Durability of PBO nets (Olyset Plus®), 12 months after their distribution in Bertoua, Cameroon

BackgroundThe spread of pyrethroid resistance in malaria vectors threatens the effectiveness of standard long-lasting insecticidal nets (LLIN). Synergist nets combine pyrethroid (Py) and piperonyl-butoxide (PBO) to enhance potency against resistance mediated by mono-oxygenase mechanisms. Our project assessed personal protection of the World Health Organization first-in-class PBO-Py LLIN (Olyset Plus) versus the standard LLIN (Olyset net) against pyrethroid-resistant Anopheles gambiae sensu lato (s.l.) and An. funestus in North-West Tanzania after 20 months of household use.MethodsFrom a household survey, 39 standard Olyset net and 39 Olyset Plus houses were selected. The physical integrity and hole index (HI) of the nets were assessed, and resting mosquitoes were collected from inside nets and from room walls. The indoor abundance was estimated using CDC light traps and species identified using PCR. The bioefficacy of PBO and standard LLINs against wild Anopheles was assessed using 30-minute cylinder bioassays.ResultsOf 2397 Anopheles collected, 8.9% (n = 213) were resting inside standard Olyset nets, while none were found inside Olyset Plus nets (PBO-Py LLINs) of any HI category. Resting density of blood-fed mosquitoes was higher on walls of sleeping rooms with Olyset nets compared to Olyset Plus (0.62 vs 0.10, density ratio [DR]: 0.03, 95% CI 0.01–0.13, p < 0.001). Mosquitoes were found inside Olyset nets of all WHO HI categories, but more were collected inside the more damaged nets (HI ≥ 643) than in less damaged (HI 0–64) nets (DR: 6.4, 95% CI 1.1–36.0, p = 0.037). In bioassay, mortality of An. gambiae s.l. was higher with Olyset Plus than with Olyset nets for new nets (76.8% vs 27.5%) and nets used for 20 months (56.8% vs 12.8%); similar trends were observed with An. funestus.ConclusionThe PBO-Py LLINs provided improved protection after 20 months of household use, as demonstrated by the higher bioassay mortality and absence of pyrethroid-resistant An. gambiae sensu stricto (s.s.) and An. funestus collected from inside Olyset Plus nets, irrespective of HI category, as compared to Olyset nets.Graphical

The ability of Anopheles mosquito to transmit malaria in nature is partly enhanced by; resistance of mosquito to insecticides, feeding preference for human host and infection by Plasmodium falciparum . An assessment was conducted to determine the status of these parameters in Anopheles populations in Mwea and Ahero rice irrigation schemes in Kenya. This was important in order to understand their potential influence on local malaria transmission. A total of 1,200 female Anopheles mosquitoes (gravid and blood fed) were sampled from both sites by indoor and outdoor methods. Anopheles samples identification to their respective species in the field was done using morphological features and taxonomic keys. In Mwea scheme, all the 600 Anopheles mosquitoes collected were An. gambiae s.l out of which 195 were gravid. In Ahero, 250 An. gambiae s.l (out of which 81 were gravid) and 350 An. funestus (out of which 181 were gravid) were collected. Gravid Anopheles mosquitoes were allowed to oviposit to give F 1 generations in the insectary. These F 1 , (four replicates of 25 mosquitoes per species per insecticide) were assessed for susceptibility to permethrin, deltamethrin, dichlorodiphenyltrichloroethane (DDT), bendiocarb or fenitrothion using standard WHO protocol. Susceptible An. gambiae s.s Kisumu strain (25 mosquitoes per the 100 test mosquitoes) was used as positive control. The 1,200 field samples were further identified to their respective species using rDNA-PCR using their legs and wings. Source (s) of blood meal in 405 An. gambiae s.l from Mwea, 169 An. gambiae s.l and 269 An. funestus from Ahero were determined using blood meal Elisa. The presence of Plasmodium falciparum Welch, 1897 in the salivary glands was assessed by sporozoite Elisa in all the field collected samples. All Anopheles mosquito samples from Mwea were Anopheles arabiensis Patton, 1905, while those from Ahero were a mixed species of Anopheles arabiensis (41.7%), Anopheles funestus sensu stricto Giles , 1900 (57%), Anopheles rivulorum Leesoni, 1935 (0.66%), Anopheles leesoni Evans, 1931 (0.3%) and Anopheles parensis Gillies, 1935 (0.3%). Mosquito samples from both study sites showed reduced susceptibility to the test insecticides. An. arabiensis mosquitoes from Mwea had a human blood meal index at 0.22 (n=405). P. falciparum circumsporozoite infection in An. arabiensis from Mwea were reported in Murinduko village at 1.5% (n=200). In Ahero, human blood meal indices were at 0.00 (n=169) and 0.17 (n=269) for An. arabiensis and An. funestus respectively. P. falciparum circumsporozoite infections in An. funestus sampled from Kamagaga and Wagai villages in Ahero were at 5% (n=147) and 2.2% (n=183) respectively.

BackgroundVector control is an effective way of reducing malaria transmission. The main vector control methods include the use of insecticide-treated bed nets and indoor residual spraying (IRS). Both interventions rely on the continuing susceptibility of Anopheles to a limited number of insecticides. However, insecticide resistance, in particular pyrethroid-DDT cross-resistance, is a challenge facing malaria vector control in Africa because pyrethroids represent the only class of insecticides approved for treating bed nets and DDT is commonly used for IRS. Here baseline data are presented on the insecticide susceptibility levels of malaria vectors prior to The Gambian indoor residual spraying intervention programme.MethodsAnopheles larvae were collected from six malaria surveillance sites (Brikama, Essau, Farafenni, Mansakonko, Kuntaur and Basse) established by the National Malaria Control Programme and the UK Medical Research Council Laboratories in The Gambia. The mosquitoes were reared to adulthood and identified using morphological keys and a species-specific polymerase chain reaction assay. Two- to three-day old adult female mosquitoes were tested for susceptibility to permethrin, deltamethrin and DDT using standard WHO protocols, insecticide susceptibility test kits and treated papers.ResultsAll Anopheles mosquitoes tested belonged to the Anopheles gambiae complex. Anopheles arabiensis was predominant (54.1%), followed by An. gambiae s.s. (26.1%) and Anopheles melas (19.8%). Anopheles gambiae s.s. and An. arabiensis were found at all six sites. Anopheles melas was recorded only at Brikama. Mosquitoes from two of the six sites (Brikama and Basse) were fully susceptible to all three insecticides tested. However, DDT resistance was found in An. gambiae from Essau where the 24 hours post-exposure mortality was <80% but 88% for permethrin and 92% for deltamethrin.ConclusionThis current survey of insecticide resistance in Anopheles provides baseline information for monitoring resistance in The Gambia and highlights the need for routine resistance surveillance as an integral part of the proposed nation wide IRS intervention using DDT.

BackgroundDespite the extensive ownership and use of insecticide-treated nets (ITNs) over the last decade, the effective lifespan of these nets, especially their physical integrity, under true operational conditions is not well-understood. Usefulness of nets declines primarily due to physical damage or loss of insecticidal activity.MethodsA community based cross-sectional survey was used to determine the physical condition and to identify predictors of poor physical condition for bed nets owned by individuals from communities in Kwale County, coastal Kenya. A proportionate hole index (pHI) was used as a standard measure, and the cut-offs for an ‘effective net’ (offer substantial protection against mosquito bites) and ‘ineffective nets’ (offer little or no protection against mosquito bites) were determined (pHI ≤88 (about ≤500 cm2 of holes surface area) and pHI of >88 (≥500 cm2 of holes surface area), respectively).ResultsThe vast majority (78%) of the surveyed nets had some holes. The median pHI was 92 (range: 1–2,980). Overall, half of the nets were categorized as ‘effective nets’ or ‘serviceable nets’. Physical deterioration of nets was associated with higher use and washing frequency. Young children and older children were found to use ineffective bed nets significantly more often than infants, while the physical integrity of nets owned by pregnant women was similar to those owned by infants. Estuarine environment inhabitants owned nets with the worst physical condition, while nets owned by the coastal slope inhabitants were in fairly good physical condition. The results suggest that bed nets are optimally utilized when they are new and physically intact. Thereafter, bed net utilization decreases gradually with increasing physical deterioration, with most net owners withdrawing physically damaged nets from routine use.This withdrawal commonly happens following 1.5 years of use, making bed net use the most important predictor of physical integrity. On average, the nets were washed twice within six months prior to the survey. Washing frequency was significantly influenced by the bed net colour and bed net age. Lack of knowledge on reasons for net retreatment and the retreatment procedure was evident, while net repair was minimal and did not seem to improve the physical condition of the nets. The “catch-up” bed net distribution strategies are sufficient for ensuring adequate ownership and utilization of ‘effective nets’ in the targeted groups, but bi-annual mass distribution is necessary to provide similar ownership and utilization for the other groups not targeted by “catch-up” strategies.ConclusionsMonitoring and maintenance strategies that will deliver locally appropriate education messages on net washing and repair will enhance the effectiveness of malaria control programmes, and further research to assess ineffective nets need is needed.

Long-lasting insecticidal nets (LLINs) are crucial for malaria prevention in Cameroon, yet their operational performance may be compromised because of deterioration of the physical integrity and bioefficacy of nets. This study evaluated LLINs, physical integrity, and bioefficacy following mass distribution campaigns in two regions in Cameroon: East (Bertoua) and Centre (Eyang). Household surveys were conducted to assess ITN ownership, usage patterns, and maintenance practices. Net condition was measured using the proportionate hole index (pHI), and bio-efficacy was assessed using WHO cone bioassays against Anopheles gambiae (s.s.) (Kisumu strain) and local field mosquitoes. A total of 55 LLINs from Bertoua and 30 from Eyang were sampled. LLIN ownership was comparable between sites (66.7% in Bertoua vs. 67.9% in Eyang), with a higher usage rate in Bertoua (73.3%) compared to 58.2% in Eyang. In Bertoua, a large percentage of LLINs (59.6%) were too torn, with Olyset Plus being the most common brand. In contrast, Eyang had a lower proportion of torn nets (44%), and households used a combination of different brands, including the Olyset net, Permanet 2.0, and Royal Sentry. Against the susceptible Kisumu strain, Bertoua's Olyset Plus nets showed optimal efficacy with a 94.6% mortality rate, exceeding the World Health Organization's (WHO) threshold of ≥ 80%. In contrast, nets from Eyang had a 79.3% mortality rate, falling short of the optimal threshold. However, when tested against local field mosquitoes, Olyset Plus (pyrethroid + PBO) showed higher efficacy (mortality rate of 31.8%) than the other brands (7.1% from Olyset net; 18.6% for Permanet 2.0; and 8.6% for Royal Sentry) (p > 0.0001). These findings underscore the crucial importance of proper LLINs maintenance, particularly regarding washing practices. The results also indicate the need to deploy newer generation LLINs to address emerging insecticide resistance and strengthen malaria control efforts.

Background Long-lasting insecticidal nets (LLINs) are effective tools at reducing malaria transmission. In Cameroon, following the first national mass distribution campaign in 2011, there has been no follow up on the efficacy of LLINs distributed. The aim of this report is to assess the physical integrity and insecticidal potency of LLINs distributed in three cities with contrasting socio economic status (SES) and to evaluate the use and care for bed nets owned by individuals.MethodsThe study was conducted in Limbe, Tiko and Buea three localities in the Fako division of the South West Region of Cameroon. Tiko had the highest SES based on the type of building materials used, followed respectively by Limbe and Buea. The use and care for bed nets was assessed using a questionnaire, the physical state of bed nets evaluated following WHOPES recommendation for determining size of holes and the residual insecticidal activity of retrieved bed nets determined through a cone bioassay using susceptible strains of mosquitoes.ResultsOf the 241 households visited in Limbe (n = 81), Tiko (n = 80) and Buea (n = 80), 186 (77.2%) had LLINs, with no significant variations from the selected study locations. However, bed net coverage was not meeting World Health Organization standards (p < 0.0001). Six different brands of LLINs were recorded, and the majority were those provided by the NMCP through the 2011 national mass campaign or antenatal care programme. Based on the calculation of the Proportionate Hole Index (PHI) as indicator of physical integrity of nets, the proportion of nets classified as serviceable (versus too torn) differed statistically according to locations (p value = 0.04), with 63.8% in Tiko, 50% in Limbe and 47% in Buea. Of the 20 nets tested for their efficacy against susceptible strains of mosquito, 42.6% (3 nets) were optimally effective in Tiko, 57.4% (4), 16.7% (1) and 14.3% (1) were minimally effective in Tiko, Buea and Limbe respectively. Finally; 85.7% (6) and 83.3% (5) were not effective in Limbe and Buea.ConclusionsThese findings pinpoint the need for more frequent replacement of LLINs especially for people with low SES and also the need for the promotion of good practices on the maintenance and washing of nets.

BackgroundThe current study was undertaken to determine the optimal wash-drying regimen and the effects of different washing procedures on the efficacy, and durability of four brands of newly introduced long-lasting insecticide-treated nets (LLINs) under tropical conditions.MethodsIn the current study, the following four LLINs were tested: Olyset®, PermaNet ®2.0, BASF® and TNT®. Nets were divided into three sets; one set was washed by hand rubbing and air-dried either hanging or spread on the ground in direct sunlight or hanging or spread on the ground under the shade. A second set was washed using the WHO protocol (machine) and the third set was washed by beating the nets on rocks. The biological activities of the nets were assessed by a three-minute bioassay cone test and the residual insecticide contents were determined using high performance liquid chromatography (HPLC) procedure.ResultsNets that were dried hanging under the shade retained more insecticide, 62.5% and recorded higher mortality compared to nets which were dried lying on the ground in direct sunlight 58.8%, nets dried under the shade spread on the ground 56.3%, and 57.8% for nets dried hanging in direct sunlight. It was also observed that nets washed by the standard WHO protocol, retained more insecticide and were more effective in killing mosquitoes compared to nets washed by local methods of hand rubbing and beating on rocks. There were significant differences between drying regimens (p < 0.0001) and between washing procedures (p < 0.001) respectively. However, the effect of net type was statistically insignificant. The statistical differences on individual nets were also compared, for PermaNet® and TNT there were no significant differences observed between the four drying regimens (p = 0.7944 and 0.4703) respectively). For BASF and Olyset, the differences were significant (p < 0.001 and p > 0.0001).ConclusionThe results of this study suggest that washing and drying regimen influence the insecticidal activity of LLINs. The standard WHOPES washing protocol underestimates the amount of insecticide washed from LLINs compared to the abrasive washing procedures that are used in the field. This suggests that there is need to educate net users to adopt a more gentle washing procedure while handling LLINs. The education should accompany net distribution campaigns.

BackgroundBed nets are the commonest malaria prevention tool and arguably the most cost-effective. Their efficacy is because they prevent mosquito bites (a function of physical durability and integrity), and kill mosquitoes (a function of chemical content and mosquito susceptibility). This essay follows the story of bed nets, insecticides and malaria control, and asks whether the nets must always have insecticides.MethodsKey attributes of untreated or pyrethroid-treated nets are examined alongside observations of their entomological and epidemiological impacts. Arguments for and against adding insecticides to nets are analysed in contexts of pyrethroid resistance, personal-versus-communal protection, outdoor-biting, need for local production and global health policies.FindingsWidespread resistance in African malaria vectors has greatly weakened the historical mass mosquitocidal effects of insecticide-treated nets (ITNs), which previously contributed communal benefits to users and non-users. Yet ITNs still achieve substantial epidemiological impact, suggesting that physical integrity, consistent use and population-level coverage are increasingly more important than mosquitocidal properties. Pyrethroid-treatment remains desirable where vectors are sufficiently susceptible, but is no longer universally necessary and should be re-examined alongside other attributes, e.g. durability, coverage, acceptability and access. New ITNs with multiple actives or synergists could provide temporary relief in some settings, but their performance, higher costs, and drawn-out innovation timelines do not justify singular emphasis on insecticides. Similarly, sub-lethal insecticides may remain marginally-impactful by reducing survival of older mosquitoes and disrupting parasite development inside the mosquitoes, but such effects vanish under strong resistance.ConclusionsThe public health value of nets is increasingly driven by bite prevention, and decreasingly by lethality to mosquitoes. For context-appropriate solutions, it is necessary to acknowledge and evaluate the potential and cost-effectiveness of durable untreated nets across different settings. Though ~ 90% of malaria burden occurs in Africa, most World Health Organization-prequalified nets are manufactured outside Africa, since many local manufacturers lack capacity to produce the recommended insecticidal nets at competitive scale and pricing. By relaxing conditions for insecticides on nets, it is conceivable that non-insecticidal but durable, and possibly bio-degradable nets, could be readily manufactured locally. This essay aims not to discredit ITNs, but to illustrate how singular focus on insecticides can hinder innovation and sustainability.

Early supplementation with high-dose vitamin A in The Gambia

Effectiveness of an early supplementation scheme of high-dose vitamin A versus standard WHO protocol in Gambian mothers and infants: a randomised controlled trial

Changing malaria epidemiology in four urban settings in sub-Saharan Africa

To evaluate the pyrrole insecticide chlorfenapyr, which has a novel non-neurotoxic mode of action and is a promising alternative to conventional adulticides, against Anopheles funestus. The toxicity of a range of concentrations of chlorfenapyr against pyrethroid resistant and susceptible laboratory reared southern African An. funestus was assessed using standard WHO protocols and analysed using probit analysis. The pyrethroid resistant strain showed consistently higher LD50 and LD95 values compared to the susceptible strain, but these differences were not statistically significant and the magnitude was twofold at most. The LD50 values recorded for An. funestus are approximately three-fold higher than those reported elsewhere for other species of anopheline. Monooxygenase based pyrethroid resistance in An. funestus does not influence the toxic effect of chlorfenapyr. It is unlikely that such a small decrease in susceptibility of An. funestus to chlorfenapyr relative to other anophelines would have any operational implications. Chlorfenapyr is an important addition to insecticides available for malaria vector control, and could be used as a resistance management tool to either circumvent or slow the development of resistance.

Background: Non-communicable diseases (NCDs) are chronic conditions that progress slowly and are rarely completely curable .These diseases such as diabetes and cardiovascular diseases, pose an increasing public health challenge in India, especially due to changes in lifestyles, behaviors and the physical and social environments in cities1.They are mainly caused by preventable behavioral risk factors, such as tobacco and alcohol consumption, unhealthy diet, and insufficient physical exercise3.It is well known that a lot of diseases can be prevented by altering the life style and habits of people. This study was undertaken with the objective of studying the prevalence of risk factors for NCDs in the Anna Nagar slum locality of Bhopal city, Madhya Pradesh. Material &amp; Methods: The study was conducted on the population of Anna nagar slums. The sample size was 180(calculated using the prevalence data of ICMR on NCDs) but 260 was covered. The household were selected using systematic random sampling and individuals from the houses were selected using KISH method as used in WHO STEPS approach. WHO STEPS questionnaire was used to collect data. Physical measurements were taken as per standard WHO protocol. Data were entered in MS-EXCEL and analysis was done using EPI INFO. Results: In the population, male members were 53% and females were 47% respectively. Mean age was 43.67±11.3 yrs.80% had not received any formal education.31% people had history of alcohol consumption and 16% of tobacco consumption. Only 36.2% participants had normal BMI. 35.8% were obese, 17.3% were overweight and 10.8% were underweight. Obesity was more in females as compared to males. Blood pressure was found to be elevated in 18.1% participants, HTN1 in 10.4% and HTN2 in 31.5% participants. 40% participants had normal blood pressure.Conclusion: The major population was illiterate. The risk factors like alcohol consumption and smoking was very prevalent and is largely attributed to the low awareness of people regarding risk factors

BackgroundArtemisinin-based combination therapy (ACT), together with other control measures, have reduced the burden of falciparum malaria in sub-Saharan countries, including Sudan. Sudan adopted ACT in 2004 with a remarkable reduction in mortality due to falciparum malaria. However, emergence of resistance to the first-line treatment artesunate and sulfadoxine/pyrimethamine (AS/SP) has created new challenges to the control of malaria in Sudan. A search for an alternative drug of choice for treating uncomplicated malaria has become inevitable. The objective of this study was to evaluate the therapeutic efficacies of dihydroartemisinin/piperaquine (DHA–PPQ) and AS/SP in an area of unstable transmission in Blue Nile State, Sudan in 2015–16.MethodsA total of 148 patients with uncomplicated malaria were recruited in the study from November 2015 to end of January 2016. Seventy-five patients received DHA–PPQ while 73 received AS/SP. Patients were monitored for clinical and parasitological outcomes following the standard WHO protocol for a period of 42 days for DHA–PPQ and 28 days for AS/SP; nested PCR (nPCR) was performed to confirm parasite re-appearance from day 7 onwards.ResultsFifty-five patients completed the DHA–PPQ arm protocol with success cure rate of 98.2% (95% CI 90.3–100%) and one late clinical failure 1.8% (95% CI 0.0–9.7%). The AS/SP showed adequate clinical and parasitological response (ACPR) of 83.6% (95% CI 71.9–91.8%), early treatment failure was 1.6% (95% CI 0.0–8.8%) and late parasitological failure (LPF) was 14.8% (95% CI 7–26.2%). The respective PCR uncorrected LPF was 20%.ConclusionDHA–PPQ is an efficacious ACT and candidate for replacement of first-line treatment in Sudan while AS/SP showed high treatment failure rate and must be replaced.

Microcos paniculata traditionally known as 'Kathgua or Fattashi' in Bangladesh is widely used for the treatment of various ailments including colds ,diarrhea, hepatitis, heat stroke, dyspepsia, wound healing, fever and as an insecticide. Hence, the present study was designed to investigate the antibacterial, toxicity & 4 th instar Culex quinquefasciatus mosquito larvicidal activities of fruit extracts of M. paniculata using a range of organic & inorganic solvents (methanol, chloroform and water). Antibacterial, toxicity & larvicidal effects were studied by means of agar disc diffusion, brine shrimp lethality bioassay (BSLB) & standard WHO protocol with slight modification. The susceptibility of the microorganisms to the plant extracts was compared with standard antibiotic flucloxacilin. Fruit methanol extract (FME) revealed a broad spectrum of antibacterial activity in contrast to other extracts (Fruit chloroform extract-FCE & Fruit water extract-FWE) , particularly significant against gram negative bacteria, Proteus mirabilis being the most (zone of inhibition 28 mm). Moreover, the FME was found to be the most toxic to brine shrimp nauplii, with LC50 of 52.7 μg/ml, indicating the possibility of finding potential toxic compounds in this plant. 4 th instar Culex quinquefasciatus larval mortality was observed and recorded after 24 h exposure period. Both FME & FCE exhibited considerable larvicidal effects with LC50 of 342.1 μg/ml &441.7 μg/ml respectively. Altogether, these results propose that the organic fractions, FME & FCE could be used as a potential sources of antibacterial agents along with their toxic & larvicidal potentiality.