Evidence of Transmission of Plasmodium vivax 210 and Plasmodium vivax 247 by Anopheles gambiae and An. coluzzii, Major Malaria Vectors in Benin/West Africa

Current diagnostic and surveillance systems in Benin are not designed to accurately identify or report non-Plasmodium falciparum (Pf) human malaria infections. This study aims to assess and compare the prevalence of circumsporozoite protein (CSP) antibodies of Pf and P. vivax (Pv) in Anopheles gambiae s.l. in Benin. For that, mosquito collections were performed through human landing catches (HLC) and pyrethrum spray catches (PSC). The collected mosquitoes were morphologically identified, and Pf, Pv 210, and Pv 247 CSP antibodies were sought in An. gambiae s.l. through the ELISA and polymerase chain reaction (PCR) techniques. Of the 32,773 collected mosquitoes, 20.9% were An. gambiae s.l., 3.9% An. funestus gr., and 0.6% An. nili gr. In An. gambiae s.l., the sporozoite rate was 2.6% (95% CI: 2.1-3.1) for Pf, against 0.30% (95% CI: 0.1-0.5) and 0.2% (95% CI: 0.1-0.4), respectively, for Pv 210 and Pv 247. P. falciparum sporozoite positive mosquitoes were mostly An. gambiae (64.35%), followed by An. coluzzii (34.78%) and An. arabiensis (0.86%). At the opposite, for the Pv 210 sporozoite-positive mosquitoes, An. coluzzii and An. gambiae accounted for 76.92% and 23.08%, respectively. Overall, the present study shows that P. falciparum is not the only Plasmodium species involved in malaria cases in Benin

Impact of operational effectiveness of long-lasting insecticidal nets (LLINs) on malaria transmission in pyrethroid-resistant areas.

BACKGROUND: A dynamic study on the transmission of malaria was conducted in two areas (R⁺ area: Low resistance area; R⁺⁺⁺ area: High resistance area) in the department of Plateau in South Eastern Benin, where the population is protected by Long Lasting Insecticidal Nets (LLINs). The aim of this study was to determine if the resistance of malaria vectors to insecticides has an impact on their behavior and on the effectiveness of LLINs in the reduction of malaria transmission. METHODS: Populations of Anopheles gambiae s.l. were sampled monthly by human landing catch in the two areas to evaluate human biting rates (HBR). Collected mosquitoes were identified morphologically and female Anopheles mosquitoes were tested for the presence of Plasmodium falciparum antigen as assessed using ELISA. The entomological inoculation rate (EIR) was also calculated (EIR = HBR x sporozoitic index [S]). We estimated the parity rate by dissecting the females of An. gambiae. Finally, window catch and spray catch were conducted in order to assess the blood feeding rate and the exophily rate of vectors. RESULTS: After 6 months of tracking the mosquito's behavior in contact with the LLINs (Olyset) in R⁺⁺⁺ and R⁺ areas, the entomological indicators of the transmission of malaria (parity rate and sporozoitic index) were similar in the two areas. Also, An. gambiae populations showed the same susceptibility to P. falciparum in both R⁺ and R⁺⁺⁺ areas. The EIR and the exophily rate are higher in R⁺ area than in R⁺⁺⁺ area. But the blood-feeding rate is lower in R⁺ area comparing to R⁺⁺⁺. CONCLUSION: The highest entomological inoculation rate observed in R⁺ area is mostly due to the strong aggressive density of An. gambiae recorded in one of the study localities. On the other hand, the highest exophily rate and the low blood-feeding rate recorded in R⁺ area compared to R⁺⁺⁺ area are not due to the resistance status of An. gambiae, but due to the differences in distribution and availability of breeding sites for Anopheles mosquitoes between areas. However, this phenomenon is not related to the resistance status, but is related to the environment instead

Resistance status of Anopheles gambiae s.l. to insecticides following the 2011 mass distribution campaign of long-lasting insecticidal nets (LLINs) in the Plateau Department, south-eastern Benin

Abstract Background In 2011, Benin’s National Malaria Control Programme (NMCP) organized a nationwide mass distribution campaign of LLINs throughout the country. Following this intervention, it was important to assess whether the level of susceptibility of malaria vectors to insecticides had remained the same as compared to the pre-intervention period. The current study investigated this. Methods Larval collections were conducted in Ifangni, Sakété, Pobè and Kétou districts located in Plateau department, Southeastern Benin before (2009) and after (2012–2013) LLIN distribution. Anopheles gambiae sensu lato (s.l.) larvae from the 4 study districts were reared to adulthood and WHO susceptibility tests were conducted. The insecticides tested were deltamethrin (0.05%), permethrin (0.75%), bendiocarb (0.1%) and DDT (4%). Molecular species identification as well as, the characterization of the kdr L1014F mutation were also performed in the An. gambiae s.l. complex using PCR method. Results Overall, a significant decrease in mortality rates of An. gambiae s.l. to deltamethrin (0.05%), permethrin (0.75%) and DDT (4%) was observed post-LLIN distribution, respectively: (100% vs 80.9%, p &lt; 0.0001), (77.5% vs 70%, p = 0.01) and, (47.8% vs 4.4%, p &lt; 0.0001). By contrast, susceptibility of vectors to bendiocarb (0.1%) remained the same (100% mortality in the WHO susceptibility tube tests) pre- and post-intervention. An increase in the kdr L1014F frequency was observed post-LLIN distribution [F(kdr) = 0.91)] compared to the pre-intervention period [F(kdr) = 0.56], p &lt; 0.0001. Anopheles coluzzii and An. gambiae were the two molecular species identified in the study area. Conclusion The decrease susceptibility to pyrethroids and DDT as well as, the increase in the frequency of the kdr L1014F mutation after the intervention stressed at the time, the need for the development and implementation of effective insecticide resistance management strategies. At present, an update of the vectors resistance status in the area is also necessary for decision-making. </jats:sec

Efficacy of pyriproxyfen-pyrethroid long-lasting insecticidal nets (LLINs) and chlorfenapyr-pyrethroid LLINs compared with pyrethroid-only LLINs for malaria control in Benin: a cluster-randomised, superiority trial.

BACKGROUND: New classes of long-lasting insecticidal nets (LLINs) combining mixtures of insecticides with different modes of action could put malaria control back on track after rebounds in transmission across sub-Saharan Africa. We evaluated the relative efficacy of pyriproxyfen-pyrethroid LLINs and chlorfenapyr-pyrethroid LLINs compared with standard LLINs against malaria transmission in an area of high pyrethroid resistance in Benin. METHODS: We conducted a cluster-randomised, superiority trial in Zou Department, Benin. Clusters were villages or groups of villages with a minimum of 100 houses. We used restricted randomisation to randomly assign 60 clusters to one of three LLIN groups (1:1:1): to receive nets containing either pyriproxyfen and alpha-cypermethrin (pyrethroid), chlorfenapyr and alpha-cypermethrin, or alpha-cypermethrin only (reference). Households received one LLIN for every two people. The field team, laboratory staff, analyses team, and community members were masked to the group allocation. The primary outcome was malaria case incidence measured over 2 years after net distribution in a cohort of children aged 6 months-10 years, in the intention-to-treat population. This study is ongoing and is registered with ClinicalTrials.gov, NCT03931473. FINDINGS: Between May 23 and June 24, 2019, 53 854 households and 216 289 inhabitants were accounted for in the initial census and included in the study. Between March 19 and 22, 2020, 115 323 LLINs were distributed to 54 030 households in an updated census. A cross-sectional survey showed that study LLIN usage was highest at 9 months after distribution (5532 [76·8%] of 7206 participants), but decreased by 24 months (4032 [60·6%] of 6654). Mean malaria incidence over 2 years after LLIN distribution was 1·03 cases per child-year (95% CI 0·96-1·09) in the pyrethroid-only LLIN reference group, 0·84 cases per child-year (0·78-0·90) in the pyriproxyfen-pyrethroid LLIN group (hazard ratio [HR] 0·86, 95% CI 0·65-1·14; p=0·28), and 0·56 cases per child-year (0·51-0·61) in the chlorfenapyr-pyrethroid LLIN group (HR 0·54, 95% CI 0·42-0·70; p<0·0001). INTERPRETATION: Over 2 years, chlorfenapyr-pyrethroid LLINs provided greater protection from malaria than pyrethroid-only LLINs in an area with pyrethroid-resistant mosquitoes. Pyriproxyfen-pyrethroid LLINs conferred protection similar to pyrethroid-only LLINs. These findings provide crucial second-trial evidence to enable WHO to make policy recommendations on these new LLIN classes. This study confirms the importance of chlorfenapyr as an LLIN treatment to control malaria in areas with pyrethroid-resistant vectors. However, an arsenal of new active ingredients is required for successful long-term resistance management, and additional innovations, including pyriproxyfen, need to be further investigated for effective vector control strategies. FUNDING: UNITAID, The Global Fund

Comparative study of the effectiveness of combination therapies based on atemisinine in Dassa Zounme and Parakou: case of Artemether lumefantrine and Artesunate amodiaquine

The National Malaria Control Program recommended in 1993, the use of Chloroquina (CQ) as first line drug for malaria treatment, and sulfadoxin pyrimethamin as second drug. After years, Benin knows resistance about these antimalarials. Quinina was to treat gravities. In 2004, the strategy of treatment changed. Treatment of malaria cases is based on use of arteminisinia therapeutic combination. The goal of this study is to be sure that these drugs are efficace before general use in the country and in some regions as Dassa Zounmè where the resistance is up (61. 3% for Chloroquina CQ and 45.9% for SP in 2002).The study is based on: comparison of therapeutic efficacy of artemether Lumefantrine and Artesunate Amodiaquine. Results show that all of the tested drugs have good therapeutic efficacy. Most important rate failure is in Dassa Zounmè (33, 86%) than Parakou (23, 44%). They are parasitologic failure and are probably due to the reinfestation of children. Two drugs have a good parasitological clearance and eliminate fever after 2 days of treatment. Published by the International journal of Microbiology and Mycology (IJMM

Baseline entomologic data on malaria transmission in prelude to an indoor residual spraying intervention in the regions of Alibori and Donga, Northern Benin, West Africa.

BACKGROUND: Despite the success of indoor residual insecticide spraying (IRS) in Africa, particularly in Benin, some gaps of information need to be filled to optimize the effectiveness of this intervention in the perspective of the country's effort to eliminate malaria. In anticipation to the 2018 IRS campaign in two targeted regions of northern Benin, this study aimed, to collect baseline information on vector composition, spatio-temporal variation and peak malaria transmission in the Alibori and Donga, two targeted regions of northern Benin. Information collected will help to better plan the implementation and later on the impact assessment of this IRS campaign. METHODS: The study was carried out in four districts of the two IRS targeted regions of northern Benin. Human landing catches and pyrethrum spray catches protocols were used to assess the biting rate (HBR) and, biting/resting behaviour of malaria vector populations. After morphological identification of collected Anopheles, the heads and thoraxes of Anopheles gambiae sensu lato (s.l.) were analysed by the ELISA CSP tests to estimate the sporozoite index (SI). The entomological inoculation rate was calculated as the product of mosquito biting rate (HBR) and the SI. RESULTS: The biting rates of An. gambiae s.l., the major vector in this study sites, varied significantly from region to region. It was higher: in rural than in urban areas, in rainy season than in dry season, indoors than outdoors. Overall, SI was comparable between sites. The highest EIRs were observed in the Donga region (16.84 infectious bites/man/month in Djougou district and 17.64 infectious bites/man/month in Copargo district) and the lowest in the Alibori region (10.74 infectious bites/man/month at Kandi district and 11.04 infectious bites/man/month at Gogounou district). CONCLUSION: This study showed the heterogeneous and various nature of malaria epidemiology in Northern Benin. Indeed, the epidemiological profile of malaria transmission in the Alibori and Donga regions is made of a single season of transmission interrupted by a dry season. This period of transmission is relatively longer in Donga region than in Alibori. This information can be used to guide the extension of IRS in the Alibori and in the Donga, by primarily targeting areas with short periods of transmission, and easy to cover

Involvement of Anopheles nili in Plasmodium falciparum transmission in North Benin.

BACKGROUND: Several studies carried out in Benin have shown the involvement of Anopheles gambiae sensu lato (s.l.), the Anopheles funestus group in malaria transmission, but none of them reported the contribution of the Anopheles nili group to the transmission of this disease. The current study investigated the question through an entomological cross-sectional survey performed in Northern Benin. METHODS: Mosquito samplings were performed in September and October 2017 in 4 villages located in two districts: Bambaba and Wodara (Kérou district) and, Péhunco 2 and Béké (Péhunco district). The collections were carried out indoors and outdoors using human landing catches (HLC) to assess the human biting rate (HBR) and pyrethrum spray catches (PSC) to evaluate the blood feeding rate and the blood meal origin using the ELISA test. All collected mosquitoes were morphologically identified and, the polymerase chain reaction (PCR) technique was used for molecular identification of sibling species of An. gambiae s.l., An. funestus group and An. nili group sporozoite index (SI) was also assessed by the ELISA test. RESULTS: Overall, An. gambiae s.l., An. funestus group and An. nili group were the three vectors found in the study area. A significantly higher human biting rate (HBR) was recorded in An. nili group (5 bites/human/night) compared to An. funestus group (0.656 bites/human/night) in the Kérou district (p < 0.0001). Anopheles gambiae s.l. displayed the highest HBR (26.19 bites/human/night) in the same district. The entomological inoculation rate (EIR) was 1.875 infected bites/human/month in An. nili group against 13.05 infected bites/human/month in An. gambiae s.l. and 0.938 infected bites/human/month in An. funestus group in Kérou. In Péhunco, the EIR was 1.02 infected bites/human/month in An. gambiae s.l. PCR results showed that An. nili sensu stricto (s.s.) and An. funestus s.s. were the only species of the An. nili and An. funestus groups, respectively. The anthropophagic character of An. gambiae s.l. was also highlighted. CONCLUSION: This study provides useful information on the contribution of An. nili group as secondary vector to malaria transmission in northern Benin. Broader studies must also be carried out in a larger study area to assess the involvement of other Anopheles species to malaria transmission. This will aid to better plan malaria vector control interventions

Microdistribution of the resistance of malaria vectors to deltamethrin in the region of Plateau (southeastern Benin) in preparation for an assessment of the impact of resistance on the effectiveness of Long Lasting Insecticidal Nets (LLINs)

BACKGROUND: This study aims to research two areas, one with a resistant and the other with a susceptible profile of An. gambiae to deltamethrin in the region of Plateau (southern Benin). In each area, eight localities were sought. Both areas were needed for the assessment of the impact of malaria vector resistance to pyrethroids on the effectiveness of Long Lasting Insecticidal Nets (LLINs). The susceptible area of An. gambiae to deltamethrin was used as a control. METHODS: In total, 119 localities in the region of Plateau were screened by sampling An. gambiae s.l larvae. Female mosquitoes resulting from these larvae were exposed to 0.05% deltamethrin following WHO standards. PCR was used to identify species and molecular forms of the dead and alive mosquitoes. Finally, we identified kdr mutations (1014 F and1014S) using the HOLA technique. RESULTS: Fifty-six out of 119 prospected localities tested positive for Anopheles gambae s.l breeding sites. The results showed that An. gambiae was resistant to deltamethrin in 39 localities and susceptible in only 2 localities; resistance to deltamethrin was suspected in 15 localities. The HOLA technique confirmed the presence of kdr 1014 F mutation and the absence of kdr 1014S mutation. The kdr 1014 F mutation was found in both M and S molecular forms at relatively high frequencies therefore confirming the susceptibility tests. CONCLUSION: We were unable to identify the eight susceptible areas due to the overall resistance of An. gambiae to deltamethrin in the region of Plateau. To implement the study, we kept two areas, one with high resistance (R(+++)) and the other with low resistance (R(+)) of An. gambiae to deltamethrin