Prevalence of non-Plasmodium falciparum species in southern districts of Brazzaville in The Republic of the Congo

Epidemiology and diversity of Plasmodium species in Franceville and their implications for malaria control

Malaria is a significant public health challenge in Gabon, with high prevalence rates in rural and semi-urban areas. This study investigated Plasmodium infection prevalence among outpatients at a medical laboratory in Franceville, Gabon, in 2020. Data from 500 patients were analyzed, revealing an overall infection rate of 33.2% and the presence of four Plasmodium species: P. falciparum, P. malariae, P. ovale, and possibly P. vivax for the first time in Gabon. Co-infections were common, with P. falciparum and P. ovale spp. being the most prevalent at 23.5%. Asymptomatic infections accounted for 81.3% of cases, while symptomatic infections were 18.7%. P. falciparum was associated with symptomatic cases, while non-falciparum species were linked to asymptomatic infections. The findings suggest Franceville has perennial malaria transmission, highlighting the role of Plasmodium species diversity in disease severity and clinical presentation, including the first report of P. vivax infection in the Gabonese population.

Profile of molecular markers of Sulfadoxine-Pyrimethamine-resistant Plasmodium falciparum in individuals living in southern area of Brazzaville, Republic of Congo

BACKGROUND

Although the seasonal and perennial malaria chemopreventions are not implemented in the Republic of Congo, resistance to Sulfadoxine-pyrimethamine (SP) threatens the intermittent preventive treatment during pregnancy (IPTp-SP) and others treatments using the drug. The objective of this study was to determine the prevalence of molecular markers of P.falciparum resistance to SP in individuals with microscopic malaria infection in the south of Brazzaville.

METHODS

Two parallel surveys (health facilities and community-based cross sectional studies) were carried out in urban and rural areas in southern Brazzaville. Between March and October 2021, blood samples were collected from 328 P. falciparum microscopic positive individuals (1-83 years old, and sex ratio female/male of 1.1) to characterize dhfr and dhps genes involved in the P.falciparum resistance to SP. Restriction Fragment Length Polymorphism PCR was used for the detection of mutations within these parasite genes.

RESULTS

High prevalence of mutations was reported within Pfdhfr gene: N51I; 328/328 (100%) ratio (prevalence) [95 CI uncertainty], C59R; 317/328 (96.6 %) [94.1-98.1%], S108N; 326/326 (100%), N164L; 3/326 (0.9%) [0.3-2.7%], and Pfdhps gene: A437G; 292/327 (89.3%) [85.5-92.2%], K540E; 140/327(42.8 %) [37.6-48.2%], A581G; 136/325 (41.8%) [36.6-42.3%]. The quintuple mutant (N51I + C59R + S108N + A437G + K540E) and sextuple mutant haplotypes (N51I + C59R + S108N + A437G + K540E + A581G) were reported for 11/144 (7.6%) [4.3-13.2%] and 5/144 (3.4%) [1.5-7.9%]) of the participants respectively. The K540E and A437G mutants were more prevalent in the rural community; 81/139 (58.3%) [50.0-66.1%] and 135/139 (97.1%) [92.8-98.9%] respectively) than in the urban community; 21/50 (46.3%) [33.7-59.4%] and 47/54(87.0%) [75.6-93.6%] (p = 0.004 and p˂0.0001 respectively) CONCLUSION: These results indicate high prevalence of SP resistance mutations within the dhfr and dhps genes of P. falciparum isolates circulating in study sites, which may limit the efficacy of treatments using SP in these settings.

Polymorphisms in the Pfcrt, Pfmdr1, and Pfk13 genes of Plasmodium falciparum isolates from southern Brazzaville, Republic of Congo

This study aimed to analyze polymorphisms in Pfcrt, Pfmdr1, and Pfk13 genes' markers of resistance to Artemisinin-based combination therapy (ACT), in Plasmodium falciparum isolates from southern Brazzaville, 15 years after the adoption of ACT in the Republic of Congo. A total of 369 microscopy-confirmed malaria-infected individuals were enrolled from March to October 2021 in the community and in health facilities during a cross-sectional study. The K76T mutation in the Pfcrt gene, N86Y and Y184F mutations in the Pfmdr1 gene were investigated using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) while the codons region (1005-1300) of the Pfmdr1gene, and Pfk13 gene were sequenced. The prevalences of K76T, N86Y, Y184F mutations were 26.0%, 6.8%, and 27.7%, respectively. However, no mutations were detected in codons 1034, 1042, and 1246 of the Pfmdr1 gene. None of the mutations previously associated with artemisinin-based resistance were detected in the Pfk13 gene. The results reveal a significant decrease in the prevalence of K76T, N86Y, Y184F mutations, in Plasmodium falciparum isolates following the change of therapeutic policy. As artemisinin resistance is emerging throughout Africa, continued surveillance for early detection of these mutations and relevant partner markers of drug resistance are recommended in the Republic of Congo.

Quality Control of Microscopic Diagnosis of Malaria in Healthcare Facilities and Submicroscopic Infections in Mossendjo, the Department of Niari, the Republic of the Congo

The control and management of malaria are linked to the quality of diagnosis. We sought to estimate the performance of routine microscopy for malaria diagnosis and assess the prevalence of submicroscopic Plasmodium (P.) falciparum infection among febrile patients in two healthcare facilities in Mossendjo, the Republic of the Congo. A cross-sectional study was conducted between January and December 2022. A total of 650 and 234 patients with signs of uncomplicated malaria were enrolled at the Centre de Sante Intégré (CSIMSJ) and Hôpital de Base (HBMSJ), respectively. Two thick blood smears were performed for each patient, one analyzed by routine microscopists and the other by an expert. The msp-1 and msp-2 genes were genotyped to detect submicroscopic P. falciparum infection. At the CSIMSJ, the sensitivity was 49.5% and the specificity was 88.6%. The positive and negative predictive values were 77.7% and 68.7%, respectively. At the HBMSJ, the sensitivity was 32.9% and the specificity was 79.4%. The positive and negative predictive values were 44.8% and 69.5%, respectively. P. falciparum was the only species detected by routine microscopists, while experts identified some cases with P. malariae and P. ovale. The proportion of submicroscopic infections was 35.75%. Children under 5 years old had higher rates of parasitemia. However, submicroscopic infections were more pronounced in the adult group. The performance of routine malaria microscopists at Mossendjo was inaccurate at both sites. With the large proportion of submicroscopic infection, malaria management at Mossendjo requires the improvement of microscopists' skills and the concomitant use of RDTs.

Plasmodium falciparum transmission based on merozoite surface protein 1 (msp1) and 2 (msp2) gene diversity and antibody responses in Ibadan, Nigeria

Background

Nigeria is a major contributor to the global malaria burden. The genetic diversity of malaria parasite populations as well as antibody responses of individuals in affected areas against antigens of the parasite can reveal the transmission intensity, a key information required to control the disease. This work was carried out to determine the allelic frequency of highly polymorphic Plasmodium falciparum genes and antibody responses against schizont crude antigens in an area of Ibadan, Nigeria.

Materials and methods

Blood was collected from 147 individuals with symptoms suspected to be malaria. Malaria infection was determined using a rapid diagnostic test (RDT), and msp1 and msp2 were genotyped by a nested PCR method. In addition, levels of IgG directed against P. falciparum FCR3S1.2 schizont extract was measured in ELISA.

Results

Approximately 25% (36/147) were positive for a P. falciparum infection in RDT, but only 32 of the positive samples were successfully genotyped. MAD20 was the most prevalent and K1 the least prevalent of the msp1 alleles. For msp2, FC27 was more prevalent than 3D7. The mean multiplicities of infection (MOI) were 1.9 and 1.7 for msp1 and msp2, respectively. IgG levels correlated positively with age, however there was no difference in median antibody levels between RDT-positive and RDT-negative individuals.

Conclusion

Low MOI has before been correlated with low/intermediate transmission intensity, however, in this study, similar levels of P. falciparum-specific antibodies between infected and non-infected individuals point more towards a high level of exposure and a need for further measures to control the spread of malaria in this area.

Malaria Species Positivity Rates Among Symptomatic Individuals Across Regions of Differing Transmission Intensities in Mainland Tanzania

BACKGROUND

Recent data indicate that non-Plasmodium falciparum species may be more prevalent than thought in sub-Saharan Africa. Although Plasmodium malariae, Plasmodium ovale spp., and Plasmodium vivax are less severe than P. falciparum, treatment and control are more challenging, and their geographic distributions are not well characterized.

METHODS

We randomly selected 3284 of 12 845 samples collected from cross-sectional surveys in 100 health facilities across 10 regions of Mainland Tanzania and performed quantitative real-time PCR to determine presence and parasitemia of each malaria species.

RESULTS

P. falciparum was most prevalent, but P. malariae and P. ovale were found in all but 1 region, with high levels (>5%) of P. ovale in 7 regions. The highest P. malariae positivity rate was 4.5% in Mara and 8 regions had positivity rates ≥1%. We only detected 3 P. vivax infections, all in Kilimanjaro. While most nonfalciparum malaria-positive samples were coinfected with P. falciparum, 23.6% (n = 13 of 55) of P. malariae and 14.7% (n = 24 of 163) of P. ovale spp. were monoinfections.

CONCLUSIONS

P. falciparum remains by far the largest threat, but our data indicate that malaria elimination efforts in Tanzania will require increased surveillance and improved understanding of the biology of nonfalciparum species.

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

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

Entomological indicators of Plasmodium species transmission in Goma Tsé-Tsé and Madibou districts, in the Republic of Congo

BACKGROUND

Malaria remains a major public health problem in the Republic of Congo, with Plasmodium falciparum being the deadliest species of Plasmodium in humans. Vector transmission of malaria is poorly studied in the country and no previous report compared rural and urban data. This study aimed to determine the Anopheles fauna and the entomological indices of malaria transmission in the rural and urban areas in the south of Brazzaville, and beyond.

METHODS

Indoor household mosquitoes capture using electric aspirator was performed in rural and urban areas during raining and dry seasons in 2021. The identification of Anopheles species was done using binocular magnifier and nested-PCR. TaqMan and nested-PCR were used to detect the Plasmodium species in the head/thorax and abdomens of Anopheles. Some entomological indices including the sporozoite infection rate, the entomological inoculation rate and the man biting rate were estimated.

RESULTS

A total of 699 Anopheles mosquitoes were collected: Anopheles gambiae sensu lato (s.l.) (90.7%), Anopheles funestus s.l. (6.9%), and Anopheles moucheti (2.4%). Three species of An. gambiae s.l. were identified including Anopheles gambiae sensu stricto (78.9%), Anopheles coluzzii (15.4%) and Anopheles arabiensis (5.7%). The overall sporozoite infection rate was 22.3% with a predominance of Plasmodium falciparum, followed by Plasmodium malariae and Plasmodium ovale. Anopheles aggressiveness rate was higher in households from rural area (1.1 bites/night) compared to that from urban area (0.8 ib/p/n). The overall entomological inoculation rate was 0.13 ib/p/n. This index was 0.17 ib/p/n and 0.092 ib/p/n in rural and in urban area, respectively, and was similar during the dry (0.18 ib/p/n) and rainy (0.14 ib/p/n) seasons.

CONCLUSION

These findings highlight that malaria transmission remains high in rural and urban area in the south of Republic of Congo despite the ongoing control efforts, thereby indicating the need for more robust interventions.

Plasmodium falciparum msp-1 and msp-2 genetic diversity and multiplicity of infection in isolates from Congolese patients in the Republic of Congo

With limited up to date data from the Republic of Congo, the aim of this study was to investigate allelic polymorphism of merozoite surface protein-1 (msp-1) and merozoite surface protein-2 (msp-2). This will help assess the genetic diversity and multiplicity of Plasmodium falciparum infection (MOI), from uncomplicated malaria individuals living in Brazzaville. Between March and October 2021, a cross-sectional study was carried out at a health center in Madibou District located in the south of Brazzaville. Plasmodium infection was diagnosed in human blood by microscopy and the block 2 of P. falciparum msp-1 and block 3 of msp-2 genes were genotyped by nested PCR. Overall, 57 genotypes with fragment sizes ranging from 110 to 410 bp were recorded for msp-1, among which 25, 21, and 11 genotypes identified for K1, MAD20, and RO33 allelic families respectively. RO33 (34.3%) and MAD20 (34.3%) allelic families were more frequent compared to K1 (31.4%) although the difference was not statistically significant. Also, 47 msp-2 genotypes were identified, including 26 FC27 genotypes type, and 21 genotypes belonging to the 3D7 allelic family. FC27 was more frequent (52.3%) compared to 3D7 (47.7%). The prevalence of the polyclonal infection was 90.0% while the MOI was 2.90 ± 1.0. The MOI and polyclonal infection were not significantly associated with the parasitaemia and anaemia. This study reveals a high genetic diversity and the trend of increasing MOI of P. falciparum isolates from the south of Brazzaville, compared to the reports from the same setting before the COVID-19 pandemic.

Comparative study of Plasmodium falciparum msp-1 and msp-2 Genetic Diversity in Isolates from Rural and Urban Areas in the South of Brazzaville, Republic of Congo

Polymorphisms in the genes encoding the merozoite surface proteins msp-1 and msp-2 are widely used markers for characterizing the genetic diversity of Plasmodium falciparum. This study aimed to compare the genetic diversity of circulating parasite strains in rural and urban settings in the Republic of Congo after the introduction of artemisinin-based combination therapy (ACT) in 2006. A cross-sectional survey was conducted from March to September 2021 in rural and urban areas close to Brazzaville, during which Plasmodium infection was detected using microscopy (and nested-PCR for submicroscopic infection). The genes coding for merozoite proteins-1 and -2 were genotyped by allele-specific nested PCR. Totals of 397 (72.4%) and 151 (27.6%) P. falciparum isolates were collected in rural and urban areas, respectively. The K1/msp-1 and FC27/msp-2 allelic families were predominant both in rural (39% and 64%, respectively) and urban (45.4% and 54.5% respectively) areas. The multiplicity of infection (MOI) was higher (p = 0.0006) in rural areas (2.9) compared to urban settings (2.4). The rainy season and the positive microscopic infection were associated with an increase in MOI. These findings reveal a higher P. falciparum genetic diversity and MOI in the rural setting of the Republic of Congo, which is influenced by the season and the participant clinical status.