Little is known about the transmission dynamics of human malaria and other vector-borne diseases,... more Little is known about the transmission dynamics of human malaria and other vector-borne diseases, partly because of the limited availability and distribution of appropriate tools for quantifying human-mosquito contact rates. Recent developments in molecular biology have allowed a significant increase in the efficacy and reliability of bloodmeal identification, and DNA-based molecular markers are now being harnessed for typing arthropod bloodmeals. The extent to which these markers have been used for analysis of mosquito bloodmeals and the potential they might have for the future is discussed, and the contributions that the advent of PCR has made are examined here.
On-host behaviour of Rhipicephalus appendiculatus was studied in the field in Bungoma County in K... more On-host behaviour of Rhipicephalus appendiculatus was studied in the field in Bungoma County in Kenya to evaluate the putative repellent effects of essential oils of Tagetes minuta and Tithonia diversifolia at its predilection feeding site. Oils of both plants caused a disruption of orientation, movement and attachment behaviour of ticks. More ticks dropped off in the treatments with the two essential oils than with the control. Treating the ear pinna with the essential oil of T. minuta caused the highest percentage of ticks to drop off the host body. No tick reached the ear pinna treated with the essential oil of T. minuta and up to 30% of ticks (from the forehead release site) reached the ear base. When the ear pinna was treated with the essential oil of T. diversifolia, one tick reached the ear pinna and up to 40% of ticks (from the dewlap release site) reached the ear base. The results show that T. minuta repels ticks more strongly than T. diversifolia. However, both essential oils offer possibilities for exploitation of potentially effective and environmentally acceptable tools for on-host tick control.
Background Identification of malaria vectors is an important exercise that can result in the depl... more Background Identification of malaria vectors is an important exercise that can result in the deployment of targeted control measures and monitoring the susceptibility of the vectors to control strategies. Although known to possess distinct biting behaviours and habitats, the African malaria vectors Anopheles gambiae and Anopheles arabiensis are morphologically indistinguishable and are known to be discriminated by molecular techniques. In this paper, Raman spectroscopy is proposed to complement the tedious and time-consuming Polymerase Chain Reaction (PCR) method for the rapid screening of mosquito identity. Methods A dispersive Raman microscope was used to record spectra from the legs (femurs and tibiae) of fresh anaesthetized laboratory-bred mosquitoes. The scattered Raman intensity signal peaks observed were predominantly centered at approximately 1400 cm− 1, 1590 cm− 1, and 2067 cm− 1. These peaks, which are characteristic signatures of melanin pigment found in the insect cuticl...
Accurate identification of disease vectors is crucial when collecting epidemiological data. In mo... more Accurate identification of disease vectors is crucial when collecting epidemiological data. In mosquitoes, which transmit diseases like malaria, yellow fever, chikungunya, and dengue fever, identification mainly relies on the observation of external morphological features at different life cycle stages. This process is tedious and labor‐intensive. In this paper, the utility of Raman spectroscopy to discriminate and classify three mosquito species, namely, Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus, is presented. The three species were chosen to represent two subfamilies of medically important mosquitoes, that is, the Anophelinae and the Culicinae. The study is primarily a proof of concept on the potential of Raman spectroscopy in mosquito taxonomy. A dispersive Raman microscope was used to record spectra from the legs (femur and tibia) of fresh anesthetized laboratory‐bred mosquitoes. Broad peaks centered around 1400, 1590, and 2060 cm−1 dominated the spectra. Thes...
The American Journal of Tropical Medicine and Hygiene
ABSTRACT. Food insecurity, recurrent famine, and poverty threaten the health of millions of Afric... more ABSTRACT. Food insecurity, recurrent famine, and poverty threaten the health of millions of African residents. Construction of dams and rural irrigation schemes is key to solving these problems. The sub-Saharan Africa International Center of Excellence for Malaria Research addresses major knowledge gaps and challenges in Plasmodium falciparum and Plasmodium vivax malaria control and elimination in malaria-endemic areas of Kenya and Ethiopia where major investments in water resource development are taking place. This article highlights progress of the International Center of Excellence for Malaria Research in malaria vector ecology and behavior, epidemiology, and pathogenesis since its inception in 2017. Studies conducted in four field sites in Kenya and Ethiopia show that dams and irrigation increased the abundance, stability, and productivity of larval habitats, resulting in increased malaria transmission and a greater disease burden. These field studies, together with hydrological...
The American Journal of Tropical Medicine and Hygiene
ABSTRACT. Malaria control programs in Africa encounter daunting challenges that hinder progressiv... more ABSTRACT. Malaria control programs in Africa encounter daunting challenges that hinder progressive steps toward elimination of the disease. These challenges include widespread insecticide resistance in mosquito vectors, increasing outdoor malaria transmission, lack of vector surveillance and control tools suitable for outdoor biting vectors, weakness in malaria surveillance, and an inadequate number of skilled healthcare personnel. Ecological and epidemiological changes induced by environmental modifications resulting from water resource development projects pose additional barriers to malaria control. Cognizant of these challenges, our International Center of Excellence for Malaria Research (ICEMR) works in close collaboration with relevant government ministries and agencies to align its research efforts with the objectives and strategies of the national malaria control and elimination programs for the benefit of local communities. Our overall goal is to assess the impact of water ...
Background: Behavioural responses of mosquito vectors to insecticide-treated materials are critic... more Background: Behavioural responses of mosquito vectors to insecticide-treated materials are critical aspects of disease control and for insecticide resistance management. Physiological resistance to insecticides may change mosquitoes’ behavioural response to insecticide-treated materials such as bed nets. Methods: Using free-flying bioassay conducted in cubic-shape cages with different net materials on different sides of the cage, we examined the behavioural responses of insecticide-resistant (Bungoma strain) and susceptible (Kisumu strain) Anopheles gambiae sensu stricto mosquitoes to different types of long-lasting insecticidal nets (LLINs) including the piperonyl butoxide treated (PBO) LLIN using untreated nets as control. We conducted video tracking of mosquito flying paths and analysed landing attempts, resting preference and resting duration on treated and untreated netting materials. Kisumu susceptible strain (An. gambiae s.s) was used as a control.Results: We found that for b...
Background The gold standard for diagnosing Plasmodium falciparum infection is microscopic examin... more Background The gold standard for diagnosing Plasmodium falciparum infection is microscopic examination of Giemsa-stained peripheral blood smears. The effectiveness of this procedure for infection surveillance and malaria control may be limited by a relatively high parasitaemia detection threshold. Persons with microscopically undetectable infections may go untreated, contributing to ongoing transmission to mosquito vectors. The purpose of this study was to determine the magnitude and determinants of undiagnosed submicroscopic P. falciparum infections in a rural area of western Kenya. Methods A health facility-based survey was conducted, and 367 patients seeking treatment for symptoms consistent with uncomplicated malaria in Homa Bay County were enrolled. The frequency of submicroscopic P. falciparum infection was measured by comparing the prevalence of infection based on light microscopic inspection of thick blood smears versus real-time polymerase chain reaction (RT-PCR) targeting ...
Little is known about the transmission dynamics of human malaria and other vector-borne diseases,... more Little is known about the transmission dynamics of human malaria and other vector-borne diseases, partly because of the limited availability and distribution of appropriate tools for quantifying human-mosquito contact rates. Recent developments in molecular biology have allowed a significant increase in the efficacy and reliability of bloodmeal identification, and DNA-based molecular markers are now being harnessed for typing arthropod bloodmeals. The extent to which these markers have been used for analysis of mosquito bloodmeals and the potential they might have for the future is discussed, and the contributions that the advent of PCR has made are examined here.
On-host behaviour of Rhipicephalus appendiculatus was studied in the field in Bungoma County in K... more On-host behaviour of Rhipicephalus appendiculatus was studied in the field in Bungoma County in Kenya to evaluate the putative repellent effects of essential oils of Tagetes minuta and Tithonia diversifolia at its predilection feeding site. Oils of both plants caused a disruption of orientation, movement and attachment behaviour of ticks. More ticks dropped off in the treatments with the two essential oils than with the control. Treating the ear pinna with the essential oil of T. minuta caused the highest percentage of ticks to drop off the host body. No tick reached the ear pinna treated with the essential oil of T. minuta and up to 30% of ticks (from the forehead release site) reached the ear base. When the ear pinna was treated with the essential oil of T. diversifolia, one tick reached the ear pinna and up to 40% of ticks (from the dewlap release site) reached the ear base. The results show that T. minuta repels ticks more strongly than T. diversifolia. However, both essential oils offer possibilities for exploitation of potentially effective and environmentally acceptable tools for on-host tick control.
Background Identification of malaria vectors is an important exercise that can result in the depl... more Background Identification of malaria vectors is an important exercise that can result in the deployment of targeted control measures and monitoring the susceptibility of the vectors to control strategies. Although known to possess distinct biting behaviours and habitats, the African malaria vectors Anopheles gambiae and Anopheles arabiensis are morphologically indistinguishable and are known to be discriminated by molecular techniques. In this paper, Raman spectroscopy is proposed to complement the tedious and time-consuming Polymerase Chain Reaction (PCR) method for the rapid screening of mosquito identity. Methods A dispersive Raman microscope was used to record spectra from the legs (femurs and tibiae) of fresh anaesthetized laboratory-bred mosquitoes. The scattered Raman intensity signal peaks observed were predominantly centered at approximately 1400 cm− 1, 1590 cm− 1, and 2067 cm− 1. These peaks, which are characteristic signatures of melanin pigment found in the insect cuticl...
Accurate identification of disease vectors is crucial when collecting epidemiological data. In mo... more Accurate identification of disease vectors is crucial when collecting epidemiological data. In mosquitoes, which transmit diseases like malaria, yellow fever, chikungunya, and dengue fever, identification mainly relies on the observation of external morphological features at different life cycle stages. This process is tedious and labor‐intensive. In this paper, the utility of Raman spectroscopy to discriminate and classify three mosquito species, namely, Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus, is presented. The three species were chosen to represent two subfamilies of medically important mosquitoes, that is, the Anophelinae and the Culicinae. The study is primarily a proof of concept on the potential of Raman spectroscopy in mosquito taxonomy. A dispersive Raman microscope was used to record spectra from the legs (femur and tibia) of fresh anesthetized laboratory‐bred mosquitoes. Broad peaks centered around 1400, 1590, and 2060 cm−1 dominated the spectra. Thes...
The American Journal of Tropical Medicine and Hygiene
ABSTRACT. Food insecurity, recurrent famine, and poverty threaten the health of millions of Afric... more ABSTRACT. Food insecurity, recurrent famine, and poverty threaten the health of millions of African residents. Construction of dams and rural irrigation schemes is key to solving these problems. The sub-Saharan Africa International Center of Excellence for Malaria Research addresses major knowledge gaps and challenges in Plasmodium falciparum and Plasmodium vivax malaria control and elimination in malaria-endemic areas of Kenya and Ethiopia where major investments in water resource development are taking place. This article highlights progress of the International Center of Excellence for Malaria Research in malaria vector ecology and behavior, epidemiology, and pathogenesis since its inception in 2017. Studies conducted in four field sites in Kenya and Ethiopia show that dams and irrigation increased the abundance, stability, and productivity of larval habitats, resulting in increased malaria transmission and a greater disease burden. These field studies, together with hydrological...
The American Journal of Tropical Medicine and Hygiene
ABSTRACT. Malaria control programs in Africa encounter daunting challenges that hinder progressiv... more ABSTRACT. Malaria control programs in Africa encounter daunting challenges that hinder progressive steps toward elimination of the disease. These challenges include widespread insecticide resistance in mosquito vectors, increasing outdoor malaria transmission, lack of vector surveillance and control tools suitable for outdoor biting vectors, weakness in malaria surveillance, and an inadequate number of skilled healthcare personnel. Ecological and epidemiological changes induced by environmental modifications resulting from water resource development projects pose additional barriers to malaria control. Cognizant of these challenges, our International Center of Excellence for Malaria Research (ICEMR) works in close collaboration with relevant government ministries and agencies to align its research efforts with the objectives and strategies of the national malaria control and elimination programs for the benefit of local communities. Our overall goal is to assess the impact of water ...
Background: Behavioural responses of mosquito vectors to insecticide-treated materials are critic... more Background: Behavioural responses of mosquito vectors to insecticide-treated materials are critical aspects of disease control and for insecticide resistance management. Physiological resistance to insecticides may change mosquitoes’ behavioural response to insecticide-treated materials such as bed nets. Methods: Using free-flying bioassay conducted in cubic-shape cages with different net materials on different sides of the cage, we examined the behavioural responses of insecticide-resistant (Bungoma strain) and susceptible (Kisumu strain) Anopheles gambiae sensu stricto mosquitoes to different types of long-lasting insecticidal nets (LLINs) including the piperonyl butoxide treated (PBO) LLIN using untreated nets as control. We conducted video tracking of mosquito flying paths and analysed landing attempts, resting preference and resting duration on treated and untreated netting materials. Kisumu susceptible strain (An. gambiae s.s) was used as a control.Results: We found that for b...
Background The gold standard for diagnosing Plasmodium falciparum infection is microscopic examin... more Background The gold standard for diagnosing Plasmodium falciparum infection is microscopic examination of Giemsa-stained peripheral blood smears. The effectiveness of this procedure for infection surveillance and malaria control may be limited by a relatively high parasitaemia detection threshold. Persons with microscopically undetectable infections may go untreated, contributing to ongoing transmission to mosquito vectors. The purpose of this study was to determine the magnitude and determinants of undiagnosed submicroscopic P. falciparum infections in a rural area of western Kenya. Methods A health facility-based survey was conducted, and 367 patients seeking treatment for symptoms consistent with uncomplicated malaria in Homa Bay County were enrolled. The frequency of submicroscopic P. falciparum infection was measured by comparing the prevalence of infection based on light microscopic inspection of thick blood smears versus real-time polymerase chain reaction (RT-PCR) targeting ...
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Papers by Wolfgang Mukabana