopic observations of ß Pictoris reveal a high rate of transits of small evaporating bodies, that is, exocomets. Here we report an analysis of more than 1,000 archival spectra gathered between 2003 and 2011, which provides a sample of about 6,000 variable absorption signatures arising from exocomets transiting the disk of the parent star. Statistical analysis of the observed properties of these exocomets allows us to identify two populations with different physical properties. One family consists of exocomets producing shallow absorption lines, which can be attributed to old exhausted (that is, strongly depleted in volatiles) comets trapped in a mean motion resonance with a massive planet. Another family consists of exocomets producing deep absorption lines, which may be related to the recent fragmentation of one or a few parent bodies. Our results show that the evaporating bodies observed for decades in the ß Pictoris system are analogous to the comets in our own Solar System.

A transiting giant planet with a temperature between 250 K and 430 K.

Of the over 400 known exoplanets, there are about 70 planets that transit their central star, a situation that permits the derivation of their basic parameters and facilitates investigations of their atmospheres. Some short-period planets, including the first terrestrial exoplanet (CoRoT-7b), have been discovered using a space mission designed to find smaller and more distant planets than can be seen from the ground. Here we report transit observations of CoRoT-9b, which orbits with a period of 95.274 days on a low eccentricity of 0.11 +/- 0.04 around a solar-like star. Its periastron distance of 0.36 astronomical units is by far the largest of all transiting planets, yielding a 'temperate' photospheric temperature estimated to be between 250 and 430 K. Unlike previously known transiting planets, the present size of CoRoT-9b should not have been affected by tidal heat dissipation processes. Indeed, the planet is found to be well described by standard evolution models with an inferred interior composition consistent with that of Jupiter and Saturn.

An extended upper atmosphere around the extrasolar planet HD209458b.

The planet in the system HD209458 is the first one for which repeated transits across the stellar disk have been observed. Together with radial velocity measurements, this has led to a determination of the planet's radius and mass, confirming it to be a gas giant. But despite numerous searches for an atmospheric signature, only the dense lower atmosphere of HD209458b has been observed, through the detection of neutral sodium absorption. Here we report the detection of atomic hydrogen absorption in the stellar Lyman alpha line during three transits of HD209458b. An absorption of 15 +/- 4% (1sigma) is observed. Comparison with models shows that this absorption should take place beyond the Roche limit and therefore can be understood in terms of escaping hydrogen atoms.

Deficiency of molecular hydrogen in the disk of beta Pictoris.

Molecular hydrogen (H2) is by far the most abundant material from which stars, protoplanetary disks and giant planets form, but it is difficult to detect directly. Infrared emission lines from H2 have recently been reported towards beta Pictoris, a star harbouring a young planetary system. This star is surrounded by a dusty 'debris disk' that is continuously replenished either by collisions between asteroidal objects or by evaporation of ices on Chiron-like objects. A gaseous disk has also been inferred from absorption lines in the stellar spectrum. Here we present the far-ultraviolet spectrum of beta Pictoris, in which H2 absorption lines are not seen. This allows us to set a very low upper limit on the column density of H2: N(H2) 6 x 10-4. As CO would be destroyed under ambient conditions in about 200 years (refs 9, 11), our result demonstrates that the CO in the disk arises from evaporation of planetesimals.

[Epidemiologic study of the main human intestinal nematodes in the middle west of Madagascar]. / Etude épidémiologique des principales nématodoses intestinales humaines dans le Moyen-ouest de Madagascar.

An epidemiological study of human intestinal helminthiasis was conducted during July and August 1995, in the middle west of Madagascar, with 4571 adults and children ranging from six months to 90 years, in 61 communities between Betafo and Miandrivazo. Faecal examination utilising the MIF concentration method revealed that ascariasis was the dominant nematodosis in the middle west with high prevalences in the high-altitude communities. Ascaris lumbricoides prevalences increase among children and women. Interesting more than 50% of the pattern, ascariasis is a public health problem and its association with infant malnutrition is statistically significant. Hookworm infection prevalence is higher in low-altitude communities, it increases among adults. The Trichuris trichiura prevalences were lower than the prevalences of ascariasis and hookworm infection in all of the communities. Important variations of the prevalences of intestinal helminthiasis are observed essentially in relation with climatic conditions.

Indoor resting by outdoor biting females of Anopheles gambiae complex (Diptera:Culicidae) in the Sahel of northern Senegal.

Three villages in the Senegal River basin were selected to study the biting and resting behavior of Anopheles gambiae s.l. in relation to human habits, rainfalls, and rice culture irrigation. All inhabitants sleep outside throughout the year, mainly under poor quality bednets. Mosquitoes were collected host-seeking during the night on human bait outside and resting during the day inside and outside in pit shelters. An. gambiae s.s. and An. arabiensis fed mainly outside, the only place where hosts are available; fed and gravid females resting indoors fed outside. The proportions of An. gambiae s.s. and An. arabiensis in outdoor biting catches and in indoor spray catches were not significantly different, but they differed from year to year with the latter sampling method, An. gambiae s.s. predominated in 1990, a more wet and humid year, whereas An. arabiensis was more common in 1991, which was an arid year. Both species are highly endophilic in this arid area where outdoor-resting places are limited.

[Natural vector capacity level of Simulium damnosum s.l. (Diptera: Simuliidae) at the ecology station of Tai (Côte d'Ivoire)]. / Capacités vectrices naturelles du complexe Simulium damnosum s.l. (Diptera:Simuliidae) au niveau de la station écologique de Taï (Côte d'Ivoire).

Several studies have been carried out on the transmission of Onchocerciasis by Simulium damnosum s.l. in the forest zone of Côte d'Ivoire. This study, carried out in 1979-1980 was devoted to determine the risk of onchocerciasis transmission inside and outside the rain forest of Taï (5 degrees 50' N-7 degrees 25' W). We present the vectorial capacity of S. sanctipauli in the region of Taï before massive flow of refugees from areas of Liberia without any control Programme. The results of micromorphological technics for determination of S. damnosum adults, showed that mainly females of S. sanctipauli were present. The studied populations had low parturity rates: 39.2% outside and 30.9% of parous flies inside the rain forest. The parasitic rates (0.4% of infectious females outside and 0.1% inside) and their parasitic loads (15 and 3 infective larvae per 1000 parous female respectively outside and inside the rain forest) were low, consequently their vectorial capacity with Onchocerca volvulus was almost non-existent in natural conditions. Before massive flow of refugees including persons carrying microfilariae, there were no problem of onchocerciasis within and outside the rain forest of Taï. However, the massive flow of refugees and the deforestation for growing crops can create situations favourable to the installation of more efficient vectors, increase man/vector contact and contribute to more intense onchocerciasis transmission. The monitoring of onchocerciasis transmission is necessary.

[Window traps and displacement of adult Simulium damnosum s.l. along a line of breeding sites in a forest zone of Côte d'Ivoire]. / Vitres-pièges et déplacement des adultes de Simulium damnosum s.l. le long d'une ligne de gîtes en zone forestière de Côte d'Ivoire.

The displacement of adult black flies along a line of breeding sites has been studied in savannah area and in pre-forest zone. This paper presents the results of studies carried out in forest zone of Côte d'Ivoire. Interception traps made with sticky window traps were vertically displayed cross the river. The results showed that the displacement of adult S. damnosum s.l. along a line of breeding sites is correlated with the river flow. In a period of low discharge, adult black flies present a marked tendency to fly up stream. But in period of heavy discharge, they do not show any tendency; they may fly ever up stream or down stream. They fly essentially at the water level during the period of low flow and at a height between 0.5 to 1.5 m during heavy flow of the river.

[Drought and malaria decrease in the Niayes area of Senegal]. / La sécheresse et la baisse du paludisme dans les Niayes du Sénégal.

The Niayes is geographically characterized by an alternating succession of sand dunes and wet depressions, 20 km wide, which are behind the offshore bars from Saint-Louis to Dakar. Since 1970, the area has been affected by drought. The rainfall which was around 700 mm per year before 1960 has fallen below 500 mm during the last 30 years. In 1991 it was only 350 mm and in 1992, 260 mm. The vegetation has become impoverished in the depressions which are now more and more cultivated for vegetables. Entomological, parasitological and clinical studies on malaria were carried out in 1991 and 1992 in three villages and the results were compared with data gathered from 1967 to 1968 with comparable methods. The main points concerning the evolution of malaria are listed as follows. An. funestus, which was previously the predominant malaria vector, has almost disappeared. An. gambiae has regressed ahead of its sibling species An. arabiensis, a less competent vector. These changes in vector populations have led to lower malaria transmission and consequently a decrease of the endemicity. The children parasitic index, which was between 40 to 80% according to the localities in 1967, fell to 10% or less in 1991 and 1992. Finally, the incidence of clinical cases, calculated on a cohort of 100 children was only 4% in 1992, which is very low for an African endemic country. We conclude that drought and human activities have modified the environment such that malaria endemicity has seriously decreased. However, the risk of epidemic remains with the eventual occurrence of heavy rains. Therefore a surveillance of the area is needed to prevent a future epidemic.

[Malaria and rice growing in the Senegal River delta (Senegal)]. / Paludisme et riziculture dans le delta du fleuve Senegal (Sénégal).

An epidemiological survey of malaria was carried out from September 1992 to November 1994 in three villages located in the Senegal river delta, two villages growing rice in irrigated fields and one practicing traditional rain water agriculture. Entomological observations showed that Anopheles pharoensis is the main anopheline species caught in the area with a high population density in the rice growing villages. The population density of species of the An. gambiae complex, represented by An. gambiae s.s., An. arabiensis and An. melas is low. Agressivity rates and anthropophlic indexes of An. pharoensis females are high but their parity rates are low. The malaria transmission is weak and was not perceptible in the area as shown by the negative results obtained with the ELISA tests and the examination of salivary glands. Parasitological indexes, malaria morbidity and incidence rates are low and are in agreement with the entomological data. In the Senegal river delta, irrigation has, on the whole, increased the An. pharoensis density but both malaria transmission and incidence rates did not rise.

[Comparison of the transmission of malaria in 2 epidemiological patterns in Senegal: the Sahel border and the Sudan-type savanna]. / Comparaison de la transmission du paludisme dans deux faciès épidémiologiques au Sénégal: la zone côtière sahélienne et la zone méridionale soudanienne.

From September 1992 to October 1993 a longitudinal entomological study was carried out in two villages located in different ecological conditions of Senegal, a sahelian area and a sudan-type savanna. Mosquitoes were sampled by night-bites catches and by daytime pyrethrum spray collections. In both villages Anopheles gambiae s.l. is the main vector with An. gambiae in the savanna area of Wassadou and An. arabiensis in the sahelian area of Thiaye. Malaria transmission is mainly seasonal with a man biting rate (ma) and an entomological inoculation rate (h) higher in Wassadou than in Thiaye. In this last one (sahelian area), a high variation of An. gambiae s.l. density was observed, females disappear in the dry season. In the rainy season the main biting rate increases but no infected bite was recorded. In Wassadou (sudan-type savanna), a great difference in An. gambiae s.l. specific composition was observed with An. gambiae predominant in the rainy season and An. arabiensis generally more abundant in the dry season. The biting and inoculation rates were minimum during the dry season (ma = 4 bites/man/night; h = 0.07 infected bites/man/night-, they increase during the rainy season (ma: 52 bites/man/night; h = 1.6 infected bites/man/night). An inhabitant of this village gets annually some 63, bites and 220 infected bites of An. gambiae s.l., mainly during the six months of the rainy season and the early dry season.

Antibody responses in forest and savanna onchocerciasis in Ivory Coast.

Three foci of onchocerciasis transmission (two forest and one savanna, respectively) in the Republic of Ivory Coast were chosen for a comparative analysis of Onchocerca volvulus antigens and of patients' antibody responses. Clear differences between frequency and intensity of ocular pathology existed between the forest foci and the savanna focus. We found heterogeneity of SDS-PAGE-separated components of female worms with respect to the mobility of three protein bands of the 100 KD region and to the ability of an 80 KD band to bind horseradish peroxidase. These variations were clearly not associated with the degree of ocular pathology. No differences in the composition of worm antigens were detected by immunoblotting. A variable with a possible relation to ocular pathology was the antibody response of patients: individuals from the savanna focus, where a high degree of ocular pathology is observed, tended to have a stronger and more differentiated IgG antibody response against O. volvulus antigens than patients from the forest foci. However, no antigens specifically recognized by patients from either forest or savanna were detected.

[Ivermectin and the reduction of the rate of infection of simuliids in a forest focus of human onchocerciasis]. / Ivermectine et modalités de la réduction de l'infection des simulies dans un foyer forestier d'onchocercose humaine.

Eight patients from a forest onchocercian area "Grandes rivières", in Ivory Coast, were treated with a single oral dose of ivermectin (12 mg). The density of dermic microfilariae was estimated at days 0, 7 and 180; the mean numbers of ingested microfilariae and of developing larvae in the vectors S. soubrense-S. sanctipauli, engorged on the treated patients were recorded. Comparisons were made with non treated patients, having a similar density of microfilariae than the 8 treated patients at day 7. Results confirm the reduction induced by ivermectin of the dermic microfilarial density and the resulting reduction of the infection of the simuliids. Furthermore 7 days after treatment, a new phenomenon is demonstrated: for a similar dermic microfilarial density, simuliids take up a number of microfilariae 100 times lower from treated than from untreated patients. To explain this phenomenon, it is suggested that ivermectin induces a change in the microfilarial distribution in the layers of the dermis. Six months after treatment, this low uptake of microfilariae by the vectors had disappeared, and the infection rate of the engorged similiids was much higher than at day 7 although the dermic microfilarial density was similar.

Studies on the protein and antigen composition of individual female Onchocerca volvulus after collagenase digestion.

The composition of proteins and antigens of female Onchocerca volvulus from one focus of transmission was studied by SDS-PAGE and immunoblotting. Worms that had been exposed to collagenase digestion of onchocercomata for different periods of time and parasites of different age and status of reproduction were tested. Some O. volvulus antigens were found to be sensible to prolonged digestion (molecular weights: 18 KD, 21 KD, 24 KD) but the majority of the antigens was stable up to 64 hours of incubation at 34 degrees C. The composition of proteins and antigens varied with the age and the status of reproduction of the worms. Slight differences between individual filariae were found, even when worms of comparable age and status of reproduction were tested that had been exposed to nodule digestion for comparable time.

[Ecology of Culex pipiens fatigans larvae in an area of high endemicity of Bancroftian filariasis (author's transl)]. / Ecologie larvaire de culex pipiens fatigans Wiedemann, 1828 (Diptera, Culcidae) dans une zone de haute endemie filarienne (Mayotte, archipel des comores)

Culex pipiens fatigans in the main vector of bancroftian filariasis in the Mayotte island (Comores) where it imposes an important health problem. The breeding-sites of C. p. fatigans are either man-made (latrines, cesspools, various containers), or natural (polluted water of estuaries of some rivers). The man-made breeding-sites are not similarly distributed in the different localities of the island. Their distribution varies according to the customs of the inhabitants, size and site of the community. They are mainly represented by latrines, where Anjouan ethnic group is predominent; by cesspools in localities inhabited by Sakalava (a Malagasian ethnic group) and by other latrines and cesspools in mahoraises (inhabitants of Mayotte) and cosmopolitan localities. In rural areas, the percentage of habitations with cesspools usually increases with the size of the villages. The various breeding-sites are primarily productive when they are built on a ground with poor permeability. The importance of the present information is further discussed with relation to the population dynamics of C.p. fatigans and to the measures which may be useful for a control program of this mosquito.