Defining the origin of Plasmodium falciparum resistant dhfr isolates in Senegal

We previously reported a high baseline prevalence of mutations in the dhfr and dhps genes of Plasmodium falciparum throughout Senegal. The highest prevalence of the triple dhfr pyrimethamine associated mutations were found in isolates obtained in the western part of the country near the capital city of Dakar. In this study, we sought out to determine the relatedness of dhfr wild type and mutated strains by analyzing three microsatellite regions upstream of the dhfr locus. Twenty-six of the 31 wild type strains had a unique microsatellite pattern. In contrast, of the 17 isolates containing the triple mutation in dhfr, 11 had an identical microsatellite pattern. Diverse geographical isolates in Senegal containing the triple dhfr mutation have arisen from a limited number of ancestral strains. In addition, we demonstrate that these isolates have shared ancestry with the previously reported triple mutation haplotype found in Tanzania, South Africa, and southeast Asia. This common ancestry may have implications for the malaria control strategy for reducing the spread of sulfadoxine-pyrimethamine resistance in Senegal and elsewhere in Africa.     

Mutations in PFCRT K76T do not correlate with sulfadoxine–pyrimethamine–amodiaquine failure in Pikine,Senegal

In 2003, the high level of chloroquine (CQ) treatment failure for uncomplicated Plasmodium falciparum malaria cases has led Senegal to adopt a new combination therapy with sulfadoxine-pyrimethamine and amodiaquine (SP-AQ). From September through November 2004, we used the 14-day World Health Organization follow-up protocol to assess the therapeutic response in patients with uncomplicated P. falciparum malaria in an area of high prevalence of pfcrt T76 mutant allele and SP resistance mutations. Of the 82 patients who were recruited, 68 (82.9%) completed follow-up. The response of the patients to treatment was adequate clinical response for 63 out of 68 patients (92.6%), while five (7.4%) clinical failures were recorded, four early treatment failures, and one late treatment failure. The prevalence of the pfcrt T76 allele at day 0 was 59.5%. The two-sided Fisher's exact test did not show an association between pfcrt T76 allele and treatment failure (p=0.167). The transitory treatment is effective and safe. However, the presence of high levels of mutant alleles points out the need to closely monitor the new therapeutic regimen.     

Hepatitis B, C seroprevalence and delta viruses in HIV-1 Senegalese patients at HAART initiation (retrospective study)

The aim of this study was to determine hepatitis co-infection in a cohort of HIV infected patients at their inclusion in the Senegalese Initiative of ART Access. B, C, and D Hepatitis viruses serological markers were checked retrospectively on 363 stored plasma. For HBV, the Abbott laboratories equipment IMx was used to detect HBs Ag and anti Core Ab on negative HBs Ag samples. For HDV, anti Delta Ab was performed using the Abbott Murex Kit on all HBs Ag positive samples. For HCV, anti HCV Ab was detected by IMx as double screening test and confirmed by INNO-LIA(TM) HCV Core of Innogenetics laboratories. The statistical analysis was done with STATA V8. The study population was composed of 164 men and 199 women aged between 16 and 66 years. The immune and virological markers averages at their enrollment were 154 cell/mm(3) for TLCD4+ (n = 355 patients) and 4.9 log for viral load (n = 277 patients). HBs Ag was found in 61 patients or 16.8% and the prevalence of anti-HBc Ab was 83.2% (252/295). 2 patients or 3% on HBs Ag positive sample presents HBV/HDV co-infection Ab anti HCV was detects in 6 patients or 1.6% after confirmation and 2 patients had triple infection with HBV. These results showed that the prevalence of HBV and HCV in the population of persons living with HIV/AIDS in Senegal is similar to that found in the general population. Our data indicated that hepatitis pathology in the PLwHIV was essentially due to HBV. Further studies are needed to diagnose occult hepatitis in order to set up therapeutic strategies taking into account co-infections by hepatitis viruses in the ART programmes.     

PCR method to identify Salmonella enterica serovars Typhi, Paratyphi A, and Paratyphi B among Salmonella Isolates from the blood of patients with clinical enteric fever

PCR methodology was developed to identify Salmonella enterica serovars Typhi, Paratyphi A, and Paratyphi B. One multiplex PCR identifies serogroup D, A, and B and Vi-positive strains; another confirms flagellar antigen "d," "a," or "b." Blinded testing of 664 Malian and Chilean Salmonella blood isolates demonstrated 100% sensitivity and specificity.     

Hepatitis B at the Dakar Dental School

Numerous studies have revealed the personal risk of contamination of the virus hepatitis B (HBV). Dental surgeons are chiefly concerned about their almost continual contact, professionally, with blood and saliva. The authors report the results of a study done at the Dental Institute of Dakar. This study revealed the importance of AgHBS and its different functions during the period of observation. A particular point of this study is to emphasis subjects of serology, notably AgHBS+ Anti HBC-, which produce an alternative virus. This study, which is being followed up, has already enabled the commencement of disease prevention programmes of hepatitis through the vaccination of some students: protecting both the dental surgeons and their patients.     

Mutations in Plasmodium falciparum dihydrofolate reductase and dihydropteroate synthase genes in Senegal

Senegal recently (2004) switched to sulfadoxine-pyrimethamine (SP) with amodiaquine as first line therapy for malaria in response to increasing chloroquine resistance. In anticipation of emerging resistance to SP as a result of this change in drug pressure, we set out to define the baseline prevalence of SP-associated mutations in the dhfr and dhps genes in Plasmodium falciparum using geographically diverse and longitudinally collected samples. A total of 153 blood samples were analysed from patients (5 years or older) with mild malaria after informed consent was obtained. Longitudinal samples were collected between 2000 and 2003 in Pikine, a suburb of Dakar. Geographically diverse site sampling was carried out in 2003. The mutation prevalence in DHFR codons 51, 59 and 108 is 65%, 61% and 78% in Pikine, 2003. The overall prevalence of the triple mutation that is associated with high-level pyrimethamine resistance is 61%. The mutation prevalence rate in DHPS codons 436 and 437 is 21% and 40%, respectively. There is significant geographic variation in genotypic resistance, as samples from Pikine in 2003 had higher mutation prevalence in the pfdhfr and pfdhps genes compared to samples from Tambacounda (P < 0.015). In summary, this study demonstrates a high background prevalence of SP resistance mutations already present in P. falciparum in Senegal.     

Accuracy of two enzyme immunoassays and cell culture in the detection ofChlamydia trachomatis in low and high risk populations in senegal

Two enzyme immunoassays (EIAs), Chlamydiazyme (CZ; Abbott Laboratories) and Pathfinder (PF; Kallestadt), were compared with a cell culture technique in the detection of cervicalChlamydia trachomatis infection in 670 women in urban settings in Senegal (377 pregnant women and 293 prostitutes). Positive CZ and positive PF specimens were tested a second time using a monoclonal antibody blocking technique. True positive specimens were defined as those positive on culture or positive on EIA with confirmation of the result after blocking. Using this definition, the prevalence of genital chlamydial infection was 14.6 % and 14.3 % in pregnant women and prostitutes respectively. An important difference between the two populations was that the pregnant women were younger than the prostitutes, which might explain the fact that the prevalence of infection among the pregnant women was as high as that among the prostitutes, although the age-adjusted prevalence was higher among prostitutes than among pregnant women. The chlamydial detection rates of cell culture, CZ and PF were 62 % (26/42), 69 % (29/42) and 86 % (36/42) respectively in prostitutes and 76 % (42/55), 40 % (22/55) and 53 % (29/55) respectively in pregnant women. Agreement between the tests was 89 %, 85 % and 88 % for culture/CZ, culture/PF and CZ/PF respectively. However, when data were adjusted for chance agreement, kappa coefficients were 0.40 for culture/CZ, 0.34 for culture/PF and 0.48 for CZ/PF. These results indicate that the accuracy of the EIAs and cell culture may vary greatly in different populations: both EIAs showed a distinctly higher detection rate than culture in prostitutes and a significantly lower detection rate in pregnant women. Confirmation of positive EIA results with a blocking assay greatly enhanced the specificity of the antigen detection tests and should be obtained when using the EIAs in a clinical setting.     

First attempt to validate the gSG6‐P1 salivary peptide as an immuno‐epidemiological tool for evaluating human exposure to Anopheles funestus bites

Objective The development of a biomarker of exposure based on the evaluation of the human antibody response specific to Anopheles salivary proteins seems promising in improving malaria control. The IgG response specific to the gSG6‐P1 peptide has already been validated as a biomarker of An. gambiae exposure. This study represents a first attempt to validate the gSG6‐P1 peptide as an epidemiological tool evaluating exposure to An. funestus bites, the second main malaria vector in sub‐Saharan Africa. Methods A multi‐disciplinary survey was performed in a Senegalese village where An. funestus represents the principal anopheline species. The IgG antibody level specific to gSG6‐P1 was evaluated and compared in the same children before, at the peak and after the rainy season. Results Two‐thirds of the children developed a specific IgG response to gSG6‐P1 during the study period and – more interestingly – before the rainy season, when An. funestus was the only anopheline species reported. The specific IgG response increased during the An. funestus exposure season, and a positive association between the IgG level and the level of exposure to An. funestus bites was observed. Conclusions The results suggest that the evaluation of the IgG response specific to gSG6‐P1 in children could also represent a biomarker of exposure to An. funestus bites. The availability of such a biomarker evaluating the exposure to both main Plasmodium falciparum vectors in Africa could be particularly relevant as a direct criterion for the evaluation of the efficacy of vector control strategies.