Arega Tsegaye1,2,3, Assalif Demissew4,5,6, Dawit Hawaria5,7,6, Hallelujah Getachew5,8,6, Kassahun Habtamu9,6,10, Abebe Asale11, Guiyun Yan12, Delenasaw Yewhalaw5,6. 1. Department of Biology, College of Natural Science, Jimma University, Jimma, Ethiopia. 2003arega@gmail.com. 2. School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia. 2003arega@gmail.com. 3. Tropical and Infectious Diseases Research Center (TIDRC), Jimma University, Jimma, Ethiopia. 2003arega@gmail.com. 4. Department of Medical Laboratory Sciences, College of Medicine and Health Sciences, Ambo University, Ambo, Ethiopia. 5. School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia. 6. Tropical and Infectious Diseases Research Center (TIDRC), Jimma University, Jimma, Ethiopia. 7. School of Public Health, Hawassa University, Hawassa, Ethiopia. 8. Department of Medical Laboratory Sciences, Arbaminch College of Health Sciences, Arbaminch, Ethiopia. 9. Department of Medical Laboratory Sciences, Menelik II College of Medicine and Health Science, Kotebe University of Education, Addis Ababa, Ethiopia. 10. Department of Microbial, Cellular & Molecular Biology, Addis Ababa University, Addis Ababa, Ethiopia. 11. International Centre of Insect Physiology and Ecology (ICEPE), LRI Campus, Gurd Shola, Addis Ababa, Ethiopia. 12. Program in Public Health, University of California at Irvine, Irvine, CA, 92697, USA.
Abstract
BACKGROUND: Insecticide-based vector control interventions in combination with case management with artemisinin-based combination therapy has reduced malaria incidence and prevalence worldwide. Current control methods focus on the primary malaria vectors, Anopheles gambiae sensu lato (s.l.) and the An. funestus group; however, the impact of secondary and suspected vectors has been either sidelined or received limited attention. Defining the susceptibility of secondary, suspected vector species to different parasites in time and space is essential for efficient malaria control and elimination programs. The aim of this study was to assess the susceptibility of An. gambiae s.l., An. coustani complex and An. pharoensis to Plasmodium vivax and P. falciparum infection in Ethiopia. METHODS: Larvae of Anopheles spp. were collected from different aquatic habitats and reared to adults under laboratory conditions, with the temperature and humidity maintained at 27 ± 1 °C and 75 ± 5%, respectively. Adult female mosquitoes were identified to species as An. gambiae s.l., An. coustani complex and An. pharoensis. Females of these three Anopheles spp. were allowed to feed in parallel feeding assays on infected blood containing the same gametocytes isolated from P. falciparum and P. vivax gametocyte-positive patients by indirect membrane feeding assays. All blood-fed mosquitoes were held under laboratory conditions. After 7 days, all surviving mosquitoes were dissected to detect mid-gut oocyst and enumerated under a microscope. RESULTS: Of 5915 female Anopheles mosquitoes exposed to gametocyte-infected blood, 2106 (35.6%)s fed successfully in the 32 independent infection experiments. There was a significant variation in feeding rates among An. gambiae s.l., An. pharoensis and An. coustani complex (G-test = 48.43, P = 3.049e-11). All three exposed mosquito species were receptive to P. vivax and P. falciparum infection development. The percentage of infected mosquitoes following feeding on an infected blood meal was significantly different among species (G-test = 6.49, P = 0.03886). The median infection intensity (II) for An. coustani complex, An. gambiae s.l. and An. pharoensis was 1.16, 2.00 and 1.25, respectively. Although the proportion of infected mosquitoes significantly differed in terms of II, infection rate (IR) and mean oocyst density among the species, mean oocyst density and IR were highly correlated with gametocyte density in all tests (P < 0.001). CONCLUSION: Primary, secondary and suspected vectors were experimentally susceptible to both P. vivax and P. falciparum infection. An effective malaria elimination program might include surveillance and control tools which target secondary and suspected vectors that might play an outdoor transmission role, possibly resulting in reduced focal malaria transmission. Comparison of the three species' mean infection rates with standard deviation.
BACKGROUND: Insecticide-based vector control interventions in combination with case management with artemisinin-based combination therapy has reduced malaria incidence and prevalence worldwide. Current control methods focus on the primary malaria vectors, Anopheles gambiae sensu lato (s.l.) and the An. funestus group; however, the impact of secondary and suspected vectors has been either sidelined or received limited attention. Defining the susceptibility of secondary, suspected vector species to different parasites in time and space is essential for efficient malaria control and elimination programs. The aim of this study was to assess the susceptibility of An. gambiae s.l., An. coustani complex and An. pharoensis to Plasmodium vivax and P. falciparum infection in Ethiopia. METHODS: Larvae of Anopheles spp. were collected from different aquatic habitats and reared to adults under laboratory conditions, with the temperature and humidity maintained at 27 ± 1 °C and 75 ± 5%, respectively. Adult female mosquitoes were identified to species as An. gambiae s.l., An. coustani complex and An. pharoensis. Females of these three Anopheles spp. were allowed to feed in parallel feeding assays on infected blood containing the same gametocytes isolated from P. falciparum and P. vivax gametocyte-positive patients by indirect membrane feeding assays. All blood-fed mosquitoes were held under laboratory conditions. After 7 days, all surviving mosquitoes were dissected to detect mid-gut oocyst and enumerated under a microscope. RESULTS: Of 5915 female Anopheles mosquitoes exposed to gametocyte-infected blood, 2106 (35.6%)s fed successfully in the 32 independent infection experiments. There was a significant variation in feeding rates among An. gambiae s.l., An. pharoensis and An. coustani complex (G-test = 48.43, P = 3.049e-11). All three exposed mosquito species were receptive to P. vivax and P. falciparum infection development. The percentage of infected mosquitoes following feeding on an infected blood meal was significantly different among species (G-test = 6.49, P = 0.03886). The median infection intensity (II) for An. coustani complex, An. gambiae s.l. and An. pharoensis was 1.16, 2.00 and 1.25, respectively. Although the proportion of infected mosquitoes significantly differed in terms of II, infection rate (IR) and mean oocyst density among the species, mean oocyst density and IR were highly correlated with gametocyte density in all tests (P < 0.001). CONCLUSION: Primary, secondary and suspected vectors were experimentally susceptible to both P. vivax and P. falciparum infection. An effective malaria elimination program might include surveillance and control tools which target secondary and suspected vectors that might play an outdoor transmission role, possibly resulting in reduced focal malaria transmission. Comparison of the three species' mean infection rates with standard deviation.
Authors: Jennifer Keiser; Marcia Caldas De Castro; Michael F Maltese; Robert Bos; Marcel Tanner; Burton H Singer; Jürg Utzinger Journal: Am J Trop Med Hyg Date: 2005-04 Impact factor: 2.345
Authors: Christen M Fornadel; Laura C Norris; Veronica Franco; Douglas E Norris Journal: Vector Borne Zoonotic Dis Date: 2010-12-13 Impact factor: 2.133
Authors: Márcia A Alexandre; Cynthia O Ferreira; André M Siqueira; Belisa L Magalhães; Maria Paula G Mourão; Marcus V Lacerda; Maria das Gracas C Alecrim Journal: Emerg Infect Dis Date: 2010-10 Impact factor: 6.883