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Phylogenetic evidence suggests that endemic and epidemic dengue viruses (DENV), transmitted among humans by the anthropophilic mosquitoes Aedes aegypti and Ae. albopictus, emerged when ancestral, sylvatic DENV transmitted among nonhuman primates by sylvatic Aedes mosquitoes adapted to these peridomestic vectors. We tested this hypothesis by retrospectively examining evidence for adaptation of epidemic and endemic versus sylvatic strains of DENV-2 to Ae. albopictus and Ae. aegypti. First and second-generation offspring of mosquitoes from different geographic regions in the Americas and Southeast Asia were tested for their susceptibility to epidemic/endemic and sylvatic DENV-2 isolates from West Africa, Southeast Asia, and Oceania. Both Aedes species were highly susceptible (up to 100% infected) to endemic/epidemic DENV-2 strains after ingesting artificial blood meals but significantly less susceptible (as low as 0%) to sylvatic DENV-2 strains. Our findings support the hypothesis that adaptation to peridomestic mosquito vectors mediated dengue emergence from sylvatic progenitor viruses.

Rice is becoming increasingly important as a staple food in West Africa and there is a need to increase production to meet the demand and one way to achieve this is to harvest two annual crops. It is possible that such intensified irrigation could affect transmission of schistosomes and this study attempts to compare schistosome transmission in single and double-cropped areas of an irrigation scheme, 'Office du Niger', in Mali. Double cropping has been practised for some years in the Niono area while in the Kolongotomo area still only a single crop is grown. Parasitological surveys conducted in 10 villages (5 from each of these 2 areas) showed that Schistosoma haematobium was less prevalent in the area with single cropping than in the area with double cropping. In order to compare transmission patterns between the two areas, all human-water contact sites around four villages (two from each area) were identified and included in transmission studies. From August 1996 to June 1997, eight surveys were conducted, at intervals of approximately 45 days, in each of these sites to record density of the intermediate hosts, density of infected snails, environmental factors (especially density of aquatic macrophytes), and frequency of human-water contacts. Although the data provide useful information on transmission patterns in Niono and Kolongotomo areas, they fail to demonstrate clear-cut differences in snail population dynamics and transmission patterns between the two areas. A key element in snail habitats in both areas is the abundance of aquatic macrophytes, especially the submerged species. Snail control using environmental modification should focus on controlling these plants in human-water contact sites.

Scleroma is a chronic and specific granulomatous disease of bacterial origin. Klebsialla rhinoscleromatis, a gram-negative bacillus. The majority of cases affect the upper airways, particularly the nose, thus justifying the term of rhinoscleroma. Extension to the palate, the upper lip and the skin is possible. A new case of rhinoscleroma with skin extension is reported. To us, this is the second case in Senegal (Casamance). Epidemiological, clinical, bacteriological and histological aspects of the disease are reviewed. Under suitable antibiotic, evolution is currently favorable.

This study was carried out in the village of Faladié, Mali located in the malaria-endemic Kati region, two years after routine use of chloroquine prophylaxis was discontinued in children 0 to 9 years old. The main purpose of this study was to assess changes in chloroquine resistance. Two cross-sectional surveys in association with WHO in vivo chloroquine sensitivity testing were conducted, i.e., one in September 2000 and one in December 2002. Findings in 2000 showed that 77.5% of mothers administered chloroquine prophylaxis to their children in compliance with physician orders. The plasmodic index was 62%. The overall level of parasitologic resistance (based on the 1996 WHO in vivo tests) was 80%. The overall therapeutic failure rate was 17.5%. Findings in 2002 demonstrated a plasmodic index of 28%, an overall parasitologic resistance rate of 45% (based on WHO in vivo tests), and an overall therapeutic failure rate of 15%. The diminution of resistance in 2002 may be due to the decrease of drugs pressure and to low exposure of individuals to mosquitoes at the end of transmission season. Althougt these data indicate a 44% drop in chloroquine resistance (P=0.0001), no increase in the clinical efficacy of chloroquine was observed (P=0.05). In view of these results we propose more emphasis on information campaigns to increase public awareness of the need for chemoprophylaxis only for pregnant women, on the promotion of the use of bednets and insecticide-impregnated materials, and on environmental management.

Tuberculosis is a public health priority especially in developing countries. A variety of control programs have been implemented. The purpose of this survey was to study the perceptions and practices of the victims of this disease "in the field". The findings of this survey carried out in a cohort of 65 patients and their families in Conakry, Guinea underline the importance of popular perceptions of the disease in care-seeking behavior. This survey also shows that health care workers share the same perceptions as the general population, which constitutes a major impediment for screening and treatment.

Malaria infection and anemia during pregnancy are the primary causes of maternal and fetal morbidity and mortality. The aims of this study were to identify risk factors for malaria infection and to assess the relationship between malaria infection and anemia in pregnant women. Two cross-sectional surveys were conducted in September 1993 and then again in May 1994 (the end of the rainy and dry seasons respectively). A total of 235 pregnant women were randomly selected from both the rural and urban areas of Bandiagara, Mali. According to results from multivariate analysis, the risk of malaria infection was significantly higher during the rainy season (OR= 4.85, 95% CI 2.42-9.75) the first trimester of gestation (OR= 2.21, 95% CI 1.00-4.87, in younger women (OR= 2.48, 95% CI 1.19-5.16), and in women living in the rural area (2.49, 95% CI 0.99-6.27). The risk of anemia was also higher during the rainy season (OR= 1.93, 95% CI 1.10-3.39, in the rural area (OR= 3.55, 95% CI 1.46-8.62). The risk of anemia was lower during the first trimester of gestational age (OR= 0.45, 95% CI 0.22-0.92). The relationship between malaria infection and anemia also varied with season. During the rainy season, the risk for anemia was similar among malaria-infected and non-infected pregnant women. In contrast, the risk was higher among infected pregnant women during the dry season (OR= 3.43, 95% CI 1.09-10.07). In conclusion, the data suggest, that earlier gestation age, living in the rural area, and young age rather than parity are important risk factors for malaria infection in pregnant women. Further, malaria infection is strongly associated with anemia in pregnant women particularly during the dry season and is most likely the cause of anemia. Thus, control measures against malaria infection should target younger rural women in their first trimester of pregnancy.

We carried out five cross sectional surveys between 1993 and 1994 to assess the epidemiology of malaria in the village of Bancoumana, located in the Sudanese savannah areas of Mali. Each survey included a collection of entomological, clinical, parasitological and immunological data. The study population involved 1600 children from six months to 9 years of age. The main vector was Anopheles gambiae s.l., man bite rate and entomological inoculation rate were maximum respectively in August (peak of the transmission season) and October (end of transmission season). Plasmodium. falciparum was the main parasite species observed. Spleen enlargement rate, parasite rate, gametocyte rate and parasite density varied significantly with age and season. The parasite rate, gametocyte rate and parasite density were significantly low in October 1994 compared with October 1993 while the entomologic parameter did not show any variation over the two years. This reduction of parasitologic index between 1993 and 1994 may be related to an increase of anti-malarial drug use in the population. Our results show that malaria is hyperendemic in the village of Bancoumana.

Vaccine development research is an important component of malaria control strategies. Thrombospondin related anonymous protein (TRAP) and the circumsporozoite (CS) protein are two antigens of sporozoite surface. Immune response to these two antigens may contribute to the development of anti-sporozoite vaccine. Recent studies suggest that antibodies anti-TRAP may partially block sporozoites penetration in hepatocyte, and thereby reducing malaria morbidity. We carried out a study to assess the seroprevalence of anti-TRAP and anti-CS antibodies and to identify a possible role of these antibodies on malaria morbidity in children 1-9 years old living in a rural hyperendemic village. We performed 5 cross sectional surveys and a longitudinal follow up in 1993 and 1994. During each cross sectional study, children were examined for fever and splenomegaly; all febrile children received thick film examination, and serologic analysis was performed in one third of these, randomly selected. The results show that the seroprevalence of anti-TRAP and anti-CS varied with age and season (p < 0.05). Association between the prevalence of anti-TRAP and splenomegaly was observed during two cross sectional surveys (June and October 1993). The presence of anti-TRAP antibody was associated with Plasmodium falciparum infection at the beginning of the transmission season (June 1993 and July 1994). A negative association between the level of anti-TRAP title and parasitemia was observed (March and October 1994). These findings suggest no clear evidence of the protective role of anti-TRAP antibodies in uncomplicated malaria, possibly due to the limited persistence of these antibodies under natural situations.

After 8 years of silence, dengue virus serotype 2 (DENV-2) reemerged in southeastern Senegal in 1999. Sixty-four DENV-2 strains were isolated in 1999 and 9 strains in 2000 from mosquitoes captured in the forest gallery and surrounding villages. Isolates were obtained from previously described vectors, Aedes furcifer, Ae. taylori, Ae. luteocephalus, and--for the first time in Senegal--from Ae. aegypti and Ae. vittatus. A retrospective analysis of sylvatic DENV-2 outbreaks in Senegal during the last 28 years of entomologic investigations shows that amplifications are periodic, with intervening, silent intervals of 5-8 years. No correlation was found between sylvatic DENV-2 emergence and rainfall amount. For sylvatic DENV-2 vectors, rainfall seems to particularly affect virus amplification that occurs at the end of the rainy season, from October to November. Data obtained from investigation of preimaginal (i.e., nonadult) mosquitoes suggest a secondary transmission cycle involving mosquitoes other than those identified previously as vectors.

We report epidemiological and clinical characteristics of 17 consecutives patients with Behçet disease during 26 years in Dakar(Sénégal). All the patients were black, with a mean age of 27.5 years (11- 42 years) and the disease was more common between 20 and 30 years. The sex ratio was 2.4 (12 men -5 women). The majority live in cost area (64.7). Clinical features frequencies were as follow muco-cutaneous (94.11%), ocular (58.82%) neurological (47.05%) articular (47.05) psychiatric (41.17%) vascular (35.29%) digestives (11.76%). Epidemiological characteristics of Behçet disease in Sénégal are common however, the important frequency of neuropsychiatrics manifestations is remarkable.

We performed a retrospective study in order to characterize epidemiological data and signs of systemic scleroderma in Sénégal. All patients with the diagnosis according the ACR's criteria of scleroderma were recruited. We included 92 patients, the mean age was 33 years and sex ratio male to female was 0.19 (15 men and 77 women). There were 8 children in our series (8.9%). The initial complaints were cutaneous manifestations (64%) and Raynaud's syndrome (16.3%). Clinical manifestations at admission were muco-cutaneous (100%), osteo-articular and muscular (59%) and Raynaud's syndrome (57%). Focal hypopigmentation was common (70%). Anti-nuclear antibodies were present in 67.4% of patients. Skin biopsy was contributive in all patients in which it was performed (79 cases). Electrocardiogram was abnormal in 55%, non specific inflammatory syndrome was present in 44% and pulmonary function was abnormal in 52%. Our data suggest that systemic scleroderma is more common in younger people in black population. Disorders of pigmentation are common and Raynaud's syndrome is uncommon.

Recently, double-stranded RNA (dsRNA)-mediated RNA interference (RNAi) has rapidly developed to a powerful instrument for specific silencing of gene expression in several organisms, including Caenorhabditis elegans, Drosophila melanogaster, and plants. The finding that synthetic small interfering RNAs (siRNAs) of 21 nt as well as stable, endogenously expressed, large dsRNA are suited to specifically induce gene silencing in mammalian cells offered the possibility of expanding this technique to mammalian systems. In this work, we engineered stably transfected human cells that express large dsRNAs mediating specific posttranscriptional silencing of genes. We used this technique to specifically silence genes coding for glucosylceramide synthase (GCS), the sphingolipid activator protein precursor (SAP), and glucocerebrosidase (GBA), all implicated in glycosphingolipid metabolism. From a 1600-bp inverted repeat DNA template, a dsRNA of 800 bp is expressed and predicted to mediate the specific suppression of the corresponding gene by RNAi. Remarkably, we were able to use this method to achieve complete inhibition of those genes we targeted in different cultured human cell lists. These findings testify to the generality of RNAi application in suppressing gene expression in mammalian cells.

Reverse transcriptase PCR (RT-PCR) for diagnosis of Rift Valley fever (RVF) was evaluated by using 293 human and animal sera sampled during an RVF outbreak in Mauritania in 1998. Results of the RT-PCR diagnostic method were compared with those of virus isolation (VI) and detection of immunoglobulin M (IgM) antibodies. Our results showed that RT-PCR is a specific, sensitive tool for RVF diagnosis in the early phase of the disease and that its results do not differ significantly from those obtained by VI. Moreover, the combined results of RT-PCR and IgM antibody detection were in 100% concordance with the results of VI.

The behavioural response to several culicine and anopheline mosquitoes to the odour of alternative hosts (human vs monkey) arranged in a choice set-up using odour-baited entry traps (OBETs) was assessed in a field experiment in south-eastern Senegal. The experimental protocol followed procedures analogous to those adopted in olfactometer laboratory tests. Two adult Cercopithecus aethiops and a child of similar mass slept inside separate tents and their odours were drawn to each one of two paired OBETs so that approaching mosquitoes could experience both odour-laden streams before "choosing" to fly against one of the two air currents and into the trap. The traps were set up in a riverine forest clearing near the town of Kedougou, where primates (Papio papio, Cercopithecus aethiops, and Erythrocebus patas) are common. A total of 192 mosquitoes belonging to 4 genera was captured during 8 trap nights. All major human malaria vectors including Anopheles gambiae sensu lato, An. funestus, and An. nili, which constituted the bulk of the trap catch (N = 153), clearly expressed a preference for human odour, with > 90% of captured mosquitoes caught in the human-baited trap. A sub-sample of specimens belonging to the An. gambiae complex caught in both traps was identified by rDNA-PCR and RFLP as An. gambiae sensu stricto molecular form S (7/10), and An. arabiensis (3/10). The only species that did not show a preference for the alternative odour-laden air streams, among those caught in significant numbers, were mosquitoes of the genus Mansonia, with both Ma. uniformis and Ma. africana weakly preferring human odour, but not at a statistically significant level. These results are in accordance with the hypothesis that the strongly anthropophilic feeding preferences of An. gambiae did not evolve from an ancestral association with non-human primates.

A Rift Valley fever outbreak occurred in Mauritania in 1998. Seroepidemiologic and virologic investigation showed active circulation of the Rift Valley fever virus, with 13 strains isolated, and 16% (range 1.5%-38%) immunoglobulin (Ig) M-positivity in sera from 90 humans and 343 animals (sheep, goats, camels, cattle, and donkeys). One human case was fatal.

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.

Following the reemergence of Rift Valley fever (RVF) virus in southeastern Mauritania in 1998, an entomological survey was undertaken in the boundary area in Senegal to assess the extent of the virus circulation. During this study, RVF virus (36 strains) was isolated for the first time from Culex poicilipes in nature. The possible role of Cx. poicilipes as an RVF vector is discussed regarding its biology and ecology.

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.

The dynamics of reinfection by Schistosoma haematobium and Schistosoma mansoni after repeated treatment with praziquantel (40 mg/kg body weight, single dose) was studied in a cohort of schoolchildren living in an endemic area. A total of 214 urine and 220 stool samples were collected and examined at three different times, i.e., February 1989, July 1989 and February 1990. Mass chemotherapy was administered at the beginning of study (February 89). Treatment was repeated in children with positive tests at each subsequent sampling. Prevalence rates were 55.1 p. 100, 3.7 p. 100, and 35.0 p. 100 for Schistosoma haematobium and 62.7 p. 100, 46.3 p. 100 and 73.1 p. 100 for Schistosoma mansoni in February 1989, July 1989 and February 1990 respectively (p < 0.001). From July 1989 to February 1990, reinfection was observed in 84.5 p. 100 of children by Schistosoma haematobium versus 57.8 p. 100 by Schistosoma mansoni. The risk of reinfection by Schistosoma haematobium was higher in children between the ages of 7 and 10 years than in children between the ages of 11 and 15 years (p < 0.001), The incidence of intense Schistosoma haematobium egg excretion rose from 0 p. 100 in July 1989 to 6.0 p. 100 in February 1990. The incidence of intense Schistosoma mansoni excretion in February 1990 was 4.5 p. 100. The reinfection rate at 7 months was over 50 p. 100 for both parasite species despite repeated treatment. This finding demonstrates that additional measures such as proper sanitation and vector control are needed to control human schistosomiasis in irrigated rice paddies.

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.

To assess pyrimethamine-sulfadoxine (PS) efficacy in Mali, and the role of mutations in Plasmodium falciparum dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) in in vivo PS resistance, 190 patients with uncomplicated P. falciparum malaria were treated with PS and monitored for 56 days. Mutation-specific polymerase chain reactions and digestion with restriction endonucleases were used to detect DHFR and DHPS mutations on filter paper blood samples from pretreatment and post-treatment infections. Only one case each of RI and RII level resistance and no cases of RIII resistance or therapeutic failure were observed. Post-PS treatment infections had significantly higher rates of DHFR mutations at codons 108 and 59. No significant selection for DHPS mutations was seen. Pyrimethamine-sulfadoxine is highly efficacious in Mali, and while the low level of resistance precludes assessing the utility of molecular assays for in vivo PS resistance, rapid selection of DHFR mutations supports their role in PS failure.

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.

Thirteen cases of genital tuberculosis are reported to make emphasis onto the difficulties of diagnosis, management and prognosis of the disease. The average age of the patients is 31 years. Most of them were under 30. The circumstances of diagnosis were variable. The diagnosis was essentially made thanks to histology. The evolution was favorable under antibiotics. But clinical sequels as amenorrhea and infertility are frequent.

We report one case of thrombocytopaenia purpura associated with an auto-immune haemolytic anaemia (positive erythrocyte Coombs test) or Fisher-Evans syndrome, found in a child aged 6 and a half years. Etiopathogenic, clinical, therapeutic as well as evolutive aspects are discussed. Response to corticoids is satisfactory in case our patient, in opposite to most cases described in the literature.

In November 1996 a yellow fever (YF) outbreak occurred near Kaffrine in the central part of Senegal. Thirty-six deaths were notified, all children under 15 years of age. The YF diagnosis was confirmed by MAC-ELISA or by virus isolation. The immune status against YF virus of a sample population of 449 individuals was determined, and 31 confirmed cases and 69 asymptomatic cases were reported. Distribution of YF cases and incidence rate decreased with age, while the attack rate was stable in all age groups. Larva indices were high and Aedes aegypti was common in all villages, causing man-to-man transmission. The greatest risk of YF disease was lack of immunity, especially in individuals <20 years of age. The outbreak was rapidly controlled by an emergency immunization campaign. YF epidemics occurred in Senegal over two consecutive years. The last outbreak reached the main road to Dakar and the risk of spread to urban areas has increased.

Infectivity of gametocytemic volunteers living in Bancoumana, a village 60 km from Bamako, Mali, was determined by direct feeds of laboratory-reared Anopheles gambiae s. l. Gametocytemic adolescents (10-18 years old) were as infectious to mosquitoes as younger volunteers and appear to be a more suitable population for testing transmission-blocking efficacy as compared with adults (> 18 years old). To begin to validate the membrane-feeding assay, sera collected from these same volunteers were subjected to a standard membrane-feeding assay. The data suggest that areas with intense but seasonal transmission might be feasible sites for testing transmission-blocking vaccines because of the high gametocytemic rates, high mosquito infectivity rates, and lack of pre-existing humoral-mediated transmission-blocking activity. The differences observed between field-based direct mosquito feeds and laboratory-based membrane feeding assays suggests that caution be used in interpreting Phase I study results in which laboratory-based membrane-feeding assays are used as a surrogate for vaccine efficacy.

An outbreak of yellow fever (YF) occurred in the central part of Senegal during October 1995. Thirty-one probable cases were detected and 79 cases were confirmed either by IgM ELISA or by virus isolation (30 strains isolated). The case fatality rate was 18.9%. Incidence of the infection was evaluated by a serosurvey in the area. Males 10-29 years old belonging to the Peul ethnic group were more affected. Moreover, 28 YF virus strains were isolated from mosquitoes and larvae pools and vertical transmission of YF virus by Aedes aegypti was also demonstrated for the first time in the field. This outbreak occurred after the major amplification of the wild cycle of YF virus in 1993 in West Africa. This epidemic represented a typical example of intermediate transmission of YF: both humans and wild vertebrates are involved in the virus cycle through wild mosquitoes with semidomestic habits, mainly Ae. furcifer, Ae. luteocephalus, and domestic vector Ae. aegypti. It was controlled by a prompt immunization campaign. The impact of inclusion of YF vaccine in the Expanded Program of Immunization, which has been conducted in Senegal for eight years, is discussed.

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.

The role of odors in mosquito host preferences was studied in a village near Ouagadougou, Burkina Faso. Two odor-baited entry-traps were put beside one another and a choice of host odor-laden air was blown out of them. Odors of a human and a calf (of similar mass) were drawn from two tents in which each was separately concealed. Allowances were made for trap position, differences in human-subject attractiveness, CO2 levels, and trap contamination with alternative host odors. Choices for the human-baited trap greater than the 0.5 random expectation were made by Anopheles gambiae s.l. (0.96) and An. pharoensis (0.68). The choices for the human-baited trap of Culex antennatus were significantly lower than 0.5 (0.25), whereas for the Cx. decens species group (0.56), the difference was not significant. Interpretation of the latter result was complicated by the significant effect of CO2 levels on the index. Species caught in low numbers but whose trap distribution showed a bias towards the human-baited trap were An. funestus (total numbers in the human-baited trap to the calf-baited trap = 9:0), Mansonia africana (17: 1), Aedes dalzieli (22:4), and Ae. hirsutus (13:1); species showing bias towards the calf-baited trap were An. rufipes (0:11), Cx. duttoni (0:17), and Cx. nebulosus (2:35). Mansonia uniformis was the only species distributed randomly between the two traps. Molecular identification of the An. gambiae s.l. samples revealed a marked difference in trap distribution: for the human-baited trap the ratio was 52% An. arabiensis to 48% An. gambiae s.s.; for the calf-baited trap, it was 92% An. arabiensis to 8% An. gambiae s.s.

Entomological investigations were conducted in 1995 in Senegal, following a yellow fever (YF) outbreak. A total of 1125 mosquitoes collected in the field, including males, females and 12-48 h old newly emerged adults reared from wild-caught larvae, were tested for YF virus. Among the 22 species captured, Aedes aegypti was the most common. 'Wild' vectors of YF were also captured, including A. furcifer, A. metallicus and A. luteocephalus. In all, 28 YF virus isolations were made: 19 from A. aegypti females, including 2 from newly emerged specimens; 5 were obtained from A. aegypti males, including one from a pool of newly emerged specimens, 2 from A. furcifer females, and one each from a female A. metallicus and a female A. luteocephalus. The true infection rates (TIRs) were much higher in adult A. aegypti than in specimens reared from larvae--8.2% and 31.4% for female and male A. aegypti captured on human volunteers, respectively (P < 0.0001). The TIRs for A. aegypti reared from larvae were 1.4% and 0.5% for females and males, respectively (P > 0.05). This outbreak was an intermediate YF epidemic, involving 4 vector species. Our data provide the first evidence of vertical transmission of YF virus in nature by A. aegypti, its main vector to humans, and strongly suggest that vertical transmission played a major role in the spread of the epidemic.

Background and Objectives: Antimicrobial resistant strains of Neisseria gonorrhoeae have spread with remarkable rapidity in many African countries. Chromosomal resistance to penicillin, tetracycline, and thiamphenicol is frequent now, and reported prevalences of penicillinase-producing N. gonorrhoeae isolates vary between 15% and 80%. Plasmid-mediated tetracycline-resistant N. gonorrhoeae isolates have been observed in several African countries., Goals: To characterize gonococcal isolates from three sites in West and Central Africa, to determine antimicrobial susceptibility patterns, to document the spread of plasmid-mediated resistance to penicillin and tetracycline in these three sites, and to discuss the consequences of rising antimicrobial resistance on the management of gonococcal infection in Africa., Study Design: Over time, a total of 2,288 gonococcal isolates were obtained from Abidjan, Ivory Coast (1992-1993, n = 251), from Kigali, Rwanda (1988-1993, n = 952), and from Kinshasa, Zaire (1988-1990, n = 1,085). The isolates were characterized by auxotyping and serotyping. Plasmid-mediated resistance to penicillin and to tetracycline was determined. Antimicrobial susceptibility testing to ceftriaxone, ciprofloxacin, penicillin, spectinomycin, tetracycline, and thiamphenicol was performed with an agar dilution method., Results: The prevalence of penicillinase-producing N. gonorrhoeae increased significantly over time from 44% to 57% in Kigali and remained stable at a high level in Abidjan (73%) and in Kinshasa (67%). The frequency of tetracycline-resistant N. gonorrhoeae increased significantly during the observation periods in all three sites: from 20% to 65% in Abidjan, from 0% to 64% in Kigali, and from 14% to 41% in Kinshasa. Chromosomal resistance to penicillin was common in Kigali and Kinshasa, and chromosomal resistance to tetracycline and thiamphenicol was frequent in all three sites. All gonococcal isolates were susceptible to ceftriaxone, ciprofloxacin, and spectinomycin. Prototrophic and proline requiring strains were predominant, and IA-6 was the most common serovar in the three sites. IB-specific serovars were more common among penicillinase-producing N. gonorrhoeae and IA-specific serovars were more frequent among tetracycline-resistant N. gonorrhoeae, but there was no evidence for a clonal spread of resistant strains., Conclusions: This study illustrates the high frequency of resistant gonococci in Africa and shows that tetracycline-resistant N. gonorrhoeae have become highly endemic in different geographic areas of the continent. The use of effective drugs is essential to reduce gonorrhea transmission. Surveillance of temporal changes in antimicrobial resistance in gonococcal strain populations should be part of sexually transmitted diseases control programs.

During the 1993 rainy season, 15,806 mosquitoes, including 14,304 Aedes ssp., were collected and tested for virus infection in 702 and 547 pools, respectively. Aedes furcifer (Edwards) was the most abundant species collected throughout the survey period. Yellow fever (YF) virus was detected in 187 pools: Ae. furcifer (123 isolates), Ae. taylori (Edwards) (41 isolates), and Ae. luteocephalus (Newstead) (23 isolates). A high prevalence of immunoglobulin (IgG) antibodies was found in human and simian populations. Results clearly indicated that increased sylvatic YF activity in eastern Senegal has the increased the risk of YF transmission among rural populations in West Africa. Our results showed that a minimal survey period may be effective in detecting the circulation of YF in the Kedougou area.

Ngari virus (NRI) (Bunyaviridae, genus Bunyavirus) was isolated first from male Aedes simpsoni mosquitoes in Southeastern Senegal in 1979. Then, it was recovered from several mosquito species in Senegal, Burkina Faso, Central African Republic and Madagascar. A potential pathogenicity of NRI virus in humans was suspected when the virus was isolated from two patients in Dakar in October and November 1993. The large diversity of Culicidae vectors and feeding patterns showed a large heterogeneity of vertebrate hosts. The wide geographical distribution of NRI virus in different bioclimatic areas indicated an important adaptability of the virus. Ngari virus epidemiology will need further investigations in order to approach the real pathogenicity of such emerging virus.

Thirteen strains of Rift Valley fever virus were isolated from Aedes vexans and Ae. ochraceus mosquitoes collected in October and November 1993 in northern Senegal. Entomologic and serologic data show that the risk of a new epizootic is increasing in this region.

Olfaction is a crucial function in most fish species, but little is known about biotransformation enzymes in the olfactory organ. This study demonstrates that biotransformation enzymes usually found in the rainbow trout liver, are present in the olfactory organ as well. While microsomal cytochrome P450 reductase, p-nitrophenol hydroxylase and cytosolic glutathioneS-transferase presented similar levels in both the olfactory organ and the liver, microsomal 7-ethoxyresorufinO-deethylase (EROD), 7-ethoxycoumarinO-deethylase, and 7-pentoxyresorufinO-deethylase were much lower in the olfactory organ (77-, 35-, 200-times respectively). Furthermore, microsomes from the olfactory organ were able to perform testosterone hydroxylation only in the 16α-position while testosterone was hydroxylated in the 16β-position by liver microsomes. Using polyclonal antibodies raised against perch cytochrome P4501A1, the immunoreactive protein was shown to be strongly expressed in various cellular types forming the nonsensory epithelium. Some immunostaining was also reported in the nonsensory cellular elements constituting the sensory epithelium, while olfactory receptor cells failed to show cytochrome P4501A1-immunoreactivity. Finally, the exposure of rainbow trout to waterborne β-naphthoflavone (0.1 μg ml(-1)) for 2 or 4 days resulted in a higher induction of EROD activity in the olfactory organ compared to the liver. The presence of biotransformation enzymes in the olfactory organ of rainbow trout addresses the question of their involvement in the detoxication/toxication of pollutants as well as in the olfactory function.

A new case of rare neonatal alloimmune thrombocytopenia, due to an IgG anti-HPA-1b in a mother HPA-1 (a+, b-), was diagnosed using monoclonal antibody-specific immobilization of platelet antigens. Clinically, it was similar to the 2 previously reported observations and confirmed that, in this particular case of anti-HPA-1b, the treatment with random platelet pools may be as effective as selected single-donor platelet units when maternal platelets are unusable. The HLA-DR, -DQ, -DP genotypes of the family were obtained by PCR-SSO. The mother's typing, compared to the HLA-DR of the 6 similar cases reported in Europe, suggests that a combined effect of two rare HLA haplotypes might enhance this immunization.

Thrombospondin-related anonymous protein (TRAP) of the malaria parasite Plasmodium falciparum shares two sequence motifs with other proteins which possess adhesive properties. Recently, findings indicate that TRAP is an antigen which contributes to antisporozoite immunity. We have cloned and expressed the TRAP coding sequences in Escherichia coli to investigate the human humoral immune response against this protein in a region of malaria endemicity of West Africa characterized by a seasonal transmission. Our results show that antibodies against TRAP are present in infected individuals. The anti-TRAP antibodies were analyzed in both a longitudinal and a prospective study. The longitudinal analysis shows seasonal fluctuations of the levels of specific antibodies as well as age-dependent quantitative differences. The immune response is long-lived in most of the adults and some of the older children but short-lived in young children. More importantly, the prospective analysis suggests that the presence of anti-TRAP antibodies in older children before the beginning of malaria transmission correlates with the subsequent control of parasite densities.

From may 1989 to january 1990, we have studied parasitologic index in snails population, stools and urines examination in children (1-15 years) in one of the greatest "spontaneous" quarter of Bamako. 584 stools samples and 563 urines were tested. 4.717 snails were captured during six months. From all these data, we conclude that in Bankoni S. haematobium is mesoendemic (36.6%) and S. mansoni hypoendemic (3.4%). B. truncatus is the most important host for urogenital schistosomiasis. The two seasonal revers (Tienkole and Bankoni) are unfavourable to B. pfeifferi's production. B. globosus and B. forskalii are not frequent in this suburban area. This investigation, shows that a selective mass treatment with praziquantel is the better public health care strategy in Bankoni quarter.

A study on the incidence and gravity of malaria among children suffering of sickle cell anemia was carried out in the pediatric hospital of Bamako-Mali. On the 236 cases of fever studied, 54.2% were malaria infected and 21.2% were carriers of the sicklemic trait. There was a significant difference between malaria affecting AA children and HbS children, specially concerning parasites load.