First screening of Aedes albopictus immunogenic salivary proteins.

Study of the human antibody (Ab) response to Aedes salivary proteins can provide new biomarkers to evaluate human exposure to vector bites. The identification of genus- and/or species-specific proteins is necessary to improve the accuracy of biomarkers. We analysed Aedes albopictus immunogenic salivary proteins by 2D immunoproteomic technology and compared the profiles according to human individual exposure to Ae. albopictus or Ae. aegypti bites. Strong antigenicity to Ae. albopictus salivary proteins was detected in all individuals whatever the nature of Aedes exposure. Amongst these antigenic proteins, 68% are involved in blood feeding, including D7 protein family, adenosine deaminase, serpin and apyrase. This study provides an insight into the repertoire of Ae. albopictus immunogenic salivary proteins for the first time.

Natural vertical transmission of dengue viruses by Aedes aegypti in Bolivia.

The natural transmission of dengue virus from an infected female mosquito to its progeny, namely the vertical transmission, was researched in wild caught Aedes aegypti during an important outbreak in the town of Santa Cruz de la Sierra, Bolivia. Mosquitoes were collected at the preimaginal stages (eggs, larvae and pupae) then reared up to adult stage for viral detection using molecular methods. Dengue virus serotypes 1 and 3 were found to be co-circulating with significant higher prevalence in male than in female mosquitoes. Of the 97 pools of Ae. aegypti (n = 635 male and 748 female specimens) screened, 14 pools, collected in February-May in 2007, were found positive for dengue virus infection: five DEN-1 and nine DEN-3. The average true infection rate (TIR) and minimum infection rate (MIR) were respectively 1.08% and 1.01%. These observations suggest that vertical transmission of dengue virus may be detected in vectors at the peak of an outbreak as well as several months before an epidemic occurs in human population.

Geographic and ecological distribution of the dengue and chikungunya virus vectors Aedes aegypti and Aedes albopictus in three major Cameroonian towns.

Aedes albopictus (Diptera: Culicidae) was first reported in Central Africa in 2000, together with the indigenous mosquito species Aedes aegypti (Diptera: Culicidae). Because Ae. albopictus can also transmit arboviruses, its introduction is a public health concern. We undertook a comparative study in three Cameroonian towns (Sahelian domain: Garoua; equatorial domain: Douala and Yaoundé) in order to document infestation by the two species and their ecological preferences. High and variable levels of pre-imaginal Ae. aegypti and Ae. albopictus infestation were detected. Only Ae. aegypti was encountered in Garoua, whereas both species were found in Douala and Yaoundé, albeit with significant differences in their relative prevalence. Peridomestic water containers were the most strongly colonized and productive larval habitats for both species. No major differences in types of larval habitat were found, but Ae. albopictus preferentially bred in containers containing plant debris or surrounded by vegetation, whereas Ae. aegypti tended to breed in containers located in environments with a high density of buildings. These findings may have important implications for vector control strategies.

Christophers' stage durations and effect of interrupted blood meal in the mosquito Aedes caspius (Diptera: Culicidae).

Christophers' stages durations and effect of interrupted blood meal were investigated in laboratory to study the gonotrophic cycle of Aedes caspius (Pallas, 1771). A first experiment was done with replete females (full blood meal) and females with an interrupted blood meal. Females were then regularly dissected, the durations of Christophers' stages I, II, III, IV, V were up to 8, 8, 32, 8, 48 h, respectively. A second experiment was done with replete females, females with an interrupted blood meal and females with an interrupted blood meal completed 24 h later. Interrupted females matured 21 +/- 5 follicles, interrupted-completed females 92 +/- 11, and replete females 120 +/- 8 follicles.

Deciphering the nitric oxide to carbon monoxide lung transfer ratio: physiological implications.

Using simultaneous nitric oxide and carbon monoxide lung transfer measurements (T(LNO) and T(LCO)), the membrane transfer capacity (D(m)) and capillary lung volume (V(c)) as well as the dimensionless ratio T(LNO)/T(LCO) can be calculated. The significance of this ratio is yet unclear. Theoretically, the T(LNO)/T(LCO) ratio should be inversely related to the product of both lung alveolar capillary membrane (mu) and blood sheet thicknesses (K). NO and CO transfers were measured in healthy subjects in various conditions likely to be associated with changes in K and/or mu. Experimentally, deflation of the lung from 7.4 to 4.8 l decreased the T(LNO)/T(LCO) ratio from 4.9 to 4.2 (n=25) which was consistent mainly with a thickening of the blood sheet. Compared with continuous negative pressure breathing, continuous positive pressure breathing increased this ratio suggesting a thinning of the capillary sheet. It was also observed with 12 healthy subjects that slight haemodilution that may thicken the blood sheet decreased the T(LNO)/T(LCO) ratio from 4.85 to 4.52. In conclusion, the T(LNO)/T(LCO) ratio is related to the thickness of the alveolar blood barrier. This ratio provides novel information for the analysis of the diffusion properties.

Dyeing process may alter the efficacy of insecticide-treated nets.

The biological efficacy as judged by mortality against Anopheles gambiae s.s. of three net samples, one white and two colored, treated with deltamethrin by conventional dipping was compared. Efficacy as well as chemical analysis results showed that uptake of insecticide by white net material was much higher than by colored nets. After a single wash, efficacy of colored nets was reduced significantly below 80% mortality, which is the minimum acceptable level for a field application. This unexpected result could be because of either low uptake of insecticide by colored fibers or high alkalinity on the fibers, resulting from the dyeing process (reduction clearing). alpha-Cyanopyrethroids, such as deltamethrin, have a low stability in alkaline conditions and rapidly degrade. Practical implications of this finding are of primary importance because the majority of nets currently purchased by institutional buyers for malaria prevention are colored.

Lethal and behavioural effects of three synthetic repellents (DEET, IR3535 and KBR 3023) on Aedes aegypti mosquitoes in laboratory assays.

The knock-down, mortality and 'irritancy' effects of three synthetic repellents (DEET, IR3535 and KBR 3023) on Aedes aegypti (L) (Diptera: Culicidae) were evaluated in the laboratory in the absence of animal bait. Filter paper tests were carried out to assess the knock-down effect (KDt(50) and KDt(95)) and mortality (LC(50) and LC(95)) induced by each repellent. 'Irritancy' tests were carried out to compare the flight response (time to first take-off, or FT) to increasing concentrations of repellents (2-7%) and at five distances from the treated surface (0-40 mm). DEET had an insecticidal effect (KDt(50) = 9.7 min at 7%; CL(50)= 1165 mg/m(2)), whereas IR3535 and KBR 3023 did not. Relative to an untreated control, IR3535 was an irritant (relative irritancy or RI > 1) at doses of 5% and 7% (RI = 17.7 and 9.9, respectively), whereas DEET was an irritant at lower concentrations (RI = 12.3 at 2% DEET). KBR 3023 was the weakest irritant over the same range of concentrations (RI(max) = 3.6 at 6%). DEET was more of an irritant (RI(20) = 9.4) than IR3535 (RI(20) = 2.9) over a range of distances (0-20 mm), and KBR 3023 was not an irritant unless mosquitoes made contact with the treated surface. All three repellents had a significant effect on mosquitoes, but DEET exhibited a more complex mode of action than the others due to its insecticidal properties. The repellents do not behave as a single class of compounds with a common mode of action, but most probably affect different physiological systems in insects. The physiological and molecular mechanisms of repellents, especially DEET, should be investigated to ensure a better use of these molecules for skin applications and/or for treating materials against mosquitoes.

Membrane conductance in trained and untrained subjects using either steady state or single breath measurements of NO transfer.

The aim of this work was to define the relationship between membrane conductance for NO (Dm) and physical activity by using either the steady state NO transfer (T(LNO)SS) or the single breath method (T(LNO)SB), making the hypothesis that NO transfer is only limited by the membrane. Alterations in T(LNO)SS with lung volume during tidal ventilation were measured in six subjects at rest and during steady exercise at 30, 60, and 80% of maximal aerobic power (MAP). A fast responding chemoluminescent NO analyser was used. Two calculation methods were used by sampling NO: (1) at mid-tidal volume, (2) in the middle of the alveolar plateau. T(LNO)SB at rest and maximal oxygen consumption (V(.-)O(2)max) were also measured in 18 other subjects. At rest T(LNO)SS with method 2 was 192% of the value given by method 1. T(LNO)SS with method 1 increased by 50% with 80% MAP as it did not change with method 2. Method 2 seemed inaccurate. T(LNO)SB at rest, which is closely related to Dm, was correlated to age and V(.-)O(2)max, T(LNO)SB=182-1.2 age+24.3 V(.-)O(2) max(l min(-1)) (p<0.01, r(2)=0.72). The T(LNO)SS and T(LNO)SB versus lung volume relationships suggest an influence of the breathing pattern on Dm. Dm can be estimated either by these two NO transfer methods, however the use of the T(LNO)SS method is highly sensitive to the alveolar sampling level. Dm increase during exercise is a function of MAP. Dm at rest decreases with age as it increases with MAP.

Microsatellite markers for population genetic studies in Aedes aegypti (Diptera: Culicidae) from Côte d'Ivoire: evidence for a microgeographic genetic differentiation of mosquitoes from Bouaké.

In West Africa, Aedes aegypti (Diptera: Culicidae) (Linnaeus, C., 1762. Zweyter Theil, enhalt Beschreibungen veschiedener wichtiger Naturalien. In: Hasselquist, F. (Ed.), Reise nach Palastina in den Jahren von 1749 bis 1752, Rostock, Germany, pp. 267-606) represents the principal vector of yellow fever. This study reports the use of microsatellite markers to characterise various A. aegypti populations from Côte d'Ivoire according to a north-south transect, and to perform a temporal genetic survey of the mosquitoes. Three microsatellite loci were used to analyse individuals from four different places: Kabolo, Bouaké, and two different districts of Abidjan. We found that the four populations are genetically distinct except the two Abidjan populations. In the Bouaké population, the coexistence of two cryptic species, not morphologically distinguishable, seems to account for the extensive heterozygote deficiency observed. Comparison of mosquitoes from Bouaké 1 year apart indicated that a dramatic change occurred in the structuring of this population over time. Taken together these results indicate that microsatellite markers could be useful for identifying various populations of A. aegypti on a microgeographic scale and to assess for temporal variation within mosquito populations.

Experimental and molecular genetic analysis of the impact of pyrethroid and non-pyrethroid insecticide impregnated bednets for mosquito control in an area of pyrethroid resistance.

Experimental huts in Côte d'Ivoire were used to evaluate the pyrethroid alpha-cypermethrin, the non-ester pyrethroid etofenprox, the organophosphate pirimiphos-methyl and the carbamate carbosulfan on bednets against pyrethroid-resistant Anopheles gambiae Giles. To test for selection for the resistance gene by the treated nets, A. gambiae collected live or dead from the huts were kept and analysed for the presence of the kdr gene using a new polymerase chain reaction followed by sequence-specific oligonucleotide probing (PCR-SSOP) for kdr-genotyping. Deliberately holed bednets freshly treated with pirimiphos-methyl or carbosulfan caused over 90% kill of A. gambiae s.s. and Culex spp. However, the mortality with alpha-cypermethrin or etofenprox treated nets was similar to that with untreated nets. Bloodfeeding of A. gambiae s.s. on the sleepers under the nets was only significantly reduced by alpha-cypermethrin and carbosulfan. Tests of the residual activity of the bednets after seven months showed that pirimiphos-methyl had lost its efficacy while carbosulfan still performed well. Once again the pyrethroid treated nets gave similar results to the untreated nets. Selection for the kdr-allele by alpha-cypermethrin and etofenprox, but not by carbosulfan, was indicated by PCR-SSOP genotyping of mosquitoes. Thus carbamates such as carbosulfan, or organophosphates of longer persistence than pirimiphos-methyl and of low mammalian toxicity, would seem to be a promising alternative to be used on bednets, particularly in areas of pyrethroid resistance.

[Prediction and prevention of malaria epidemics in the valley of the Senegal River]. / Prévision et prévention des épidémies de paludisme dans la vallée du fleuve Sénégal.

The Sahel region has been suffering from severe drought for the last thirty years, with large deficits and a high degree of variability in the amount of annual rainfall. Agricultural production in the Sahelian zone of the Senegal River valley depends on the flooding of the river. The management of this flooding affects malaria transmission. The area is prone to malaria epidemics because the immunity level of the population is low. We studied epidemiological, meteorological and river level data to identify epidemic risk factors. We propose an epidemiological and managerial system for the early detection of risks and early intervention. This system is based mainly on the water level of the Senegal River and the early detection of unusual increases in the number of cases.

Comparison of human and murine isolates of Schistosoma mansoni from Richard-Toll, Senegal, by isoelectric focusing.

Studies on human and murine isolates of Schistosoma mansoni, from Richard-Toll, Senegal, were carried out by isoelectric focusing in polyacrylamide gels. Seven enzyme systems; lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G6PD), acid phosphatase (AcP), hexokinase (HK), glucose phosphate isomerase (GPI), and phosphoglucomutase (PGM), were used to compare the two isolates. All systems tested, apart from LDH, were found to be polymorphic for both isolates. Interestingly, one phenotype is more frequent than the remainder. The results show that there is no significant genetic variation between the S. mansoni isolates from man and the rodents, Arvicanthis niloticus and Mastomys huberti.

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.

Susceptibility of rodents to infection with Schistosoma mansoni in Richard-Toll (Senegal).

The susceptibility of Arvicanthis niloticus, Mastomys huberti, Mastomys erythroleucus and Mus musculus was studied to assess the capacity of these rodents to transmit Schistosoma mansoni. The susceptibility was determined by the percentage of adult schistosomes recovered, the number of eggs per gramme of faeces, the viability of these eggs and the capacity of the rodents to maintain the life cycle of Schistosoma mansoni. The percentages of adult worms recovered were respectively 18%, 11.5%, 8.4% and 20.5% in A. niloticus, M. huberti, M. erythroleucus and M. musculus. After infection, they liberate in the environment viable eggs whose miracidia are infectious for the intermediate host (Biomphalaria pfeifferi). The mean egg load was 300 +/- 327.8 in A. niloticus; 664 +/- 673.5 in M. huberti; 240 +/- 304.8 in M. erythroleucus; 400 +/- 361.5 in M. musculus.

[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.

[Malaria in the Saharan region of Senegal. 2. Parasitological indices]. / Le paludisme en zone sahélienne du Sénégal. 2. Indices parasitaires.

The malaria parasitological indexes have been studied in three villages situated in the Senegal river central valley. Near one of them an irrigated rice field has been operational since July 1989. Each village has its own health care unit and the consumption of antimalarial drugs, especially chloroquine, is important. The parasitological indexes in children 0 to 9 years old and in patients presenting with symptoms evocative of malarial attacks are low. Irrigation of the rice field area does not seem to be an increasing factor for the malaria parasite rates in the area.

[Malaria in the Saharan region of Senegal. 1. Entomological transmission findings]. / Le paludisme en zone saheliénne du Sénégal. 1. Données entomologiques sur la transmission.

An 18 months longitudinal survey on the entomological aspects of the transmission of malaria has been carried out in a village practising rice field irrigation and in another village with traditional rain water agriculture. Both are located in the Sahelian area of the Senegal river central valley, in Senegal. The study is based on mosquito samples caught on human baits. The vectors A. arabiensis and A. gambiae could be found all year long in the village with rice field irrigation, but only during the rainy season in the other village distant from the rice field area. The average aggressive density decreases with the remoteness from the rice field area. From 16 bites/man/night (BMN) in the rice field area, it decreases to 7 BMN at 500 m and to 1 BMN at 5 km distance. The malaria transmission rate is weak and was not perceptible in the villages located far away from the rice field area. In the village close to the irrigated rice field, only one infected A. gambiae s.l. has been caught during the period of study. Physiological age is higher in the rice field area, but the anthropophilic index is lower. The different parameters involved in malaria transmission show important seasonal and yearly variations. Irrigation has, on the whole, increased mosquito population densities and particularly that of A. gambiae s.l., but malaria transmission does not seem to be influenced by this increase.

[Thyroid cancer revealed by a suppressive hot nodule]. / Cancer thyroïdien révélé par un nodule chaud extinctif.

We report the case of a 62-year old woman in euthyroidism who presented with a thyroid cancer located within a hot nodule. The nodule was partially extinctive, and the triiodothyronine test showed incomplete suppression. Fine needle cytology showed no malignant cells. Systematic lobectomy was performed, and the diagnosis of cancer was made at pathology. This rare situation does not mean that all non-toxic hot nodules must be removed, but if surgery is decided an extemporaneous histological examination is mandatory. Besides, such cases provide an additional argument in favour of surgery or treatment of toxic adenomas.