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D Fontenille

Publications and source records attributed to D Fontenille.

134 records · Page 8Linked to original sources
PubMedDate not supplied

A cohort study of Plasmodium falciparum diversity during the dry season in Ndiop, a Senegalese village with seasonal, mesoendemic malaria.

Prolonged carriage of Plasmodium falciparum in humans during the dry season is critical for parasite survival, as the infected subjects constitute a major reservoir in the absence of transmission. Yet, very little is known about the host/parasite interactions contributing to parasite persistence. In order to study the characteristics of P. falciparum infections during the dry season, we have genotyped parasites collected from untreated, asymptomatic individuals during 3 cross-sectional surveys conducted during the dry season in Ndiop, a Senegalese village with seasonal, mesoendemic malaria. Monthly entomological surveillance did not detect any transmission during that period. Parasite prevalence decreased markedly in the children aged < 7 years after 7 months of undetected transmission, but was stable in older children and adults throughout the dry season. In all chronically infected individuals, infection complexity remained stable, but there were substantial fluctuations of individual genotype(s), reflecting complex dynamics of multiple-clone infections during chronic asymptomatic parasite carriage. This fluctuation resulted in changes in the msp1 and msp2 allelic distribution within the cohort after 7 months of undetected transmission, contrasting with the stability observed during the preceding rainy season in that village.

Adolescent↗
PubMedDate not supplied

A microsatellite map of the African human malaria vector Anopheles funestus.

Microsatellite markers and chromosomal inversion polymorphisms are useful genetic markers for determining population structure in Anopheline mosquitoes. In Anopheles funestus (2N = 6), only chromosome arms 2R, 3R, and 3L are known to carry polymorphic inversions. The physical location of microsatellite markers with respect to polymorphic inversions is potentially important information for interpreting population genetic structure, yet none of the available marker sets have been physically mapped in this species. Accordingly, we mapped 32 polymorphic A. funestus microsatellite markers to the polytene chromosomes using fluorescent in situ hybridization (FISH) and identified 16 markers outside of known polymorphic inversions. Here we provide an integrated polytene chromosome map for A. funestus that includes the breakpoints of all known polymorphic inversions as well as the physical locations of microsatellite loci developed to date. Based on this map, we suggest a standard set of 16 polymorphic microsatellite markers that are distributed evenly across the chromosome complement, occur predominantly outside of inversions, and amplify reliably. Adoption of this set by researchers working in different regions of Africa will facilitate metapopulation analyses of this primary malaria vector.

Africa↗
PubMedDate not supplied

New vectors of Rift Valley fever in West Africa.

After an outbreak of Rift Valley fever in Southern Mauritania in 1987, entomologic studies were conducted in a bordering region in Sénégal from 1991 to 1996 to identify the sylvatic vectors of Rift Valley fever virus. The virus was isolated from the floodwater mosquitoes Aedes vexans and Ae. ochraceus. In 1974 and 1983, the virus had been isolated from Ae. dalzieli. Although these vectors differ from the main vectors in East and South Africa, they use the same type of breeding sites and also feed on cattle and sheep. Although enzootic vectors have now been identified in West Africa, the factors causing outbreaks remain unclear.

Aedes↗
PubMedDate not supplied

Aedes (Stegomyia) albopictus (Skuse), a potential new Dengue vector in southern Cameroon.

Aedes albopictus, a mosquito vector of Dengue virus, has been recorded for the first time in Cameroon. Entomologic surveys in 2000 demonstrated that it is widespread in southern Cameroon, colonizing a wide variety of breeding sites and biting humans in every district surveyed. The presence of this vector increases the risk for emergence of dengue in Cameroon.

Aedes↗
PubMedDate not supplied

[Anopheline population genetics].

Population genetic studies of vectors are essential for (i) the determination of their taxonomic status and consequently the definition of their vectorial role in the transmission of pathogenic agents; (ii) the evaluation of the species genetic variability and the estimation of their capacities of adaptation to selection pressure; (iii) an estimation of gene flow among populations in order to evaluate their degree of isolation and gene circulation, especially resistance genes. Among the malaria vectors taken as examples on three continents, Africa, South-East Asia and Latin America, the large majority of the species showed an important polymorphism. The Gambiae Complex, which is by far the most studied one, includes at present 7 species with the recent description of An. quadriannulatus A and B from Ethiopia. An. gambiae s.s. includes itself 5 chromosomal forms. One of them, the Mopti form, should be considered as a species unto itself. For An. arabiensis, a strong differentiation has been observed among the populations from Senegal and the Indian Ocean Islands. The kdr mutation, which confers resistance to pyrethroid knockdown effect, has never been found either in the Mopti form, or An. arabiensis, indicating a restricted gene flow between these latter two and An. gambiae s.s. The speciation process of the Gambiae Complex seems to be a recent phenomenon due to environmental selection pressure. Species of the Funestus Group are distinguishable by morphological characters. The genetic study of An. funestus s.s. did not show the presence of a complex, in spite of high polymorphism and population structure. Anophelines from eastern areas present an important biodiversity. The Minimus Complex includes two species, A and C, which are widely distributed in South-East Asia. Species A is strongly endophilic, on the contrary species C is at once more exophilic and zoophilic. The latter species might have been selected by DDT indoor house spraying. After numerous taxonomic investigations, the Dirus Complex includes now 7 species. In Latin America, An. pseudopunctipennis clustered into three geographic populations which are under a speciation process. One covers North America and Guatemala, the other South America and Belize, whilst the last one is restricted to Grenada Island. On the contrary, An. darlingi showed little morphologic and genetic variability throughout the species geographic range suggesting the existence of a single species. The main objective of these studies is to implement a more selective approach of vector control programs in relation to the incriminated species, their bioecology and their role in malaria transmission. The improvement of efficiency and selectivity of vector control is becoming a major goal in order to make the best out of the available tools and control the impact of interventions on the environment.

Africa↗
PubMedDate not supplied

[Drought and malaria decrease in the Niayes area of Senegal].

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.

Animals↗