Prevalence of Malaria and the Use of Long-lasting Insecticide Treated Bed Nets in Households of Rural and Semi-urban Communities in Mbengwi Health District, North West Region, Cameroon

Aims: In Cameroon, on August 2011 and October 2015 the Ministry of Public Health launched the national campaign for distribution of long-lasting insecticide-treated bed nets (LLINs) to all families as a means of effectively fighting malaria transmission. The study area Mbengwi Health District found in the North West Region of Cameroon benefitted from this distribution of LLINs, but the impact of this intervention has not been evaluated. This study was designed to assess the use of LLINs in selected households of rural and semi-urban communities in Mbengwi Health District. Study Design: A cross sectional study was conducted in households, between July 2017 to September 2017 in Mbengwi health district. Methodology: Two questionnaires were administered; one to the household head and the other to the occupants. Blood samples were obtained to diagnose and quantify malaria parasite and to determine hemoglobin concentrations (HB). A total of 93 households and 440 inhabitants of all sexes and age groups were surveyed. Results: Of the 440 participants, 49 were positive for malaria parasite giving an overall prevalence of 11.1%. From the questionnaires it was observed that 87 (93.5%) of the households owned LLINs, with up to 82 (94.3%) sleeping under the nets. All the owners of LLINs (87; 100%) obtained the nets from the government free of charge. There was no significant difference in bed-net ownership (p=0.978) and usage (p=0.664) between the rural and semi-urban communities. Malaria prevalence was significantly lower among users of LLINs (4.8%) than non-users (23.5%, p<0.001). Malaria parasite density negatively correlated significantly with HB (r= -0.097, p=0.041). Conclusion: Overall, there was a high degree ownership and usage of LLINs by households in both rural and semi-urban communities, which was associated with protection from malaria infection.

IMPLICATIONS OF LONG-LASTING INSECTICIDE-TREATED BED NETS (LLINs) FOR MALARIA CONTROL AND PREVENTION IN SOMALIA

In Sub-Saharan Africa, bed nets are mainly aimed at the prevention of the nuisance of mosquito biting rather than against malaria. The species that are involved in malaria infection are all present in Somalia with the leading one being Plasmodium falciparum that causes about 98% of all infections in the country. This alarming spread of malaria underscores the need to develop interventions that can effectively curb the malaria menace. This study sought to examine the implications of the utilization of long-lasting insecticide-treated bed nets (LLINs) for malaria control and prevention. The population constituted 1,100 pregnant women attending MCH clinics and the two thousand two hundred heads of households, totalling three thousand three hundred. A simple random sampling technique was used to obtain a representative sample of households. In surveying 110 pregnant women attending Maternal Child Health (MCH) clinics and 220 heads of households in the Belet Hawo district in Somalia in 2019, the study found that the majority of households knew the effect of LLINs on preventing malaria. They were also knowledgeable about how to control malaria while facing limited access to LLINs. Furthermore, LLIN usage helped households to raise awareness and knowledge about the effect of LLINs on preventing malaria. This study provided the Somalian government with a better understanding of the causes, control, and prevention of malaria.

Modelling New Insecticide-Treated Bed-Nets for Malaria-Vector Control: How to Strategically Manage Resistance?

Background: The programme to eradicate malaria is at a critical juncture as a new wave of insecticides for mosquito control enter their final stages of development. Previous insecticides have been deployed one-at-a-time until their utility was compromised, without the strategic management of resistance. But recent investment has led to the near-synchronous development of new insecticides, and with it the current opportunity to build resistance management into mosquito-control methods to maximize the chance of eradicating malaria. Methods: Here, building on the parameter framework of an existing mathematical model, resistance-management strategies using multiple insecticides are compared to suggest how to deploy combinations of available and new insecticides on bed-nets to achieve maximum impact. Results: Although results support the use of different strategies in different settings, deploying new insecticides ideally together in (or at least as a part of) a mixture is shown to be a robust strategy across most settings. Conclusions: Substantially building on previous works, we find alternative solutions for the resistance management of new insecticides to be used in bed-nets for malaria vector control. Our results support a mixture product concept as the most robust way to deploy new insecticides, even if they are mixed with a pyrethroid that has lower effectiveness due to pre-existing resistance. These results can help deciding on deployment strategies and policies around the sustainable use of these new anti-malaria tools.

Emerging properties of malaria transmission and persistence in urban Accra, Ghana: evidence from a participatory system approach

Background Several studies that aim to enhance the understanding of malaria transmission and persistence in urban settings failed to address its underlining complexity. This study aims at doing that by applying qualitative and participatory-based system analysis and mapping to elicit the system’s emergent properties. Methods In two experts’ workshops, the system was sketched and refined. This system was represented through a causal loop diagram, where the identification of leverage points was done using network analysis. Results 45 determinants interplaying through 56 linkages, and three subsystems: urbanization-related transmission, infection-prone behaviour and healthcare efficiency, and Plasmodium resistance were identified. Apart from the number of breeding sites and malaria-positive cases, other determinants such as drug prescription and the awareness of householders were identified by the network analysis as leverage points and emergent properties of the system of transmission and persistence of malaria. Conclusion Based on the findings, the ongoing efforts to control malaria, such as the use of insecticide-treated bed nets and larvicide applications should continue, and new ones focusing on the public awareness and malaria literacy of city dwellers should be included. The participatory approach strengthened the legitimacy of the recommendations and the co-learning of participants.

Control measures of malaria transmission in Rwanda based on SEIR SEI mathematical model

This research paper investigated the dynamics of malaria transmission in Rwanda using the nonlinear forces of infections which are included in SEIR-SEI mathematical model for human and mosquito populations. The mathematical modeling of malaria studies the interaction among the human and mosquito populations in controlling malaria transmission and eventually eliminating malaria infection. This work investigates the optimal control strategies for minimizing the rate of malaria transmission by applying three control variables through Caputo fractional derivative. The optimal control problems for malaria model found the control parameters which minimize infection. The numerical simulation showed that the number of exposed and infected people and mosquito population are decreased due to the control strategies. Finally, this work found out that the transmission of malaria in Rwanda can be minimized by using the combination of controls like Insecticide Treated bed Nets (ITNs), Indoor Residual Spray (IRS) and Artemisinin based Combination Therapies (ACTs).

Preventive Measures Against The Vectors Of Malaria In Akanda, Southwest Gabon: Knowledge, Attitudes, Practices, And Beliefs

Background: Reliable data on the Knowledge, Attitudes, Beliefs, and Practices (KABP) of the indigenes of Akanda and its environs on the different approaches to fight against vectors of malaria is lacking. Objective: To evaluate the KABP of the indigenes of Akanda and its environs on the different techniques used to fight against vectors of malaria. Materials and Methods: A cross sectional survey using semi-structured questionnaires was conducted on heads of randomly selected households at Akanda from April to June 2019. Results: We interviewed 369 heads of households and the population had a high literacy rate. It was noticed that 94% of respondents knew that mosquitoes could transmit malaria. More than 80% believed that Insecticide-Treated bed Nets (ITNs) could protect them from malaria infection. There was no preference in ITNs usage with age cohorts and seasons of the year. The ITNs owned by respondents were mostly purchased from shops. Respondents underlined that their reluctance to sleep under ITNs was because of their inability to breath under such conditions. Also, apart from the use of ITNs for malaria control, Indoor Residual Spraying (IRS) using insecticides (mostly Rambo®) purchased from shops and cleaning around house surroundings were practiced by >50% of respondents. Conclusion: Despite respondent’s awareness of mosquitoes as vectors of malaria as well as the use of ITNs, IRS, and cleaning of home surroundings to reduce malaria vectors burden, the ITNs coverage rate is very weak and more sensitization is also required at Akanda in Gabon.

Chloroquine and Sulfadoxine–Pyrimethamine Resistance in Sub-Saharan Africa—A Review

Malaria is a great concern for global health and accounts for a large amount of morbidity and mortality, particularly in Africa, with sub-Saharan Africa carrying the greatest burden of the disease. Malaria control tools such as insecticide-treated bed nets, indoor residual spraying, and antimalarial drugs have been relatively successful in reducing the burden of malaria; however, sub-Saharan African countries encounter great challenges, the greatest being antimalarial drug resistance. Chloroquine (CQ) was the first-line drug in the 20th century until it was replaced by sulfadoxine–pyrimethamine (SP) as a consequence of resistance. The extensive use of these antimalarials intensified the spread of resistance throughout sub-Saharan Africa, thus resulting in a loss of efficacy for the treatment of malaria. SP was replaced by artemisinin-based combination therapy (ACT) after the emergence of resistance toward SP; however, the use of ACTs is now threatened by the emergence of resistant parasites. The decreased selective pressure on CQ and SP allowed for the reintroduction of sensitivity toward those antimalarials in regions of sub-Saharan Africa where they were not the primary drug for treatment. Therefore, the emergence and spread of antimalarial drug resistance should be tracked to prevent further spread of the resistant parasites, and the re-emergence of sensitivity should be monitored to detect the possible reappearance of sensitivity in sub-Saharan Africa.

A singularly perturbed vector-bias malaria model incorporating bed-net control

A malaria transmission disease model with host selectivity and Insecticide treated bed nets (ITNs), as an intervention for controlling the disease, is formulated. Since the vector is an insect, the vector time scale is much more expeditious than the host time scale. This leads to a singularly perturbed model with two distinctive intrinsic time scales, two-slow for the host and one-fast for the vector. The basic reproduction number R0 is calculated and the local stability analysis is performed at equilibria of the model when the perturbation parameter ɛ > 0. The model is analyzed when ɛ → 0 using asymptotic expansions technique. Merging bed-net control, vector-bias, and singular perturbation have a notable effect on the model dynamics. It is shown that if over %30 of humans use ITNs, malaria disease burden can be reduced. The dynamics on the slow surface indicate that the infected vectors decays very fast when ɛ = 0.001 according to the numerical simulations.

Intensity and mechanisms of deltamethrin and permethrin resistance in Anopheles gambiae s.l. populations in southern Benin

Background Insecticide resistance is threatening the effectiveness of efforts to control malaria vectors in Benin. This study explores the levels and mechanisms of insecticide resistance in An. gambiae s.l. to pyrethroids. Methods Larvae were collected from August 2017 to July 2018 in five communes in southern Benin (Adjohoun, Allada, Bohicon, Cotonou, and Porto-Novo) representing diverse ecological regions, and were reared in Benin’s insectary. Two- to five-day-old female mosquitoes from each district were exposed to multiple doses of deltamethrin and permethrin (1×, 2×, 5×, and 10×) using the WHO insecticide resistance intensity bioassay. The effect of pre-exposure to the synergist, piperonyl butoxide (PBO), was also tested at different pyrethroid doses. Molecular allele frequencies of kdr (1014F) and ace-1R (119S) insecticide resistance mutations and levels of detoxification enzymes were determined for mosquitoes sampled from each study area. Results An. gambiae s.l. were resistant to pyrethroid-only exposure up to 10× the diagnostic doses in all the study sites for both deltamethrin and permethrin. Mortality was significantly higher in An. gambiae s.l. pre-exposed to PBO followed by exposure to deltamethrin or permethrin compared to mosquitoes exposed to deltamethrin or permethrin only (p < 0.001). The difference in mortality between deltamethrin only and PBO plus deltamethrin was the smallest in Cotonou (16–64%) and the greatest in Bohicon (12–93%). The mortality difference between permethrin only and PBO plus permethrin was the smallest in Cotonou (44–75%) and the greatest in Bohicon (22–72%). In all the study sites, the kdr resistance allele (1014F) frequency was high (75–100%), while the ace-1 resistance allele (G119S) frequency was low (0–3%). Analysis of the metabolic enzymatic activity of An. gambiae s.l. showed overexpression of nonspecific esterases and glutathione S-transferases (GST) in all study sites. In contrast to the PBO results, oxidase expression was low and was similar to the susceptible An. gambiae s.s. Kisumu strain in all sites. Conclusion There is high-intensity resistance to pyrethroids in southern Benin. However, pre-exposure to PBO significantly increased susceptibility to the pyrethroids in the different An. gambiae s.l. populations sampled. The use of PBO insecticide-treated bed nets may help maintain the gains in An. gambiae (s.l.) control in southern Benin. Graphical Abstract