Browsing by Author "Iwiru, Tereza"

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    High insecticide resistances levels in Anopheles gambiaes s.l. in northern Uganda and its relevance for future malaria control
    (BMC research notes, 2020) Echodu, Richard; Iga, Julius; Oyet, William Samuel; Mireji, Paul; Anena, Juliet; Onanyang, David; Iwiru, Tereza; Lutwama, Julius Julian; Auma Opiyo, Elizabeth
    The aim of the study was to determine the level of insecticide resistance and diversity in Anopheles mosquitoes in northern Uganda. Standard WHO insecticide susceptibility test assays were used to test for susceptibility to 0.5% malathion, 0.1% bendiocarb, 0.05% deltamethrin and 0.75% permethrin on 3–5 day old generation one progeny. We also screened for species diversity and knockdown resistance using PCR assay. Results: Anopheles gambiae s.s. is the predominant malaria vector in northern Uganda followed by An. arabiensis. An. gambiae s.s. was susceptible to malathion and bendiocarb with the observed mortality rate of 100% and 98–100% observed respectively while very high resistance was observed with deltamethrin and permethrin. Minimal KDReastern variant homozygous forms of 8.3% in An. gambiae s.s. were detected in Oyam district. In conclusion, this study confirms that An. gambiae s.s. females are susceptible to malathion and bendiocarb while high intensity of resistance was observed with deltamethrin and permethrin in the same area. Use of carbamate and organophosphate insecticides bendiocarb and malathion for indoor residual spraying activities in northern Uganda is highly recommended since high levels of pyrethroids resistance (deltamethrin and permethrin) was detected in the area.
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    High level of resistance in Anopheles arabiensis mosquito to pyrethroid insecticides from low malaria transmission zone of Moroto district, Karamoja region, Uganda: Implication for malaria vector control
    (Research Square, 2020) Echodu, Richard; Anena, Juliet; Iwiru, Tereza; Mireji, Paul; Malinga, Geoffrey Maxwell; Opiyo, Elizabeth A.; Iga, Julius; David, Onanyang
    Karamoja region of Uganda previously classified as low malaria transmission zone is currently experiencing significant upsurge of malaria incidences. Long lasting insecticidal nets (LLINs) impregnated with pyrethroids constitute a major tool for malaria control in this region. Efficacy of this tool can be hampered by resistance to the pyrethroids in the Anopheles mosquito vectors. Resistance status of these mosquitoes in this region is poorly understood, effectively hampering better understanding of the impact of LLINs in the malaria control initiative. Here, we assessed susceptibility of the Anopheles arabiensis from the region to deltamethrin, permethrin (pyrethroids) and pirirmiphos-methyl (organophosphate) insecticides. Method: We collected anopheline mosquito larvae from their natural habitats and reared them to adult emergence in situ field insectary in Karamoja region. We then identified them morphological to species level and exposed 513 emerge adult female An gambiae s.l., mosquitoes to diagnostic dosages of deltamethrin (0.05%), permethrin (0.75%) and pirimiphos-methyl (0.25%) pyrethroids exposure using the standard WHO insecticide susceptibility test assay. Synergic assays using piperonyl butoxide (PBO) were done to check for the involvement of detoxification enzymes in pyrethroid resistant populations. We then screened for knockdown resistance (KDR) and mosquito species diversity using Polymerase Chain Reaction (PCR). Results: Majority (96%) of the mosquitoes we sampled were identified as An. arabiensis and 4% as An. gambiae sensu stricto. We observed cross-resistance to both deltamethrin (11.9%) and permethrin (47%) but susceptibility (100% mortality) to pirimiphos-methyl in An. arabiensis. The pre-exposure to PBO ameliorated the resistance to both pyrethroids. We detected homozygous KDR -eastern variant in 1.8 and 50% of the An. arabiensis and An. gambiae s.s. respectively. Conclusion: Anopheles arabiensis and An. gambiae s.s. are the malaria vector in Karamoja region with An. arabiensis predominating. Both species are susceptible to pirimiphos-methyl but resistant to both deltamethrin and permethrin, through a metabolic process (phenotype). Mosquotoes with genetic (kdr) mutations for resistance were minimal and hence have minimal contribution to the pyrethroid resistance profile. An. arabiensis can thus be controled in Karamoja region using deltamethrin and/or permethrin impregnated mosquito nets integrated with PBO and/or through indoor residual spraying of sprayable human dwellings with pirimiphos-methyl.
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    Household Predictors of Incidence of Malaria in Northern Uganda: Its Implication for Future Malaria Control
    (Research Square, 2020) Echodu, Richard; Oyet, William Sam; Iwiru, Tereza; Apili, Felister; Lutwama, Julius Julian; Auma Opiyo, Elizabeth; Otim, Ochan
    Use of indoor residual spraying (IRS), long-lasting insecticidal nets (LLINS) and treatment with artemisinin-based combination therapy (ACT) have been greatly promoted in northern Uganda but the region still records highest number of malaria cases with prevalence up to 63%. This study assesses household predicators of malaria in the region and its impact on incidence of malaria at household levels. Methods: A cross-sectional study was conducted in four districts of Gulu, Oyam, Kitgum and Agago covering sixteen known hyper-endemics villages with high malaria burden in northern Uganda. In total, 193 households were surveyed. Data was collected through pre-tested structured questionnaires and systematically coded and analyzed using R software. Results: Women headed 58% of the 193 households surveyed. Six hundred and five (605) individuals were declared to have spent a night in the 193 households surveyed. Nighttime is when mosquitoes mostly gain access to victims in the study area. On average, there were two bed nets per household and out of the 605 individuals declared, 502 502 (86%) spent the night prior to interview under a bed net. Despite this effort, these households still reported malaria incidences in the last three months. Overall, children were prone to malaria more than adults by a ratio of 3:2, and in general, malaria incidences were strongly related to lack of bed nets or use thereof, and also linked directly to the number of individuals in a house. Households without bed nets controlled malaria by means of IRS in combination with closing doors (with the hope of keeping mosquitos at bay), draining stagnant water pool where mosquitos lay their eggs, trimming mosquito covers (grass) around homestead and/or receiving treatment after malaria incidences. When given a choice between insecticides (IRS) and treated bed nets, 1 in 3 households preferred treated bed nets. At the same time, bed nets were perceived unnecessary once IRS was applied. If true, the driving force to spraying insecticides indoor then becomes lack of a bed net. Conclusions: Household predicators of incidence of malaria in northern Uganda includes bed nets, use of treated bed nets, and indoor residual spraying with households not practicing any of these bearing the heaviest burden of malaria. Hierarchical clustering on principal components (HCPC) clusters households into four types in northern Uganda, 1) household that use bed nets and sleep in houses sprayed with insecticides; 2) households that use bed nets but no indoor residual spraying with insecticides; 3) households that have no bed nets and no indoor residual spraying; and 4) test bed nets before use. An opportunity therefore arises for tailoring malaria messages to fit each cluster of households given that clustering here appears not to be random. Malaria incidence was higher in children as compared to the adults that necessities having guidelines for management of interventions in local community setting.
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    Household Predictors of Malaria Episode in Northern Uganda: Its Implication for Future Malaria Control
    (Research Square, 2021) Echodu, Richard; Oyet, William Sam; Iwiru, Tereza; Apili, Felister; Lutwama, Julius Julian; Auma Opiyo, Elizabeth; Otim, Ochan
    Uses of indoor residual spraying (IRS), long-lasting insecticidal nets (LLINS) and treatment with artemisinin-based combination therapy (ACT) are greatly promoted in northern part of Uganda as mitigating strategies for malaria episodes. Unfortunately, the region still records the highest malaria prevalence of 63%. This study assesses household predicators of malaria in the region and their impact on malaria episodes at the household levels. Methods: A cross-sectional study was conducted in four districts of Gulu, Oyam, Kitgum and Agago covering sixteen villages in northern Uganda. In total, 193 households were surveyed. Data was collected through pre-tested structured questionnaire and systematically coded for analysis using R software. Results: Women headed 58% of the 193 households surveyed. Six hundred and five (605) individuals were declared to have spent the previous night in these households. On average, there were two bed nets per household and 502 (86%) spent the night prior to interview under a bed net. Overall, malaria episodes were strongly related to lack of bed nets or lack of use thereof, and directly linked to the number of individuals in a household. Children were prone to malaria more than adults by a ratio of 2:1. When given a choice between insecticides (IRS) and treated bed nets, 1 in 3 households preferred treated bed nets. At the same time, data suggests that bed nets were perceived unnecessary once IRS was applied. If true, the driving force to spraying insecticides indoor then becomes lack of a bed net. Conclusions: Household predicators of incidence of malaria in northern Uganda includes bed nets, use of treated bed nets, and indoor residual spraying with households not practicing any of these bearing the heaviest burden of malaria. Hierarchical clustering on principal components (HCPC) clusters households into four types in northern Uganda, 1) household that use bed nets and sleep in houses sprayed with insecticides; 2) households that use bed nets but no indoor residual spraying with insecticides; 3) households that have no bed nets and no indoor residual spraying; and 4) test bed nets before use. Malaria incidence was higher in children as compared to the adults.