Biomedical subjects

D Fontenille

Publications and source records attributed to D Fontenille.

At least 37 records · Page 2Linked to original sources

PubMed2001

Use of circumsporozoite protein enzyme-linked immunosorbent assay compared with microscopic examination of salivary glands for calculation of malaria infectivity rates in mosquitoes (Diptera: Culicidae) from Cameroon.

A survey in Cameroon compared the usefulness of the circumsporozoite protein enzyme-linked immunosorbent assay (CSP ELISA) to dissection and microscopic examination of anopheline salivary glands for measuring infectivity rates in anopheline mosquitoes. The salivary glands of 375 females, belonging to four species were examined for sporozoites. After microscopic examination, the glands as well as all the remaining heads and thoraces were tested by ELISA. The sensitivity of ELISA was 100% (18/18), confidence interval (CI) (78.1-100) and the specificity was 99.7% (357/358), CI (98.2 100). The Kappa value, agreement between examination of the glands and salivary gland ELISA, was 0.97. The head thorax CSP ELISA overestimated the true salivary gland infection rate by 12.0%. The results obtained in Central Africa in a village with perennial transmission highly justified the use of the ELISA for measuring the entomological inoculation rate.

Animals↗

PubMed2001

Arbovirus surveillance from 1990 to 1995 in the Barkedji area (Ferlo) of Senegal, a possible natural focus of Rift Valley fever virus.

Surveillance for mosquito-borne viruses was conducted in Barkedji area from 1990 to 1995, following an outbreak of Rift Valley fever (RVF) virus in southern Mauritania. Mosquitoes, sand flies, and midges were collected from human bait and trapped by solid-state U.S. Army battery-powered CDC miniature light traps baited with dry ice or animals (sheep or chickens) at four ponds. Overall, 237,091 male and female mosquitoes representing 52 species in eight genera, 214,967 Phlebotomine sand flies, and 2,527 Culicoides were collected, identified, and tested for arboviruses in 9,490 pools (7,050 pools of female and 331 of male mosquitoes, 2,059 pools of sand flies and 50 pools of Culicoides). Viruses isolated included one Alphavirus, Babanki (BBK); six Flaviviruses, Bagaza (BAG), Ar D 65239, Wesselsbron (WSL), West Nile (WN), Koutango (KOU), Saboya (SAB); two Bunyavirus, Bunyamwera (BUN) and Ngari (NRI); two Phleboviruses, Rift Valley fever (RVF) and Gabek Forest (GF); one Orbivirus, Ar D 66707 (Sanar); one Rhabdovirus, Chandipura (CHP); and one unclassified virus, Ar D 95537. Based on repeated isolations, high field infection rates and abundance, Culex appeared to be the vectors of BAG, BBK, Ar D 65239 (BAG-like), and WN viruses, Ae. vexans and Ae. ochraceus of RVF virus, Mansonia of WN and BAG viruses, Mimomyia of WN and BAG viruses, and Phlebotomine of SAB, CHP, Ar D 95537, and GF viruses. Our data indicate that RVF virus circulated repeatedly in the Barkedji area.

Animals↗

PubMed2001

[Feeding behaviour of Anopheles funestus resting females in Senegal].

The feeding behaviour of An. funestus resting females was studied in eleven sites in Senegal along a west-east transect in two biogeographical zones (the Sudanese and Sudanese-Guinean zones) by an ELISA technique. Mosquitoes were collected by pyrethrum spray catches. For the 1563 blood meals tested, the main hosts were humans, cows, sheep and horses representing respective proportions of 85%, 9.9%, 1.3% and 3.8%. No blood meal was taken on chicken. The percentage of non-reacting blood meals was 2.6%. A heterogenity of feeding behaviour was observed in the sample locations. The anthropophilic rates were higher in the northern Sudanese zone as versus the southern Sudanese and Sudano-Guinean zones.

Animals↗

PubMed2000

Increased susceptibility to malaria during the early postpartum period.

BACKGROUND: Pregnancy is associated with increased susceptibility to malaria. It is generally agreed that this increased risk ends with delivery, but the possible persistence of increased susceptibility during the puerperium had not been investigated. METHODS: From June 1, 1990, to December 31, 1998, we monitored exposure to malaria, parasitemia, and morbidity among the residents of a village in Senegal in which the rate of transmission of malaria was high. In this population we analyzed 71 pregnancies in 38 women from the year before conception and through one year after delivery. RESULTS: Among the 38 women, there were 58 episodes of clinical Plasmodium falciparum malaria during 61,081 person-days of observation. The incidence of malaria was 20.2 episodes per 1000 person-months during the year preceding conception and 12.0 episodes per 1000 person-months during the period from 91 to 365 days after delivery. The incidence of episodes of malaria increased significantly during the second and third trimesters of pregnancy and reached a maximum of 75.1 episodes per 1000 person-months during the first 60 days after delivery. The adjusted relative risk of an episode of malaria was 4.1 (95 percent confidence interval, 1.8 to 9.5) during the first 60 days post partum, as compared with the year preceding pregnancy. The duration of fever during the episodes of malaria was longer and the prevalence and density of asymptomatic malarial parasitemia were significantly higher during pregnancy and the early postpartum period than during the other periods. CONCLUSIONS: Among women who live in areas with high rates of transmission of malaria, the susceptibility to malaria is highest during the second and third trimesters of pregnancy and the early postpartum period.

Adolescent↗

PubMed2000

Persistence of Anopheles arabiensis during the severe dry season conditions in Senegal: an indirect approach using microsatellite loci.

Variation at nine microsatellite loci was investigated to understand how Anopheles arabiensis populations survive the dry season in the sahelian region of Senegal. Low estimates of genetic differentiation (F(ST) = 0.012, R(ST) = 0.009) between two populations, 250 km apart, suggested extensive gene flow across this distance. Despite extreme seasonal fluctuation in abundance with dry season minima in which mosquitoes virtually disappeared, allele frequencies remained stable over time in the village of Barkedji from August 1994 to December 1997 (including four rainy seasons and three dry seasons). The effective population size (Ne) was estimated to be 601 with 95% CI (281, 1592), providing strong evidence against annual bottlenecks. Differences in measures of genetic diversity and linkage disequilibrium between the dry and the rainy seasons were not detected. These results suggest that despite extreme minima in local density, An. arabiensis maintains large permanent deme spread out over large area.

Alleles↗

PubMed2000

Spatial and temporal variations of the chromosomal inversion polymorphism of Anopheles funestus in Senegal.

The polymorphism of paracentric inversions of An. funestus polytene chromosomes was studied along a transect in Senegal in order to assess their variations at the spatial and temporal level. There was an increase in the degree of chromosomal polymorphism from the West to South-East. At the geographical level the variations in inversion frequencies were highly significant whatever the chromosomal arm considered. However, the variations in the chromosomal inversion frequencies did not change significantly over either seasons or years, except for inversion 3b in the village of Dielmo. Such geographical variability within a relatively limited area, associated to temporal stability, suggest a restricted gene flow between the populations studied, probably due to discontinuities in the An. funestus distribution and to its bioecology.

Animals↗

PubMed2000

Vertical transmission of the yellow fever virus by Aedes aegypti (Diptera, Culicidae): dynamics of infection in F1 adult progeny of orally infected females.

Vertical transmission of yellow fever virus from orally infected females to their progeny was experimentally demonstrated in 2 Aedes aegypti colonies from the Dakar and Koungheul regions in Senegal. A total of 10,530 F1 adult mosquito progeny were tested. The overall vertical transmission rate was 0.97%, with no significant difference between the Dakar and Koungheul colonies. The infection rates were significantly higher in females (1.15%) than in males (0.74%) in both colonies. The virus was not isolated from the progeny of the first oviposition cycle (OVC1). The true infection rates were 0.27% and 1.99%, respectively, for the OVC2 and OVC3 progeny in the Dakar colony, and 1.1% and 1.48%, respectively, for the OVC2 and OVC3 progeny in the Koungheul colony. The infection rates increased with extrinsic incubation in both male and female offspring of the 2 colonies, reaching 5.2% in 20-day-old OVC3 female progeny in the Dakar colony. The epidemiologic consequences of these results are discussed.

Aedes↗

PubMed2000

Chromosomal inversion polymorphism of Anopheles funestus from forest villages of South Cameroon.

The polymorphism of paracentric inversions of Anopheles funestus polytene chromosomes was studied in three villages (Nkoteng, Obala, and Simbock) located in a forest area of South Cameroon in order to analyse the genetic structure of these populations. A total of 146-210 chromatids could be scored from specimens collected over about two years. A low degree of chromosomal polymorphism was observed with two floating inversions on chromosomal arm 2 (2h and 2d), and three fixed arrangements on arms 3 (3a and 3b), and 5 (5a). Such arrangement of inversions has never been recorded elsewhere so far. The chromosome analysis indicated that the population from Obala was in Hardy-Weinberg equilibrium, whereas the samples from Nkoteng and Simbock showed a significant excess and deficit of heterokaryotypes, respectively. Significant differences in inversion frequencies on chromosomal arm 2 among villages lying in contrasting eco-climatic settings suggested an adaptive role of these inversions.

Animals↗

PubMed1999

Variation of Plasmodium falciparum msp1 block 2 and msp2 allele prevalence and of infection complexity in two neighbouring Senegalese villages with different transmission conditions.

To investigate the impact of transmission on the development of immunity to malaria and on parasite diversity, longitudinal surveys have been conducted for several years in Dielmo and Ndiop, 2 neighbouring Senegalese villages with holo- and mesoendemic transmission conditions, respectively. We analysed Plasmodium falciparum msp1 block 2 and msp2 genotypes of isolates collected from 58% of the Dielmo villagers during the same week as those studied recently from Ndiop. Allele frequencies differed in both villages, indicating considerable microgeographical heterogeneity of parasite populations. The complexity of the infections, estimated using individual or combined msp1 and msp2 genotyping, in Dielmo was more than double that in Ndiop and it was age-dependent in Dielmo but not in Ndiop. Thus, this study confirmed the influence of age on the complexity of asymptomatic malaria infections in a holoendemic area. The age distribution of complexity in Dielmo substantiates the interpretation that the number of parasite types per isolate reflects acquired antiparasite immunity. This cross-sectional survey also confirms that the sickle cell trait has no impact on complexity but influences the distribution of P. falciparum genotypes.

Adolescent↗

PubMed1999

Mitochondrial and ribosomal internal transcribed spacer (ITS2) diversity of the African malaria vector Anopheles funestus.

The pattern of sequence variation in the mitochondrial DNA cytochrome b gene (cyt-b) and ribosomal DNA internal transcribed spacer 2 (ITS2) was examined in Anopheles funestus from Senegal and Burkina Faso in West Africa and Kenya in East Africa. From both West African countries, samples included individuals hypothesized to represent reproductively isolated taxa based upon different karyotypes and behaviours. Analysis of the cyt-b data revealed high haplotypic diversity (86%) and an average pairwise difference per site of 0.42%. Sequence variation was not partitioned by geographical origin or karyotype class. The most common haplotype was sampled across Africa (approximately 6000 km). Analysis of the ITS2 data revealed one of the longest spacers yet found in anophelines (approximately 704 bp). In common with other anopheline ITS2 sequences, this one had microsatellites and frequent runs of individual nucleotides. Also in common with data from other anopheline ITS2 studies, the An. funestus sequences were almost monomorphic, with only two rare polymorphisms detected. The results from both markers are congruent and do not support the hypothesis of reproductively isolated chromosomal taxa within An. funestus. Whether the lack of support by mitochondrial DNA (mtDNA) and ribosomal DNA (rDNA) sequences is a result of the recent origin of the presumptive taxa, or of the absence of barriers to gene flow, remains to be elucidated, using more rapidly evolving markers such as microsatellites.

Africa↗

PubMed1999

[Experimental transmission of Crimean-Congo hemorrhagic fever virus: role of 3 vector species in the maintenance and transmission cycles in Senegal].

In this article, we published the role of three species of ticks Amblyomma variegatum (Fabricius, 1974), Hyalomma marginatum rufipes (Koch, 1844) and Hyalomma truncatum (Koch, 1844) in the maintenance and transmission of the CCHF virus. The imagos of these species were infected by intracoelomic route. Vertical transmission (transtasial and transovarial) and horizontal transmission for different stases were studied by isolation on newborn mice, polymerase chain reaction, indirect immunofluorescence and ELISA. Our results proved that 15 days after inoculation, infection rates of 100% were noted with Hyalomma marginatum rufipes and Hyalomma truncatum. This rate is about 60% for Amblyomma variegatum. The imagos of the three species infected have transmitted the virus to their host during blood feeding (100%). A high transovarial transmission for Hyalomma marginatum rufipes and Hyalomma truncatum were observed (respectively 53 and 50%). This rate is about 12% for Amblyomma variegatum. The tick infection does not persist up to the first generation for the three species studied. Ticks are temporary reservoirs vectors but not permanent reservoirs of CCHF virus.

Animals↗

PubMed1999

High amounts of genetic differentiation between populations of the malaria vector Anopheles arabiensis from West Africa and eastern outer islands.

Polymorphism at nine microsatellite loci was examined to assess the level of genetic differentiation between four Anopheles arabiensis populations from Senegal, the high plateau of Madagascar, and Reunion and Mauritius islands. Eight of nine loci showed great polymorphism (2-16 alleles/locus) and significant genetic differentiation was revealed between all four populations by F- and R-statistics, with Fst estimates ranging from 0.080 to 0.215 and equivalent Rst values ranging between 0.022 and 0.300. These high amounts of genetic differentiation are discussed in relation to geographic distance including large bodies of water, and history of mosquito settlement, and insecticide use on the islands. The results suggest that historical events of drift rather than mutation are probably the forces generating genetic divergence between these populations, with homogenization of the gene pool by migration being drastically restricted across the ocean.

Animals↗

PubMed1999

Vectors of Chikungunya virus in Senegal: current data and transmission cycles.

Chikungunya fever is a viral disease transmitted to human beings by Aedes genus mosquitoes. From 1972 to 1986 in Kédougou, Senegal, 178 Chikungunya virus strains were isolated from gallery forest mosquitoes, with most of them isolated from Ae. furcifer-taylori (129 strains), Ae. luteocephalus (27 strains), and Ae. dalzieli (12 strains). The characteristics of the sylvatic transmission cycle are a circulation periodicity with silent intervals that last approximately three years. Few epidemics of this disease have been reported in Senegal. The most recent one occurred in 1996 in Kaffrine where two Chikungunya virus strains were isolated from Ae. aegypti. The retrospective analysis of viral isolates from mosquitoes, wild vertebrates, and humans allowed to us to characterize Chikungunya virus transmission cycles in Senegal and to compare them with those of yellow fever virus.

Aedes↗

PubMed1999

[Chikungunya virus outbreak in Senegal in 1996 and 1997].

Chikungunya disease is generally recognized in Africa by serosurveys conducted in rural areas. Epidemics are rarely documented. We report two outbreaks in Senegal: one having occurred near Kaffrine in 1996 during an epidemic of yellow fever (YF), the second in Niakhar in 1997. Both diagnoses were conducted by IgM antibodies captures and confirmed by virus isolations. In Kaffrine, a randomised study was carried out on 447 blood donors whose serum was systematically tested for the most frequently encountered arboviruses in Senegal. The incidence rate was higher for the unrecognized Chikungunya infection (35.3%) than for the notified YF infection (21%). In Niakhar, Chikungunya infection was initially detected through three cases having occurred in health workers. A serosurvey was then conducted to define the area of prevalence. We report the clinical forms of Chikungunya virus infections, the interest in detecting IgM for recent arbovirus infections and the duration of these IgM. The difficulties of diagnosis of Chikungunya infection in malaria endemic areas are stressed. The occurrence of arbovirus infections, Yellow fever and Chikungunya viruses, transmitted by the same vectors (Aedes aegypti) in Kaffrine are also discussed.

Aedes↗

PubMed1999

[Phlebotomus of Senegal: survey of the fauna in the region of Kedougou. Isolation of arbovirus].

Phlebotomine sand-flies were captured on a bimonthly basis from April 1995 to March 1996 in the Kedougou district of south-east Senegal. In all, 6,642 specimens were identified belonging to 25 species. Eleven species were captured in tree holes, 17 in termites hills, 19 in rodent burrows and 23 on grass. Sergentomyia buxtoni, S. clydei, S. dubia, S. squamipleuris et S. schwetzi were the most abundant. Species from the genus Sergentomyia accounted for 99.3% versus 0.7% for the genus Phlebotomus, Phlebotomus duboscqi, the leishmaniasis vector in Senegal, was very rare. The male of S. edentula and S. herollandi were recorded for the first time. The sand-fly population was observed to peak in April. The most populated resting sites were, in decreasing order, termite-hills, burrows and tree-holes. Thirty virus strains from 5 different viruses (Saboya, Chandipura, Tete, ArD 95737, ArD 111740) were isolated from 30,482 specimens tested.

Animals↗

PubMed1999

A description and morphometric comparison of eggs of species of the Anopheles gambiae complex.

Eggs of the 6 named species of the Anopheles gambiae complex are described from scanning electron micrographs of specimens obtained from laboratory colonies or wild-caught females. Morphometric measurements of eggs from 5 sources of Anopheles arabiensis, 2 of Anopheles gambiae, one of Anopheles quadriannulatus, 2 of Anopheles bwambae, 2 of Anopheles merus, and one of Anopheles melas are compared, and relationships are analyzed by multivariate statistics. No morphologic characters were species-diagnostic, although tendencies of the saltwater species An. merus and An. melas to have wider decks and shorter floats were confirmed. Species and populations overlapped considerably in principal components and discriminant function analyses based on 10 attributes of eggs. Nevertheless, discriminant functions revealed similarities in eggs of species believed to be most closely related, namely, An. gambiae and An. arabiensis, An. merus and An. melas, and An. quadriannulatus and An. bwambae.

Animals↗

PubMed1999

[Experimental transmission of Crimean-Congo hemorrhagic fever virus by Rhipicephalus evertsi evertsi (Acarina:Ixodidae)].

We have conducted experiments to assess the ability of Rhipicephalus evertsi evertsi tick to transmit the Crimean-Congo haemorrhagic fever (CCHF) and determine their reproductive cycle. The Rh. e. evertsi was infected by intracoelomic (transparietal and intra-anal) inoculation during the imaginal stases and by oral feeding on an infected viremic goat during imaginal and nymphal stases. The infection rate, transovarial and trans-stasial CCHF virus transmission were monitored for virus reisolation after suckling mice inoculation and the virus identified by ELISA and IFA for antigen detection. After intracoelomic inoculation, unfed adults had viral titers ranging from 0.67 to 2.9 log DL50/0.02 ml and had transmitted the virus to their vertebrate hosts by blood feeding. After 8 to 10 days of blood feeding duration, infection rates were respectively 36% and 100% for male and female ticks. In two instances out of seven transovarial transmission was observed and the virus reisolated from larvae of first generation. However, the virus was not detected after nymphal metamorphosis. After blood feeding on viremic goats, 71% of the nymphae were infected. After metamorphoses 22% of the males and 42% of the females had a low virus titer. Rh. e. evertsi appears to have a limited efficacy in transmitting and replicating the CCHF virus but must be not neglected as a potential vector during an epizootic manifestation.

Animals↗

PubMed1999

[Evaluation of the vectorial capacity of Anopheles arabiensis (Diptera:Culicidae) on the island of Réunion: an approach to the health risk of malaria importation in an area of eradication].

Following intensive control measures, malaria was eradicated from La Réunion Island (Indian Ocean) in 1979. However, potential vectors remain in coastal areas and, each year Public Health Services detect some imported cases from surrounding countries. Anopheles arabiensis is the only species which can be responsible for local transmission though its brief life cycle and its exophilic and zoophilic behaviour were found to be key elements in maintaining the eradication status of the disease on the island. Its vectorial capacity was measured at different seasons and in different areas with a view to assessing the health risks due to imported malaria and suggesting a more pertinent strategy of vector control.

Animals↗