Browsing by Author "Kobe, Dickson"

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Estimating the hole surface area of insecticide-treated nets using image analysis, manual hole counting and exact hole measurements
(BMC, 2025-03-14) Mbuba, Emmanuel; Mañas‑Chavernas, Natalia; Moore, Sarah; Ruzige, Philipo; Kobe, Dickson; Moore, Jason; Philipo, Rose; Kisoka, Noela; Pontiggia, Gianpaolo; Chacky, Frank; Mwalimu, Charles; Cattin, Philippe; Wolleb, Julia; Sandkuehler, Robin; Ross, Amanda
Background The physical integrity of insecticidal‑treated nets (ITNs) is important for creating a barrier against host seeking mosquitoes and, therefore, influences people’s perception of the net’s effectiveness and their willingness to use it. Monitoring the physical integrity of ITNs over time provides information for replenishment schedules and purchasing decisions. Currently, the assessment of physical integrity of ITNs is conducted by manually counting holes and estimating their size to class the net as functional or not. This approach is laborious to routinely conduct during field surveys of ITNs. Automated image analysis may provide a rapid assessment of the physical integrity of ITNs but it is not known if the images can capture sufficient information. As a first step, this study aimed to assess the agreement between estimated hole surface areas derived from (1) manually segmented images, (2) manual hole counting compared to (3) ground truth obtained by calibrated close‑up shots of individual holes. Methods The physical integrity of 75 ITNs purposely selected from an ongoing study was assessed by manual hole counting, image analysis and ground truth. For the image analysis, a graphical user interface was developed and used for the segmentation of holes visible in photographs taken from each side of the net. The hole surface area was then computed from this data. The agreement between the estimates from image analysis and manual hole counting was compared to the ground truth using the Bland–Altman method. Results There was substantial agreement between the manually segmented image analysis estimates and the ground truth hole surface areas. The overall bias was small, with a mean ratio of the hole surface area from image analysis to the ground truth of 0.70, and the 95% limits of agreement ranging from 0.35 to 1.38. Manual hole counting underestimated the hole surface area compared to the ground truth, particularly among nets with holes above 10 cm in diameter. Conclusion Images coupled with manual segmentation contain sufficient information to calculate hole surface area. This lays the groundwork for incorporating automatic hole detection, and then assessing whether this method will offer a fast and objective method for routine assessment of physical integrity of ITNs. While the WHO
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.