In silico models for predicting vector control chemicals targeting Aedes aegypti.

Human arboviral diseases have emerged or re-emerged in numerous countries worldwide due to a number of factors including the lack of progress in vaccine development, lack of drugs, insecticide resistance in mosquitoes, climate changes, societal behaviours, and economical constraints. Thus, Aedes aegypti is the main vector of the yellow fever and dengue fever flaviviruses and is also responsible for several recent outbreaks of the chikungunya alphavirus. As for the other mosquito species, the A. aegypti control relies heavily on the use of insecticides. However, because of increasing resistance to the different families of insecticides, reduction of Aedes populations is becoming increasingly difficult. Despite the unquestionable utility of insecticides in fighting mosquito populations, there are very few new insecticides developed and commercialized for vector control. This is because the high cost of the discovery of an insecticide is not counterbalanced by the 'low profitability' of the vector control market. Fortunately, the use of quantitative structure-activity relationship (QSAR) modelling allows the reduction of time and cost in the discovery of new chemical structures potentially active against mosquitoes. In this context, the goal of the present study was to review all the existing QSAR models on A. aegypti. The homology and pharmacophore models were also reviewed. Specific attention was paid to show the variety of targets investigated in Aedes in relation to the physiology and ecology of the mosquito as well as the diversity of the chemical structures which have been proposed, encompassing man-made and natural substances.

[Control of mosquitos in Martinique. A collective public health action and improvement of the quality of life]. / La lutte contre les moustiques en Martinique. Une action collective de santé publique et d'amélioration du cadre de vie.

Aedes aegypti control program in Martinique started en 1968. The Aedes aegypti major breeding sites are associated with flowers vases, drums, used tyres, artificial containers and watering places. However, Culex quinquefasciatus is the main nuisance mosquito in all the island. This species is unpleasant, especially in urban areas. Over 200 Culex quinquefasciatus bites per person per night have been observed in several localities of the island. Culex quinquefasciatus breeding sites are mostly associated with sewage treatment plants, septic tanks and stagnant drains. In order to reduce this nuisance and to improve the quality of life-the Conseil General initiated a large mosquito control program since 1991. This global mosquito control is based on: information and health education, environmental management (source reduction, drainage...), use of chemical insecticides.

[Control of Aedes aegypti in Martinique. Contribution of entomology studies]. / Lutte contre aedes aegypti en martinique. Apport des études entomologiques.

The dengue prevention activities in Martinique are based on: Entomological surveillance (including the use of insecticide in all parts of the Island). Epidemiological (clinical, serological and virological) surveillance. Health Education (radio, TV, exhibitions, talks in primaries and secondaries schools, in associations,...). The main breeding sites of Aedes aegypti are maintained by human practices: flowers vases, containers, used tyres, waste... The role of those human practices in the standing of Aedes aegypti populations at high level in Martinique have lead us to emphasize entomological observations and Health education. The calculation of classical Breteau Index abstracts the nature and the productivity of the breeding sites (f.e.: no difference between a flower vase and a drum). In operational way, we have introduced a new approach for calculating the Breteau index value which includes the breeding sites nature and productivity. This approach permit us to adapt the Health education message in each geographical sector.

Detoxifying esterases in Culex pipiens quinquefasciatus from the Caribbean countries.

Several over-produced esterases confer resistance to organophosphorus insecticides in the Culex pipiens complex. We describe their distribution in islands and countries of the Caribbean region based on new collections and previous studies, and discuss the need to: 1) undertake DNA studies to correctly identify the esterase B alleles that are amplified in different regions, and 2) investigate the variability among gene copies within each amplification system in order to fully understand their origin and their evolution through time.

Resistance to organophosphorous insecticides in Culex pipiens quinquefasciatus (Diptera: Culicidae) from Martinique.

Before beginning a widespread control program against Culex pipiens quinquefasciatus in Martinique, resistance to temephos, chlorpyrifos, and two organophosphorous insecticides, was investigated at seven breeding sites. At LC95, populations exhibited resistance ratios between 6.9 and 11.6 for temephos and between 6.4 and 51.4 for chlorpyrifos. Overproduced esterases A2-B2 and B1, known to be involved in organophosphorous-resistance, were present at all breeding sites; esterases A2-B2 frequency was > 50% at all sites but one; and esterase B1 frequency was < 7%. Experimental treatment of three breeding sites with temephos induced no significant increase in resistance, but our esterase studies indicated a significant increase in the frequencies of esterase B1 and of a new highly active esterase C2. These results indicate that a large-scale C. p. quinquefasciatus control program with organophosphorous insecticides will induce a rapid increase of these resistance genes throughout Martinique. However, this may not necessarily result in high levels of resistance, because, at present, the level of gene amplification of esterase B still appears to be low.

Prevalence of depigmentation of the shins: a simple and cheap way to screen for severe endemic onchocerciasis in Africa.

The prevalence of skin depigmentation in the pretibial region is closely correlated in the adult Congolese population with conventional indices (microfilarial index, mean microfilarial density, cyst index) for the evaluation of endemic onchocerciasis. Individuals over 15 years of age in endemic villages who had a microfilarial index of 80-90%, had a cystic index of 60-70% and a pretibial depigmentation index about 20% (30-40% for individuals aged > 50 years). Thus, in Africa, this new evaluation index offers a simple, noninvasive, quick and cheap way to identify areas where the level of endemic onchocerciasis is probably high and which are likely to benefit from an anti-onchocerciasis campaign.

PIP: Skin depigmentation is a classic diagnostic sign of onchocerciasis and presents typically as an irregular, flat spot surrounded by slightly hyperpigmented zones. The depigmentation occurs mainly on the shins. The prevalence of skin depigmentation has been proposed as a marker for evaluating the endemicity of onchocerciasis in Nigeria, but has been contested for use in South America on the grounds of non-specificity. The microfilarial index currently used to assess the level of onchocerciasis endemicity is relatively time-consuming, costly, and harbors the risk of transmitting viral infections during mass screenings. 991 people over 15 years of age of mean age 55.4 years in five villages in the Congo endemic for onchocerciasis participated in this study. Individuals who had a microfilarial index of 80-90% had a cystic index of 60-70% and a pretibial depigmentation index of approximately 20%. The authors conclude that the existence of shin depigmentation as an evaluation index in Africa offers a simple, noninvasive, quick, and inexpensive way to identify areas where the level of endemic onchocerciasis is probably high and which are likely to benefit from an anti-onchocerciasis campaign. Although the new index does not allow total specificity, the incidence of shin depigmentation among patients with African onchocerciasis is such that there is probably little risk of confusing holo- or hyperendemic zones with an area where leprosy or treponema are endemic. In the absence of onchocerciasis, bites from Simulium spp. flies may also be responsible for skin depigmentation, as may be streptocerciasis. In this latter condition, however, the predominant site of depigmentation is not the shin. The authors have observed no notable prevalence of shin depigmentation in northern Congo, which is infested with S. albivirgulatum flies, but with no onchocerciasis transmission, and where there are also zones of streptocerciasis.

Premiere description de foyers d'onchocercose humaine au Gabon

Des foyers d'onchocercose a Onchocerca volvulus sont decrits pour la premiere fois au Gabon. Au cours des memes enquetes on note de fortes prevalences de porteurs de M. streptocerca et la premiere description chez l'homme de M. Rodhaini. 4922 sujets au cours de 10 enquetes portant sur l'ensemble du territoire gabonais ont subi une biopsie cutanee exsangue; un prelevement sanguin; un examen clinique. La prevalence globale des porteurs de O. volvulus est de 19;4 pour cent. Les regions les plus touchees sont : Makokou; Lebamba; Fougamou; Lastourville. Les hommes sont plus atteints que les femmes. L'infestation debute tot : 1;9 pour cent des enfants de 0-4 ans sont porteurs de microfilaires. La charge microfilarienne moyenne est de 30;7 microfilaires d'O. volvulus par biopsie. Les manifestations cliniques sont pauvres comparees a l'Afrique de l'Ouest : 36;3 pour cent des onchocerquiens sont porteurs de nodules. Les etudes des lesions oculaires n'ont porte que sur le segment anterieur de l'oeil; le pour centage de keratites ponctuees est moins important qu'en Afrique Sahelien

[Epidemiological status of onchocerciasis in the Congo]. / Situation épidémiologique de l'onchocercose au Congo.

Analysis of 25 surveys carried out in the Congo between 1978 and 1987 (covering nine of the ten administrative regions), during which 6,215 subjects were examined, showed that onchocerciasis is endemic in the southern part of the country. Two main foci meeting at the southern exit of Brazzaville (Pool region) were identified. One focus in the Djoué basin. The other is the zone along the Congo river stretching from below Brazzaville south west to the Zaire border. Two secondary foci were noted, one in the region of the Bouenza and the other west of the Mayombe mountains. Surveys carried out in the north of the country and in the west did not reveal any onchocerciasis. However, certain areas of primary forest in these regions were found to be endemic for Mansonella streptocerca. Simulium damnosum s.l. in the sole vector of onchocerciasis. In both the Pool foci, and in the Mayombe focus, prevalences assessed from microfilarial and cyst counts were high but the mean microfilarial densities were relatively low. In certain villages over 90% of the population aged over 14 years may present with microfilariae and nearly 70% may present cysts.

[Evaluation of serum immunoglobulins E in onchocercosis in the People's Republic of the Congo]. / Evaluation des immunoglobulines E sériques dans l'onchocercose en République Populaire du Congo.

Evaluation of IgE levels, determined by micro ELISA method, was carried out on 90 Congolese people: 42 patients suffering from onchocerciasis and 48 control subjects. The mean levels were respectively: 9,673 and 780 UI/ml. No significant differences were observed with sexes. Therefore in onchocerciasis there is a tendency to increase with age.

[Onchocerciasis in the Brazzaville region (Congo). Preliminary note]. / L'onchocercose dans la région de Brazzaville (Congo). Note préliminaire.

The authors give the results of a global and rapid study, using a simple methodology, of a suburban onchocerciasis focus located in the vicinity of Brazzaville. It follows, from the entomological, parasitological and clinical data, that the transmission is high inside this focus and therefore, it seems necessary to take, all measures in order to eradicate the focus.