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Contribution of Anopheles gambiae sensu lato mosquitoes to malaria transmission during the dry season in Djoumouna and Ntoula villages in the Republic of the Congo

Parasites & Vectors volume 17, Article number: 104 (2024) Cite this article

Abstract

Background

Mosquitoes belonging to the Anopheles gambiae sensu lato complex play a major role in malaria transmission across Africa. This study assessed the relative importance of members of An. gambiae s.l. in malaria transmission in two rural villages in the Republic of the Congo.

Methods

Adult mosquitoes were collected using electric aspirators from June to September 2022 in Djoumouna and Ntoula villages and were sorted by taxa based on their morphological features. Anopheles gambiae s.l. females were also molecularly identified. A TaqMan-based assay and a nested polymerase chain reaction (PCR) were performed to determine Plasmodium spp. in the mosquitoes. Entomological indexes were estimated, including man-biting rate, entomological inoculation rate (EIR), and diversity index.

Results

Among 176 mosquitoes collected, An. gambiae s.l. was predominant (85.8%), followed by Culex spp. (13.6%) and Aedes spp. (0.6%). Three members of the An. gambiae s.l. complex were collected in both villages, namely An. gambiae sensu stricto (74.3%), Anopheles coluzzii (22.9%) and Anopheles arabiensis (2.8%). Three Plasmodium species were detected in An. gambiae s.s. and An. coluzzii (Plasmodium falciparum, P. malariae and P. ovale), while only P. falciparum and P. malariae were found in An. arabiensis. In general, the Plasmodium infection rate was 35.1% (53/151) using the TaqMan-based assay, and nested PCR confirmed 77.4% (41/53) of those infections. The nightly EIR of An. gambiae s.l. was 0.125 infectious bites per person per night (ib/p/n) in Djoumouna and 0.08 ib/p/n in Ntoula. The EIR of An. gambiae s.s. in Djoumouna (0.11 ib/p/n) and Ntoula (0.04 ib/p/n) was higher than that of An. coluzzii (0.01 and 0.03 ib/p/n) and An. arabiensis (0.005 and 0.0 ib/p/n).

Conclusions

This study provides baseline information on the dominant vectors and dynamics of malaria transmission in the rural areas of the Republic of the Congo during the dry season. In the two sampled villages, An. gambiae s.s. appears to play a predominant role in Plasmodium spp. transmission.

Graphical Abstract

Background

Despite the efforts deployed against malaria in the last decade, the disease remains a significant public health problem worldwide, with an estimated 247 million cases and 619,000 deaths occurring globally in 2021 [1]. The World Health Organization African Region (WHO Africa) is still the hardest hit by malaria, accounting for 95% of cases and 96% of deaths [1]. In the Republic of the Congo, the estimated number of malaria cases reported in 2021 was 146,262, and the disease was the cause of 63% of medical consultations, 20% of hospitalisations and 9% of individual deaths in the country [2].

Malaria is transmitted through the bite of an infected female Anopheles mosquito, and studies conducted in the Republic of the Congo have reported species of the Anopheles gambiae sensu lato (s.l.) complex as major malaria vectors [2,3,4]. Anopheles gambiae s.l. is the most effective vector in the Afrotropical realm due to its high abundance, longevity, high propensity for feeding and high vectorial capacity [5,6,7,8].

Anopheles gambiae s.l. is a group of nine species that are indistinguishable morphologically but differ in genetic characteristics [6, 8]. They include An. gambiae sensu stricto (s.s.), An. coluzzii, An. arabiensis, An. melas, An. merus, An. bwambae, An. quadriannulatus, An. amharicus and An. fontenillei [8, 9]. These species are distributed mainly in sub-Saharan Africa and are capable of living in different environmental conditions [5, 10,11,12,13].

Five species of Plasmodium have been well described as the pathogens of malaria in humans: Plasmodium falciparum (the most prevalent species), P. malariae, P. ovale, P. vivax and P. knowlesi [13, 14]. While An. gambiae s.s., An. coluzzii and An. arabiensis are significant malaria vectors for Plasmodium spp. in Africa [8, 9, 11], other species including An. melas, An. merus, An. bwambae, An. quadriannulatus and An. fontenillei may be important in malaria transmission in specific localities [8, 9].

It is well known that malaria transmission is much higher in the rainy season than the dry season [11, 15], and some members of the An. gambiae s.l. complex disappear entirely during the long dry season and reappear in large numbers with the first rains [16, 17]. Even with a low transmission period (dry season), malaria continues to pose a major public health threat to communities [16]. Detailed knowledge of the vectors is necessary to identify effective control measures against local strains and populations of these vectors. Due to the complexity of the vector system, the precise identification of vectors of the complex/group of malaria in each area using a molecular tool is important for achieving better adapted, targeted and effective vector control.

Previous studies in the Republic of the Congo have reported the predominance of An. gambiae s.l. complex in the rural area of Djoumouna using morphological analysis, which does not allow for discrimination of its different species [18, 19]. To close this gap, this study aimed to investigate the diversity of An. gambiae s.l. mosquitoes and investigate their Plasmodium spp. infection rates during the dry season in two villages (Djoumouna and Ntoula) in the district of Goma Tsé-Tsé, in the Republic of the Congo.

Methods

Study area

The study was conducted in Ntoula and Djoumouna villages in the Goma Tsé-Tsé health district in the Republic of the Congo [20]. The region has a humid tropical climate with distinct seasons: dry (June to September and January to February) and rainy (October to January and March to May). Annual rainfall ranges from 1600 to 2000 mm. Temperatures average 20–32 °C, with humidity between 78 and 84% [20]. Djoumouna, 25 km from Brazzaville, is surrounded by four rivers (Lomba, Kinkoue, Loumbangala, and Djoumouna) feeding into fish ponds, potential malaria vector sites [4]. Ntoula, 30 km southeast of Brazzaville, has several rivers (Congo, Ntoula, Loumou), promoting the development of Anopheles mosquito larvae [19]. The primary occupations of the inhabitants of both villages are farming and fishing.

Mosquito collection and processing

The study was conducted during the dry season. Mosquito collection was carried out for four consecutive months from June to September 2022. Mosquitoes were collected indoors between 5:00 and 10:00 from 8–10 houses each week using an electric aspirator (Rule In-Line Blowers, Model 240, China). A total of 90 houses in which at least one Anopheles was collected (52 houses in Djoumouna and 38 houses in Ntoula) were included in the study. After collection, mosquitoes were kept in a small paper cup and transported to the laboratory.

Information including the number of collected mosquitoes, type of house, type of walls, number of rooms per house, number of people living in the home, number of people sleeping under the nets, date and time of collection and number of animals was recorded on the collection sheet (questionnaire). Once collected, anophelines were separated from culicines, and anopheline species were identified morphologically [21]. Each anopheline female was recorded according to the physiological status of the abdomen (unfed, blood-fed, semi-gravid, gravid). Ovarian dissection was performed on An. gambiae s.l. females with an empty stomach (unfed), as described previously by Champ et al. [22]. Mosquitoes were then individually stored in a well-labelled tube containing desiccant and kept in a freezer at −20 °C for subsequent analysis.

Molecular identification of Anopheles species

Whole mosquito DNA was extracted from 144 female mosquitoes (An. gambiae complex) using the Livak extraction method [23]. Extracted DNA samples were subjected to polymerase chain reaction (PCR) analysis [24] using SINE200 primers which target retrotransposons of An. gambiae s.l. species, thereby allowing us to distinguish An. coluzzii from An. gambiae s.s. and An. arabiensis [24]. The PCR mix was carried out in 14 µl reaction volume of master mix (1.5 µl of PCR buffer 10×, 0.75 µl of 25 mM MgCl2, 0.12 µl of 10 mM dNTPs, 0.51 µl of 10 µM SINE_Foward and 0.51 µl of 10 µM SINE_Reverse primers, 0.12 µl of KAPA Taq DNA polymerase 5U/µl, and 10.49 µl of nuclease-free water). A volume of 1 μl of genomic DNA was added to the master mix as a template, and the amplification was performed in a thermal cycler (Mastercycler X50a, Eppendorf AG, Hamburg, Germany) using initial denaturation at 95 °C for 5 min, followed by 35 cycles of denaturation at 95 °C for 30 s, annealing at 54 °C for 1 min and extension at 72 °C for 1 min, with a final extension at 72 °C for 10 min and hold at 10 °C. The details of primers targeting SINE200 retrotransposons of An. gambiae s.l. are presented in Additional file 1: Table S1. PCR products and the 100-base-pair (bp) molecular weight marker were stained with SYBR Green solution (1:1, v/v), electrophoresed at 100 V for 50 min in a 1.5% agarose gel and visualised on a GelDoc™ EZ Imager (Bio-Rad Laboratories, Hercules, CA, USA). A sample was considered positive for An. gambiae, An. coluzzii or An. arabiensis if a 249-bp, 479-bp or 223-bp band was detected, respectively.

Detection of Plasmodium spp. in An. gambiae s.l.

A TaqMan assay was used to detect the Plasmodium species in females of some species of An. gambiae s.l. This very sensitive method enables the detection of P. falciparum but cannot differentiate P. malariae from P. ovale and P. vivax. Briefly, the amplification was performed in a reaction volume of 10 µl comprising 1 µl of matrix DNA, 5 µl (1 µM) of SensiMix II Probe (1.25 ml), 0.8 µl (10 mM) of PlasF (forward primer), 0.8 µl (10 mM) of PlasR (reverse primer), 0.3 µl of Falcip+, 0.2 µl of OVM+ and 1.9 µl of nuclease-free water. The samples were amplified in a LightCycler 480 real-time PCR system (Roche, SN: 20726) using the following conditions: pre-denaturation at 95 °C for 10 min, followed by 40 cycles of 15 s at 92 °C and 1 min at 60 °C. The primers (Falcip+ and Plas-F) were used together with two probes tagged with fluorophores (FAM for the detection of P. falciparum and HEX to detect P. ovale, P. malariae and P. vivax). Two P. falciparum samples and a mix of P. ovale, P. vivax and P. malariae were used as positive controls. Details of the primers targeting the 18S ribosomal RNA (rRNA) gene of Plasmodium spp. and probes are provided in Additional file 1: Table S1. TaqMan-positive samples were subjected to nested PCR to confirm and discriminate P. malariae from P. ovale and P. vivax [25].

The first round of the nested PCR reaction consisted of selectively amplifying the DNA of the genus Plasmodium. This first-round PCR was carried out in a reaction volume of 20 μl consisting of PCR buffer 10×, 10 nM dNTPs, 25 mM MgCl2, 5U/µl DreamTaq DNA polymerase, distilled water, 10 µM rPLU5 forward and 10 µM rPLU6 reverse primers, and 2 µl of genomic DNA. The amplification was performed in a thermal cycler (Mastercycler X50a, Eppendorf AG, Hamburg, Germany) using an initial denaturation at 94 °C for 4 min, followed by 35 cycles of denaturation at 94 °C for 30 s, annealing at 55 °C for 1 min and extension at 72 °C for 1 min, with a final extension at 72 °C for 4 min. The second-round PCR reaction was intended for the speciation of the malaria parasite using the product of the first-round PCR reaction as a template and the primers designed to amplify the specific sequences of P. falciparum (rFAL1/rFL2), P. ovale (rOVA1/rOVA2), P. malariae (rMAL1/rMAL2) and P. vivax (rVAV1/rVAV2) as presented in Additional file 1: Table S1. For this second-round PCR reaction, 1 μl of the product of the first-round PCR was added in 19 μl of master mix prepared as described above and amplified using the thermal cycler under the same cycling conditions as described for the first-round PCR reaction, except that the annealing temperature was 58 °C. Details of the primers used are provided in the Additional file 1: Table S1.

PCR products and the 100-bp molecular weight marker were stained with SYBR Green solution (1:1, v/v), electrophoresed at 100 V for 45 min in a 1.5% agarose gel and visualised on the GelDoc™ EZ Imager (Bio-Rad Laboratories, Hercules, CA, USA). A sample was considered positive for P. falciparum, P. malaria, P. ovale and P. vivax if a 205-bp, 144-bp, 800-bp or 120-bp band was detected. The known Plasmodium-positive samples from our library and distilled water served as positive and negative controls in every set of reactions.

Data analysis

All statistical tests were performed using GraphPad Prism 6.01 software. Categorical variables were represented in proportions. Fisher’s exact test was used to compare proportions of species of An. gambiae complex and their contribution to the transmission of Plasmodium species in Ntoula village versus Djoumouna. The Chi-square test was used to compare mosquito species abundance in Djoumouna and Ntoula or to compare the parity rate of the mosquitoes between the two settings. The significance threshold was set at P < 0.05.

The entomological indexes of malaria transmission included in this study are the man-biting rate, infection rate, entomological inoculation rate (EIR), parity rate, and resting Anopheles density.

The man-biting rate (ma), also called aggressive density, is the product of anopheline density in contact with humans (m) and the anthropophilia rate (a). It is calculated by dividing the total number of engorged females (F) of a species captured by the total number of people (W) who spent the night in the rooms where the captures occurred. The man-biting rate is expressed as the number of Anopheles mosquito bites per person per night.

$${\varvec{m}}{\varvec{a}}={\varvec{F}}\div {\varvec{W}}$$

The Plasmodium infection rate (s) is the proportion of mosquitoes infected or carrying sporozoites in their salivary glands. This index is expressed as a percentage (number of infected mosquitoes out of the number of mosquitoes examined × 100).

$${\varvec{s}}=\frac{{\varvec{N}}{\varvec{u}}{\varvec{m}}{\varvec{b}}{\varvec{e}}{\varvec{r}}\,\boldsymbol{ }{\varvec{o}}{\varvec{f}}\,\boldsymbol{ }{\varvec{m}}{\varvec{o}}{\varvec{s}}{\varvec{q}}{\varvec{u}}{\varvec{i}}{\varvec{t}}{\varvec{o}}{\varvec{e}}{\varvec{s}}\,\boldsymbol{ }{\varvec{p}}{\varvec{o}}{\varvec{s}}{\varvec{i}}{\varvec{t}}{\varvec{i}}{\varvec{v}}{\varvec{e}}}{{\varvec{N}}{\varvec{u}}{\varvec{m}}{\varvec{b}}{\varvec{e}}{\varvec{r}}\boldsymbol{ }{\varvec{o}}{\varvec{f}}\,\boldsymbol{ }{\varvec{m}}{\varvec{o}}{\varvec{s}}{\varvec{q}}{\varvec{u}}{\varvec{i}}{\varvec{t}}{\varvec{o}}{\varvec{e}}{\varvec{s}}\,\boldsymbol{ }{\varvec{t}}{\varvec{e}}{\varvec{s}}{\varvec{t}}{\varvec{e}}{\varvec{d}}}\boldsymbol{ }{\varvec{X}}\boldsymbol{ }100$$

The EIR is the number of infectious bites from Anopheles during a given period. It is expressed as infectious bites per person per night/day/week/month or year. \({\varvec{E}}{\varvec{I}}{\varvec{R}}=\left[\mathbf{M}\mathbf{a}\mathbf{n}-\mathbf{b}\mathbf{i}\mathbf{t}\mathbf{i}\mathbf{n}\mathbf{g}\,\mathbf{r}\mathbf{a}\mathbf{t}\mathbf{e}\,\left(\mathbf{m}\mathbf{a}\right)\right]\mathbf{x}\left[\mathbf{s}\mathbf{p}\mathbf{o}\mathbf{r}\mathbf{o}\mathbf{z}\mathbf{o}\mathbf{i}\mathbf{t}\mathbf{e}\,\mathbf{r}\mathbf{a}\mathbf{t}\mathbf{e}\left(\mathbf{s}\right)\right]={\varvec{m}}{\varvec{a}}\boldsymbol{ }\mathbf{x}{\varvec{s}}\)

The density of resting Anopheles (D) is the number of resting mosquitoes inside households distributed over the number of houses surveyed and the number of nights of capture. It is expressed as the number of female mosquitoes per house per night.

$${\varvec{D}}=(\frac{{\varvec{n}}{\varvec{u}}{\varvec{m}}{\varvec{b}}{\varvec{e}}{\varvec{r}}\,\boldsymbol{ }{\varvec{o}}{\varvec{f}}\,\boldsymbol{ }{\varvec{f}}{\varvec{e}}{\varvec{m}}{\varvec{a}}{\varvec{l}}{\varvec{e}}{\varvec{s}}}{{\varvec{n}}{\varvec{u}}{\varvec{m}}{\varvec{b}}{\varvec{e}}{\varvec{r}}\,\boldsymbol{ }{\varvec{o}}{\varvec{f}}\,\boldsymbol{ }{\varvec{h}}{\varvec{o}}{\varvec{u}}{\varvec{s}}{\varvec{e}}\,\boldsymbol{ }{\varvec{p}}{\varvec{r}}{\varvec{o}}{\varvec{t}}{\varvec{e}}{\varvec{c}}{\varvec{t}}{\varvec{e}}{\varvec{d}}\boldsymbol{ }})/{\varvec{N}}{\varvec{u}}{\varvec{m}}{\varvec{b}}{\varvec{e}}{\varvec{r}}\,\boldsymbol{ }{\varvec{o}}{\varvec{f}}\,\boldsymbol{ }{\varvec{n}}{\varvec{i}}{\varvec{g}}{\varvec{h}}{\varvec{t}}{\varvec{s}}$$

The parity rate (P) is the proportion of parous females (females having spawned at least once) divided by the total number of mounted Anopheles (dissected). Older mosquito populations will show higher parity rates. Older populations are more likely to transmit malaria because they have lived long enough for the parasite to develop.

$${\varvec{P}}=\frac{{\varvec{n}}{\varvec{u}}{\varvec{m}}{\varvec{b}}{\varvec{e}}{\varvec{r}}\,\boldsymbol{ }{\varvec{o}}{\varvec{f}}\,\boldsymbol{ }{\varvec{p}}{\varvec{a}}{\varvec{r}}{\varvec{o}}{\varvec{u}}{\varvec{s}}\,\boldsymbol{ }{\varvec{A}}{\varvec{n}}{\varvec{o}}{\varvec{p}}{\varvec{h}}{\varvec{e}}{\varvec{l}}{\varvec{e}}{\varvec{s}}}{{\varvec{T}}{\varvec{o}}{\varvec{t}}{\varvec{a}}{\varvec{l}}\,\boldsymbol{ }{\varvec{n}}{\varvec{u}}{\varvec{m}}{\varvec{b}}{\varvec{e}}{\varvec{r}}\,\boldsymbol{ }{\varvec{o}}{\varvec{f}}\,\boldsymbol{ }{\varvec{A}}{\varvec{n}}{\varvec{o}}{\varvec{p}}{\varvec{h}}{\varvec{e}}{\varvec{l}}{\varvec{e}}{\varvec{s}}\,\boldsymbol{ }{\varvec{d}}{\varvec{i}}{\varvec{s}}{\varvec{s}}{\varvec{e}}{\varvec{c}}{\varvec{t}}{\varvec{e}}{\varvec{d}}}\mathbf{X}100$$

Diversity index

The Shannon–Weaver (H′) and Simpson (D) diversity index were also determined in order to evaluate the diversity of An. gambiae complex within each surveyed site. These indexes consider either the number of anopheline species or the distribution of individuals within these species [26].

The Shannon–Weaver index (H) was developed within the framework of information theory, which assumes that the diversity of species can be measured as the information contained in a code or a message [27] to determine the diversity of species in a given environment. The Shannon index has no unit and is calculated from the following formula:

$$H=-\sum\nolimits_{n=1}^{s}{{\text{log}}}_{2}ni/N$$

where H is the Shannon–Weaver index, N is the total number, ni is the frequency of the species in the sampled area and S is the total number of species present in the sampled area.

This index varies between 0 and 5; a value close to 0 indicates very low diversity.

Simpson’s index (D) measures the probability that two randomly chosen individuals do not belong to the same species. It is inversely proportional to diversity. This formula was used to establish an index directly representative of heterogeneity by subtracting the Simpson index from its maximum value, which is 1 [26]. For an infinite sample, the index is given by the following formula:

$${\mathbf{D}}\, = \,\frac{{\sum {{\text{n}}\,\left( {{\text{n}}\, - \,1} \right)} }}{{{\text{N}}\,\left( {{\text{N}}\, - \,1} \right)}}$$

where D is the Simpson index, n is the number of individuals of a species and N is the total number of species captured. This index varies between 0 and 1; a value of 1 indicates a 100% chance of encountering the same species within a sample.

Results

Mosquito species composition

A total of 176 mosquitoes were collected in the Ntoula and Djoumouna villages. In both villages, An. gambiae s.l. was the most abundant species (85.8%, 151/176), followed by Culex spp. (13.6%, 24/176) and Aedes spp. (0.6%, 1/176) (χ2 = 333.7, degrees of freedom [df] = 2, P < 0.0001). In addition, 86.6% (97/112) and 84.4% (54/64) An. gambiae s.l. were recorded in Djoumouna and Ntoula, respectively (Table 1). The presence of Culex spp. was similar in Ntoula (14.1%, 9/64) and Djoumouna (13.4%, 15/112) (P = 0.99, odds ratio [OR] = 1.06, 95% confidence interval [CI] 0.44–2.58). Aedes spp. were only observed in Ntoula village, at 1.5% (1/64) frequency (Table 1).

Table 1 Mosquito species composition between Djoumouna and Ntoula, Goma Tsé-Tsé district
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Distribution of An. gambiae s.l. species in study sites

Following the molecular identification of An. gambiae s.l. mosquitoes, three species including An. gambiae, An. coluzzii and An. arabiensis were found in both Djoumouna and Ntoula. Among these species, An. gambiae s.s. was the predominant species in Djoumouna (81.7%, 76/93) versus An. coluzzii (16.1%, 15/93) and An. arabiensis (2.2%, 2/93) (χ2 = 151.1, df = 2, P < 0.0001). Similar results were obtained in Ntoula (An. gambiae s.s. 60.8% [31/51], An. coluzzii 35.3% [18/51] and An. arabiensis 3.9% [2/5]) (χ2 = 37.2, df = 2, P < 0.0001). In addition, An. gambiae s.s. was more abundant in Djoumouna (81.7%, 76/93) than in Ntoula (60.8, 31/51) (P = 0.009, OR = 2.88, 95% CI 1.34–6.12), while the converse was observed with An. coluzzii, reported at 35.3% (18/51) in Ntoula and 16.1% (15/93) in Djoumouna (P = 0.014, OR = 2.84, 95% CI 1.24–6.14). No significant difference in terms of An. arabiensis (P = 0.61, OR = 0.53, 95% CI 0.08–3.53) was found between the two settings (2.2%, 2/93 in Djoumouna and 3.9%, 2/51 in Ntoula) (Table 1). A total of seven mosquitoes out of the 151 An. gambiae s.l. analysed were not discriminated; thus, they could belong to other species of An. gambiae complex.

Diversity of An. gambiae complex

Two diversity indexes (Shannon–Weaver and Simpson) were used to assess the specific richness within each species of An. gambiae s.l. in the two surveyed villages. Shannon index data revealed that the Ntoula site had a higher diversity index score (1.15) than Djoumouna (0.78). However, according to the Simpson index, the probability of encountering An. gambiae s.l. was higher in Djoumouna (0.58) than in Ntoula (0.39).

Plasmodium infection rates

Out of 151 An. gambiae s.l. analysed by TaqMan assay, 35.1% (53/151) were infected with Plasmodium spp. in both villages. Plasmodium spp. infection rates were 41.3% (40/97) and 24.1% (13/54) in Djoumouna and Ntoula, respectively. Overall, An. gambiae s.l. mosquitoes were mainly infected with P. falciparum (19.2%, 29/151) followed by OVM+ (non-P. falciparum species: P. ovale, P. vivax or P. malariae) at 7.9% (12/151) and co-infection with P. falciparum with at least one of the non-P. falciparum species at 7.9% (12/151).

In this study, three Plasmodium species were detected in An. gambiae s.l.: P. falciparum, P. malariae and P. ovale. Among mosquito specimens testing positive by TaqMan, the nested PCR assay confirmed that 77.4% (41/53) were infected, with 51.2% (21/41) of the specimens being infected with P. falciparum, 24.4% (10/41) with P. malariae, 2.4% (1/41) with P. ovale, 17.1% (7/41) with P. falciparum/P. malariae and 4.9% (2/414) with P. falciparum/P. ovale (Fig. 1). In Djoumouna, 29 An. gambiae s.l. were infected, with 62.1%, 24.1%, 3.5%, 3.5% and 6.9% of them harbouring P. falciparum, P. malariae, P. ovale, P. falciparum/P. malariae and P. falciparum/P. ovale, respectively. In Ntoula, 12 An. gambiae s.l. were infected with Plasmodium spp., with 25%, 25% and 50% of them harbouring P. falciparum, P. malariae and P. falciparum/P. malariae, respectively (Table 2).

Table 2 Infectivity of An. gambiae s.l. from Djoumouna and Ntoula using nested PCR
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Fig. 1
figure 1

Discrimination of Plasmodium infection in An. gambiae s.l.

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Overall, the Plasmodium spp. infection rate was higher in An. arabiensis (50%, 2/4) than in An. gambiae s.s. (20%, 31/107) and An. coluzzii (24.2%, 8/33), although the difference was not statistically significant (χ2 = 1.2, df = 2, P = 0.54). Moreover, there was no significant difference in terms of Plasmodium spp. infection rate between An. arabiensis (50%, 1/2), An. gambiae s.s. (32.9%, 25/76) and An. coluzzii (20%, 3/15) in Djoumouna (χ2 = 1.3, df = 2, P = 0.52). A similar trend was found in Ntoula (An. arabiensis [50%, 1/2], An. coluzzii [27.8%, 5/18] and An. gambiae s.s. [19.4%, 6/31]) (χ2 = 1.2, df = 2, P = 0.53) (Table 3). The proportion of mono-infection in An. gambiae was 15.9% for P. falciparum, 7.5% for P. malariae and 0.9% for P. ovale. The co-infection in An. gambiae s.s. was 3.7% and 0.9% from P. falciparum/P. malariae and P. falciparum/P. ovale, respectively (Fig. 2). Moreover, the proportion of infection among An. coluzzii was 9.1% and 6.1% for mono-infection with P. falciparum and P. malariae, respectively. The co-infection cases included 6.1% and 3.0% for P. falciparum/P. malariae and P. falciparum/P. ovale, respectively. The infection rate in An. arabiensis was 25% for both P. falciparum mono-infection and P. falciparum/P. malariae co-infection (Fig. 2). Plasmodium falciparum was the most prevalent Plasmodium spp. in all An. gambiae s.l. sibling species.

Table 3 Entomological indexes of An. gambiae s.l. mosquitoes
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Fig. 2
figure 2

Distribution of Plasmodium spp. in An. gambiae s.l.

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Density of resting Anopheles mosquitoes

Data generated from this study revealed relatively high resting density in Djoumouna and Ntoula (0.79 mosquitoes per house per night [m/h/n] and 0.49 m/h/n) for An. gambiae s.s.. The resting density of An. coluzzii was 0.16 m/h/n in Djoumouna and 0.20 m/h/n in Ntoula. The lowest resting density was recorded in An. arabiensis (0.02 m/h/n in Djoumouna and 0.03 m/h/n in Ntoula). These species of An. gambiae s.l. had higher resting density, with 0.26 m/h/n (8.58 mosquitoes per house per month [m/h/m]) in Ntoula, versus Djoumouna, where the resting density was 0.19 m/h/n (5.7 m/h/m) (Table 3).

Anopheline man-biting rate

In Djoumouna village, persons received an average of 0.35 bites from An. gambiae s.s. per night, while 0.20 bites from An. gambiae s.s. per person per night were recorded in Ntoula village. Anopheles coluzzii had a man-biting rate of 0.10 bites per night in Ntoula compared with 0.07 bites per night in Djoumouna. Anopheles arabiensis was found to be less aggressive, with 0.01 bites per night in Djoumouna and 0.02 bites per night in Ntoula villages (Table 3).

Entomological inoculation rate

The annual entomological inoculation rate was 37.4 infectious bites per person per year (ib/p/y) in all study sites. This entomological inoculation rate of the endophilic vector population was higher in Djoumouna (0.125 infectious bites per person per night [ib/p/n] or 45.6 ib/p/y) than in Ntoula (0.08 ib/p/n or 29.2 ib/p/y). The biting rates of An. gambiae s.s. were 0.11 ib/p/n (or 40.2 ib/p/y) and 0.04 ib/p/n (or 14.6 ib/p/y) in Djoumouna and Ntoula, respectively. The entomological inoculation rate was higher with An. coluzzii in Ntoula (0.03 ib/p/n or 11 ib/p/y) than in Djoumouna (0.01 ib/p/n or 3.7 ib/p/y). The lower entomological inoculation rates were recorded with An. arabiensis (0.005 ib/p/n and 0.01 ib/p/n in Djoumouna and Ntoula, respectively) (Table 3).

Parity rate

Overall, out of 61 An. gambiae s.l. dissected, the parity and nulliparity rates were 52.5% (32/61) and 47.5% (29/61), respectively, in the Goma Tsé-Tsé district. A higher parity rate was recorded at Djoumouna (77.0%) than at Ntoula (23.0%) (P < 0.0001, OR = 11.7, 95% CI 4.83–25.23) (Table 3). In Djoumouna, the parity rate in An. gambiae s.s. was 85.7%, while that of An. coluzzii was 50%. Only An. coluzzii was parous in Ntoula, with a 75% parity rate (Table 3).

Discussion

This study provides baseline entomological data on the composition of vector species involved in malaria transmission in the rural areas of Djoumouna and Ntoula (Republic of the Congo) during the dry season. Anopheles gambiae s.l. was the predominant mosquito species and the only anopheline mosquito found in the study area, and has been implicated in malaria transmission in Africa [16, 28]. The predominance of An. gambiae s.l. could be explained by the fact that they are ubiquitous species able to colonise several biotopes [29]. In fact, temporary puddles, residual pools of stagnant sunny surfaces, and ponds with erect vegetation have been found in these areas [30]. Previous studies carried out in the Republic of the Congo have also reported An. gambiae s.l. as a major malaria vector in savannah, forest, rural and urban areas [31,32,33].

Anopheles gambiae s.l. was more abundant in Djoumouna than in Ntoula, as compared with other mosquitoes. Indeed, Djoumouna village is surrounded by the presence of several permanent breeding sites, where secondary forest, farming activity and urbanisation, rainwater reservoirs and a combination of puddles, lakes, rivers, swamps and vegetable crops favour the development of Anopheles [31]. Ntoula is bordered by clean waterways such as the Congo River and various other rivers, which, in addition to the vegetable crops, favour the proliferation of Anopheles mosquitoes. In addition, according to the Simpson index in this study, the probability of encountering An. gambiae s.l. is significantly higher in Djoumouna than in Ntoula. Environmental changes induced by urbanisation (i.e. higher temperatures and lower relative humidity) could also provide favourable environments for the development of An. gambiae s.l. larvae in Djoumouna [5, 32].

This study is the first to report the different species of An. gambiae s.l. complex in rural areas of Djoumouna and Ntoula in the Republic of the Congo, since previous studies carried out in this setting used only morphological analysis for the identification of An. gambiae s.l. complex [34, 35]. Very few An. arabiensis specimens (4/144) were found in both villages, likely because anthropogenic actions such as deforestation and urbanization have destroyed its natural habitats, but this was not investigated herein. Anopheles arabiensis found in this study was a more exophilic and exophagic species. This behaviour was also reported in previous studies from Gambia [16, 34], Burkina-Faso [11], Benin [29] and Kenya [36].

Only P. falciparum, P. ovale and P. malariae were found in An. gambiae s.l. Our observations differ from the findings reported by Carnevale et al. [18] showing only P. falciparum in the Republic of the Congo. Plasmodium falciparum was the most prevalent species in An. gambiae s.l. mosquitoes, followed by P. malariae and P. ovale, which were found in mono- or co-infection with P. falciparum in An. coluzzii, An. gambiae s.s. and An. arabiensis, and this explains its high prevalence previously reported in humans from the same area [19, 37].

Anopheles coluzzii was infected by mono-infection with P. falciparum or P. malariae. These results differ from the observations in Côte d'Ivoire [12], where P. falciparum, P. malariae and P. ovale were found in An. coluzzii and P. falciparum and P. ovale in An. gambiae s.s. The presence of P. malariae and P. ovale infections in An. gambiae s.l. in the present study is consistent with previous reports [12] and indicates the need for a national malaria control program to consider these two Plasmodium spp. when designing future measures for effective control and malaria treatment. As a limitation of the study, Plasmodium spp. detection was performed by PCR from the DNA extracted from the whole mosquitoes and not from the head–thorax only, which thus may have overestimated the indexes of infection rate. In addition, the origin of the Anopheles spp. blood meal was not investigated.

The cycle of aggression of An. gambiae s.l. shows that Djoumouna inhabitants received more bites per night than those of Ntoula. Anopheles gambiae s.s. was more aggressive than An. coluzzi and An. arabiensis in both villages. The biting activity of Anopheles gambiae s.s. was slightly higher in Djoumouna than in Ntoula, but the opposite was shown in An. coluzzii and An. arabiensis in Ntoula. This study also showed possible malaria transmission by different mosquito species in the study area, as previously found in several sites in Central African [33, 41] and West African countries [33, 39]. Overall, the estimated entomological inoculation rate was 37.4 ib/p/y. This rate is higher than that observed by Trape and Zoulani [30] (22.5 ib/p/y) in Brazzaville in 1987. This can be explained by the fact that Ntoula and Djoumouna belong to rural areas known to be associated with high malaria transmission [33, 42].

Ovarian dissection was performed to determine the parity status of An. gambiae s.l. females. The parturition rate observed in this study indicates an older population of An. gambiae s.l., which is associated with increased vectorial capacity as reported previously [11]. Most An. gambiae s.l. females caught in Djoumouna were parous, whereas those caught in Ntoula were mostly nulliparous. Anopheles gambiae s.s. caught at Ntoula and An. arabiensis from both Ntoula and Djoumouna villages were nulliparous, although the infection rates with Plasmodium species in these two Anopheles spp. were 0.19 and 0.5, respectively. This can be explained by the small sample size of mosquitoes included in the parity investigation test. Indeed, the very limited sample size (only 176 mosquitoes) is a major limitation of the present study, so all data analysis results reported herein should be interpreted with caution.

Conclusions

This study provides baseline information on the dominant vectors and dynamics of malaria transmission in rural areas in the Republic of the Congo during the dry season. In the two sampled villages, An. gambiae complex mosquitoes, and An. gambiae s.s. in particular, play a predominant role in transmitting multiple Plasmodium species in the region. These findings highlight the need for improved vector control strategies and continuous monitoring of mosquito vectors to effectively combat malaria in the area.

Availability of data and materials

All data are fully available without restriction. Data are available from the Fondation Congolaise pour la Recherche Medical (FCRM) Institutional Data Access. All requests for data should be addressed to the Executive Director of FCRM, reachable at the following address: Prof. Francine Ntoumi, Villa D6, Cité OMS-Djoué, Brazzaville, République du Congo (Tel. +242-06-9977980, email: francine.ntoumi@uni-tuebingen.de.

Abbreviations

CeRMI:

Centre de recherche sur les maladies infectieuses-Christoph Merieux

LBDEA:

Laboratoire de la Biodiversité et Ecologie Animales

FST:

Faculté des Sciences et Techniques

UMNG:

Université Marien Ngouabi

References

  1. WHO. World malaria report 2022. Geneva: World Health Organization; 2022.

    Google Scholar 

  2. PNLP. Rapport d'activités du Programme National de Lutte contre le Paludisme (PNLP) République du Congo. 2021.

  3. PNLP. Plan stratégique national de lutte contre le paludisme 2013–2015, Programme de lutte contre le paludisme. Congo. Congo-Brazzaville. 2015.

  4. Nianga BGOT, Bitsindou P, Lenga A. Impact of the use of mosquito nets on malaria transmission in Djoumouna (Brazzaville-Congo). Int J Adv Res. 2019. 7:285–294. https://doi.org/10.21474/IJAR01/9501.

    Article  Google Scholar 

  5. Fournet F, Adja AM, Adou KA, Dahoui MMC, Coulibaly B, Assouho KF, et al. First detection of the malaria vector Anopheles arabiensis in Côte d’Ivoire: urbanization in question. Malar J. 2022;8:275–21.https://doi.org/10.1186/s12936-022-04295-3.

    Article  PubMed  PubMed Central  Google Scholar 

  6. Mahande A, Mosha F, Mahande J, Kweka E. Feeding and resting behaviour of malaria vector, Anopheles arabiensis with reference to zooprophylaxis. Malar J. 2007; 30:6:100. https://doi.org/10.1186/1475-2875-6-100.

    Article  PubMed  PubMed Central  Google Scholar 

  7. Adugna T, Getu E, Yewhelew D. Parous rate and longevity of anophelines mosquitoes in Bure district, northwestern Ethiopia. PLoS ONE. 2022; 17(2):e0263295. https://doi.org/10.1371/journal.pone.0263295. eCollection 2022.

    Article  PubMed  PubMed Central  Google Scholar 

  8. Loughlin SO. The expanding Anopheles gambiae species complex. Path Glob Health. 2020. 114(1):1. https://doi.org/10.1080/20477724.2020.1722434.

    Article  Google Scholar 

  9. Barrón MG, Paupy C, Rahola N, Akone-Ella O, Ngangue MF, Wilson-Bahun TA, et al. A new species in the major malaria vector complex sheds light on reticulated species evolution. Sc Rep. 2019; 9(1):14753. https://doi.org/10.1038/s41598-019-49065-5.

    Article  Google Scholar 

  10. el Niang HA, Konaté L, Diallo M, Faye O, Dia I. Reproductive isolation among sympatric molecular forms of An. gambiae from inland areas of south-eastern Senegal. PLoS ONE. 2014. 9(8): e104622. https://doi.org/10.1371/journal.pone.0104622.

    Article  PubMed  PubMed Central  Google Scholar 

  11. Epopa PS, Collins CM, North A, Millogo AA, Benedict MQ, Tripet F, et al. Seasonal malaria vector and transmission dynamics in western Burkina Faso. Malar J. 2019; 18(1):113. https://doi.org/10.1186/s12936-019-2747-5.

    Article  PubMed  PubMed Central  Google Scholar 

  12. Zoh DD, Yapi A, Adja MA, Guindo-Coulibaly N, Kpan DMS, Sagna AB, et al. Role of Anopheles gambiae s.s. and Anopheles coluzzii (Diptera: Culicidae) in human malaria transmission in rural areas of Bouaké, in Côte d’Ivoire. J Med entomol. 2020; 57(4):1254–61. https://doi.org/10.1093/jme/tjaa001.

    Article  PubMed  Google Scholar 

  13. Singh B, Kim-Sung L, Matusop A, Radhakrishnan A, Shamsul SS, Cox-Singh J, et al. A large focus of naturally acquired Plasmodium knowlesi infections in human beings. Lancet. 2004; 363(9414):1017–24. https://doi.org/10.1016/s0140-6736(04)15836-4.

    Article  PubMed  Google Scholar 

  14. White NJ, Pukrittayakamee S, Hien TT, Faiz MA, Mokuolu OA, Dondorp AM. Malaria. Lancet. 2014; 383(9918):723–35. https://doi.org/10.1016/s0140-6736(13)60024-0.

    Article  PubMed  PubMed Central  Google Scholar 

  15. Ba O, Sow A, Ba H, Dahdi S, Lo B. Seasonal transmission of malaria in the Senegal River Valley: case study of the city of Kaedi-Mauritanie. The Pan Afric med J. 2019; 7:156. https://doi.org/10.11604/pamj.2019.34.185.20011.

    Article  Google Scholar 

  16. Jawara M, Pinder M, Drakeley CJ, Nwakanma DC, Jallow E, Bogh C, et al. Dry season ecology of Anopheles gambiae complex mosquitoes in The Gambia. Malar J. 2008. https://doi.org/10.1186/1475-2875-7-156.

    Article  PubMed  PubMed Central  Google Scholar 

  17. Lehmann T, Dao A, Yaro AS, Adamou A, Kassogue Y, Diallo M, et al. Aestivation of the African malaria mosquito, Anopheles gambiae in the Sahel. Am J Trop Med Hyg. 2010; 83(3):601–6. https://doi.org/10.4269/ajtmh.2010.09-0779.

    Article  PubMed  PubMed Central  Google Scholar 

  18. Carnevale P, Bosseno MF, Zoulani A, Michel R, Molez JF. La dynamique de la transmission du paludisme humain en zone de savane herbeuse et de forêt dégradée des environs nord et sud de Brazzaville, R.P. du Congo. Entomol Méd et Parasitol. 1985; 23:95–11.

    Google Scholar 

  19. Mbama Ntabi JD, Lissom A, Djontu JC, Diafouka-Kietela S, Vouvoungui C, Boumpoutou RK, et al. Prevalence of non-Plasmodium falciparum species in southern districts of Brazzaville in The Republic of the Congo. Parasit Vectors. 2022. https://doi.org/10.1186/s13071-022-05312-9.

    Article  PubMed  PubMed Central  Google Scholar 

  20. Getamap.net. Geography of the Republic of Congo. Jan 2022. http://fr.getamap.net/cartes/republic_of_the_congo/pool/_djoumouna/ Accessed on 2 Feb 2018.

  21. Gillies MT, De Meillon B. The Anophelinae of Africa South or the Sahara (Ethiopian Zoogeographical Region). Johannesburg: South African Institute for Medical Research; 1968.

    Google Scholar 

  22. Aschale Y, Ayehu A, Worku L, Addisu A, Zeleke AJ, Bayih AG, et al. Anopheles gambiae s.l. (Diptera: Culicidae) seasonal abundance, abdominal status and parity rates in Metema-Armachiho lowland, Northwest Ethiopia. BMC Infect Dis. 2020; 107(4): 611–634. https://doi.org/10.1186/s12879-020-05068-6.

    Article  PubMed  PubMed Central  Google Scholar 

  23. Livak KJ. Organization and mapping of a sequence on the Drosophila melanogaster X and Y chromosomes that is transcribed during spermatogenesis. Genet. 1984. https://doi.org/10.1093/genetics/107.4.611.

    Article  Google Scholar 

  24. Santolamazza F, Mancini E, Simard F, Qi Y, Tu Z, Della Torre A. Insertion polymorphisms of SINE200 retrotransposons within speciation islands of Anopheles gambiae molecular forms. Malar J. 2008; 7:163. https://doi.org/10.1186/1475-2875-7-163.

    Article  PubMed  PubMed Central  Google Scholar 

  25. Snounou G, Pinheiro L, Gonçalves A, Fonseca L, Dias F, Brown KN, et al. The importance of sensitive detection of malaria parasites in the human and insect hosts in epidemiological studies, as shown by the analysis of field samples from Guinea Bissau. Trans Royal Soc Trop Med Hyg. 1993; 87(6):649–53. https://doi.org/10.1016/0035-9203(93)90274-t.

    Article  Google Scholar 

  26. Pielou EC. An introduction to mathematical ecology. New York: Witley-Internat Sc; 1969.

    Google Scholar 

  27. Peet K, R. The measurement of species diversity. Ann Rev Ecol Syst. 1974; 5:285–330.

    Article  Google Scholar 

  28. Animut A, Negash Y. Dry season occurrence of Anopheles mosquitoes and implications in Jabi Tehnan District, West Gojjam Zone, Ethiopia. Malar J. 2018; 17(1):445. https://doi.org/10.1186/s12936-018-2599-4.

    Article  PubMed  PubMed Central  Google Scholar 

  29. Salako AS, Ossè R, Padonou GG, Dagnon F, Aïkpon R, Kpanou C, et al. Population dynamics of Anopheles gambiae s.l. and Culex quinquefasciatus in rural and urban settings before an indoor residual spraying campaign in Northern Benin. Vect Borne Zoonot Dis. 2019; 19(9):674–684. https://doi.org/10.1089/vbz.2018.2409.

    Article  Google Scholar 

  30. Trape JF, Zoulani A. Malaria and urbanization in central Africa: the example of Brazzaville. Part II: results of entomological surveys and epidemiological analysis. Royal Soc Trop Med Hyg. 1987; 81(2):10–8. https://doi.org/10.1016/0035-9203(87)90472-x.

    Article  Google Scholar 

  31. Machault V, Gadiaga L, Vignolles C, Jarjaval F, Bouzid S, Sokhna C, et al. Highly focused anopheline breeding sites and malaria transmission in Dakar. Malar J. 2009. https://doi.org/10.1186/1475-2875-8-138.

    Article  PubMed  PubMed Central  Google Scholar 

  32. Sylla EH, Kun JF, Kremsner PG. Mosquito distribution and entomological inoculation rates in three malaria-endemic areas in Gabon. Trans Royal Soc Trop Med Hyg. 2000; 94(6):652–6. https://doi.org/10.1016/s0035-9203(00)90219-0.

    Article  Google Scholar 

  33. Wondji C, Simard F, Petrarca V, Etang J, Santolamazza F, Torre AD, et al. Species and populations of the Anopheles gambiae complex in Cameroon with special emphasis on chromosomal and molecular forms of Anopheles gambiae s.s. J Med Entomol. 2005; 42:98–101.

    Article  Google Scholar 

  34. Caputo B, Nwakanma D, Jawara M, Adiamoh M, Dia I, Konate L, et al. Anopheles gambiae complex along the Gambia river, with particular reference to the molecular forms of An. gambiae s.s. Malar J. 2008; 22:7:182. https://doi.org/10.1186/1475-2875-7-182.

    Article  PubMed  PubMed Central  Google Scholar 

  35. Tirados I, Costantini C, Gibson G, Torr SJ. Blood-feeding behaviour of the malarial mosquito Anopheles arabiensis: implications for vector control. Med Veter Entomol. 2006; 20(4):425–37. https://doi.org/10.1111/j.1365-2915.2006.652.x.

    Article  Google Scholar 

  36. Mala AO, Irungu LW, Shililu JI, Muturi EJ, Mbogo CC, Njagi JK, et al. Dry season ecology of Anopheles gambiae complex mosquitoes at larval habitats in two traditionally semi-arid villages in Baringo, Kenya. Parasit Vectors. 2011;28:4:25. https://doi.org/10.1186/1756-3305-4-25.

    Article  PubMed  PubMed Central  Google Scholar 

  37. Tsumori Y, Ndounga M, Sunahara T, Hayashida N, Inoue M, Nakazawa S, et al. Plasmodium falciparum: differential selection of drug resistance alleles in contiguous urban and peri-urban areas of Brazzaville, Republic of Congo. PLoS ONE. 2011; 6(8): e23430. https://doi.org/10.1371/journal.pone.0023430.

    Article  PubMed  PubMed Central  Google Scholar 

  38. Bigoga JD, Manga L, Titanji VPK, Coetzee M, Leke RFG. Malaria vectors and transmission dynamics in coastal south-western Cameroon. Malar J. 2007; 821:146339. https://doi.org/10.1186/1475-2875-6-5.

    Article  PubMed  PubMed Central  Google Scholar 

  39. Tchuinkam T, Simard F, Lélé-Defo E, Téné-Fossog B, Tateng-Ngouateu A, Antonio-Nkondjio C, et al. Bionomics of Anopheline species and malaria transmission dynamics along an altitudinal transect in Western Cameroon. BMC Infect Dis. 2010; 15(1):217. https://doi.org/10.1186/1471-2334-10-119.

    Article  PubMed  PubMed Central  Google Scholar 

  40. Kamdem C, Tene Fossog B, Simard F, Etouna J, Ndo C, Kengne P, et al. Anthropogenic habitat disturbance and ecological divergence between incipient species of the malaria mosquito Anopheles gambiae. PLoS ONE. 2012; 19(1):119. https://doi.org/10.1371/journal.pone.0039453.

    Article  PubMed  PubMed Central  Google Scholar 

  41. Nkemngo FN, Mugenzi LMJ, Tchouakui M, Nguiffo-Nguete D, Wondji MJ, Mbakam B, et al. Xeno-monitoring of molecular drivers of artemisinin and partner drug resistance in P. falciparum populations in malaria vectors across Cameroon. Gene. 2022; 17(6)5. https://doi.org/10.1016/j.gene.2022.146339.

    Article  PubMed  PubMed Central  Google Scholar 

  42. Boussougou-Sambe ST, Woldearegai TG, Doumba-Ndalembouly AG, Ngossanga B, Mba RB, Edoa JR, et al. Assessment of malaria transmission intensity and insecticide resistance mechanisms in three rural areas of the Moyen Ogooué Province of Gabon. Parasit Vectors. 2022; 7(6):e39453. https://doi.org/10.1186/s13071-022-05320-9.

    Article  PubMed  PubMed Central  Google Scholar 

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Acknowledgements

We thank the population of Djoumouna and Ntoula for their participation in the study. We are grateful to Mr Aimé Mamboueni and Mayangui Célestin as facilitators in different houses where mosquitoes were collected. We also thank Destin Tati for logistic assistance and Armel Batchi-Bouyou for contributing to the manuscript editing.

Funding

This study was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) grant (DFG BO 2494/3-1) awarded to the CoMAL project consortium. The Fondation Merieux supports AL and JCD. This work also received support from the Central Africa Clinical Research Network, CANTAM (EDCTP-CSA2020NoE-3100) and the Central Africa Humboldt Research Hub (HR-Coca) funded by Alexander von Humboldt Foundation. The funders did not play a role in the study design, the collection, analysis, or interpretation of the data, or the writing of the manuscript.

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Authors and Affiliations

  1. Fondation Congolaise Pour La Recherche Médicale, Brazzaville, Republic of the Congo

    Jacques Dollon Mbama Ntabi, Espoir Divin Malda Bali, Abel Lissom, Jean Claude Djontu, Georges Missontsa, Freisnel Hermeland Mouzinga, Marcel Tapsou Baina & Francine Ntoumi

  2. Faculté des Sciences et Techniques, Université Marien Ngouabi, Brazzaville, Republic of the Congo

    Jacques Dollon Mbama Ntabi, Espoir Divin Malda Bali, Freisnel Hermeland Mouzinga, Marcel Tapsou Baina & Arsène Lenga

  3. Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany

    Ayola Akim Adegnika, Steffen Borrmann & Francine Ntoumi

  4. Department of Biological Sciences, Faculty of Science, University of Bamenda, Bamenda, Cameroon

    Abel Lissom

  5. Fondation Pour La Recherche Scientifique (FORS), ISBA, BP: 88, Cotonou, Bénin

    Romaric Akoton & Ayola Akim Adegnika

  6. Centre de Recherche Médicale de Lambaréné, Lambaréné, Gabon

    Ayola Akim Adegnika

  7. German Center of Infection Research (DZIF), Tübingen, Germany

    Ayola Akim Adegnika & Steffen Borrmann

  8. Department of Parasitology and Medical Entomology, Center for Research in Infectious Diseases (CRID), Yaoundé, Cameroon

    Charles Wondji

  9. Department of Vector Biology, Liverpool School of Tropical Medicine (LSTM), Liverpool, United Kingdom

    Charles Wondji

  10. Tropical Infectious Diseases Research Center (TIDRC), University of Abomey-Calavi, Cotonou, Bénin

    Luc Djogbenou

  11. Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala, Cameroon

    Cyrille Ndo

  12. Department of Parasitology and Microbiology, Center for Research in Infectious Diseases (CRID), Yaoundé, Cameroon

    Cyrille Ndo

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  1. Jacques Dollon Mbama Ntabi
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Contributions

Study design: JDMN, FN. Field and lab investigation: JDMN, MEB, GM. Supervision of the study: FN, AL. Data analysis: JDMN, JCD. Manuscript writing: JDMN, JCD, FM, MTB, RA, LD, CD, AL, FN, AAA, SB.

Corresponding authors

Correspondence to Jacques Dollon Mbama Ntabi or Francine Ntoumi.

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Ethics approval and consent to participate

This study received ethical approval from the Institutional Ethics Committee of the FCRM (No. 013/CIE/FCRM/2018), administrative authorisations from Marien Ngouabi University (No. 317/Université Marien Ngouabi [UMNG] Faculté des Sciences et Techniques [FST] DFD.FD-SBIO) and the administrative authorisation of the Goma Tsé-Tsé district sub-prefecture (N° 002/MATDDUDP/DGTT/SG-02). Before the mosquito collection, a consent form was signed by the head of each household giving access to homes to capture mosquitoes. A questionnaire was administered before or after the agreement of participation of the head of household.

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Supplementary Information

Additional file 1: Table S1

: Primers used in the molecular identification of An. gambiae s.l. and the detection of Plasmodium spp.

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Mbama Ntabi, J.D., Malda Bali, E.D., Lissom, A. et al. Contribution of Anopheles gambiae sensu lato mosquitoes to malaria transmission during the dry season in Djoumouna and Ntoula villages in the Republic of the Congo. Parasites Vectors 17, 104 (2024). https://doi.org/10.1186/s13071-023-06102-7

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Parasites & Vectors

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