Four years trends of malaria admissions in rural and urban Kandi health facilities in northeast of Benin Republic

Malaria clinical data from health facility records are used for evaluating control programmes’ impact and providing insights of epidemiological situation. In the present study we assessed trend of malaria admissions between 2009 and 2012 in rural and urban health facilities of the district of Kandi, a very arid area with particularly severe drought lasting up to 6 months. Curative care records in the Gansosso urban health facility and Sonsoro rural health facility were consulted and all uncomplicated and severe cases of malaria in local population between 2009 and 2012 were reported. For each malaria case, information on age, gender, origin of the patient were collected on electronic forms using tablets installed with Open Data Kit (ODK) Collect. Characteristics of patients positive to malaria, change in age groups and monthly variation were compared between the urban and rural health facilities. Of the 21,008 febrile patients consulted, a total of 7,990 cases (38%; 95% CI 37-39) were detected positive to malaria by the means of RDTs or microscopy. The number of confirmed malaria cases in rural and urban Kandi were respectively 2,911 (36%, 95% CI 35-37) and 5,079 (39%, 95% CI 38-40) (p<0.001). Severe cases were recorded at a lower frequency in the rural health facility, as compared to the urban one (1% vs 25%, p<0.001) with most of cases diagnosed in patients from neighbouring villages. Both facilities records showed higher prevalence in females as compared to males (51% vs 49%; p =0.97). At rural Kandi, the age group hardest hit was under 5 years representing 40% (95% CI: 38-42) while in urban Kandi, malaria prevalence was higher in the age group older than 15 years (53%; 95% CI: 52-54). Between 2009 and 2012, monthly malaria prevalence was generally higher in rural areas than in urban ones. Except for 2012, peaks of malaria cases occurred earlier in the rural area than in the urban area. Our study indicated that malaria occurs throughout the year, regardless of the seasons, and affected all age groups in both rural and urban localities. This is of a programmatic interest in designing and planning vector control interventions particularly in endemic settings

Seasonal change in species composition and target-site mutations in Anopheles gambiae s.l. in the severe drought area of Kandi, North-eastern Benin

The persistence of malaria transmission in areas with very arid environmental conditions remains enigmatic. The present study investigated seasonal variation of mosquito species composition and Kdr and Ace-1 mutations in Anopheles gambiae s.l. in the very arid district of Kandi in North-eastern Benin.Adult mosquitoes were sampled over 1 year using both human landing catches (HLC) and pyrethrum spray catches in 4 villages belonging to 2 areas of different levels of aridity. The collections were carried out on a bi-monthly basis in the wet season, and once every month in the dry season to better capture the entomological situation in drought period. Females An. gambiae sl specimens were kept aside and analysed by PCR for species identification. Presence of kdr and Ace-1 mutations was also assessed in the An. gambiae s.l. collection.A total of 2,211 host-seeking mosquitoes belonging to 15 species were collected in the study area. An. gambiae s.l. was the most abundant species and represented 67% of the collection. Other Anopheles species were found at very low frequency among which An. funestus, An. pharoensis, An. broheri and An. coustani. Molecular species identification showed in dry season a significantly higher frequency of An. coluzzii over An. gambiae s. s. in both less dry (70% vs 29% with p < 0.001) and driest (70% vs 30% and p = 0.034) areas of the district of Kandi. In the rainy season, there was similar frequency of An. coluzzii and An. gambiae s. s. in the less arid area (53% vs 45%; p = 0.153), while An. coluzzii remained significantly predominant (62% vs 38%; p = 0.012) in the driest zone. The frequency of kdr mutation was significantly higher in dry season than in rainy season (93% vs 84%; p<0.001), while no Ace-1 mutation was detected in the collection.In the current context of climate change marked by increasingly high temperatures and longer droughts, suitable vector control should be designed taking into account characteristics of the vector population maintaining malaria transmission in such arid environmental conditions

Blood feeding behaviour comparison and contribution of Anopheles coluzzii and Anopheles gambiae, two sibling species living in sympatry, to malaria transmission in Alibori and Donga region, northern Benin, West Africa

Background: The main goal of this study was to assess the blood feeding behaviour and the contribution Anopheles coluzzii and Anopheles gambiae, 2 sibling species of An. gambiae sensu stricto. present and living in sympatry in 2 regions of northern Benin targeted for indoor residual spraying (IRS).Methods: The study was carried out in 6 districts of 2 regions of Benin (Alibori and Donga). Human landing catches (HLC) performed inside and outside of the households and pyrethrum spray captures (PSC) carried out in bedrooms were used to sample vector populations (An. gambiae and An. coluzzii). Collected mosquitoes were analysed to esti-mate the human biting rate indoors and outdoors, the circumsporozoite antigen positivity, and the anthropophagic index using ELISA methodology. Polymerase chain reaction was used to estimate the frequency of the knockdown resistance (kdr) L1014F and the ace-1 mutations, 2 markers associated respectively with pyrethroids and carbamate/organophosphate insecticide resistance.Results: A higher blood feeding rate was observed in An. gambiae compared to An. coluzzii as well as, a non-pro-nounced outdoor biting behavior in both species. The latter showed similar anthropophagic and sporozoite rates. However the analysis indicates a seasonal difference in the contribution of each species to malaria transmission associated with shifts in resting behaviour. Anopheles coluzzii females accounted for most of the detected infections: 86% in Alibori and 79% in Donga, during the dry season versus 14.4% and 21.2%, respectively for An. gambiae during the same period. This relationship was reversed in Donga during the rainy season (66% for An. gambiae against 34% for An. coluzzii). Results also indicated lower frequencies of kdr L1014F and ace-1 in An. coluzzii versus An. gambiae.Conclusion: Despite similarity in some parameters related to malaria transmission in both surveyed species, An. coluzzii is potentially a more important malaria vector because of high density in the region. It is also charac-terized by lower frequencies of the ace-1 mutation than is An. gambiae. The ongoing use of pirimiphos methyl (organophosphate) for IRS should continue to show a good impact in Alibori and Donga because of the very low level of the ace-1 mutation in both species

Anopheles stephensi: The emerging vector of malaria in the Republic of Djibouti, Horn of Africa

The present study investigated mosquito species composition and phenotypic insecticide resistance profile to support decision-making in vector control in the Republic of Djibouti at the Horn of Africa. Adult mosquitoes were collected between December 2016 and December 2017 across 20 sentinel sites established in the 6 regions of the country using both Centers for Disease Control (CDC) miniature light traps and pyrethrum spray catches (PSC). Female mosquitoes were kept aside, for morphological identification to species by an expert entomologist using appropriate taxonomic keys by Gillies & Coetzee and Glick. Bioassays were also conducted in An. stephensi from Djibouti-ville against nine insecticides used in public health. A total number of 12,538 host-seeking mosquitoes belonging to four genera (Anopheles, Culex, Aedes, Uranotaenia) comprising 12 species were collected. Among these, A. gambiae S.L. and A. stephensi were the two major malaria vectors identified while secondary malaria vectors such as A. nili somalicus, A. dthali and A. azaniae were also collected. Culex quinquefasciatus was the most abundant mosquito species in the 6 regions. WHO susceptibility tests performed on A. stephensi population from Djibouti-ville showed resistance to pyrethroids, organophosphates, carbamates and DDT. The resistance intensity bioassays indicated low to moderate intensity of resistance with pyrethroid insecticides and the organophosphate pirimiphos methyl. Meanwhile pre-exposure to PBO suggested involvement of P450 detoxification enzymes in pyrethroid resistance. These findings revealed the urgent need to develop and implement a programme for monitoring and managing insecticide resistance in local vector populations with efficient control strategies in Djibouti

The effects of oviposition site deprivation up to 40 days on reproductive performance, eggs development, and ovipositional behaviour in Anopheles gambiae (Diptera, Nematocera, Culicidae)

The African malaria mosquito, Anopheles gambiae, depends on availability of suitable surface water for oviposition. The scarcity of breeding sites that characterizes droughts force gravid mosquitoes to delay oviposition and retain eggs in their ovaries. In laboratory conditions, we explored the possible consequences of preset duration of oviposition delay on reproductive capacity, egg viability, emergence and ovipositional behavior in gravid females of A. gambiae waiting for eggs laying in a context of oviposition delay. Overall, the mean anopheles egg batch size was not affected by the duration of the oviposition site deprivation. The embryo rates, hatchability and emergence rates decreased significantly gradually as the retention time is extended. However, the oviposition site deprivation has not been identified as a factor that can change the behavior of Anopheles in their choice of oviposition site

A shift from Indoor Residual Spraying (IRS) with bendiocarb to Long-Lasting Insecticidal (mosquito) Nets (LLINs) associated with changes in malaria transmission indicators in pyrethroid resistance areas in Benin

BACKGROUND: Indoor residual spraying (IRS) was implemented in the department of Ouémé-Plateau, southern Benin, in 2008 and withdrawn in 2011, when long lasting insecticidal nets (LLINs) were distributed to the communities that were previously targeted by IRS. Did the LLIN strategy provide a better level of protection against malaria transmission than IRS? METHODS: Entomological surveillance was carried out to assess indicators of transmission risk during the last year of IRS and the first year after the LLIN intervention was put in place (2010–2011). Mosquito biting density was sampled by human landing collection (HLC). Females of Anopheles gambiae s.l. were dissected to estimate the parity rates and the blood meal index. A subsample of the An. gambiae s.l. collection was tested for presence of Plasmodium falciparum sporozoites. In addition, window exit traps and pyrethrum spray catches were performed to assess exophagic behavior of Anopheles vectors. RESULTS: There were significant increases in all the indicators following withdrawal of IRS. Vector biting density (p<0.001) and longevity (OR=3.81[3.01-4.82] 95% CI; p<0.001) of the An. gambiae s.l. increased significantly; so too did the blood meal index (OR=1.48 [1.1-1.99] 95% CI; p<0.001). Entomological inoculation rate, after IRS withdrawal at one surveillance site, Adjohoun, rose two fold (9.0 infected bites/person/9 months (Apr-Dec 2011) versus 3.66 infective bites/person during the 9 months preceding IRS (Apr-Dec 2010). A second site, Missérété, experienced a six-fold increase after IRS cessation (15.1 infective bites/person/9 months versus 2.41 during IRS). Exophily after IRS cessation decreased significantly in all areas (p<0.001) suggesting that mosquitoes were more likely to rest in houses with LLINs, than in houses subjected to IRS. CONCLUSION: LLINs did not impact on indicators of transmission to the same levels as did IRS after IRS withdrawal

Physical integrity and survivorship of long-lasting insecticidal nets distributed to households of the same socio-cultural community in Benin, West Africa

Abstract Background Long-lasting insecticidal nets (LLINs) are designed to survive and sustain their physical barrier for 3 years in household conditions. However, studies have shown that most of these nets are usually torn or no longer present in the households in less than 3 years. This study was initiated in Benin to compare the survivorship and physical integrity of seven types of LLINs in a same socio-geographic area. Methods In August 2017, 1890 households were selected in 9 villages in the municipality of Zagnanado in central Benin. Each one of the selected households received one of the seven LLIN products: Aspirational®, DawaPlus® 2.0, OlysetNet®, PermaNet® 2.0, PermaNet® 3.0, Royal Sentry® and Yorkool®. Overall, 270 LLINs of each type were freely distributed in Zagnanado, at a rate of 30 LLINs per type per village. These bed nets have been monitored and evaluated every 6 months to identify the most resilient and preferred LLINs in the community. Net survivorship was assessed using the rate of net loss and physical condition. Results The survivorship of all types of LLIN was estimated at 92% (95% CI 90.33–92.96) after 6 months and 70% (95% CI 67.25–71.81) after a year of use. At 12 months, all bed nets monitored were below the NetCalc model threshold of 92.8% for an LLIN with a lifespan of 3 years. Only 1.73% of all types of LLIN had a visible loss of integrity after 6 months with a median proportionate hole index (PHI) estimated at zero. The percentage significantly increased after 12 months with 10.41% of damaged nets (all types of LLINs). The median PHI for each brand of net was 23, 196, 141, 23, 23, 121 and 72, respectively for Aspirational®, DawaPlus® 2.0, OlysetNet®, PermaNet® 2.0, PermaNet® 3.0, Royal Sentry® and Yorkool®. A significant difference was noted between the PHI at 6 and 12 months (p &lt; 0.0001). After 12 months, the DawaPlus®2.0, OlysetNet® and Royal Sentry® suffered significantly more damage compared to the others (p &lt; 0.001). Conclusion The results of this study showed that after a year of use, the survivorship of the 7 LLIN products in households was lower than expected. However, all the LLIN products successfully met WHO standards for physical integrity after 12 months of use. The monitoring continues. The next steps will help to identify the most sustainable LLINs. </jats:sec

Dry season refugia for anopheline larvae and mapping of the seasonal distribution in mosquito larval habitats in Kandi, northeastern Benin

BACKGROUND: The dynamics of mosquito populations depends on availability of suitable surface water for oviposition. It is well known that suitable management of mosquito larval habitats in the sub-Saharan countries, particularly during droughts, could help to suppress vector densities and malaria transmission. We conducted a field survey to investigate the spatial and seasonal distribution of mosquito larval habitats and identify drought-refugia for anopheline larvae. METHODS: A GIS approach was used to identify, geo-reference and follow up longitudinally from May 2012 to May 2013, all mosquito breeding sites in two rural sites (Yondarou and Thui), one urban (Kossarou), and one peri-urban (Pèdè) site at Kandi, a municipality in northeastern Benin. In Kandi, droughts are excessive with no rain for nearly six months and a lot of sunshine. A comprehensive record of mosquito larval habitats was conducted periodically in all sites for the identification of drought-refugia of anopheline larval stages. With geospatialisation data, seasonal larval distribution maps were generated for each study site with the software ArcGIS version 10.2. RESULTS: Overall, 187 mosquito breeding sites were identified of which 29.95% were recorded during drought. In rural, peri-urban and urban sites, most of the drought-refugia of anopheline larvae were domestic in nature (61.54%). Moreover, in rural settings, anopheline larvae were also sampled in cisterns and wells (25% of larval habitats sampled during drought in Yondarou and 20% in Thui). The mapping showed a significant decrease in the spatial distribution of mosquito larval habitats in rural, peri-urban and urban sites during drought, except in Yondarou (rural) where the aridity did not seem to influence the distribution of larval habitats. CONCLUSION: Our data showed that the main drought-refugia of anopheline larvae were of a domestic nature as well as wells and cisterns. A suitable management of mosquito larvae in sub-Saharan countries, particularly during droughts, should target such larval habitats for a meaningful impact on the dynamics of mosquito populations and malaria transmission

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