ABSTRACT
The health district of Sakassou is one of the 83 health districts in Côte d'Ivoire, located in a zone with very high malarial transmission rates, with an incidence rate of ≥40% Therefore, to guide vector control methods more effectively, it was crucial to have a good understanding of the vectors in the area. This study aimed to determine the level of malarial transmission during the dry season in Sakassou, Côte d'Ivoire. Female Anopheles mosquitoes were sampled using human landing catches (HLCs) and pyrethrum spraying catches (PSCs). The larvae were collected using the ‘dipping’ method. A total of 10,875 adult female mosquitoes of Anopheles gambiae were collected. The PCR analysis revealed that all individuals were Anopheles coluzzii. The geographical distribution of potential breeding sites of Anopheles showed the presence of An. coluzzii in all the wetlands of the city of Sakassou. During the dry season, the human-biting rate of An. coluzzii was 139.1 bites/person/night. An exophagic trend was displayed by an adult female of An. coluzzii. The entomological inoculation rate during the dry season was 1.49 infectious bites/person/night. This study demonstrated that An. coluzzii was the main vector of malarial transmission in Sakassou, and the intensity of transmission remains high throughout the dry season.
HIGHLIGHTS
Effect of rice-growing regions on malarial transmission during the dry season in Sakassou was studied.
Provide novel insights into the dynamics of transmission during this period.
Areas used for irrigation of rice are potential breeding sites of Anopheles coluzzii.
This geographical focus provides valuable information for targeted vector control interventions in specific areas.
Offering critical information for malaria control programs.
BACKGROUND
Malaria remains one of the world's most serious diseases. In 2021, the World Health Organization (WHO) reported 247 million malarial cases, with 95% of infection and 96% of deaths occurring in Africa. The diversity of malarial epidemiological profiles is related to climatic, hydrographic, and ecological conditions. At the ecological level, some agricultural practices, such as growing rice in shallow irrigated areas, lead to proliferation of mosquito-breeding sites and often increase malaria incidence.
In sub-Saharan Africa, the proliferation of Anopheles gambiae, the main vector of malaria, is associated with rice-growing practices (Reimer et al. 2005). In these rice-growing areas, the implementation of hydraulic structures raises significant public health concerns (Klinkenberg et al. 2005). Several studies conducted in sub-Saharan Africa indicated that the expansion of irrigated areas leads to an increase in the number of vectors and their long-term reproduction, thereby intensifying human–vector contact (Sissoko et al. 2004; Diuk-Wasser et al. 2005; Walker & Lynch 2007). Consequently, an upsurge in the prevalence and incidence rates of various vector-borne diseases, including malaria, has been reported in some regions (Plaen & Geneau 2002).
In Côte d'Ivoire, numerous previous studies showed that An. gambiae s.l., An. funestus s.l., and An. nili s.l. are responsible for the transmission of three Plasmodium species to humans in the country, namely Plasmodium falciparum, Plasmodium malariae, and Plasmodium ovale (Zoh et al. 2020). The transformation of wetland areas to grow rice in several localities in the country led to a significant increase in An. gambiae densities, which fortunately is not always followed by a rise in malarial transmission (Dossou-Yovo et al. 1998a, 1998b). Studies conducted in the savanna areas indicated that an increased density of Anopheles mosquitoes does not necessarily influence malarial transmission. However, in the forest area in western Côte d'Ivoire, the high density of An. funestus led to a malarial transmission upsurge in villages practicing annual rice growth.
Several studies carried out in central of Côte d'Ivoire, in the Gbêkê region (in the savanna areas), revealed a high malaria endemicity caused by the three Plasmodium species identified in Côte d'Ivoire, with a peak during the rainy season (Dossou-Yovo et al. 1998a, 1998b; Zoh et al. 2020). Studies in this region also showed the agricultural practices impact on malarial vector proliferation (Dossou-Yovo et al. 1998a, 1998b).
Sakassou City, located in the Gbêkê region, is characterized by the presence of irrigated wetlands extending across urban and rural areas. Over 900 ha of these areas are dedicated to year-round irrigation of rice growing, resulting in the availability of permanent breeding sites for malarial vectors, even during the dry season. In general, malarial transmission is observed in the Gbêkê region during the rainy season, with a significant decrease during the dry season. However, with the presence of irrigated wetlands and their year-round exploitation, what would be the malarial transmission situation in Sakassou during the dry season?
This study aimed to determine the malarial transmission level during the dry season in Sakassou. This study could provide the National Malaria Control Program (NMCP) precise information on when vector control should be implemented in this type of area.
MATERIALS AND METHODS
Study sites
Sakassou (7°27′16″ N; 5°17′33″ W) is located in the north-central region, 43 km from Bouaké. The city has a humid tropical climate, with annual precipitation ranging from 1,500 to 2,200 mm. A Guinean forest–savanna mosaic belt characterizes the vegetation. There are two main seasons in this locality: a dry season from December to February and a rainy season from March to November. The study was conducted in a village (Kpétébonou) and an urban district (Habitat-Texas) of Sakassou.
The village of Kpétébonou, is approximately 5 km from Sakassou northwest. The village is surrounded by wetlands. The majority of families practice livestock farming with oxen, sheep, and goats. There are also rice farming and vegetable crops such as tomatoes and okra in the surrounding areas. According to the latest census conducted in 2014, Kpétébonou has a population of 505 inhabitants.
Georeferencing of potential breeding sites of mosquitoes
Surveys were conducted in March 2019 in both study sites. All water points that could potentially serve as permanent or temporary breeding sites for Anopheles mosquitoes were studied. The larvae were collected using the ‘dipping’ method. All sampling points were georeferenced with a GPS version Garmin eTrex 20x and all mosquito-breeding sites were described to determine their distribution in each study site. The studied site was considered positive with all breeding sites containing at least one mosquito larva or pupa.
The Anopheles larvae were collected at different breeding sites and transported to the insectarium where the collected larvae were counted and reared in the water from the original breeding site until they emerged at room temperature. The adult stage was determined by the Anophelinae of Gillies and Meillon (Gillies & De Meillon 1968) key determination. The breeding sites were labeled according to their location and origin.
Adult mosquito sampling
Adult female mosquitoes were collected using human landing catches (HLCs) from November 2018 to March 2019 in 10 capture sessions, totaling 80 person-nights. These captures took place both inside and outside dwellings from 6 p.m. to 6 a.m. The captures were carried out in two teams, with the first team working from 6 p.m. to 12 a.m. and the second from 12 a.m. to 6 a.m. This method involved a catcher seated on a chair or stool with bare legs up to the knees, capturing all mosquitoes that landed on them before biting. The captured mosquitoes were carefully stored in closed hemolysis tubes with cotton and kept in pockets labeled by the time and location of the capture. A circular permutation of the catchers was necessary to limit the margin of error. The determination keys of the Anophelinae of Gillies and DeMeillon (Gillies & De Meillon 1968) were used for morphological identification of mosquitoes. Only female mosquitoes of the malarial vector species collected by HLCs were kept for ovary dissection according to Detinova (Detinova 1962).
Laboratory processing
The head and thorax of each mosquito were carefully separated from the rest of the body and placed in new coded tubes for the detection of P. falciparum circumsporozoite protein (CSP) according to Burkot et al. (1984); Wirtz et al. (1987). The rest of the mosquito body (abdomen and legs) was preserved for molecular identification of species. DNA from the abdomen and legs of each Anopheles was extracted. Species molecular identification was performed using PCR SINE 200 Amplification.
Entomological parameters in the dry season
Several entomological indicators were used, including:
- (i)
The human-biting rate (HBR): the number of Anopheles bites per person per night (b/p/n).
- (ii)
The infection rate (IR): the proportion of female mosquitoes infected by P. falciparum.
- (iii)
The parity rate (PR): the proportion of parous female mosquitoes.
- (iv)
The Entomological Inoculation Rate (EIR), which is the number of infective bites per person per night by anopheline mosquitoes, was calculated as the product of the HBR and the IR of mosquitoes collected on humans. The overall EIR for a given period was calculated as the sum of the EIR of each mosquito species.
Statistical analysis
For statistical analysis, the data were entered into Microsoft Office Excel 2007 software. The HBR, PR, and IR were calculated using the STATA version 8.0 software (College Station, TX: StataCorp LP). A 95% confidence interval was used, and statistical significance was determined at P < 0.05 using Mann–Whitney and χ2 tests to compare the HBR and different rates between both study sites.
RESULTS
Anopheles breeding sites and Anopheles coluzzii larval distribution in study sites
In total, 47 potential breeding sites were characterized in both study sites. Among these 47 potential breeding sites, 38 (80.85%) were found positive for anopheline larvae. Molecular identification at the adult stage of anopheline larvae showed that all larvae were An. coluzzii. These larvae were found in six (6) types of breeding sites, namely rice fields, ponds, mangroves, puddles, swamps, and abandoned containers. The majority of these breeding sites were permanent except puddles (Table 1).
Characterization of breeding sites of An. coluzzii during March 2019 in Sakassou
Breeding sites . | Kpétébonou . | Habitat-Texas . | Total . | ||
---|---|---|---|---|---|
N (+) . | Periodicity . | N (+) . | Periodicity . | ||
Rice field | 24 (24) | Permanent | 10 (8) | Permanent | 34 (32) |
Pond | 1 (1) | Permanent | 2 (2) | Permanent | 3 (3) |
Mangrove | 1 (1) | Permanent | 0 | – | 1 (1) |
Puddle | 4 (0) | Temporal | 1 (0) | Permanent | 5 (0) |
Swamp | 1 (1) | Permanent | 1 (1) | Permanent | 2 (2) |
Abandoned container | 0 | – | 2 (0) | Permanent | 2 (0) |
Total | 31 (27) | 16 (11) | 47 (38) |
Breeding sites . | Kpétébonou . | Habitat-Texas . | Total . | ||
---|---|---|---|---|---|
N (+) . | Periodicity . | N (+) . | Periodicity . | ||
Rice field | 24 (24) | Permanent | 10 (8) | Permanent | 34 (32) |
Pond | 1 (1) | Permanent | 2 (2) | Permanent | 3 (3) |
Mangrove | 1 (1) | Permanent | 0 | – | 1 (1) |
Puddle | 4 (0) | Temporal | 1 (0) | Permanent | 5 (0) |
Swamp | 1 (1) | Permanent | 1 (1) | Permanent | 2 (2) |
Abandoned container | 0 | – | 2 (0) | Permanent | 2 (0) |
Total | 31 (27) | 16 (11) | 47 (38) |
N indicates the number of potential breeding sites; (+) indicates the number of positive breeding sites.
Anopheline fauna collected by HLCs in sakassou study sites
A total of 11,142 anopheline species was collected in both study sites of Sakassou, with 8,094 (72.64%) in Kpétébonou village and 3,048 (27.36%) in the Habitat-Texas district. Three species were morphologically identified in this study, namely An. gambiae complex, An. Funestus, and An. pharoensis. However, molecular identification showed that all An. gambiae complex species belonged to An. coluzzii.
In Kpétébonou village, two species of Anopheles were identified with An. coluzzii as the predominate Anopheles species (97%) and An. pharoensis (2%).
In the Habitat-Texas district, all three Anopheles species were collected and mainly dominated by An. coluzzii (97%), followed by An. pharoensis (2%) and An. funestus (less than 1%) (Table 2).
Composition of mosquito fauna collected by HLCs during the dry season in Sakassou
Species . | Kpétébonou . | Habitat-Texas . | ||||
---|---|---|---|---|---|---|
Indoor . | Outdoor (%) . | Total (%) . | Indoor . | Outdoor (%) . | Total (%) . | |
An. gambiaes.l. | 3,707 | 4,190 | 7,897 (97.57) | 1,361 | 1,617 | 2,978 (97.70) |
An. funestus s.l. | 0 | 0 | 0 | 2 | 1 | 3 (0.10) |
An. pharoensis | 89 | 108 | 197 (2.43) | 17 | 50 | 67 (2.20) |
Total | 3,796 | 4,298 | 8,094 | 1,380 | 1,668 | 3,048 |
Species . | Kpétébonou . | Habitat-Texas . | ||||
---|---|---|---|---|---|---|
Indoor . | Outdoor (%) . | Total (%) . | Indoor . | Outdoor (%) . | Total (%) . | |
An. gambiaes.l. | 3,707 | 4,190 | 7,897 (97.57) | 1,361 | 1,617 | 2,978 (97.70) |
An. funestus s.l. | 0 | 0 | 0 | 2 | 1 | 3 (0.10) |
An. pharoensis | 89 | 108 | 197 (2.43) | 17 | 50 | 67 (2.20) |
Total | 3,796 | 4,298 | 8,094 | 1,380 | 1,668 | 3,048 |
In this study, 10,875 female mosquitoes of An. coluzzii were identified in both study sites as main vectors. In total, three (03) female mosquitoes of An. funestus were collected only in Habitat-Texas with a low proportion. So, only An. coluzzii has been considered for the rest of the study.
Biting behavior of An. coluzzii
Conducting catches both inside and outside dwellings facilitated the study of the biting behavior of An. coluzzii female mosquitoes.
In Kpétébonou and Habitat-Texas, female mosquitoes of An. coluzzii have presented an exophagic trend (53.06%), indicating a preference for outdoor biting.
Malarial transmission during the dry season in Kpétébonou and Habitat-Texas
Biting rate of An. coluzzii
The average HBR of An. coluzzii female mosquitoes recorded in Sakassou during this study was 139.10 bites per person per night (b/p/n). The average biting rate of An. coluzzii in Kpétébonou village was 197.43 b/p/n (CI = 178.01–216.83). This rate was significantly higher (P < 0.0001) than that recorded in the Habitat-Texas district, with 80.78 b/p/n (CI = 64.66–96.89).
In the dry season (December, January, and February), the biting rate recorded in study sites was 110.56 b/p/n. In Kpétébonou, the average biting rate recorded during this season was 168.70 b/p/n (CI = 149.30–188.10). This rate was comparable (P = 0.0938) to that recorded at the rainy season in November (209.88 b/p/n, CI = 160–259.76) but, lower (P = 0.0001) than that recorded at the start of the rainy season in March (271.13 b/p/n, CI = 247.14–295.11). In Habitat-Texas, the average biting rate of An. coluzzii was 52.42 b/p/n (CI = 39.88–64.96) in the dry season and that was significantly lower than those recorded at the start and the end of the rainy season (121.13 b/p/n, CI = 92.39–149.86 and 125.5, CI = 78.50–172.50, respectively).
In both study sites, the average biting rate of An. coluzzii recorded during this season was also higher (P < 0.0001) in Kpétébonou than in Habitat district (Table 3).
Biting rate of An. coluzzii from November 2018 to March 2019 at study sites
. | Period . | m.a. (b/p/n) . | CI . | Dry season average . |
---|---|---|---|---|
Kpétébonou | ||||
End of rainy season | Nov-18 | 209.88 | 160–259.76 | |
Dry season | Dec-18 | 159.88 | 106.22–213.53 | 168.7 (CI = 149.30–188.10) |
Jan-19 | 173.13 | 137.40–208.85 | ||
Feb-19 | 173.13 | 148.77–197.48 | ||
Start of rainy season | March-19 | 271.13 | 247.14–295.11 | |
Kpétébonou average | 197.43 | 178.01–216.83 | ||
Habitat-Texas | ||||
End of rainy season | Nov-18 | 121.13 | 92.39–149.86 | |
Dry season | Dec-18 | 67.86 | 34.88–100.87 | 52,42 (CI = 39.48–104.96) |
Jan-19 | 50.36 | 31.85–68.90 | ||
Feb-19 | 39 | 23–55 | ||
Start of rainy season | March-19 | 125.5 | 78.50–172.50 | |
Habitat-Texas average | 80.78 | 64.66–96.89 | ||
Average | 139.10 | 110.56 |
. | Period . | m.a. (b/p/n) . | CI . | Dry season average . |
---|---|---|---|---|
Kpétébonou | ||||
End of rainy season | Nov-18 | 209.88 | 160–259.76 | |
Dry season | Dec-18 | 159.88 | 106.22–213.53 | 168.7 (CI = 149.30–188.10) |
Jan-19 | 173.13 | 137.40–208.85 | ||
Feb-19 | 173.13 | 148.77–197.48 | ||
Start of rainy season | March-19 | 271.13 | 247.14–295.11 | |
Kpétébonou average | 197.43 | 178.01–216.83 | ||
Habitat-Texas | ||||
End of rainy season | Nov-18 | 121.13 | 92.39–149.86 | |
Dry season | Dec-18 | 67.86 | 34.88–100.87 | 52,42 (CI = 39.48–104.96) |
Jan-19 | 50.36 | 31.85–68.90 | ||
Feb-19 | 39 | 23–55 | ||
Start of rainy season | March-19 | 125.5 | 78.50–172.50 | |
Habitat-Texas average | 80.78 | 64.66–96.89 | ||
Average | 139.10 | 110.56 |
m.a., biting rate; CI, confidence interval; b/p/n, bites per person per night.
PR of An. coluzzii
During the study, of 2,179 female An. coluzzii mosquitoes dissected in two study sites, 61.59% were found to be parous. The PR of An. coluzzii female mosquitoes were 60.80% (n = 1,176, CI = 58–63.59) in Kpétébonou and 62.51% (n = 1,003, CI = 59.51–65.51) in Habitat, and did not vary significantly (P = 0.4382) between the two environments. In the dry season, the PR was estimated at 57.44% in Kpétébonou and 61.59% in Habitat-Texas.
Plasmodium IR and EIR
Head and thorax of 1,126 Anopheles analyzed by ELISA-CSP revealed a CSP rate of 1.07%. In the village of Kpétébonou, the IR of P. falciparum was 0.68% (n = 587, CI = 0.01–1.35). P. falciparum infections were observed throughout the study except in March at the start of the rainy season. The rates recorded ranged from 0.59 to 1.20%. In Habitat-Texas, the IR was 1.49% (n = 539, CI = 0.46–2.51). P. falciparum was detected in the months of November, February, and March, with rates between 1.79% and 3.77%. The rate of P. falciparum infection did not vary between both study sites (P = 0.2487). In Kpétébonou, P. falciparum was detected each month in the dry season with an average rate of 1% (n = 299, CI = 0–2.14), while in Habitat-Texas, P. falciparum was only detected in the month of February (1.90%), with an infectivity rate of 0.62% (n = 321, CI = 0–1).
This rate was significantly lower (P = 0.0356) than that recorded at the end of the rainy season (3.77%), but comparable (P = 0.2760) to the start of the rainy season (1.79%). However, the infectivity rates recorded between these sites were comparable (P = 0.6761) in the dry season.
The EIR of An. coluzzii recorded in Sakassou was 1.49 infectious bites/person/night (ib/p/n), or 44.7 ib/p/month. In Kpétébonou, malarial transmission was permanent during the dry season, with P. falciparum inoculation rates ranging from 1.49 to 2.08 ib/p/n, with an average rate of 1.69 ib/p/n, i.e. around 51 infectious bites received per person per month. In this village, transmission begins at the end of the rainy season, remains higher during the dry season, and ceases at the start of the rainy season. However, in Habitat-Texas, P. falciparum was only transmitted in February, with a rate of 0.74 ib/p/n. The average inoculation rate during the dry season was estimated at 0.33 ib/p/n or 10 ib/p/month. Transmission remains higher at the end and at the start of the rainy season, with rates of 4.57 and 2.25 ib/p/n, respectively. During the dry season in Sakassou, a person living in a rural area receives five times more P. falciparum-infected bites than a person living in an urban area (Table 4).
IR (%) and EIR (ib/p/n) to Plasmodium of An. coluzzii from November 2018 to March 2019 at study sites
. | Period . | N . | S (95% CI) . | SDS average . | EIR (ib/p/n) . | EIR DS average . |
---|---|---|---|---|---|---|
Kpétébonou | ||||||
End of rainy season | Nov-18 | 170 | 0.59 (0–1.75) | 1.24 | ||
Dry season | Dec-18 | 108 | 0.93 (0–2.76) | 1 (0–2.14) | 1.49 | 1.69 |
Jan-19 | 83 | 1.2 (0–3.60) | 2.08 | |||
Feb-19 | 108 | 0.93 (0–2.76) | 1.61 | |||
Start of rainy season | March-19 | 118 | 0 | 0 | ||
Kpétébonou average | 587 | 0.68 (0.01–1.35) | 1.34 | |||
Habitat-Texas | ||||||
End of the rainy season | Nov-18 | 106 | 3.77 (0.09–7.46) | 4.57 | ||
Dry season | Dec-18 | 101 | 0 | 0.62 (0–1) | 0 | 0.33 |
Jan-19 | 115 | 0 | 0 | |||
Feb-19 | 105 | 1.90 (0–4.56) | 0.74 | |||
Start of rainy season | March-19 | 112 | 1.79 (0–4.28) | 2.24 | ||
Habitat-Texas average | 539 | 1.49 (0.46–2.51) | 0.54 | |||
Average | 1,126 | 1.07 | 0.8 | 1.49 | 0.88 |
. | Period . | N . | S (95% CI) . | SDS average . | EIR (ib/p/n) . | EIR DS average . |
---|---|---|---|---|---|---|
Kpétébonou | ||||||
End of rainy season | Nov-18 | 170 | 0.59 (0–1.75) | 1.24 | ||
Dry season | Dec-18 | 108 | 0.93 (0–2.76) | 1 (0–2.14) | 1.49 | 1.69 |
Jan-19 | 83 | 1.2 (0–3.60) | 2.08 | |||
Feb-19 | 108 | 0.93 (0–2.76) | 1.61 | |||
Start of rainy season | March-19 | 118 | 0 | 0 | ||
Kpétébonou average | 587 | 0.68 (0.01–1.35) | 1.34 | |||
Habitat-Texas | ||||||
End of the rainy season | Nov-18 | 106 | 3.77 (0.09–7.46) | 4.57 | ||
Dry season | Dec-18 | 101 | 0 | 0.62 (0–1) | 0 | 0.33 |
Jan-19 | 115 | 0 | 0 | |||
Feb-19 | 105 | 1.90 (0–4.56) | 0.74 | |||
Start of rainy season | March-19 | 112 | 1.79 (0–4.28) | 2.24 | ||
Habitat-Texas average | 539 | 1.49 (0.46–2.51) | 0.54 | |||
Average | 1,126 | 1.07 | 0.8 | 1.49 | 0.88 |
N, number of An. coluzzii female tested; S, infectivity rate; SDS, infectivity rate in dry season ; EIR, entomological inoculation rate.; ib/p/n, infectious bite received per person per night; DS, dry season.
DISCUSSION
This study contributes valuable insights into the dynamics of malarial transmission during the dry season in Sakassou, a region with a notorious prevalence of malaria. The predominance of An. coluzzii and its identification as the only malarial vector were due to the availability of specific breeding sites for this species. These breeding sites such as rice fields, ponds, swamps, and mangroves, identified in both study sites are mainly permanent and constitute preferential breeding sites for An. coluzzii (Lehmann & Diabate 2008; Simard et al. 2009; Kudom 2015).
The exophagic behavior of An. coluzzii observed in both study sites would suggest that malarial transmission occurs mainly outdoors. This behavior would be influenced by vector control measures such as insecticide-impregnated bed nets, which can have a repellent effect on vectors. However, comparative analyses between malarial transmission levels inside and outside the home could confirm or refute this suggestion. In addition, knowledge of vector behavior can contribute to the design and implementation of effective control strategies specific to biting behaviors of each vector.
In the dry season, the biting rate of An. coluzzii, although higher in Kpétébonou village, remains important (52.42 b/p/n) in Habitat-Texas, in urban areas. This rate remains higher than that recorded in Bouaké urban areas (4.2 b/p/n).
Despite the P. falciparum detection throughout the dry season in Kpétébonou, and only in February in Habitat-Texas, the IR remains comparable between the two study sites. This suggests that the risk of malarial transmission is the same in both Sakassou's rural and urban areas in the dry season. P. falciparum transmission recorded in the dry season in Kpétébonou was five times higher than that recorded in Habitat-Texas. This difference observed in Plasmodium transmission level between study sites was related to vector density, as the IR was similar in both sites. In Kpétébonou, Plasmodium transmission was observed throughout the dry season and remained very high during this period. The same trend was observed in Petessou village in Bouaké where high Plasmodium transmission was observed during the dry season (Zoh et al. 2020). However, in Habitat-Texas, transmission was less high and only observed in February, but was three times higher than that recorded in Kennedy neighborhood in Bouaké. A study in the rainy season would be necessary to determine the vectorial transmission dynamic throughout the year.
CONCLUSIONS
This study revealed a diversity of breeding sites for An. coluzzii, the only malarial vector identified in the Sakassou area. These female mosquitoes showed a general tendency to exophagy and a high PR. Although the IR was similar between both study sites, malarial transmission in Kpétébonou, a rural area, was five times higher than in Habitat-Texas, an urban area. In the Sakassou area, malarial transmission was high during the dry season and was observed throughout the season in the rural area. For better vector control in Sakassou, the vector control must be carried out throughout the dry season. This should include the treatment of breeding sites.
ETHICS APPROVAL AND CONSENT TO PARTICIPATE
The study protocol was approved by the National Ethics Committee. All the mosquito collectors were adult volunteers from the study village and the neighborhood of Habitat-Texas. Each of these volunteers gave his or her informed consent, were protected with appropriate antimalarial prophylaxis, and were immunized against yellow fever.
FUNDING
This study is a part of the project vectorlink in Côte d'Ivoire, which received financial support from PMI/USAID.
ACKNOWLEDGEMENTS
We acknowledge people from Sakassou's community, and their regional and departmental health directorate. We would like to thank the technical personnel of IPR and CSRS. The authors also thank the other team members for their assistance during data collection.
DATA AVAILABILITY STATEMENT
Data cannot be made publicly available; readers should contact the corresponding author for details.
CONFLICT OF INTEREST
The authors declare there is no conflict.