Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Gametocytemia and Attractiveness of Plasmodium falciparum-Infected Kenyan Children to Anopheles gambiae Mosquitoes
    Busula, Annette O. ; Bousema, Teun ; Mweresa, Collins K. ; Masiga, Daniel ; Logan, James G. ; Sauerwein, Robert W. ; Verhulst, Niels O. ; Takken, Willem ; Boer, Jetske G. de - \ 2017
    The Journal of Infectious Diseases 216 (2017)3. - ISSN 0022-1899 - p. 291 - 295.
    chemical ecology - host finding - malaria transmission - olfactory behavior - vector control
    It has been suggested that Plasmodia manipulate their vertebrate hosts to enhance parasite transmission. Using a dual-choice olfactometer, we investigated the attraction of Anopheles gambiae to 50 Kenyan children (aged 5-12 years) who were naturally infected with Plasmodium falciparum or noninfected controls. Microscopic gametocyte carriers attracted almost 2 times more mosquitoes than children who were parasite free, harbored asexual stages, or had gametocytes at submicroscopic densities. By using highly sensitive stage-specific molecular methods to detect P. falciparum, we show that gametocytes-and not their noninfectious asexual progenitors-induce increased attractiveness of humans to mosquitoes. Our findings therefore support the parasite host manipulation hypothesis.
    Effects of fungal infection on feeding and survival of Anopheles gambiae (Diptera: Culicidae) on plant sugars
    Ondiaka, S.N. ; Masinde, E.W. ; Koenraadt, C.J.M. ; Takken, W. ; Mukabana, W.R. - \ 2015
    Parasites & Vectors 8 (2015). - ISSN 1756-3305 - 11 p.
    metarhizium-anisopliae - entomopathogenic fungus - culex-quinquefasciatus - schistocerca-gregaria - beauveria-bassiana - malaria transmission - vectorial capacity - food-consumption - desert locust - western kenya
    Background The entomopathogenic fungus Metarhizium anisopliae shows great promise for the control of adult malaria vectors. A promising strategy for infection of mosquitoes is supplying the fungus at plant feeding sites. Methods We evaluated the survival of fungus-exposed Anopheles gambiae mosquitoes (males and females) fed on 6% glucose and on sugars of Ricinus communis (Castor oil plant) and Parthenium hysterophorus (Santa Maria feverfew weed). Further, we determined the feeding propensity, quantity of sugar ingested and its digestion rate in the mosquitoes when fed on R. communis for 12 hours, one and three days post-exposure to fungus. The anthrone test was employed to detect the presence of sugar in each mosquito from which the quantity consumed and the digestion rates were estimated. Results Fungus-exposed mosquitoes lived for significantly shorter periods than uninfected mosquitoes when both were fed on 6% glucose (7 versus 37 days), R. communis (7 versus 18 days) and P. hysterophorus (5 versus 7 days). Significantly fewer male and female mosquitoes, one and three days post-exposure to fungus, fed on R. communis compared to uninfected controls. Although the quantity of sugar ingested was similar between the treatment groups, fewer fungus-exposed than control mosquitoes ingested small, medium and large meals. Digestion rate was significantly slower in females one day after exposure to M. anisopliae compared to controls but remained the same in males. No change in digestion rate between treatments was observed three days after exposure. Conclusions These results demonstrate that (a) entomopathogenic fungi strongly impact survival and sugar-feeding propensity of both sexes of the malaria vector An. gambiae but do not affect their potential to feed and digest meals, and (b) that plant sugar sources can be targeted as fungal delivery substrates. In addition, targeting males for population reduction using entomopathogenic fungi opens up a new strategy for mosquito vector control.
    Development and optimization of the Suna trap as a tool for mosquito monitoring and control
    Hiscox, A.F. ; Otieno, B. ; Kibet, A. ; Mweresa, C.K. ; Omusula, P. ; Geier, M. ; Rose, A. ; Mukabana, W.R. ; Takken, W. - \ 2014
    Malaria Journal 13 (2014). - ISSN 1475-2875 - 14 p.
    human-landing catches - cdc light-trap - anopheles-gambiae - carbon-dioxide - malaria transmission - field-evaluation - diptera-culicidae - equatorial-guinea - vector control - western kenya
    Background Monitoring of malaria vector populations provides information about disease transmission risk, as well as measures of the effectiveness of vector control. The Suna trap is introduced and evaluated with regard to its potential as a new, standardized, odour-baited tool for mosquito monitoring and control. Methods Dual-choice experiments with female Anopheles gambiae sensu lato in a laboratory room and semi-field enclosure, were used to compare catch rates of odour-baited Suna traps and MM-X traps. The relative performance of the Suna trap, CDC light trap and MM-X trap as monitoring tools was assessed inside a human-occupied experimental hut in a semi-field enclosure. Use of the Suna trap as a tool to prevent mosquito house entry was also evaluated in the semi-field enclosure. The optimal hanging height of Suna traps was determined by placing traps at heights ranging from 15 to 105 cm above ground outside houses in western Kenya. Results In the laboratory the mean proportion of An. gambiae s.l. caught in the Suna trap was 3.2 times greater than the MM-X trap (P <0.001), but the traps performed equally in semi-field conditions (P = 0.615). As a monitoring tool , the Suna trap outperformed an unlit CDC light trap (P <0.001), but trap performance was equal when the CDC light trap was illuminated (P = 0.127). Suspending a Suna trap outside an experimental hut reduced entry rates by 32.8% (P <0.001). Under field conditions, suspending the trap at 30 cm above ground resulted in the greatest catch sizes (mean 25.8 An. gambiae s.l. per trap night). Conclusions The performance of the Suna trap equals that of the CDC light trap and MM-X trap when used to sample An. gambiae inside a human-occupied house under semi-field conditions. The trap is effective in sampling mosquitoes outside houses in the field, and the use of a synthetic blend of attractants negates the requirement of a human bait. Hanging a Suna trap outside a house can reduce An. gambiae house entry and its use as a novel tool for reducing malaria transmission risk will be evaluated in peri-domestic settings in sub-Saharan Africa.
    Is aging raw cattle urine efficient for sampling Anopheles arabiensis Patton?
    Mahande, A.M. ; Mwang'onde, B.J. ; Msangi, S. ; Kimaro, E. ; Mnyone, L.L. ; Mazigo, H.D. ; Mahande, M.J. ; Kweka, E.J. - \ 2010
    Bmc Infectious Diseases 10 (2010). - ISSN 1471-2334
    malaria transmission - glossina-pallidipes - western kenya - northern tanzania - gambiae complex - vector control - diptera - culicidae - behavior - tsetse
    Background: To ensure sustainable routine surveillance of mosquito vectors, simple, effective and ethically acceptable tools are required. As a part of that, we evaluated the efficiency of resting boxes baited with fresh and aging cattle urine for indoor and outdoor sampling of An. arabiensis in the lower Moshi rice irrigation schemes. Methods: A cattle urine treatment and re-treatment schedule was used, including a box with a piece of cloth retreated with urine daily, and once after 3 and 7 day. Resting box with piece of black cloth not treated with urine was used as a control. Each treatment was made in pair for indoor and outdoor sampling. A 4 by 4 Latin square design was used to achieve equal rotation of each of the four treatments across the experimental houses. Sampling was done over a period of 6 months, once per week. Results: A total of 7871 mosquitoes were collected throughout the study period. 49.8% of the mosquitoes were collected from resting box treated with urine daily; 21.6% and 20.0% were from boxes treated 3 and 7 days respectively. Only 8.6% were from untreated resting box (control). The proportion collected indoors was similar to 2 folds greater than the outdoor. Of all mosquitoes, 12.3% were unfed, 4.1% full fed, 34.2% semi-gravid and 49.4% gravid. Conclusion: Fresh and decaying cattle urine odour baited resting boxes offer an alternative tool for sampling particularly semi-gravid and gravid An. arabiensis. Evaluation in low density seasons of An. arabiensis in different ecological settings remains necessary. This sampling method may be standardized for replacing human landing catch.
    Observations and model estimates of diurnal water temperature dynamics in mosquito breeding sites in western Kenya
    Paaijmans, K.P. ; Jacobs, A.F.G. ; Takken, W. ; Heusinkveld, B.G. ; Githeko, A.K. ; Dicke, M. ; Holtslag, A.A.M. - \ 2008
    Hydrological Processes 22 (2008)24. - ISSN 0885-6087 - p. 4789 - 4801.
    anopheles-gambiae diptera - aquatic stages - malaria transmission - culicidae larvae - land-cover - habitats - survival - highlands - reservoir - village
    Water temperature is an important determinant of the growth and development of malaria mosquito immatures. To gain a better understanding of the daily temperature dynamics of malaria mosquito breeding sites and of the relationships between meteorological variables and water temperature, three clear water pools (diameter × depth: 0·16 × 0·04, 0·32 × 0·16 and 0·96 × 0·32 m) were created in Kenya. Continuous water temperature measurements at various depths were combined with weather data collections from a meteorological station. The water pools were homothermic, but the top water layer differed by up to about 2 °C in temperature, depending on weather conditions. Although the daily mean temperature of all water pools was similar (27·4-28·1 °C), the average recorded difference between the daily minimum and maximum temperature was 14·4 °C in the smallest versus 7·1 °C in the largest water pool. Average water temperature corresponded well with various meteorological variables. The temperature of each water pool was continuously higher than the air temperature. A model was developed that predicts the diurnal water temperature dynamics accurately, based on the estimated energy budget components of these water pools. The air-water interface appeared the most important boundary for energy exchange processes and on average 82-89% of the total energy was gained and lost at this boundary. Besides energy loss to longwave radiation, loss due to evaporation was high; the average estimated daily evaporation ranged from 4·2 mm in the smallest to 3·7 mm in the largest water pool
    Zoophilic Anopheles quadriannulatus species B found in a human habitation in Ethiopia
    Pates, H.V. ; Takken, W. ; Curtis, C.F. ; Jamet, E. - \ 2006
    Annals of Tropical Medicine and Parasitology 100 (2006)2. - ISSN 0003-4983 - p. 177 - 179.
    gambiae complex - malaria transmission - arabiensis - plasmodium - mosquitos - behavior
    The presence of Plasmodium falciparum gametocytes in human blood increases the gravidity of Anopheles gambiae mosquitoes
    Ferguson, H.M. ; Gouagna, L.C. ; Obare, P. ; Read, A.F. ; Babiker, H. ; Githure, J.I. ; Beier, J.C. - \ 2005
    American Journal of Tropical Medicine and Hygiene 73 (2005)2. - ISSN 0002-9637 - p. 312 - 320.
    western kenya - yoelii-nigeriensis - aedes-aegypti - seasonal transmission - malaria transmission - egg development - body-size - infection - fecundity - stephensi
    We conducted a field study in an area of endemic malaria transmission in western Kenya to determine whether mosquitoes that feed on gametocyte-infected blood but do not become infected have reduced or enhanced fecundity in comparison to mosquitoes fed on uninfected blood. Fifteen paired membrane-feeding experiments were conducted in which two strains of Anopheles gambiae mosquitoes were simultaneously fed on either Plasmodium falciparum¿infected blood from children or uninfected control blood from adults. The presence of noninfecting gametocytes in blood increased the probability that An. gambiae would produce eggs after one blood meal by sixfold (odds ratio for control relative to infected blood group 0.16; 95% CI 0.10¿0.23). This result could not be explained by variation in blood meal size or hemoglobin content between hosts. When children cleared their infections, the difference in gravidity between mosquitoes fed on their blood and uninfected adults disappeared, suggesting this phenomenon is due to the presence of Plasmodium gametocytes in blood and not to host-specific factors such as age. This result was observed in two mosquito strains that differ in their innate fecundity, suggesting it may apply generally. To our knowledge, this is the first time that Plasmodium has been implicated as enhancing vector gravidity
    Effect of larval crowding on mating competitiveness of Anopheles gambiae mosquitoes
    Ng'habi, K.R. ; John, B. ; Nkwengulila, G. ; Knols, B.G.J. ; Killeen, G.F. ; Ferguson, H.M. - \ 2005
    Malaria Journal 4 (2005). - ISSN 1475-2875 - 9 p.
    genetically-modified mosquitos - aedes-aegypti diptera - treated bed nets - western kenya - adult size - malaria transmission - transgenic mosquitos - wing length - insecticide resistance - swarming behavior
    Background: The success of sterile or transgenic Anopheles for malaria control depends on their mating competitiveness within wild populations. Current evidence suggests that transgenic mosquitoes have reduced fitness. One means of compensating for this fitness deficit would be to identify environmental conditions that increase their mating competitiveness, and incorporate them into laboratory rearing regimes. Methods: Anopheles gambiae larvae were allocated to three crowding treatments with the same food input per larva. Emerged males were competed against one another for access to females, and their corresponding longevity and energetic reserves measured. Results: Males from the low-crowding treatment were much more likely to acquire the first mating. They won the first female approximately 11 times more often than those from the high-crowding treatment (Odds ratio = 11.17) and four times more often than those from the medium-crowding treatment (Odds ratio = 3.51). However, there was no overall difference in the total number of matings acquired by males from different treatments (p = 0.08). The survival of males from the low crowding treatment was lower than those from other treatments. The body size and teneral reserves of adult males did not differ between crowding treatments, but larger males were more likely to acquire mates than small individuals. Conclusion: Larval crowding and body size have strong, independent effects on the mating competitiveness of adult male An. gambiae. Thus manipulation of larval crowding during mass rearing could provide a simple technique for boosting the competitiveness of sterile or transgenic male mosquitoes prior to release
    The practical importance of permanent and semipermanent habitats for controlling aquatic stages of Anopheles gambiae sensu lato mosquitoes: operational observations from a rural town in western Kenya
    Fillinger, U. ; Sonye, G. ; Killeen, G.F. ; Knols, B.G.J. ; Becker, N. - \ 2004
    Tropical Medicine and International Health 9 (2004)12. - ISSN 1360-2276 - p. 1274 - 1289.
    entomologic inoculation rates - malaria transmission - larval habitats - culicidae - diptera - africa - vectors - area - prevalence - venezuela
    Control of aquatic-stage Anopheles is one of the oldest and most historically successful interventions to prevent malaria, but it has seen little application in Africa. Consequently, the ecology of immature afrotropical Anopheles has received insufficient attention. We therefore examined the population dynamics of African anopheline and culicine mosquitoes using operationally practicable techniques to examine the relative importance and availability of different larval habitats in an area of perennial malaria transmission in preparation for a pilot-scale larval control programme. The study was conducted in Mbita, a rural town on the shores of Lake Victoria in Western Kenya, over 20 months. Weekly larval surveys were conducted to identify the availability of stagnant water, habitat characteristics and larval densities. Adult mosquitoes were collected indoors at fortnightly intervals. Availability of aquatic habitats and abundance of mosquito larvae were directly correlated with rainfall. Adult mosquito densities followed similar patterns but with a time-lag of approximately 1 month. About 70% of all available habitats were man-made, half of them representing cement-lined pits. On average, 67% of all aquatic habitats on a given sampling date were colonized by Anopheles larvae, of which all identified morphologically were A. gambiae sensu lato. Natural and artificial habitats were equally productive over the study period and larval densities were positively correlated with presence of tufts of low vegetation and negatively with non-matted algal content. The permanence of a habitat had no significant influence on larval productivity. We conclude that A. gambiae is broadly distributed across a variety of habitat types, regardless of permanence. All potential breeding sites need to be considered as sources of malaria risk at any time of the year and exhaustively targeted in any larval control intervention.
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