Background Although malaria and Anopheles mosquito vectors are highly prevalent in Côte d’Ivoire, limited data are available to help understand the malaria vector density and transmission dynamics in areas bordering the country. To address this gap, the Anopheles mosquito species diversity, the members of the Anopheles gambiae complex and the transmission of malaria were assessed in four health districts along the borders of Côte d’Ivoire. Methods From July 2016 through December 2016 and July 2017 through December 2017, adult Anopheles mosquitoes were collected in four health districts of Côte d’Ivoire (Aboisso, Bloléquin, Odienné and Ouangolodougou) using standardized window exit trap (WET) and pyrethrum knockdown spray collection (PSC) methods. The collected mosquitoes were identified morphologically at species level and the members of the An. gambiae complex were separated using short interspersed nuclear element-based polymerase chain reaction (SINE-PCR). Anopheles gambiae sensu lato (s.l.), Anopheles funestus s.l. and Anopheles nili specimens were analysed for malaria Plasmodium parasite detection using the cytochrome oxidase I gene (COX-I), and malaria prevalence among human population through local Ministry of Health (MoH) statistical yearbooks. Results A total of 281 female Anopheles were collected in Aboisso, 754 in Bloléquin, 1319 in Odienné and 2443 in Ouangolodougou. Seven Anopheles species were recorded including An. gambiae s.l. (94.8–99.1%) as the main vector, followed by An. funestus s.l. (0.4–4.3%) and An. nili (0–0.7%). Among An. gambiae s.l., Anopheles coluzzii represented the predominant species in Aboisso (89.2%) and Bloléquin (92.2%), while An. gambiae sensu stricto (s.s.) was the major species in Odienné (96.0%) and Ouangolodougou (94.2%). The Plasmodium sporozoite infection rate in An. gambiae s.l. was highest in Odienné (11.0%; n = 100) followed by Bloléquin (7.8%, n = 115), Aboisso (3.1%; n = 65) and Ouangologoudou (2.5%; n = 120). In An. funestus s.l., Plasmodium falciparum sporozoite infection rate was estimated at 6.2% (n = 32) in Bloléquin, 8.7% (n = 23) in Odienné. No An. funestus s.l. specimens were found infected with P. falciparum sporozoite infection in Ouangolodougou and Aboisso. No P. falciparum sporozoite was detected in An. nili specimens in the four health districts. Among the local human populations, malaria incidence was higher in Odienné (39.7%; n = 45,376) and Bloléquin (37.6%; n = 150,205) compared to that in Ouangolodougou (18.3%; n = 131,629) and Aboisso (19.7%; n = 364,585). Conclusion Anopheles vector species diversity, abundance and Plasmodium sporozoite infection were high within the health districts along the borders of the country of Côte d’Ivoire, resulting in high malaria transmission among the local populations. Anopheles gambiae s.l. and An. funestus s.l. were found to be highly infected with Plasmodium in the health districts of Bloléquin and Odienné where higher malaria incidence was observed than the other districts. This study provides important information that can be used to guide Côte d’Ivoire National Malaria Control Programme for vector control decision-making, mainly in districts that are at the country borders.

Background Lymphatic filariasis (LF) is widely endemic in Cô te d'Ivoire, and elimination as public health problem (EPHP) is based on annual mass drug administration (MDA) using ivermectin and albendazole. To guide EPHP efforts, we evaluated Wuchereria bancrofti infection indices among humans, and mosquito vectors after four rounds of MDA in four cross-border health districts of Cô te d'Ivoire. Methodology We monitored people and mosquitoes for W. bancrofti infections in the cross-border health districts of Aboisso, Blolé quin, Odienné and Ouangolodougou, Cô te d'Ivoire. W. bancrofti circulating filarial antigen (CFA) was identified using filariasis test strips, and antigen-positive individuals were screened for microfilaremia. Moreover, filarial mosquito vectors were sampled using window exit traps and pyrethrum sprays, and identified morphologically at species level. Anopheles gambiae s.l. and Culex quinquefasciatus females were analyzed for W. bancrofti infection using polymerase chain reaction (PCR) technique. Principal findings Overall, we found a substantial decline in W. bancrofti infection indices after four rounds of MDA compared to pre-MDA baseline data. CFA prevalence fell from 3.38-5.50% during pre-MDA to 0.00-1.53% after MDA interventions. No subjects had detectable levels of CFA in Ouangolodougou. Moreover, post-MDA CFA prevalence was very low, and below the 1%

Background Although malaria and Anopheles mosquito vectors are highly prevalent in Côte d'Ivoire, data are still lacking on disease transmission dynamics in cross-border areas. To address this lack of information, we assessed the Anopheles mosquito vector species diversity, the An. gambiae complex members and the transmission of malaria in four cross-border areas of Côte d'Ivoire.Method From July 2016 to December 2017, we collected adult Anopheles mosquitoes in four cross-border health districts of Côte d’Ivoire (Aboisso, Bloléquin, Odienné and Ouangolodougou) using standardized window exit trap (WET) and pyrethrum knockdown spray collection (PSC) methods. We identified collected mosquitoes morphologically at species level and An. gambiae complex members using short interspersed nuclear element-based polymerase chain reaction (SINE-PCR). We analyzed An. gambiae, An. funestus and An. nili specimens for malaria Plasmodium parasite infection using the cytochrome oxidase I gene (COX-I), and malaria prevalence among human population through local Ministry of Health (MoH) statistical yearbooks.Results In total, 281, 754, 1,319 and 2,443 specimens of Anopheles adult females were collected in Aboisso, Bloléquin, Odienné and Ouangolodougou, respectively. We found seven Anopheles species dominated by An. gambiae s.l. (94.8%-99.1%), followed by An. funestus (0.4%-4.3%) and An. nili (0%-0.7%). Among An. gambiae s.l., An. coluzzii predominated in Aboisso (89.2%) and Bloléquin (92.2%), while An. gambiae s.s. was present at the highest frequency in Odienné (96.0%) and Ouangolodougou (94.2%). The Plasmodium sporozoite infection rate in An. gambiae s.l. was highest in Odienné (11.0 %; n = 100) followed by Bloléquin (7.8%, n = 115), Aboisso (3.1%; n = 65) and Ouangologoudou (2.5%; n = 120). In An. funestus, P. falciparum sporozoite infection rate was estimated at 6.2% (n = 32) in Bloléquin, 8.7% (n = 23) in Odienné. No An. funestus specimens were found infected with P. falciparum sporozoite infection in Ouangolodougou and Aboisso. No P. falciparum sporozoite was detected in An. nili specimens in the four health districts. Among the local human populations, malaria prevalence rate was higher in Odienné (39.7%; n = 45,376) and Bloléquin (37.6%; n = 150,205) compared with that in Ouangolodougou (18.3%; n = 131,629) and Aboisso (19.7%; n = 364,585).Conclusion In cross-border health districts of Côte d’Ivoire, Anopheles vector species diversity and abundance and Plasmodium sporozoite infection were high, thus resulting in high transmission of malaria to local populations. An. gambiae and An. funestus were found to be highly Plasmodium-infected in the health districts of Bloléquin and Odienné where malaria prevalence among humans was particularly high. This study provides important information that can be used to guide national malaria control programme strategies in Côte d’Ivoire, mainly in cross-border settings.