Malaria Control In Africa Research Articles

The Role of the Plasmodium falciparum Chloroquine Resistance Transporter Gene in Malaria Drug Resistance and its implication on malaria control in Africa

The Role of the Plasmodium falciparum Chloroquine Resistance Transporter Gene in Malaria Drug Resistance and its implication on malaria control in Africa

Expansion of artemisinin partial resistance mutations and lack of histidine rich protein-2 and -3 deletions in Plasmodium falciparum infections from Rukara, Rwanda

BackgroundEmerging artemisinin partial resistance and diagnostic resistance are a threat to malaria control in Africa. Plasmodium falciparum kelch13 (k13) propeller-domain mutations that confer artemisinin partial resistance have emerged in Africa. k13-561H was initially described at a frequency of 7.4% from Masaka in 2014–2015, but not present in nearby Rukara. By 2018, 19.6% of isolates in Masaka and 22% of isolates in Rukara contained the mutation. Longitudinal monitoring is essential to inform control efforts. In Rukara, an assessment was conducted to evaluate recent k13-561H prevalence changes, as well as other key mutations. Prevalence of hrp2/3 deletions was also assessed.MethodsSamples collected in Rukara in 2021 were genotyped for key artemisinin and partner drug resistance mutations using molecular inversion probe assays and for hrp2/3 deletions using qPCR.ResultsClinically validated k13 artemisinin partial resistance mutations continue to increase in prevalence with the overall level of mutant infections reaching 32% in Rwanda. The increase appears to be due to the rapid emergence of k13-675V (6.4%, 6/94 infections), previously not observed, rather than continued expansion of 561H (23.5% 20/85). Mutations to partner drugs and other anti-malarials were variable, with high levels of multidrug resistance 1 (mdr1) N86 (95.5%) associated with lumefantrine decreased susceptibility and dihydrofolate reductase (dhfr) 164L (24.7%) associated with a high level of antifolate resistance, but low levels of amodiaquine resistance polymorphisms with chloroquine resistance transporter (crt) 76T: at 6.1% prevalence. No hrp2 or hrp3 gene deletions associated with diagnostic resistance were found.ConclusionsIncreasing prevalence of artemisinin partial resistance due to k13-561H and the rapid expansion of k13-675V is concerning for the longevity of artemisinin effectiveness in the region. False negative RDT results do not appear to be an issue with no hrp2 or hpr3 deletions detected. Continued molecular surveillance in this region and surrounding areas is needed to follow artemisinin partial resistance and provide early detection of partner drug resistance, which would likely compromise control and increase malaria morbidity and mortality in East Africa.

A review of the impact of COVID-19 pandemic on malaria control in Africa

A review of the impact of COVID-19 pandemic on malaria control in Africa

Impact of the COVID-19 Pandemic on Malaria Control in Africa: A Preliminary Analysis

Malaria remains a significant public health concern in Africa, and the emerging coronavirus disease 2019 (COVID-19) pandemic may have negatively impacted malaria control. Here, we conducted a descriptive epidemiological analysis of malaria globally, and preliminarily explored the impact of COVID-19 on the malaria elimination program in regions of Africa (AFR). The present analysis found that there was a vast heterogeneity of incidence of deaths caused by malaria globally in different continents, and the highest malaria burden was observed in AFR. In 2020, there was an obviously increasing trend in the malaria epidemic in AFR, while the other four continents exhibited stable and declining patterns. Historically, malaria has been largely concentrated in high-malaria-burden regions, such as West Africa, and there has been an obvious increasing trend in Nigeria. These data suggest that dynamic changes in the malaria epidemic situation worldwide have primarily originated from AFR, and West Africa has played an important role in the global malaria increase in recent years. Under the coercion of COVID-19, multiple factors have co-driven the increase in malaria in AFR, including insufficient financial investments, a high native malaria burden, weak surveillance systems, limited medical resources, and low socioeconomic development levels. In addition, the shift of medical resources (e.g., health workers and personal protective equipment (PPE), the manufacturing of diagnostic reagents, and drugs) from malaria control to emergency COVID-19 response in the pandemic's early stage caused disruptions, reductions, and delays in pillar malaria control measures, leading to a significant negative impact on malaria control. In particular, a funding shortfall at both the international and domestic levels led to a "significant threat," resulting in vast gaps in access to proven malaria control tools. Although there has been a declining trend in malaria control over time due to COVID-19, the effect still cannot be ignored. Hence, we recommend the implementation of medical and technical resource assistance as a priority strategy to support Africa (West Africa) in order to curb further transmission.

Characterizing pyrethroid resistance and mechanisms in Anopheles gambiae (s.s.) and Anopheles arabiensis from 11 districts in Uganda

Insecticide resistance threatens recent progress on malaria control in Africa. To characterize pyrethroid resistance in Uganda, Anopheles gambiae (s.s.) and Anopheles arabiensis were analyzed from 11 sites with varied vector control strategies. Mosquito larvae were collected between May 2018 and December 2020. Sites were categorized as receiving no indoor-residual spraying (‘no IRS’, n ​= ​3); where IRS was delivered from 2009 to 2014 and in 2017 and then discontinued (‘IRS stopped’, n ​= ​4); and where IRS had been sustained since 2014 (‘IRS active’, n ​= ​4). IRS included bendiocarb, pirimiphos methyl and clothianidin. All sites received long-lasting insecticidal nets (LLINs) in 2017. Adult mosquitoes were exposed to pyrethroids; with or without piperonyl butoxide (PBO). Anopheles gambiae (s.s.) and An. arabiensis were identified using PCR. Anopheles gambiae (s.s.) were genotyped for Vgsc-995S/F, Cyp6aa1, Cyp6p4-I236M, ZZB-TE, Cyp4j5-L43F and Coeae1d, while An. arabiensis were examined for Vgsc-1014S/F. Overall, 2753 An. gambiae (s.l.), including 1105 An. gambiae (s.s.) and 1648 An. arabiensis were evaluated. Species composition varied by site; only nine An. gambiae (s.s.) were collected from ‘IRS active’ sites, precluding species-specific comparisons. Overall, mortality following exposure to permethrin and deltamethrin was 18.8% (148/788) in An. gambiae (s.s.) and 74.6% (912/1222) in An. arabiensis. Mortality was significantly lower in An. gambiae (s.s.) than in An. arabiensis in ‘no IRS’ sites (permethrin: 16.1 vs 67.7%, P ​< ​0.001; deltamethrin: 24.6 vs 83.7%, P ​< ​0.001) and in ‘IRS stopped’ sites (permethrin: 11.3 vs 63.6%, P ​< ​0.001; deltamethrin: 25.6 vs 88.9%, P ​< ​0.001). When PBO was added, mortality increased for An. gambiae (s.s.) and An. arabiensis. Most An. gambiae (s.s.) had the Vgsc-995S/F mutation (95% frequency) and the Cyp6p4-I236M resistance allele (87%), while the frequency of Cyp4j5 and Coeae1d were lower (52% and 55%, respectively). Resistance to pyrethroids was widespread and higher in An. gambiae (s.s.). Where IRS was active, An. arabiensis dominated. Addition of PBO to pyrethroids increased mortality, supporting deployment of PBO LLINs. Further surveillance of insecticide resistance and assessment of associations between genotypic markers and phenotypic outcomes are needed to better understand mechanisms of pyrethroid resistance and to guide vector control.

Marketing Malaria Control: Nets, Neoliberalism, and a New Approach to Fighting Malaria

Summary This article examines how malaria control in Africa became a neoliberal enterprise that privileged market mechanisms as an ideal way to disseminate health interventions. It does so by tracking efforts to sell insecticide-treated nets on the continent as these tools transformed from cheap stopgap measures intended for primary health care programmes in the early 1980s to a major target of global health aid by the 2000s. Even though experience showed that selling insecticide-treated nets to African populations did not lead to high levels of uptake, malaria programme leaders continued to tinker with market mechanisms to scale up the intervention in line with the interests of prominent donors. Narrating this history as it unfolded across different African countries, this paper shows that the neoliberalisation of malaria control was a contingent and fragmented process that depended as much on local experiences with particular health technologies as it did on high-level policy-making.

In Vitro Assessment of anti plasmodial activity of Albizia chevalieri extracts against Plasmodium falciparum

Medicinal plants play a key role in malaria control in Africa, especially in remote areas where health facilities are limited. This study was carried out with the aim to investigate the anti plasmodial activity of Albizia chevalieri against Plasmodium falciparum. The three aerial parts of Albizia chevalieri were extracted using methanol via maceration process. Anti plasmodial assay was carried out in duplicate in the 96-well microtitre plate. The anti Plasmodial activity of A. chevalieri methanolic extracts observed in this study may be attributed to the presence of some bioactive compounds. The effect of A. chevalieri methanolic extracts and reference drugs showed a decrease in percentage parasitaemia with increasing concentration. With regard to concentrations administered, a dose-dependent antimalarial activity was clearly shown for crude extract, isolates and the reference drugs. Artemether, the root isolate and leaf isolate exhibited a remarkable antiplasmodial activity. Root, leaf extracts and the pure isolates when compared with the standard drug that has the highest percentage inhibition shows no significance difference at (P&gt;0.05). However, when compared with the other drugs such as Chloroquine, Quinine shows a significance percentage inhibition difference at (P&gt;0.05). Considering the inhibitory effect of A. chevalieri methanol extracts on the growth of P. falciparum as reported in this study, it is concluded that the anti plasmodial activity of the plant on P. falciparum suggests its potency in the treatment of malaria infection. Further study on this plant is on-going to isolate, identify and characterize the bioactive compounds from this plant responsible for this bioactivity, and also to carry- out the drug synthesis.

World’s first malaria vaccine and its significance to malaria control in Africa

World’s first malaria vaccine and its significance to malaria control in Africa

Insecticide-treated net ownership, utilization and knowledge of malaria in children residing in Batoke\u2013Limbe, Mount Cameroon area: effect on malariometric and haematological indices

BackgroundInsecticide-treated nets (ITNs) are the most widely used interventions for malaria control in Africa. The aim of this study was to assess the ownership and utilization of ITNs and the knowledge of malaria and their effects on malariometric and haematological indices in children living in the Mount Cameroon area.MethodsA community-based cross-sectional study involving a total of 405 children aged between 6 months and 14 years living in Batoke–Limbe was carried out between July and October 2017. A semi-structured questionnaire was used to document demographic status, knowledge on malaria and ITN ownership and usage. Venous blood sample was collected from each child to determine the prevalence and intensity of parasitaemia by Giemsa-stained microscopy and full blood count by auto haematology analysis to obtain white blood cell (WBC) and red blood cell (RBC) counts, haemoglobin (Hb) level, haematocrit (Hct), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC). A multilinear regression model was used to determine the relationship between haematological parameter as dependent variable and the independent variables.ResultsThe overall prevalence of parasitaemia, anaemia, knowledge about malaria, ITN ownership, usage and effective usage was 46.7%, 54.7%, 40.7%, 78.8%, 50.9% and 29.9%, respectively. The prevalence of parasitaemia was significantly higher (P < 0.001) in children who ineffectively utilized ITNs (54.9%) than effective users (27.3%). Having knowledge of malaria, negatively correlated with WBC counts (P = 0.005), but positively correlated with Hb levels (P < 0.001), RBC counts (P < 0.001), Hct (P < 0.001), MCV (P < 0.001) and MCH (P < 0.001). ITN use positively correlated with WBC counts (P = 0.005) but negatively with Hb levels (P = 0.004), RBC counts (P = 0.006), and MCH (P < 0.001). Meanwhile, parasitaemia negatively correlated with Hb levels (P = 0.004), RBC counts (P = 0.01), Hct (P = 0.04) and MCHC (P = 0.015).ConclusionThere is need for more sensitization on the benefits of using the ITNs to meet up with the intended and expected impact of the free distribution of ITNs.

Spatial\u2013temporal clustering of malaria using routinely collected health facility data on the Kenyan Coast

BackgroundThe over-distributed pattern of malaria transmission has led to attempts to define malaria “hotspots” that could be targeted for purposes of malaria control in Africa. However, few studies have investigated the use of routine health facility data in the more stable, endemic areas of Africa as a low-cost strategy to identify hotspots. Here the objective was to explore the spatial and temporal dynamics of fever positive rapid diagnostic test (RDT) malaria cases routinely collected along the Kenyan Coast.MethodsData on fever positive RDT cases between March 2018 and February 2019 were obtained from patients presenting to six out-patients health-facilities in a rural area of Kilifi County on the Kenyan Coast. To quantify spatial clustering, homestead level geocoded addresses were used as well as aggregated homesteads level data at enumeration zone. Data were sub-divided into quarterly intervals. Kulldorff’s spatial scan statistics using Bernoulli probability model was used to detect hotspots of fever positive RDTs across all ages, where cases were febrile individuals with a positive test and controls were individuals with a negative test.ResultsAcross 12 months of surveillance, there were nine significant clusters that were identified using the spatial scan statistics among RDT positive fevers. These clusters included 52% of all fever positive RDT cases detected in 29% of the geocoded homesteads in the study area. When the resolution of the data was aggregated at enumeration zone (village) level the hotspots identified were located in the same areas. Only two of the nine hotspots were temporally stable accounting for 2.7% of the homesteads and included 10.8% of all fever positive RDT cases detected.ConclusionTaking together the temporal instability of spatial hotspots and the relatively modest fraction of the malaria cases that they account for; it would seem inadvisable to re-design the sub-county control strategies around targeting hotspots.

Epidemiologial Survey on the Utilization of Insecticide Treated Mosquito Nets in Malaria Control among Gyadi-Gyadi Communities in Kano, Nigeria

Background: Malaria causes an overwhelmingly large number of cases and deaths round the globe every year. Insecticide treated mosquito nets (ITNs) have raised a renewed interest to serve as tools for malaria control in Africa. This survey was, therefore, designed to provide information about the knowledge, attitude and experience of the community about malaria as a disease and its preventive methods, particularly acceptability, affordability and compliance to the use of insecticide treated mosquito nets, and factors influencing its possession and utilization of ITNs among Gyadi-Gyadi communities in Kano, Nigeria. Methods: A community based cross-sectional study was conducted in Gyadi-Gyadi from March 2019 to April 2019. Data was collected using a pretested structured questionnaire. Descriptive analysis was performed to obtain the frequency distribution of the variables. Results: The result shows that 341 participants responded to the questionnaire. 64.5% of the respondents had heard about the mosquito net. 45% of the respondents in the survey reported the presence of at least one mosquito net in their households. 69.2% of the participants perceived fever, headache and chilling of the body as the main symptoms of malaria. Conclusion: The utilization of mosquito nets at the time of the study was very low. However, acceptability and willingness to use ITNs for malaria prevention was very high. It is recommended that communities should be strongly sensitized on the importance of ITNs for malaria control, and the availability and affordability should be insured.

Hybrid mosquitoes? Evidence from rural Tanzania on how local communities conceptualize and respond to modified mosquitoes as a tool for malaria control

BackgroundDifferent forms of mosquito modifications are being considered as potential high-impact and low-cost tools for future malaria control in Africa. Although still under evaluation, the eventual success of these technologies will require high-level public acceptance. Understanding prevailing community perceptions of mosquito modification is, therefore, crucial for effective design and implementation of these interventions. This study investigated community perceptions regarding genetically-modified mosquitoes (GMMs) and their potential for malaria control in Tanzanian villages where no research or campaign for such technologies has yet been undertaken.MethodsA mixed-methods design was used, involving: (i) focus group discussions (FGD) with community leaders to get insights on how they frame and would respond to GMMs, and (ii) structured questionnaires administered to 490 community members to assess awareness, perceptions and support for GMMs for malaria control. Descriptive statistics were used to summarize the findings and thematic content analysis was used to identify key concepts and interpret the findings.ResultsNearly all survey respondents were unaware of mosquito modification technologies for malaria control (94.3%), and reported no knowledge of their specific characteristics (97.3%). However, community leaders participating in FGDs offered a set of distinctive interpretive frames to conceptualize interventions relying on GMMs for malaria control. The participants commonly referenced their experiences of cross-breeding for selecting preferred traits in domestic plants and animals. Preferred GMMs attributes included the expected reductions in insecticide use and human labour. Population suppression approaches, requiring as few releases as possible, were favoured. Common concerns included whether the GMMs would look or behave differently than wild mosquitoes, and how the technology would be integrated into current malaria control policies. The participants emphasised the importance and the challenge of educating and engaging communities during the technology development.ConclusionsUnderstanding how communities perceive and interpret novel technologies is crucial to the design and effective implementation of new vector control programmes. This study offers vital clues on how communities with no prior experience of modified mosquitoes might conceptualize or respond to such technologies when deployed in the context of malaria control programmes. Drawing upon existing interpretive frames and locally-resonant analogies when deploying such technologies may provide a basis for more durable public support in the future.

Antiplasmodial Activity of compounds isolated from Albizia chevalieri against Plasmodium falciparum

Therapeutic plants play a key position in malaria control in Africa, especially in public areas where health facilities are insufficient. In order to charge their much-admired potentials, this study is aimed to determine the in-vitro antiplasmodial activity of the compound isolated from Albizia chevalieri against plasmodium falciparum. The three Arial parts of the plant was extracted with methanol via maceration method. The most active extracts were isolated for bioactive compounds using column chromatographic technique while Antiplasmodial assay for the isolated compounds was also carried out in duplicate in the 96-well microtitre plate; Exactly 100µl of culture medium was dispensed into all the wells in a 96-well microtitre plate leaving only the “A” series. Then, 100µl of the working solutions (isolated compounds and standard drugs) were pipette in to the well “A” series. Serial dilutions were then prepared by pipetting 50µl of the solutions from the “A” series well down the rows up to the” G”series wells, leaving series 12 from wells, down the rows to “H” only with the culture medium, serving as control. The extra 50 µl of test substance dilution series were discarded. Exactly 25 µl of the infected red cells was separated and were added into all the wells in the test plates using the multi-channel micropipette and were mixed by swirling with the tips to ensure homogeneity. The microtitre plates were incubated in CO2 condition at 370C in candle jar for 30 hours. The effect of A.chevalieri compounds isolates and reference drug showed a decrease in percentage parasitaemia with increasing concentration. With regard to concentrations administered, a dose-dependent antimalarial activity was clearly shown for isolates and the reference drugs. artemether, root isolate and leaf isolate exhibited a remarkable antiplasmodial activity, the pure isolates when compared with the standard drug that has the highest percentage inhibition shows no significance difference at (P>0.05), but when compared with the other drugs such as Chloroquine, Quinine shows a significance difference at (P>0.05). It is concluded that the antiplasmodial activity of the plant on P. falciparum suggests its effectiveness in the treatment of malaria infection. The work also confirms the likelihood of conducting in-vivo antiplasmodial activity of the isolated compounds from Albizia chevalier.

Fighting COVID-19 at the Expense of Malaria in Africa: The Consequences and Policy Options.

.Malaria remains a major global health burden, killing hundreds of thousands annually, especially in sub-Saharan Africa. In December 2019, a novel illness termed COVID-19, caused by SARS-CoV-2, was reported in China. This disease soon spread around the world and was declared a pandemic by the WHO on March 11, 2020. Considering that the malaria burden is high in many low-income tropical countries with little capacity to fund malaria control and eradication programs, the fight against malaria in these regions is likely to be hindered by COVID-19. Indeed, access to health care has generally been limited during the pandemic, whereas malaria interventions, such as seasonal malaria chemoprevention, and distribution of long-lasting insecticide-treated bed nets, have been suspended because of lockdowns. Likewise, the repurposing of antimalarials for the treatment of COVID-19 and a shift in focus from the production of malaria rapid diagnostic tests to COVID-19 rapid diagnostic tests are causes for concern in malaria-endemic regions. COVID-19 has disproportionately affected developed countries, threatening their capacity to aid in malaria control efforts. Here, we address impacts of the COVID-19 pandemic on the management and control of malaria in Africa.

The relationship between facility-based malaria test positivity rate and community-based parasite prevalence.

IntroductionMalaria surveillance is a key pillar in the control of malaria in Africa. The value of using routinely collected data from health facilities to define malaria risk at community levels remains poorly defined.MethodsFour cross-sectional parasite prevalence surveys were undertaken among residents at 36 enumeration zones in Kilifi county on the Kenyan coast and temporally and spatially matched to fever surveillance at 6 health facilities serving the same communities over 12 months. The age-structured functional form of the relationship between test positivity rate (TPR) and community-based parasite prevalence (PR) was explored through the development of regression models fitted by alternating the linear, exponential and polynomial terms for PR. The predictive ranges of TPR were explored for PR endemicity risk groups of control programmatic value using cut-offs of low (PR <5%) and high (PR ≥ 30%) transmission intensity.ResultsAmong 28,134 febrile patients encountered for malaria diagnostic testing in the health facilities, 12,143 (43.2%: 95% CI: 42.6%, 43.7%) were positive. The overall community PR was 9.9% (95% CI: 9.2%, 10.7%) among 6,479 participants tested for malaria. The polynomial model was the best fitting model for the data that described the algebraic relationship between TPR and PR. In this setting, a TPR of ≥ 49% in all age groups corresponded to an age-standardized PR of ≥ 30%, while a TPR of < 40% corresponded to an age-standardized PR of < 5%.ConclusionA non-linear relationship was observed between the relative change in TPR and changes in the PR, which is likely to have important implications for malaria surveillance programs, especially at the extremes of transmission. However, larger, more spatially diverse data series using routinely collected TPR data matched to community-based infection prevalence data are required to explore the more practical implications of using TPR as a replacement for community PR.

Epidemiological Survey on the Utilization of Insecticide Treated Mosquito Nets in Malaria Control among Gyadi-Gyadi Communities in Kano, Nigeria.

Background: Malaria causes an overwhelmingly large number of cases and deaths round the globe every year. Insecticide treated mosquito nets (ITNs) have raised a renewed interest to serve as tools for malaria control in Africa. This survey was, therefore, designed to provide information about the knowledge, attitude and experience of the community about malaria as a disease and its preventive methods, particularly acceptability, affordability and compliance to the use of insecticide treated mosquito nets, and factors influencing its possession and utilization of ITNs among Gyadi-Gyadi communities in Kano, Nigeria. Methods: A community based cross-sectional study was conducted in Gyadi-Gyadi from January, 2020 to February, 2020. Data was collected using a pretested structured questionnaire. Descriptive analysis was performed to obtain the frequency distribution of the variables. Results: The result shows that 341 participants responded to the questionnaire. 64.5% of the respondents had heard about the mosquito net. 45% of the respondents in the survey reported the presence of at least one mosquito net in their households. 69.2% of the participants perceived fever, headache and chilling of the body as the main symptoms of malaria. Conclusion: The utilization of mosquito nets at the time of the study was very low. However, acceptability and willingness to use ITNs for malaria prevention was very high. It is recommended that communities should be strongly sensitized on the importance of ITNs for malaria control and the availability and affordability should be insured.

A new species in the major malaria vector complex sheds light on reticulated species evolution

Complexes of closely related species provide key insights into the rapid and independent evolution of adaptive traits. Here, we described and studied Anopheles fontenillei sp.n., a new species in the Anopheles gambiae complex that we recently discovered in the forested areas of Gabon, Central Africa. Our analysis placed the new taxon in the phylogenetic tree of the An. gambiae complex, revealing important introgression events with other members of the complex. Particularly, we detected recent introgression, with Anopheles gambiae and Anopheles coluzzii, of genes directly involved in vectorial capacity. Moreover, genome analysis of the new species allowed us to clarify the evolutionary history of the 3La inversion. Overall, An. fontenillei sp.n. analysis improved our understanding of the relationship between species within the An. gambiae complex, and provided insight into the evolution of vectorial capacity traits that are relevant for the successful control of malaria in Africa.

Cross-resistance profiles of malaria mosquito P450s associated with pyrethroid resistance against WHO insecticides

Extensive use of pyrethroids for malaria control in Africa has led to widespread pyrethroid resistance in the two major African vectors of malaria An. gambiae and An. funestus. This is often associated with constitutively elevated levels of cytochrome P450s involved with pyrethroid metabolism and detoxification. P450s have the capacity to metabolise diverse substrates, which raises concerns about their potential to cause cross-resistance. A bank of seven recombinant P450s from An. gambiae (CYPs 6M2, 6P2, 6P3, 6P4, 6P5, 9J5) and An. funestus (CYP6P9a) commonly associated with pyrethroid resistance were screened against twelve insecticides representing the five major classes of insecticides recommended by WHO for malaria control; permethrin, etofenprox and bifenthrin (type I pyrethroids), deltamethrin, lambda cyhalothrin and cypermethrin (type II pyrethroids), DDT (organochlorine), bendiocarb (carbamate), malathion, pirimiphos methyl and fenitrothion (organophosphates) and pyriproxyfen (juvenile hormone analogue). DDT was not metabolised by the P450 panel, while bendiocarb was only metabolised by CYP6P3. Pyrethroids and pyriproxyfen were largely susceptible to metabolism by the P450 panel, as were organophosphates, which are activated by P450s. Primiphos-methyl is increasingly used for malaria control. Examination of the pirimiphos-methyl metabolites generated by CYP6P3 revealed both the active pirimiphos-methyl-oxon form and the inactive oxidative cleavage product 2-diethylamino-6-hydroxy-4-methylpyrimidine. The inhibition profile of CYPs 6M2, 6P2, 6P3, 6P9a and 9J5 was also examined using diethoxyfluorescein (DEF) as the probe substrate. Bendiocarb was the weakest inhibitor with IC50 > 100 μM across the P450 panel, while CYP6M2 showed strongest inhibition by malathion (IC50 0.7 μM). The results suggest that P450s present at elevated levels in two major Anopheline vectors of malaria in Africa have the capacity to metabolise a diverse range of pyrethroid and organophosphate insecticides as well as pyriproxyfen that could impact vector control.

A marker of glutathione S-transferase-mediated resistance to insecticides is associated with higher Plasmodium infection in the African malaria vector Anopheles funestus

Metabolic resistance to insecticides is threatening malaria control in Africa. However, the extent to which it impacts malaria transmission remains unclear. Here, we investigated the association between a marker of glutathione S-transferase mediated metabolic resistance and Plasmodium infection in field population of Anopheles funestus s.s. in comparison to the A296S-RDL target site mutation. The 119F-GSTe2 resistant allele was present in southern (Obout) (56%) and central (Mibellon) (25%) regions of Cameroon whereas the 296S-RDL resistant allele was detected at 98.5% and 15% respectively. The whole mosquito Plasmodium and sporozoite infection rates were 57% and 14.8% respectively in Obout (n = 508) and 19.7% and 5% in Mibellon (n = 360). No association was found between L119F-GSTe2 genotypes and whole mosquito infection status. However, when analyzing oocyst and sporozoite infection rates separately, the resistant homozygote 119F/F genotype was significantly more associated with Plasmodium infection in Obout than both heterozygote (OR = 2.5; P = 0.012) and homozygote susceptible (L/L119) genotypes (OR = 2.10; P = 0.013). In contrast, homozygote RDL susceptible mosquitoes (A/A296) were associated more frequently with Plasmodium infection than other genotypes (OR = 4; P = 0.03). No additive interaction was found between L119F and A296S. Sequencing of the GSTe2 gene showed no association between the polymorphism of this gene and Plasmodium infection. Glutathione S-transferase metabolic resistance is potentially increasing the vectorial capacity of resistant An. funestus mosquitoes. This could result in a possible exacerbation of malaria transmission in areas of high GSTe2-based metabolic resistance to insecticides.

LLIN Evaluation in Uganda Project (LLINEUP): a cross-sectional survey of species diversity and insecticide resistance in 48 districts of Uganda

BackgroundLong-lasting insecticidal nets (LLINs) are the principal tool for malaria control in Africa and are presently treated with a single class of insecticide; however, increasing levels of insecticide resistance threaten their success. In response to this threat nets have been developed that incorporate the synergist, piperonyl butoxide (PBO), which inhibits the activity of cytochrome P450s which is one main mechanisms of insecticide resistance, allowing resistance to pyrethroids to be reversed. However, data on the value and cost effectiveness of these nets is lacking. A large-scale cluster randomised trial of conventional LLINs and PBO-LLINs was conducted in Uganda in 104 health sub-districts (HSDs) in 2017–2019. Prior to the mass distribution of LLINs, a baseline entomological survey was carried out, the results of which are reported herein. Ten households from each HSD were randomly selected for entomological surveillance at baseline which included household mosquito collections.ResultsPrior to LLIN distribution entomological collections were carried out in 1029 houses across the 104 HSDs. Anopheles gambiae (s.l.) was the principal vector in all but 9 of the 71 HSDs that yielded vector species. Molecular analysis found An. gambiae (s.s.) to be the predominant vector collected. Plasmodium falciparum was detected in 5.5% of An. gambiae (s.s.) and in 4.0% of An. funestus (s.s.) examined. Infection rates of other plasmodium species (P. vivax, P. ovale and P. malariae) were lower with infection rates of 1.2% and 1.7% for An. gambiae (s.s.) and An. funestus (s.s.), respectively. The knockdown resistance (kdr) mutation Vgsc-L1014S was found at very high frequency in An. gambiae (s.s.) with the Vgsc-L1014F mutation at low frequency and the wild-type allele virtually absent. In An. arabiensis the wild-type allele was predominant. The resistance-associated alleles, Cyp4j5-L43F and Coeae1d were found at moderate frequencies which varied across the study site. Vgsc-N1575Y mutation was not found in any samples examined.ConclusionsNo significant differences between planned intervention arms was observed in vector densities, sporozoite infection rate or insecticide resistance marker frequency across the study site prior to the distribution of LLINs. Very high levels of kdr resistance were observed in all areas; however, the resistance-associated markers Cyp4j5-L43F and Coeae1d were found at varying frequencies across the study site which may have implications for the effectiveness of standard LLINs.Trial registration This study is registered with ISRCTN, ISRCTN17516395. Registered 14 February 2017, http://www.isrctn.com/ISRCTN17516395