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4 results on '"Simon M. Muriu"'

1. A prospective cohort study of Plasmodium falciparum malaria in three sites of Western Kenya

Author

Benyl M. Ondeto, Xiaoming Wang, Harrysone Atieli, Daibin Zhong, Guofa Zhou, Ming-Chieh Lee, Pauline Winnie Orondo, Kevin O. Ochwedo, Collince J. Omondi, Simon M. Muriu, David O. Odongo, Horace Ochanda, James Kazura, Andrew K. Githeko, and Guiyun Yan

Subjects
Malaria, Transmission, Resurgence, Plasmodium falciparum, Infectious and parasitic diseases, RC109-216
Abstract

Abstract Background Malaria in western Kenya is currently characterized by sustained high Plasmodial transmission and infection resurgence, despite positive responses in some areas following intensified malaria control interventions since 2006. This study aimed to evaluate long-term changes in malaria transmission profiles and to assess patterns of asymptomatic malaria infections in school children aged 5–15 years at three sites in western Kenya with heterogeneous malaria transmission and simultaneous malaria control interventions. Methods The study was conducted from 2018 to 2019 and is based on data taken every third year from 2005 to 2014 during a longitudinal parasitological and mosquito adult surveillance and malaria control programme that was initiated in 2002 in the villages of Kombewa, Iguhu, and Marani. Plasmodium spp. infections were determined using microscopy. Mosquito samples were identified to species and host blood meal source and sporozoite infections were assayed using polymerase chain reaction. Results Plasmodium falciparum was the only malaria parasite evaluated during this study (2018–2019). Asymptomatic malaria parasite prevalence in school children decreased in all sites from 2005 to 2008. However, since 2011, parasite prevalence has resurged by > 40% in Kombewa and Marani. Malaria vector densities showed similar reductions from 2005 to 2008 in all sites, rose steadily until 2014, and decreased again. Overall, Kombewa had a higher risk of infection compared to Iguhu (χ 2 = 552.52, df = 1, P

Published
2022
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2. Current status of insecticide resistance among malaria vectors in Kenya

Author

Benyl M. Ondeto, Christopher Nyundo, Luna Kamau, Simon M. Muriu, Joseph M. Mwangangi, Kiambo Njagi, Evan M. Mathenge, Horace Ochanda, and Charles M. Mbogo

Subjects
Insecticide resistance, Mechanism of resistance, Anopheles, Malaria, Kenya, Infectious and parasitic diseases, RC109-216
Abstract

Abstract Background Insecticide resistance has emerged as one of the major challenges facing National Malaria Control Programmes in Africa. A well-coordinated national database on insecticide resistance (IRBase) can facilitate the development of effective strategies for managing insecticide resistance and sustaining the effectiveness of chemical-based vector control measures. The aim of this study was to assemble a database on the current status of insecticide resistance among malaria vectors in Kenya. Methods Data was obtained from published literature through PubMed, HINARI and Google Scholar searches and unpublished literature from government reports, research institutions reports and malaria control programme reports. Each data source was assigned a unique identification code and entered into Microsoft Excel 2010 datasheets. Base maps on the distribution of insecticide resistance and resistance mechanisms among malaria vectors in Kenya were generated using ArcGIS Desktop 10.1 (ESRI, Redlands, CA, USA). Results Insecticide resistance status among the major malaria vectors in Kenya was reported in all the four classes of insecticides including pyrethroids, carbamates, organochlorines and organophosphates. Resistance to pyrethroids has been detected in Anopheles gambiae (s.s.), An. arabiensis and An. funestus (s.s.) while resistance to carbamates was limited to An. gambiae (s.s.) and An. arabiensis. Resistance to the organochlorine was reported in An. gambiae (s.s.) and An. funestus (s.s.) while resistance to organophosphates was reported in An. gambiae (s.l.) only. The mechanisms of insecticide resistance among malaria vectors reported include the kdr mutations (L 1014S and L 1014F) and elevated activity in carboxylesterase, glutathione S-transferases (GST) and monooxygenases. The kdr mutations L 1014S and L 1014F were detected in An. gambiae (s.s.) and An. arabiensis populations. Elevated activity of monooxygenases has been detected in both An. arabiensis and An. gambiae (s.s.) populations while the elevated activity of carboxylesterase and GST has been detected only in An. arabiensis populations. Conclusions The geographical maps show the distribution of insecticide resistance and resistance mechanisms among malaria vectors in Kenya. The database generated will provide a guide to intervention policies and programmes in the fight against malaria.

Published
2017
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3. Malaria vector bionomics and transmission in irrigated and non-irrigated sites in western Kenya

Author

Benyl M. Ondeto, Xiaoming Wang, Harrysone Atieli, Pauline Winnie Orondo, Kevin O. Ochwedo, Collince J. Omondi, Wilfred O. Otambo, Daibin Zhong, Guofa Zhou, Ming-Chieh Lee, Simon M. Muriu, David O. Odongo, Horace Ochanda, James Kazura, Andrew K. Githeko, and Guiyun Yan

Subjects
Adult, and promotion of well-being, Mosquito Control, Mycology & Parasitology, Mosquito Vectors, Microbiology, Rare Diseases, Anopheles, Animals, Humans, 2.2 Factors relating to the physical environment, Veterinary Sciences, Aetiology, Vector bionomics, Irrigation, 3.2 Interventions to alter physical and biological environmental risks, General Veterinary, Ecology, Vector density, General Medicine, Prevention of disease and conditions, Kenya, Malaria, Vector-Borne Diseases, Infectious Diseases, Good Health and Well Being, Medical Microbiology, Insect Science, Parasitology, Malaria transmission, Infection
Abstract

Irrigation not only helps to improve food security but also creates numerous water bodies for mosquito production. This study assessed the effect of irrigation on malaria vector bionomics and transmission in a semi-arid site with ongoing malaria vector control program. The effectiveness of CDC light traps in the surveillance of malaria vectors was also evaluated relative to the human landing catches (HLCs) method. Adult mosquitoes were sampled in two study sites representing irrigated and non-irrigated agroecosystems in western Kenya using a variety of trapping methods. The mosquito samples were identified to species and assayed for host blood meal source and Plasmodium spp. sporozoite infection using polymerase chain reaction. Anopheles arabiensis was the dominant malaria vector in the two study sites and occurred in significantly higher densities in irrigated study site compared to the non-irrigated study site. The difference in indoor resting density of An. arabiensis during the dry and wet seasons was not significant. Other species, including An. funestus, An. coustani, and An. pharoensis, were collected. The An. funestus indoor resting density was 0.23 in irrigated study site while almost none of this species was collected in the non-irrigated study site. The human blood index (HBI) for An. arabiensis in the irrigated study site was 3.44% and significantly higher than 0.00% for the non-irrigated study site. In the irrigated study site, the HBI of An. arabiensis was 3.90% and 5.20% indoor and outdoor, respectively. The HBI of An. funestus was 49.43% and significantly higher compared to 3.44% for An. arabiensis in the irrigated study site. The annual entomologic inoculation rate for An. arabiensis in the irrigated study site was 0.41 and 0.30 infective bites/person/year indoor and outdoor, respectively, whereas no transmission was observed in the non-irrigated study site. The CDC light trap performed consistently with HLC in terms of vector density. These findings demonstrate that irrigated agriculture may increase the risk of malaria transmission in irrigated areas compared to the non-irrigated areas and highlight the need to complement the existing malaria vector interventions with novel tools targeting the larvae and both indoor and outdoor biting vector populations. Graphical abstract

Published
2022

4. Larval density dependence in Anopheles gambiae s.s., the major African vector of malaria

Author

H. Charles J. Godfray, Simon M. Muriu, Tim Coulson, and Charles M. Mbogo

Subjects
media_common.quotation_subject, Field experiment, Anopheles gambiae, Zoology, Biology, Population density, Competition (biology), Article, Anopheles, parasitic diseases, Animals, Humans, Predator, Ecology, Evolution, Behavior and Systematics, media_common, Population Density, Larva, Ecology, fungi, biology.organism_classification, Insect Vectors, Malaria, Density dependence, Vector (epidemiology), Africa, Animal Science and Zoology
Abstract

Summary Anopheles gambiae sensu stricto is the most important vector of malaria in Africa although relatively little is known about the density-dependent processes determining its population size. Mosquito larval density was manipulated under semi-natural conditions using artificial larval breeding sites placed in the field in coastal Kenya; two experiments were conducted: one manipulating the density of a single cohort of larvae across a range of densities and the other employing fewer densities but with the treatments crossed with four treatments manipulating predator access. In the first experiment, larval survival, development rate and the size of the adult mosquito all decreased with larval density (controlling for block effects between 23% and 31% of the variance in the data could be explained by density). In the second experiment, the effects of predator manipulation were not significant, but again we observed strong density dependence in larval survival (explaining 30% of the variance). The results are compared with laboratory studies of A. gambiae larval competition and the few other studies conducted in the field, and the consequences for malaria control are discussed

Published
2016

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