Asymptomatic and submicroscopic Plasmodium infections in an area before and during integrated vector control in Homa Bay, western Kenya

Omondi, Collince J.; Otambo, Wilfred O.; Odongo, David; Ochwedo, Kevin O.; Otieno, Antony; Onyango, Shirley A.; Orondo, Pauline Winnie; Ondeto, Benyl M.; Lee, Ming‐Chieh; Zhong, Daibin; Kazura, James W.; Githeko, Andrew K.; Yan, Guiyun

doi:10.1186/s12936-022-04288-2

Cited by 7 publications

(4 citation statements)

References 51 publications

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“…Homa Bay (0°31′S, 34°27′E, 1,190 m a.s.l), in southern Homa Bay County, represents the Lake mesoendemic transmission level. Parasite prevalence in Homa Bay County was historically greater than 20%, but indoor residual spraying campaigns conducted by the Kenyan Ministry of Health and the U.S. President’s Malaria Initiative since 2018 have reduced transmission significantly [ 22 , 23 ]. At all sites, P. falciparum is the primary malaria parasite species.…”

Section: Methodsmentioning

confidence: 99%

Molecular surveillance of Kelch 13 polymorphisms in Plasmodium falciparum isolates from Kenya and Ethiopia

Jeang,

Zhong,

Lee

et al. 2024

Malar J

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Background Timely molecular surveillance of Plasmodium falciparum kelch 13 (k13) gene mutations is essential for monitoring the emergence and stemming the spread of artemisinin resistance. Widespread artemisinin resistance, as observed in Southeast Asia, would reverse significant gains that have been made against the malaria burden in Africa. The purpose of this study was to assess the prevalence of k13 polymorphisms in western Kenya and Ethiopia at sites representing varying transmission intensities between 2018 and 2022. Methods Dried blood spot samples collected through ongoing passive surveillance and malaria epidemiological studies, respectively, were investigated. The k13 gene was genotyped in P. falciparum isolates with high parasitaemia: 775 isolates from four sites in western Kenya (Homa Bay, Kakamega, Kisii, and Kombewa) and 319 isolates from five sites across Ethiopia (Arjo, Awash, Gambella, Dire Dawa, and Semera). DNA sequence variation and neutrality were analysed within each study site where mutant alleles were detected. Results Sixteen Kelch13 haplotypes were detected in this study. Prevalence of nonsynonymous k13 mutations was low in both western Kenya (25/783, 3.19%) and Ethiopia (5/319, 1.57%) across the study period. Two WHO-validated mutations were detected: A675V in three isolates from Kenya and R622I in four isolates from Ethiopia. Seventeen samples from Kenya carried synonymous mutations (2.17%). No synonymous mutations were detected in Ethiopia. Genetic variation analyses and tests of neutrality further suggest an excess of low frequency polymorphisms in each study site. Fu and Li’s F test statistic in Semera was 0.48 (P > 0.05), suggesting potential population selection of R622I, which appeared at a relatively high frequency (3/22, 13.04%). Conclusions This study presents an updated report on the low frequency of k13 mutations in western Kenya and Ethiopia. The WHO-validated R622I mutation, which has previously only been reported along the north-west border of Ethiopia, appeared in four isolates collected from eastern Ethiopia. The rapid expansion of R622I across Ethiopia signals the need for enhanced monitoring of the spread of drug-resistant P. falciparum parasites in East Africa. Although ACT remains currently efficacious in the study areas, continued surveillance is necessary to detect early indicators of artemisinin partial resistance.

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Section: Methodsmentioning

confidence: 99%

Molecular surveillance of Kelch 13 polymorphisms in Plasmodium falciparum isolates from Kenya and Ethiopia

Jeang,

Zhong,

Lee

et al. 2024

Malar J

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“…Vector control in the study area is done using ITNs and as of 2018 indoor residual spraying was introduced [ 27 ]. Significant progress in malaria reduction has been reported since the implementation of IRS [ 24 ].…”

Section: Methodsmentioning

confidence: 99%

“…Significant reductions in parasite prevalence have been reported in Homa Bay county, where malaria infections were previously above 20% [ 22 – 24 ]. The current control efforts using indoor residual spraying (IRS with an organophosphate insecticide) and long-lasting insecticide treated bed nets (LLIN) had significantly reduced malaria prevalence in the area.…”

Section: Introductionmentioning

confidence: 99%

Malaria diagnosis in rural healthcare facilities and treatment-seeking behavior in malaria endemic settings in western Kenya

Omondi

Odongo

Otambo

et al. 2023

PLOS Glob Public Health

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Accurate malaria diagnosis and timely treatment are requirements for effective management of the disease. However, treatment efficacy may be significantly reduced in resource-constrained healthcare facilities with poorly equipped laboratories and frequent drug and rapid diagnostic test kit (RDT) stock-outs. Furthermore, patient may avoid seeking treatment from such facilities. The study’s goal was to determine treatment-seeking behavior, malaria diagnosis and treatment quality, and likely treatment-seeking determinants in the local population. Passive case detection, which targeted all patients with suspected malaria cases, was conducted in ten public healthcare facilities over a three-month period. Monthly malaria cases, methods of diagnosis and antimalarial drug availability were assessed. A household-based survey was also carried out. Structured questionnaires were used to collect knowledge, attitude and practice (KAP) data from household heads. Malaria knowledge, treatment seeking behavior, and predictors of malaria treatment-seeking were all determined. Three of the seven dispensaries lacked a laboratory to conduct microscopy- diagnosis. These three dispensaries also experienced frequent RDT stock-outs, which resulted in depending on clinical signs as diagnosis for malaria. The majority of local residents with fever (50.3%) purchased antimalarial drugs from a chemist. About 37% of fever patients sought treatment at healthcare facility while the remaining 12.7% did not treat their fevers. In irrigated areas, 45.5% (46/64) of fever patients sought treatment at healthcare facilities, compared to 25% (18/64) in non-irrigated areas (p = 0.009). Most children aged below 5 who had fever (77.7%) were taken to healthcare facility for treatment compared to 31.4% of children aged 5–14 years or 20.9% of adults (0.0001). Predictors of treatment seeking included access to healthcare facility (OR = 16.23, 95% CI: 2.74–96.12), and ability to pay hospital bills (OR = 10.6, 95% CI: 1.97–57). Other factors that influenced health-seeking behavior included the severity of symptoms, the age of the patient and knowledge of malaria symptoms.

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“…The mean annual maximum temperature of the area is approximately 30 ℃ and the mean annual rainfall is around 1100 mm, with two rainy seasons. This area has been previously described in details by previous studies [ 12 , 18 – 20 ]. Briefly, the area has been modified by the construction of concrete-based irrigation canals to increase household food production.…”

Section: Methodsmentioning

confidence: 99%

Effect of predators on Anopheles arabiensis and Anopheles funestus larval survivorship in Homa Bay County Western Kenya

Orondo,

Zhou,

Ochwedo

et al. 2023

Malar J

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Background The rise of insecticide resistance against malaria vectors in sub-Saharan Africa has resulted in the need to consider other methods of vector control. The potential use of biological methods, including larvivorous fish, Bacillus thuringiensis israelensis (Bti) and plant shading, is sustainable and environmentally friendly options. This study examined the survivorship of Anopheles arabiensis and Anopheles funestus larvae and habitat productivity in four permanent habitat types in Homa Bay county, western Kenya. Methods Predator densities were studied in a laboratory setup while habitat productivity and larval survivorship was studied in field setup. Results Fish were observed as the most efficient predator (75.8% larval reduction rate) followed by water boatman (69%), and dragonfly nymph (69.5%) in predation rates. Lower predation rates were observed in backswimmers (31%), water beetles (14.9%), water spiders (12.2%), mayflies (7.3%), and tadpoles (6.9%). Increase in predator density in the field setup resulted in decreased Culex larval density. Larval and pupa age–specific distribution was determined and their survivorship curves constructed. Combined larvae (Stage I–IV) to pupa mortality was over 97% for An. arabiensis and 100% for An. funestus. The highest larval stage survival rate was from larval stages I to II and the lowest from larval stage IV to pupa. Stage-specific life tables indicated high mortality rates at every developmental stage, especially at the larval stage II and III. Conclusion Determination of the efficiency of various larval predators and habitat productivity will help with the correct identification of productive habitats and selection of complementary vector control methods through environmental management and/or predator introduction (for instance fish) in the habitats.

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Asymptomatic and submicroscopic Plasmodium infections in an area before and during integrated vector control in Homa Bay, western Kenya

Cited by 7 publications

References 51 publications

Molecular surveillance of Kelch 13 polymorphisms in Plasmodium falciparum isolates from Kenya and Ethiopia

Molecular surveillance of Kelch 13 polymorphisms in Plasmodium falciparum isolates from Kenya and Ethiopia

Malaria diagnosis in rural healthcare facilities and treatment-seeking behavior in malaria endemic settings in western Kenya

Effect of predators on Anopheles arabiensis and Anopheles funestus larval survivorship in Homa Bay County Western Kenya

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