Understanding the current state-of-the-art of long-lasting insecticide nets and potential for sustainable alternatives

Healthcare innovation adoption in Africa: the case of long-lasting insecticide nets in Ghana using protection motivation theory

OBJECTIVE

Studies have shown that healthcare innovation adoption is complex. Using Long-lasting insecticidal nets (LLINs), an innovation for malaria prevention, the study aimed to understand factors considered in the adoption of healthcare innovations in Africa.

METHODS AND MEASURES

Using qualitative methods, we interviewed 10 household heads in Ghana who had freely received LLINs during a malaria campaign. We analyzed our data using a deductive thematic analysis approach utilizing the protection motivation theory (PMT) as our framework.

RESULTS

We found that the constructs of PMT: perceived severity, perceived vulnerability, perceived response efficacy, and perceived self-efficacy influenced the adoption of healthcare innovation (i.e. LLINs). We also found that misconceptions about malaria infection and prevention influenced the perceived response efficacy of LLINs which could undermine LLINs usage.

CONCLUSION

The constructs of PMT are important in the decision to use LLINs. Misconceptions about malaria infection and prevention could undermine the decision to use LLINs. Future studies should investigate ways to address these misconceptions.

Long-lasting insecticidal nets use and the prevalence of Plasmodium falciparum infection among pregnant women attending antenatal care at the Bonassama District Hospital, Littoral Region of Cameroon: a cross-sectional study

BACKGROUND

Malaria during pregnancy continues to be a significant cause of morbidity and mortality for both infants and mothers, particularly in sub-Saharan African (SSA) countries, despite increased efforts to control it. The utilization of long-lasting insecticide-treated nets (LLINs) during pregnancy is a well-established strategy to reduce the prevalence of malaria. Nonetheless, inadequate adherence remains a persistent challenge in certain regions with high malaria endemicity. This research aimed to assess the effectiveness of long-lasting insecticidal nets in preventing asymptomatic malaria infections among pregnant women attending antenatal care at the Bonassama District Hospital in the Littoral Region of Cameroon.

METHODS

A hospital-based cross-sectional study was conducted from March to June 2022. Data on sociodemographic characteristics and LLIN usage were collected through a structured questionnaire, while asymptomatic malaria infections were identified using a PfHRP2/pLDH malaria qualitative rapid diagnostic kit. The relationship between categorical variables was analyzed using the chi-square test and logistic regression at a significance level of 5%.

RESULTS

Out of the 411 pregnant women included in the study, 35.4% were diagnosed with malaria. The LLIN utilization rate was 65.1%. The risk of malaria infection was 2.7 times higher (AOR = 2.75, 95% CI = 1.83-4.14, p < 0.001) among women who did not consistently use LLINs compared to those who did. Pregnant women in their first trimester (AOR = 3.40, 95% CI = 1.24-4.64, p = 0.010) and second trimester (AOR = 1.90, 95%CI = 0.99-3.62, p = 0.055) were more likely to sleep under net when compared to those in the third trimester. Younger women 20-29 years (71.4%), those in the first trimester (69.6%) and those who had the nets before pregnancy (68.9%) were amongst those who frequently used use the nets. Among the reasons reported for not frequently using LLINs were heat (55.2%), suffocation (13.6%) and the smell of nets (8.4%).

CONCLUSION

The use of LLIN was moderately high among the participants in this study, though still below national target. Age group, religion and gestation period were the major factors determining the use of LLINs. Considering the proven effectiveness of LLINs in reducing malaria morbidity and mortality, it is imperative for the National Malaria Control Programme (NMCP) to remain focused in promoting both LLIN ownership and utilization to achieve the national target of 100% and 80%, respectively.

Complete series method (CSM): a convenient method to reduce daily heterogeneity when evaluating the regeneration time (RT) of insecticide-treated nets (ITNs)

BACKGROUND

"Regeneration time" (RT) denotes the time required to obtain a stable mortality rate for mosquitoes exposed to insecticide-treated nets (ITNs) after three consecutive washes of a net in a day. The RT informs the wash interval used to artificially age ITNs to simulate their lifetime performance under user conditions (20 washes). RT was estimated following World Health Organization (WHO) longitudinal method (LM) procedures. Longitudinal evaluation may introduce heterogeneity due to mosquito batch variability, complicating RT determination. To overcome this, nets at each stage of regeneration (i.e., 1, 2, 3, 5 and 7 days post wash) were prepared in advance and refrigerated; then, a complete regeneration series was tested with a single mosquito batch on 1 testing day, completing four series over 4 days. This study compared the complete series method (CSM) against the LM.

METHODS

The overall heterogeneity in the methods for estimating RT of one incorporated alpha-cypermethrin and piperonyl butoxide (PBO) and one incorporated permethrin with PBO ITNs was determined using laboratory-reared resistant Anopheles arabiensis under standard laboratory conditions. LM methods and CSM were compared in two experiments with refrigerated nets acclimated for (i) 2 h (test 1) and (ii) 3 h (test 2). Four regeneration replicates per day were tested per ITN product with 50 mosquitoes exposed per replicate (equivalent sample size to LM). The heterogeneity from these methods was compared descriptively.

RESULTS

The intra-method variability for unwashed pieces was minimal, with variance of 1.26 for CSM and 1.18 for LM. For unwashed nets, LM had substantially greater variance and ratio of LM:CSM was 2.66 in test 1 and 2.49 in test 2. The magnitude of mortality measured in bioassays depended on sample acclimation after refrigeration.

CONCLUSIONS

The CSM is a convenient method for determining the regeneration times. ITNs are prepared in advance, reducing pressure to prepare all samples to start on a single day. A complete regeneration series of samples is removed from the refrigerator, defrosted and evaluated on a single day with one mosquito batch reducing the influence of mosquito batch heterogeneity on results. Replicates can be conducted over several days but do not have to be conducted on consecutive days, allowing easy facility scheduling.

Insecticidal roof barriers mounted on untreated bed nets can be as effective against Anopheles gambiae as regular insecticide-treated bed nets

Barrier bednets (BBnets), regular bednets with a vertical insecticidal panel to target mosquitoes above the bednet roof, where they are most active, have the potential to improve existing Insecticidal Treated Bednets (ITNs), by reducing the quantity of insecticide required per net, reducing the toxic risks to those using the net, potentially increasing insecticide choice. We evaluated the performance of PermaNet 3.0 (P3) and untreated (Ut) bed nets with and without pyrethroid and piperonyl butoxide roof barriers in killing pyrethroid-resistant and susceptible Anopheles gambiae, simultaneously video-recording mosquito flight tracks. Bioassay results showed that treated roof barriers, particularly the longitudinal P3 barrier (P3L) could be an effective addition to a bed net: P3 + P3L were consistently significantly more effective than the reference P3 bednet while performance of untreated nets could be raised to equal that of the reference P3 following the addition of a P3 barrier. The BBnet's potential to augment existing bednets and enhance their performance is considered.

Mosquito control exposures and breast cancer risk: analysis of 1071 cases and 2096 controls from the Ghana Breast Health Study

Epidemiologic data on insecticide exposures and breast cancer risk are inconclusive and mostly from high-income countries. Using data from 1071 invasive pathologically confirmed breast cancer cases and 2096 controls from the Ghana Breast Health Study conducted from 2013 to 2015, we investigated associations with mosquito control products to reduce the spread of mosquito-borne diseases, such as malaria. These mosquito control products were insecticide-treated nets, mosquito coils, repellent room sprays, and skin creams for personal protection against mosquitos. Multivariable and polytomous logistic regression models were used to estimate odds ratios (ORadj) and 95% confidence intervals (CI) with breast cancer risk-adjusted for potential confounders and known risk factors. Among controls, the reported use of mosquito control products were mosquito coils (65%), followed by insecticide-treated nets (56%), repellent room sprays (53%), and repellent skin creams (15%). Compared to a referent group of participants unexposed to mosquito control products, there was no significant association between breast cancer risk and mosquito coils. There was an association in breast cancer risk with reported use of insecticide-treated nets; however, that association was weak and not statistically significant. Participants who reported using repellent sprays were at elevated risks compared to women who did not use any mosquito control products, even after adjustment for all other mosquito control products (OR = 1.42, 95% CI=1.15-1.75). We had limited power to detect an association with repellent skin creams. Although only a few participants reported using repellent room sprays weekly/daily or < month-monthly, no trends were evident with increased frequency of use of repellent sprays, and there was no statistical evidence of heterogeneity by estrogen receptor (ER) status (p-het > 0.25). Our analysis was limited when determining if an association existed with repellent skin creams; therefore, we cannot conclude an association. We found limited evidence of risk associations with widely used mosquito coils and insecticide-treated nets, which are reassuring given their importance for malaria prevention. Our findings regarding specific breast cancer risk associations, specifically those observed between repellent sprays, require further study.

Manipulative neuroparasites: uncovering the intricacies of neurological host control

Manipulative neuroparasites are a fascinating group of organisms that possess the ability to hijack the nervous systems of their hosts, manipulating their behavior in order to enhance their own survival and reproductive success. This review provides an overview of the different strategies employed by manipulative neuroparasites, ranging from viruses to parasitic worms and fungi. By examining specific examples, such as Toxoplasma gondii, Leucochloridium paradoxum, and Ophiocordyceps unilateralis, we highlight the complex mechanisms employed by these parasites to manipulate their hosts' behavior. We explore the mechanisms through which these parasites alter the neural processes and behavior of their hosts, including the modulation of neurotransmitters, hormonal pathways, and neural circuits. This review focuses less on the diseases that neuroparasites induce and more on the process of their neurological manipulation. We also investigate the fundamental mechanisms of host manipulation in the developing field of neuroparasitology, which blends neuroscience and parasitology. Finally, understanding the complex interaction between manipulative neuroparasites and their hosts may help us to better understand the fundamentals of behavior, neurology, and host-parasite relationships.

Selection for insecticide resistance can promote Plasmodium falciparum infection in Anopheles

Insecticide resistance is under strong selective pressure in Anopheles mosquitoes due to widespread usage of insecticides in vector control strategies. Resistance mechanisms likely cause changes that profoundly affect mosquito physiology, yet it remains poorly understood how selective pressures imposed by insecticides may alter the ability of the mosquito to host and transmit a Plasmodium infection. From pyrethroid-resistant field-derived Anopheles gambiae s.l. mosquitoes, we established resistant (RES) and susceptible (SUS) colonies by either selection for, or loss of insecticide resistance. We show increased oocyst intensity and growth rate as well as increased sporozoite prevalence and intensity in RES compared to SUS females infected with Plasmodium falciparum. The increase in infection intensity in RES females was not associated with the presence of the kdrL1014F mutation and was not impacted by inhibition of Cytochrome P450s. The lipid transporter lipophorin (Lp), which was upregulated in RES compared to SUS, was at least partly implicated in the increased intensity of P. falciparum but not directly involved in the insecticide resistance phenotype. Interestingly, we observed that although P. falciparum infections were not affected when RES females were exposed to permethrin, these females had decreased lipid abundance in the fat body following exposure, pointing to a possible role for lipid mobilization in response to damage caused by insecticide challenge. The finding that selection for insecticide resistance can increase P. falciparum infection intensities and growth rate reinforces the need to assess the overall impact on malaria transmission dynamics caused by selective pressures mosquitoes experience during repeated insecticide challenge.