Browsing by Author "Odufuwa, Olukayode"

Now showing 1 - 9 of 9

A household randomized-control trial of insecticide-treated screening for malaria control in unimproved houses in Tanzania
(Springer Nature, 2025-06-08) Odufuwa, Olukayode; Moore, Sarah Jane; Mboma, Zawadi; Mwanga, Rehema; Matwewe, Fatuma; Hofer, Lorenz; Moore, Jason; Nguyen, Hien; Bosselmann, Rune; Skovmand, Ole; Stevenson,Jennifer; Muganga, Joseph; Bradley, John
Background Installing insecticidal netting on open eaves, windows, and holes in walls of unimproved houses is a potential malaria control tool. It prevents mosquito house-entry, induces lethal and sub-lethal effects on malaria vectors, and may reduce malaria transmission. Therefore, a household epidemiological trial was conducted to assess the efficacy of insecticide- treated screening (ITS) on malaria infection and indoor vectors in Tanzania. Methods In Chalinze district, Tanzania, 421 households were randomized into two arms. In June-July 2021, one group of households’ houses was fitted with ITS (incorporated with deltamethrin and piperonyl butoxide) on eaves, windows, and wall holes, while the second group did not receive screening. After installation, consenting household members (aged ≥ 6 months) were tested for malaria infection using quantitative polymerase chain reaction after the long rainy season (June/July 2022, primary outcome) and the short rainy season (January/February 2022, secondary outcome). Secondary outcomes included indoor total mosquito per trap/night (June–July 2022), adverse effects after one month of ITS installation (August 2021), and chemical bioavailability and retention of ITS samples after one year of field use (June/July 2022). At the end of the trial, the control group received ITS. Results Malaria prevalence among residents in the ITS arm was 19.9% (50/251) and 28.3% (65/230) in the control arm after the long rains, however, this difference was not significant [adjusted odds ratio (OR) 0.67 (95% CI 0.35–1.28), p = 0.227]. Similarly, no protection was seen for ITS after the short rains, [OR 1.27 (95% CI 0.68–2.38), p = 0.452]. However, school-age children in the ITS arm had lower malaria after the long rains [OR 0.11 (95% CI 0.02–0.73), p = 0.022]. No serious adverse effects were reported. The mean number of female Anopheles mosquitoes caught per trap/night was not significantly different between arms [1.7 vs 2.4, crude relative risk: 0.71 (95% CI 0.16–3.09), p = 0.650]. ITS showed reduced chemical bioavailability and retention post-field use. The trial reported high household refusals (17–30%) in both arms in both surveys. Conclusion The trial was inconclusive because households’ refusal resulted in low power. A large cluster randomized trial of the intervention, preferably with screens treated with longer-lasting insecticides installed in houses, is needed. Trial registry: The trial was registered at ClinicalTrials.gov (NCT05125133) on October 2021 Keywords Insecticide-treated screening, ITS, Insecticide-treated nets, ITNs, Eave nets, Malaria prevalence, Mosquitoes, Trial, House modification, Tanzania
Comparison of cone bioassay estimates at two laboratories with different Anopheles mosquitoes for quality assurance of pyrethroid insecticide-treated nets
(Springer Nature., 2022-07-07) Mbwambo, Stephen; Bubun, Nakei; Mbuba, Emmanuel; Moore, Jason; Mbina, Kasiani; Kamande, Dismas; Laman, Moses; Mpolya, Emmanuel; Odufuwa, Olukayode; Freeman, Tim; Karl, Stephan; Moore, Sarah
ckground: Quality assurance (QA) of insecticide-treated nets (ITNs) delivered to malaria-endemic countries is con ducted by measuring physiochemical parameters, but not bioefcacy against malaria mosquitoes. This study explored utility of cone bioassays for pre-delivery QA of pyrethroid ITNs to test the assumption that cone bioassays are consist ent across locations, mosquito strains, and laboratories. Methods: Double-blinded bioassays were conducted on twenty unused pyrethroid ITNs of 4 brands (100 nets, 5 subsamples per net) that had been delivered for mass distribution in Papua New Guinea (PNG) having passed pre delivery inspections. Cone bioassays were performed on the same net pieces following World Health Organization (WHO) guidelines at the PNG Institute of Medical Research (PNGIMR) using pyrethroid susceptible Anopheles farauti sensu stricto (s.s.) and at Ifakara Health Institute (IHI), Tanzania using pyrethroid susceptible Anopheles gambiae s.s. Additionally, WHO tunnel tests were conducted at IHI on ITNs that did not meet cone bioefcacy thresholds. Results from IHI and PNGIMR were compared using Spearman’s Rank correlation, Bland–Altman (BA) analysis and analysis of agreement. Literature review on the use of cone bioassays for unused pyrethroid ITNs testing was conducted. Results: In cone bioassays, 13/20 nets (65%) at IHI and 8/20 (40%) at PNGIMR met WHO bioefcacy criteria. All nets met WHO bioefcacy criteria on combined cone/tunnel tests at IHI. Results from IHI and PNGIMR correlated on 60-min knockdown (KD60) (rs=0.6,p=0.002,n=20) and 24-h mortality (M24) (rs=0.9,p<0.0001,n=20) but BA showed systematic bias between the results. Of the 5 nets with discrepant result between IHI and PNGIMR, three had confdence intervals overlapping the 80% mortality threshold, with averages within 1–3% of the threshold. Including these as a pass, the agreement between the results to predict ITN failure was good with kappa=0.79 (0.53–1.00) and 90% accuracy. Conclusions: Based on these study fndings, the WHO cone bioassay is a reproducible bioassay for ITNs with>80% M24, and for all ITNs provided inherent stochastic variation and systematic bias are accounted for. The literature
Cone Bioassays Provide Reproducible Bioefficacy Estimates with Different Anopheline Mosquitoes and Can Be Used for Quality Assurance of Pyrethroid Insecticide Treated Nets
(Research Square, 2022-01-24) Mbwambo, Stephen; Bubun, Nakei; Mbuba, Emmanuel; Moore, Jason; Mbina, Kasiani; Kamande, Dismas; Laman, Moses; Mpolya, Emmanuel; Odufuwa, Olukayode; Freeman, Tim; Karl, Stephan; Moore, Sarah
Background Quality assurance (QA) of insecticide-treated nets (ITNs) delivered to malaria-endemic countries is conducted by measuring physiochemical parameters, but not bioecacy against malaria mosquitoes. The cone bioassay provides a simple evaluation of ITN bioecacy and its conditions and parameters are prescribed by the World Health Organization (WHO). This study explored utility of cone bioassays for pre- delivery QA of pyrethroid ITNs in two test facilities using different mosquito species to test the assumption that cone bioassays are consistent and reproducible across locations, mosquito strains, and laboratories. Methods Double-blinded bioassays were conducted on unused pyrethroid ITNs of 4 brands (5 nets/brand, 5 subsamples/net) that had been delivered for mass distribution in Papua New Guinea (PNG) having passed physiochemical testing of chemical content. Cone bioassays were performed on adjacent net pieces following WHO guidelines at the PNG Institute of Medical Research (PNGIMR) using pyrethroid susceptible Anopheles farauti s.s. and at Ifakara Health Institute (IHI), Tanzania using pyrethroid susceptible Anopheles gambiae s.s. Additionally, WHO tunnel tests was conducted at IHI on ITNs that did not meet cone bioecacy thresholds. Results from IHI and PNGIMR were compared using Spearman’s Rank, Bland Altman and Cohen’s kappa. A literature review on the utility of cone bioassays for unused pyrethroid ITNs testing was also conducted. Results In cone bioassays, 13/20 nets (65%) met WHO bioecacy criteria at IHI and 8/20 (40%) at PNGIMR. All nets met WHO bioecacy criteria on combined cone/tunnel tests. Results from IHI and PNGIMR correlated on 60-minute knockdown (rs=0.6, p=0.002,n=20) and 24-hour mortality (rs=0.9, p<0.0001,n=20) but there was systematic bias between the results measured by Bland Altman. Of the 5 nets with discrepant result between IHI and PNGIMR, three had condence intervals overlapping the 80% mortality threshold, with averages within 1-3% of the threshold. The agreement between the results to predict ITN failure was good with kappa=0.79 (0.53-1.00) and 90% accuracy. Conclusions WHO cone is a reproducible means to measure pyrethroid ITN bioecacy using a combination of knockdown and mortality. In the absence of an alternative tests, cone tests could be used to assess the availability of active ingredients at the surface of ITN (where mosquitoes encounter it) as part of pre-delivery QA.
In starvation, a bone can also be meat”: a mixed methods evaluation of factors associated with discarding of long-lasting insecticidal nets in Bagamoyo, Tanzania
(Springer Nature., 2022-03-24) Madumla, Edith; Moore, Sarah; Moore, Jason; Mbuba, Emmanuel; Mbeyela, Edgar; Kibondo, Ummi; Mmbaga, Selemani; Kobe, Dickson; Baraka, Jitihada; Msellemu, Daniel; Swai, Johnson; Mboma, Zawadi; Odufuwa, Olukayode
Background: Between 2000 and 2019, more than 1.8 billion long-lasting insecticidal nets (LLINs) were distributed in Africa. While the insecticidal durability of LLINs is around 3 years, nets are commonly discarded 2 years post distribu tion. This study investigated the factors associated with the decision of users to discard LLINs. Methods: A mixed-method sequential explanatory approach using a structured questionnaire followed by focus group discussions (FGDs) to collect information on experiences, views, reasons, how and when LLINs are discarded. Out of 6,526 households that responded to the questionnaire of LLINs durability trial, 160 households were randomly selected from the households in four villages in Bagamoyo Tanzania for FGDs but only 155 households participated in the FGDs. Five of the household representatives couldn’t participate due to unexpected circumstances. A total of sixteen FGDs each comprising of 8–10 adults were conducted; older women (40–60 years), older men (40–60 years), younger women (18–39 years), younger men (18–39 years). During the FGDs, participants visually inspected seven samples of LLINs that were “too-torn” based on Proportionate Hole Index recommended by the World Health Organi zation (WHO) guidelines on LLIN testing, the nets were brought to the discussion and participants had to determine if such LLINs were to be kept or discarded. The study assessed responses from the same participants that attended FGD and also responded to the structured questionnaire, 117 participants fulflled the criteria, thus data from only 117 participants are analysed in this study. Results: In FGDs, integrity of LLIN infuenced the decision to discard or keep a net. Those of older age, women, and householders with lower income were more likely to classify a WHO “too-torn” net as “good”. The common methods used to discard LLINs were burning and burying. The fndings were seen in the quantitative analysis. For every addi tional hole, the odds of discarding a WHO “too-torn” LLIN increased [OR=1.05 (95%CI (1.04–1.07)), p<0.001]. Younger age group [OR=4.97 (95%CI (3.25–7.32)), p<0.001], male-headed households [OR=6.85 (95%CI (4.44 –10.59)), p<0.001], and wealthy households [OR=3.88 (95%CI (2.33–6.46)), p<0.001] were more likely to discard LLINs.
Long-lasting insecticidal nets retain bio-efficacy after 5 years of storage: implications for malaria control programmes
(Springer Nature, 2020-03-14) Musa, Jeremiah John; Moore, Sarah; Moore, Jason; Mbuba, Emmanuel; Mbeyela, Edgar; Kobe, Dickson; Swai, Johnson; Odufuwa, Olukayode
Background: Long-lasting insecticidal nets (LLINs) are the most sustainable and efective malaria control tool currently available. Global targets are for 80% of the population living in malaria endemic areas to have access to (own) and use a LLIN. However, current access to LLINs in endemic areas is 56% due to system inefciencies and budget limitations. Thus, cost-efective approaches to maximize access to efective LLINs in endemic areas are required. This study evaluated whether LLINs that had been stored for 5 years under manufacturer’s recommended conditions may be optimally efective against Anopheles mosquitoes, to inform malaria control programmes and governments on the periods over which LLINs may be stored between distributions, in an efort to maximize use of available LLINs. Methods: Standard World Health Organization (WHO) bioassays (cone and tunnel test) were used to evaluate the bio-efcacy and wash resistance of Olyset® and DawaPlus® 2.0 (rebranded Tsara® Soft) LLINs after 5 years of storage at 25 °C to 33.4 °C and 40% to 100% relative humidity. In addition, a small scale Ifakara Ambient Chamber test (I-ACT) was conducted to compare the bio-efcacy of one long stored LLINs to one new LLIN of the same brand, washed or unwashed. LLINs were evaluated using laboratory reared fully susceptible Anopheles gambiae sensu stricto (s.s.) (Ifakara strain) and pyrethroid resistant Anopheles arabiensis (Kingani strain). Results: After 5 years of storage, both unwashed and washed, Olyset® and DawaPlus® 2.0 (Tsara® Soft) LLINs passed WHO bio-efcacy criteria on knockdown (KD60) ≥95%, 24-h mortality ≥80% and ≥90% blood-feeding inhibition in WHO assays against susceptible An. gambiae s.s. DawaPlus® 2.0 LLINs also passed combined WHO bioassay criteria against resistant An. arabiensis. Confrmatory I-ACT tests using whole nets demonstrated that long-stored LLINs showed higher efcacy than new LLINs on both feeding inhibition and mortality endpoints against resistant strains. Conclusions: Even after long-term storage of around 5 years, both Olyset® and DawaPlus® 2.0 LLINs remain efcacious against susceptible Anopheles mosquitoes at optimal storage range of 25 °C to 33.4 °C for temperature and 40% to 100% relative humidity measured by standard WHO methods. DawaPlus® 2.0 (Tsara® Soft) remained efcacious against resistant strain.
Modified World Health Organization (WHO) Tunnel Test for Higher Throughput Evaluation of Insecticide-Treated Nets (ITNs) Considering the Effect of Alternative Hosts, Exposure Time, and Mosquito Density
(MDPI, 2022-06-21) Kamande, Dismas; Odufuwa, Olukayode; Mbuba, Emmanuel; Hofer, Lorenz; Moore, Sarah
The standard World Health Organization (WHO) tunnel test is a reliable laboratory bioassay used for “free-flying” testing of insecticide-treated nets (ITNs) bio-efficacy where mosquitoes pass through a ITN sample to reach a live animal bait. Multiple parameters (i.e., bait, exposure time, and mosquito density) may affect the outcomes measured in tunnel tests. Therefore, a comparison was conducted of alternative hosts, exposure time, and lower mosquito density against the current gold standard test (100 mosquitoes, animal bait, and 12-h exposure) as outlined in the WHO ITN evaluation guideline. This was done with the aim to make the tunnel test cheaper and with higher throughput to meet the large sample sizes needed for bio-efficacy durability monitoring of chlorfenapyr ITNs that must be evaluated in “free-flying” bioassays. Methods: A series of experiments were conducted in the WHO tunnel test to evaluate the impact of the following factors on bio-efficacy endpoints of mosquito mortality at 24-h (M24) and 72-h (M72) and blood-feeding success (BFS): (1) baits (rabbit, membrane, human arm); (2) exposure time in the tunnel (1 h vs. 12 h); and (3) mosquito density (50 vs. 100). Finally, an alternative bioassay using a membrane with 50 mosquitoes (membrane-50) was compared to the gold standard bioassay (rabbit with 100 mosquitoes, rabbit-100). Pyrethroid-resistant Anopheles arabiensis and pyrethroid susceptible Anopheles gambiae were used to evaluate Interceptor® and Interceptor® G2 ITNs. Results: Using a human arm as bait gave a very different BFS, which impacted measurements of M24 and M72. The same trends in M24, M72 and BFS were observed for both Interceptor® ITN and Interceptor® G2 unwashed and washed 20 times measured using the gold standard WHO tunnel test (rabbit-100) or rabbit with 50 mosquitoes (rabbit-50). M24, M72 and BFS were not statistically different when either 50 or 100 mosquitoes were used with rabbit bait in the tunnel bioassay for either the susceptible or resistant strains. No systematic difference was observed between rabbit-50 and rabbit-100 in the agreement by the Bland and Altman method (B&A). The mean difference was 4.54% (−22.54–31.62) in BFS and 1.71% (−28.71–32.12) in M72 for rabbit-50 versus rabbit-100. Similar M24, M72 and lower BFS was measured by membrane-50 compared to rabbit-100. No systematic difference was observed in the agreement between membrane-50 and rabbit-100, by B&A. The mean difference was 9.06% (−11.42–29.64) for BSF and −5.44% (−50.3–39.45) for M72. Both membrane-50, rabbit-50 and rabbit-100 predicted the superiority of Interceptor® G2 over Interceptor® ITN for the resistant strain on M72. Conclusion: These results demonstrate that WHO tunnel tests using rabbit bait may be run with 50 mosquitoes to increase sample sizes needed for bio-efficacy durability monitoring of ITNs in “free-flying” bioassays. Using a membrane feeder with 50 mosquitoes is a potential replacement for the WHO tunnel bioassay with animal bait if control blood feeding rates can be improved to 50% because blood feeding impacts mosquito survival after exposure to insecticides.
Plasmodium falciparum gametocyte burden in a Tanzanian heterogeneous transmission setting
(BMC, 2025-02-21) Mulamba, Charles; Odufuwa, Olukayode; Kweyamba, Prisca; Lazaro, Linda; Chabo, Muhamed; Kamage, Janeth; Kreppel, Katharina; Olotu, Ally; Williams, Chris
Background Malaria transmission depends on the presence of gametocytes in the peripheral blood of infected human hosts. Understanding malaria infectious reservoirs enables transmission-blocking interventions to target the most important hosts for the disease. This study characterized the distribution of gametocyte carriage as a baseline for the clinical evaluation of a Pfs25-based transmission-blocking vaccine candidate in Bagamoyo, Tanzania. Methods A malaria survey was conducted in five locations from May to August 2022. A total of 467 participants—192 children (5–12 years), 65 adolescents (13–17 years) and 210 adults (18–45 years)—were enrolled. Malaria was detected using three methods: rapid diagnostic tests, light microscopy and quantitative polymerase chain reaction. The geometric mean of the gametocyte density, and weighted arithmetic mean of the gametocytes sex ratio were estimated. Results Overall, 23.5% (110/467) of the participants tested positive for malaria parasites, with the majority of positives (> 92%) being Plasmodium falciparum. The overall gametocytaemia was 5.6%, with a percent positivity of 6.8% (13/192), 6.2% (4/65) and 4.3% (9/210), in children, adolescents, and adults, respectively. The geometric mean gametocyte density (gametocytes/μL) was greater in adults (124.6) than in children (71.7) and adolescents (50.5). Regression analysis revealed that gametocytes were more likely to be present among male participants than among female participants [ORa: 2.79 (95% CI: 1.19 – 6.59) p = 0.019]. The gametocyte sex ratio in children and adult gametocyte carriers was similar but greater than that in adolescents. Conclusion The observed gametocyte densities and distribution across age groups suggest the need for malaria transmission-blocking interventions to target all populations in heterogeneous transmission settings. The implication of targeting only children may leave residual malaria transmission and reinfection from the left-out groups.
Plasmodium falciparum gametocyte burden in a Tanzanian heterogeneous transmission setting
(Springer Nature, 2025-02-21) Mulamba, Charles; Odufuwa, Olukayode; Kweyamba, Prisca; Lazaro, Linda; Chabo, Muhamed; Kamage, Janeth; Kreppel, Katharina; Olotu, Ally; Williams, Chris
Background Malaria transmission depends on the presence of gametocytes in the peripheral blood of infected human hosts. Understanding malaria infectious reservoirs enables transmission-blocking interventions to target the most important hosts for the disease. This study characterized the distribution of gametocyte carriage as a base- line for the clinical evaluation of a Pfs25-based transmission-blocking vaccine candidate in Bagamoyo, Tanzania. Methods A malaria survey was conducted in five locations from May to August 2022. A total of 467 partici- pants—192 children (5–12 years), 65 adolescents (13–17 years) and 210 adults (18–45 years)—were enrolled. Malaria was detected using three methods: rapid diagnostic tests, light microscopy and quantitative polymerase chain reac- tion. The geometric mean of the gametocyte density, and weighted arithmetic mean of the gametocytes sex ratio were estimated. Results Overall, 23.5% (110/467) of the participants tested positive for malaria parasites, with the majority of posi- tives (> 92%) being Plasmodium falciparum. The overall gametocytaemia was 5.6%, with a percent positivity of 6.8% (13/192), 6.2% (4/65) and 4.3% (9/210), in children, adolescents, and adults, respectively. The geometric mean gameto- cyte density (gametocytes/μL) was greater in adults (124.6) than in children (71.7) and adolescents (50.5). Regression analysis revealed that gametocytes were more likely to be present among male participants than among female par- ticipants [ORa: 2.79 (95% CI: 1.19 – 6.59) p = 0.019]. The gametocyte sex ratio in children and adult gametocyte carriers was similar but greater than that in adolescents. Conclusion The observed gametocyte densities and distribution across age groups suggest the need for malaria transmission-blocking interventions to target all populations in heterogeneous transmission settings. The implication of targeting only children may leave residual malaria transmission and reinfection from the left-out groups
PRONet Duo insecticide-treated net incorporated with chlorfenapyr and bifenthrin is superior to Interceptor® G2 nets against pyrethroid-resistant Anopheles gambiae sensu lato: a randomized experimental hut trial in Côte d’Ivoire and Tanzania using non-inferiority design
(Frontiers, 2025-03-14) Assenga, Alphonce; Ahoua Alou, Ludovic; Camara, Soromane; Koffi, Alphonsine; N’Guessan, Raphael; Kamande, Dismas; Ngonyani, Safina; Kibondo, Ummi; Odufuwa, Olukayode; Ntabaliba, Watson; Lekundayo, Ruth; Abilah, Faraji; Madumla, Edith; Muganga, Joseph; Moore, Jason; Moore, Sarah
Background: The widespread development of pyrethroid-resistant Anopheles populations, has reduced the efficacy of pyrethroid insecticide-treated nets (ITNs), hindering malaria control efforts. This study tested PRONet Duo, a new ITN with two active ingredients-bifenthrin and chlorfenapyr. Bifenthrin is a fluorinated pyrethroid that is highly stable and more slowly detoxified by pyrethroid-resistant mosquitoes. Chlorfenapyr disrupts cellular energy production. The efficacy of PRONet Duo was compared to Interceptor® G2, an alpha-cypermethrin and chlorfenapyr ITN with proven efficacy in malaria reduction. Methods: The study was conducted in two identical 9x9 Latin square experimental hut trials against wild free-flying Anopheles gambiae sensu lato in M’Bé, Côte d’Ivoire, and Lupiro, Tanzania using 18 experimental huts over 108 nights. The primary endpoint was the proportion of 72-hour mosquito mortality (M72) and the secondary endpoint was the proportion of mosquito blood-feeding. The study was done following World Health Organization guidelines. Data were analyzed using mixed-effect linear regression with a 7% margin of non-inferiority. Data were classified as non-inferior using delta and superior using the line of no difference. Results: PRONet Duo demonstrated a non-inferior and superior mosquito mortality compared to Interceptor® G2 in both study sites. In Côte d’Ivoire, the M72 of PRONet Duo was 84% [81,88], higher than that of Interceptor® G2 (72% [68,76], OR: 1.54 [1.27,1.88]) and it was superior to MAGNet® (30% [27,34], OR: 13.74 [11.35,16.63], p<0.0001). In Tanzania, M72 of PRONet Duo was 68% [62,73], higher than that induced by Interceptor® G2 (44% [40,49], Odds Ratio (OR): 2.77 [2.31, 3.33]), and MAGNet® (36% [32,41], OR:4.82 [4.06,5.72] p<0.0001). PRONet Duo also induced non-inferior and superior prevention of blood-feeding compared to Interceptor® G2, with less than 11% feeding success observed in either trial site. Conclusion: PRONet Duo ITNs are non-inferior and superior to the first-in-class Interceptor® G2 in terms of mosquito mortality and prevention of blood-feeding demonstrating the added benefit of bifenthrin for insecticide resistance management. Both chlorfenapyr nets offered superior mortality compared to the pyrethroid-only ITN. PRONet Duo offers an additional highly effective ITN for control of pyrethroid-resistant mosquitoes in malaria endemic regions.