[Identification of anopheles breeding sites in the residual foci of low malaria transmission «hotspots» in Central and Western Senegal]

Malaria incidence has markedly declined in the Mbour, Fatick, Niakhar and Bambey districts (central and western Senegal) thanks to a scaling up of effective control measures namely LLINs (Long Lasting Insecticide Treated Net), ACTs (Artesunate Combination Therapy) and promoting care seeking. However malaria cases are now maintained by foci of transmission called hotspots. We evaluate the role of anopheles breeding sites in the identification of malaria hotspots in the health districts of Mbour, Fatick, Niakhar and Bambey. Surveys of breeding sites were made in 6 hotspot villages and 4 non-hotspot villages. A sample was taken in each water point with mosquito larvae by dipping method and the collected specimens were identified to the genus level. Additional parameters as name of the village and breeding sites, type of collection, original water turbidity, presence of vegetation, proximity to dwellings, geographic coordinates, sizes were also collected. Sixty-two water collections were surveyed and monitored between 2013 and 2014. Temporary natural breeding sites were predominant regardless of the epidemiological status of the village. Among the 31 breeding sites located within 500 meters of dwellings in hotspots villages, 70% carried Anopheles larvae during the rainy season while 43% of the 21 breeding sites located at similar distances in non-hotspot villages carried Anopheles larvae during the same period (P = 0.042). At the end of the rainy season, the trend is the same with 27% of positive breeding sites in hotspots and 14% in non-hotspots villages. The breeding sites encountered in hotspots villages are mostly small to medium size and are more productive by Anopheles larvae than those found in non-hotspot area. This study showed that the high frequency of smallest and productive breeding sites around and inside the villages can create conditions of residual transmission.

[Profile of cytokines associated with protection against malaria episodes during pregnancy in hypo-endemic area in Senegal]

Malarial infection in non immune pregnant women is a major risk factor for pregnancy failure. However in malaria endemic areas, intermittent preventive treatment (IPTp) have been adopted to prevent malaria in pregnancy women since 2003 in Senegal. The impact of IPT on the development of immunity is not very well documented. We conducted a prospective study at the Roi-Baudouin maternity hospital of Guediawaye in Senegal to assess IL10, IL12, TNFα and IFNγ cytokines production in pregnant women under IPTp. Cytokines were analyzed in 82 sera at inclusion and delivery. P. falciparum HRP2 antigen was detected in 17% of women included by rapid diagnostic test (RDT). At inclusion the mean of IL10 response was higher in P. falciparum negative women (8 UA) compare to RDT-positive women (7 UA) p=0.069 while in delivery the opposite was found p=0.014. Low production of inflammatory cytokines IL12, IFNγ and TNFα was noted in both groups. Between inclusion and delivery, a significant increase of IL-10 production was noted while a decrease of IFNγ and TNFα cytokine was noted. Thus, IL12 and IFNγ responses may synergistically associate as malaria immune response during pregnancy.

[Cryptosporidiosis in Senegalese children: prevalence study and use of ELISA serologic diagnosis]

This is a prospective, descriptive and analytic study conducted from July 2011 to September 2011 at the Children National Hospital Albert Royer of Dakar and at the Vélingara Health District. It was focused on children under 15 without reference to HIV status. For each child, a sample of stool was examined by the Ziehl-Neelsen modified staining and by ELISA using the "Cryptosporidium Antigen Detection Microwell ELISA kit" designed to detect Cryptosporidium spp antigens. The aim of our study was to determine the prevalence of cryptosporidiosis in rural and hospital areas and to measure the performance of the ELISA kit that we used. Out of the 375 stool examinations performed with the Ziehl-Neelsen modified staining, 17 had revealed the presence of Cryptosporidium spp (4.53%). The prevalence in rural areas was 2% while the hospital prevalence was 7.4%, of which 1.8% (1/57) were from urban areas and 9.8% (12/122) from suburban areas. No positive case was observed in children over 10 years. By ELISA, 23 positives cases were reported corresponding to a prevalence of 6.13% (1.8% in children living in urban areas, 13.1% in children from suburban areas and 3%living in rural areas).The correlation of this assay with the Ziehl-Neelsen modified staining, considered as the reference method, found that this assay had a sensitivity of 58.82% and a high specificity reaching 96.37%. The positive predictive value (PPV) was 43.4% while the negative predictive value was 98%. Cryptosporidiosis is a significant cause of parasitic infection among children in Senegal. Antigen detection of Cryptosporidium spp by ELISA in stool can be a complementary tool in the diagnosis of cryptosporidiosis.

[Update on toxoplasmosis prevalence based on serological tests in pregnant women in Dakar, Senegal from 2002 to 2006]

The purpose of this study was to update data on toxoplasmosis antibody prevalence based on antenatal surveillance tests in pregnant women in Dakar, Senegal. The study population consisted of 941 pregnant women referred for diagnosis of toxoplasmosis in the Laboratory of Parasitology and Mycology at Le Dantec University Hospital Center from 2002 to 2006. Two tests using the solid-phase immunoenzymatic method were performed on venous blood samples collected at 3 weeks of interval (S1 and S2). This double testing technique was designed to detect increases in IgM and IgG antibody levels in order to confirm diagnosis of toxoplasmosis by ruling out immune response, acquired immunity or nonspecific antibody fixation. Comparison of S1 and S2 results in the 941 patients indicated a prevalence of 7.7% and 0% respectively for IgM+IgG- cases, 23.3% and 24.3% respectively for IgM+IgG-cases, and 11.3% and 10.2% respectively for IgM+IgG+ cases. The overall prevalence of toxoplasmosis antibodies was 34.5%. These data showing a high prevalence of toxoplasmosis among pregnant women in Dakar underscore the need to improve serological screening and follow up.

[Interaction between malaria and intestinal helminthiasis in Senegal: influence of the carriage of intestinal parasites on the intensity of the malaria infection]

Co-infection between intestinal parasites and Plasmodium falciparum is very frequent in inter tropical zone. Our study carried out in the North of Senegal (zone of high prevalence of schistosomiasis) aimed at measuring the influence of the carriage of intestinal parasites on the intensity of malaria infection. The Plasmodium falciparum densities were significantly higher during Plasmodium falciparum/Schistosoma mansoni and Plasmodium falciparum/Ascaris lumbricoides co-infection in children under 14 years old. Other intestinal parasites did not seem to have negative influence on the intensity of Plasmodium falciparum infection.

[Epidemiological study on lymphatic filariasis (Wuchereria bancrofti) in Sénégal]

The purpose of this descriptive study conducted in an area endemic for lymphatic filariasis was to update information on the prevalence, clinical aspects, and awareness of this parasitic disease. All consenting inhabitants over 10 years old in three selected sectors were included. An entomological investigation was carried out to estimate the rate of vector infection. Out of a total of 3.359 subjects examined, 57.3% reported familiarity with the disease and provided an accurate description. The prevalence of clinical manifestations, i.e., mainly adenopathy, attributable to the disease was 14.11%. The overall prevalence rate of parasites was 4.7% with significant variations between sectors. The only parasite species found was Wuchereria bancrofti. Parasite load was low with 68.8% of subjects having less than 10 microfilariae per microliter of blood. Data analysis identified the following risk factors: age with 77.2% of microfilariae carriers over the age of 45 years, sex with 61.4% of carriers being female, and duration of residence in endemic area with 80.4% of carriers living in the area for more than 10 years. Differences were statistically significant. Dissection of 511 female culicidae showed no microfilariae carriers. These data indicate a declining ten-dency in this endemic zone in Senegal.

[Evaluation of serological tests of toxoplasmosis in pregnant women realized at the Laboratory of Parasitology and Mycology of Le Dantec Teaching Hospital in 2002]

INTRODUCTION

the toxoplasmosis can occur complications during pregnancy as serious repercussions on the foetus with the risks linked to this pathology such as abortion. However these complications can be avoided during the pregnancy by an early diagnosis. The objective of this study is to determine the prevalence of toxoplasmosis during pregnancy.

MATERIALS AND METHODS

we undertook this study on 109 pregnant women addressed to the laboratory of parasitology and mycology of the CHU Dantec for toxoplasmosis serological test on 2002. We used a immunoenzymatic technical in solid phase whose principle rests on the change of coloration in the presence of antibody of IgM or IgG; coloration whose intensity is function of the title of antibody. For that, two serological tests (S1 and S2), starting from two venous blood at 3 weeks of interval, are carried out among these pregnant women. This second serology will make it possible to confirm or cancel an evolutionary toxoplasmosis based on the variation of the title in antibody between the first (S1) and the second serology (S2). A control is carried out among these women among whom the diagnosis of the evolutionary toxoplasmosis was established.

RESULTS

they show that with the first (S1), from the 109 patients, 3% were positive with the antibodies IgM type, 22% positive with IgG, and 11% positive with IgG and IgM. 36% of the women present a positive diagnostic at the first serology (S1). The second serology (S2) shows that among the 36% of the women diagnosed positive with the first serology, 11% made an evolutionary toxoplasmosis.

CONCLUSION

This study shows a rather significant of serological toxoplasmosis discovered fortuitously among pregnant women at the time of their assessment of pregnancy.

[Placental infection by Plasmodium falciparum in an urban area of Senegal]

OBJECTIVES

This study aimed at describing the burden of malaria at delivery in a urban maternity in Senegal. We measured the prevalence of placental malaria infection. We described the association between placental malaria and low birth weight and the impact of chemoprophylaxis.

STUDY AREA

Guediawaye is the most important suburb of the city of Dakar, Senegal, surrounded by a permanent marsh (niayes). Malaria in this area is hypo endemic transmission: 1 infective bite/person/year. An. arabiensis is the principal vector and P. falciparum (98%) the most frequent species. The Maternité Roi Baudoin in Guediawaye is the gynecologic and obstetrical reference centre of this area with more than 6000 deliveries/year.

METHODS

We carried out an exhaustive survey from August 98 to December 99 at the maternité Roi Baudoin in Guediawaye. The socio-demographic data, the clinical data and information about prophylaxy were collected by questionnary. For each woman at delivery, one placental apposition was carried out. Presence of trophozoïtes or schizontes indicated malaria placental infection.

RESULTS

8310 women were included in the study. They were from 13 to 49 years old with an average age of 26.1; 28% were primigravidae. The prevalence of placental malaria infection was 8.1% (674/8310) [Ic95: 7.4-8.8%]. Schizontes were present in 80.5% of infected placenta. The prevalence was 8.8% within primigravidae group and 7.4% in the other parity groups, p = 0.28 (NS). Placental infection was present all the year long. However, there were important seasonal variations. The risk of placental infection increased during seasonal transmission (> 10%) compared to the period of low transmission (3%). The prevalence of placental malaria was lower in the group of women who declares regular chloroquine intake compared with those who declared taking no prophylaxy or irregular prophylaxy (RR = 0.78 [0.62-0.98]). The risk of low birth weight was of 1.9 [1.6-2.1] when the placenta was infected compared with non infected placenta.

CONCLUSION

This study indicates that placental malaria infection is frequent in this low transmission area where more than 70% of women declared taking regular chloroquine. This observation could be explained by a resistance of P. falciparum to chloroquine or a poor observance of chemoprophylaxis.