Entomological Characteristics of Malaria Transmission across Benin: An Essential Element for Improved Deployment of Vector Control Interventions.

Entomological surveillance in Benin has historically been limited to zones where indoor residual spraying was performed or where long-standing sentinel surveillance sites existed. However, there are significant country-wide gaps in entomological knowledge. The National Malaria Control Program (NMCP) assessed population dynamics of Anopheles vectors and malaria transmission in each of Benin's 12 departments to create an entomological risk profile. Two communes per department (24/77 communes) were chosen to reflect diverse geographies, ecologies and malaria prevalence. Two villages per commune were selected from which four households (HH) per village were used for human landing catches (HLCs). In each HH, an indoor and outdoor HLC occurred between 7 p.m. and 7 a.m. on two consecutive nights between July−September 2017. Captured Anopheles were identified, and ovaries were dissected to determine parous rate. Heads and thoraces were tested for Plasmodium falciparum sporozoites by ELISA. The Entomological Inoculation Rate (EIR) was calculated as the product of mosquito bite rate and sporozoite index. Bite rates from An. gambiae s.l., the primary vector species complex, differed considerably between communes; average sporozoite infection index was 3.5%. The EIR ranged from 0.02 infectious bites (ib) per human per night in the departments of Ouémé and Plateau to 1.66 ib/human/night in Collines. Based on transmission risk scales, Avrankou, Sakété and Nikki are areas of low transmission (0 < EIR < 3 ib/human/year), Adjarra, Adja Ouèrè, Zè, Toffo, Bopa, Pehunco, Pèrèrè and Kandi are of medium transmission (3 < EIR < 30 ib/human/year), and the other remaining districts are high transmission (EIR > 30 ib/human/year). The heterogeneous and diverse nature of malaria transmission in Benin was not readily apparent when only assessing entomological surveillance from sentinel sites. Prospectively, the NMCP will use study results to stratify and deploy targeted vector control interventions in districts with high EIRs to better protect populations most at-risk.

[Red blood cell alloimmunization among polytransfused patients in the National Hospital and University Center of Cotonou: about 51 cases]. / Allo-immunisation anti-érythrocytaire chez les polytransfusés au Centre National Hospitalier Universitaire de Cotonou: à propos de 51 cas.

Blood transfusion is a medical procedure used to treat patients with labile blood product. Each transfusion of globular concentrate exposes recipients to the risk of red blood cell alloimmunization. The test for red cell antibodies (RCA) ensures the immunohaematological safety of transfused patients. In Benin, this test is not performed in a systematic way or included either in the pre-transfusion or in the post-transfusion tests. The purpose of this study is to determine the presence of red cell antibodies among polytransfused patients. RCA was performed using indirect antiglobulin test on gel-filtration in 51 polytransfused patients including 26 selected in the Department of Hematology and 25 in the Department of Nephrology at the National Hospital and University Center of Cotonou. After phenotyping alloimmunized patients, tests for detecting signs of hemolysis were performed. Clinical data as well as those on transfusion were collected from transfusion registries and medical records. The prevalence of alloimmunization in our study population was 13.73%. The antibodies identified had the following characteristics: association of anti-RH1 and anti-RH3, anti LE1, association of anti-RH3 and anti-FY1. Alloantibodies were more frequent in patients who had received more than 15 packed red blood cells. Laboratory tests showed signs of hemolysis in one alloimmunized patient. There was no correlation between age, sex, clinical diagnosis and the occurrence of red blood cell alloimmunization. The test for red cell antibodies should be systematically performed in polytransfused patients in order to ensure better transfusion recipient safety in Benin.

Lack of artemisinin resistance in Plasmodium falciparum in northwest Benin after 10 years of use of artemisinin-based combination therapy.

AIM: In Benin, artemisinin-based combination therapy (ACT) has been recommended as the first-line treatment for uncomplicated Plasmodium falciparum malaria since 2004. The emergence in Southeast Asia of parasites that are resistant to artemisinins poses a serious threat to global control of this disease. The presence of artemisinin resistance genotypes in parasite populations in Benin is currently unknown. The present study investigated the prevalence of relevant K13-propeller gene polymorphisms in parasite isolates from the north-western region of Benin. METHOD: Plasmodium falciparum isolates were collected from children with a confirmed diagnosis of malaria aged 6 months to 5 years in two towns, Cobly and Djougou, in the north-western part of Benin. The study was conducted during the rainy season from July to November 2014 in local health facilities. The K13-propeller gene was amplified in parasite isolates using nested PCR and subsequently sequenced. RESULTS: A total of 108 children were recruited into the study. The efficiency of amplification reactions was 72% (78/108). The propeller domain of the K13 gene was successfully sequenced in 78 P. falciparum isolates; all of them were wild type with no polymorphisms detectable. CONCLUSION: The absence of mutations in the K13 gene indicates that P. falciparum parasite populations in the study area are still fully susceptible to artemisinins.

Genetic polymorphism of merozoite surface protein-1 and merozoite surface protein-2 in Plasmodium falciparum isolates from children in South of Benin.

The aim of this study was to determine the genetic diversity of Plasmodium falciparum by analyzing the polymorphism of the msp-1 and msp-2 genes and the multiplicity of infection in children with uncomplicated malaria in southern Benin. Blood samples of children with fever or history of fever with thick smear positive P. falciparum were collected on filter paper. After extraction of DNA by Chelex®, the samples underwent nested PCR. 93 isolates from children were genotyped. For the msp-1 gene, the K1 and R033 sequences were the most represented in the study population with 85.2% and 83% prevalence, respectively. Regarding the msp-2 gene, the FC27 family was more highly represented with 99% prevalence against 81.5% for 3D7. Mixed infections accounted for 80.4% of the samples. Twenty-five alleles were identified for msp-1 and 28 for msp-2. Fourteen and ten alleles belonged to the K1 (100-500 bp) and MAD20 (100-500 bp) families, respectively. The RO33 sequence did not show any polymorphism, with only one variant (160 bp) detected. The msp-2 gene was present as 16 FC27 family fragments (250-800 bp) and 12 of the 3D7 family (350-700 bp). The multiplicity of infection was estimated at 3.8 for msp-1 and 3.9 for msp-2 with 77 (87.5%) and 84 (91.3%) samples harboring more than one parasite genotype for msp-1 and msp-2, respectively. The multiplicity of infection (MOI) was influenced neither by age nor by parasite density. This study shows a significant diversity of P. falciparum in southern Benin with an MOI unaffected by age or by parasite density.

Evaluation of the coverage and effective use rate of long-lasting insecticidal nets after nation-wide scale up of their distribution in Benin.

BACKGROUND: In Benin, around four million Long-Lasting Insecticide-treated Nets were freely distributed to household to prevent malaria in 2011. In contrast to a previous campaign that targeted only children under 5 years and pregnant women, this distribution campaign was conducted in order to achieve universal coverage. This study presents the results of LLIN coverage and utilization after the distribution campaign. METHODS: The study was a cross-sectional household survey which utilized a stratified two-stage cluster sampling design. The strata represented the twelve departments covered by the national distribution campaign in 2011 and included a total of 4,800 households randomly selected in the country. A questionnaire adapted from the standard Malaria Indicator Survey (MIS) Household Questionnaire was used. Data were entered using QPS software and analyzed with R 2.14.1. RESULTS: LLIN ownership was 86.4% (74 - 94). On average, each household received 3 LLINs (2-4). The proportion of households that met the ratio one net for two persons was 77%.The proportions of individuals sleeping under LLINs were high (84.8%). LLIN use among urban residents was 10% lower than in effective users from rural areas (P = 0.00224). CONCLUSIONS: The universal distribution campaign conducted in Benin has increased LLIN ownership and use in the community. But additional efforts are need to improve and maintain LLIN coverage.

Dramatic decrease in malaria transmission after large-scale indoor residual spraying with bendiocarb in Benin, an area of high resistance of Anopheles gambiae to pyrethroids.

In 2008, the National Malaria Control Program in Benin implemented a vector control intervention based on indoor residual spraying (IRS). Four districts of high resistance of Anopheles gambiae to pyrethroids were sprayed with bendiocarb. More than 350,000 inhabitants have been protected. Entomologic parameters in the control area were compared with those in intervention sites. The study has shown a drastic decrease in the An. gambiae biting rate in the sprayed areas. Results of an enzyme-linked immunosorbent assay were negative for Plasmodium falciparum antigen during the entire period of the intervention. No household members received infected bites (entomologic inoculation rate = 0 during January-July). Parous rates were low in areas covered by IRS because bendiocarb is not conducive to long-term mosquito survival. Bendiocarb was found to be a good alternative insecticide for IRS in Benin, in areas where An. gambiae has developed high resistance to pyrethroids.