Browsing by Author "Koenraadt, C. J. M."
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Item Anopheline and culicine mosquitoes are not repelled by surfaces treated with the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana(Parasites & Vectors, 2010) Mnyone, L. L.; Koenraadt, C. J. M.; Lyimo, I. N.; Mpingwa, M. W.; Takken, W.; Russell, T. L.Background: Entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, are promising bio-pesticides for application against adult malaria mosquito vectors. An understanding of the behavioural responses of mosquitoes towards these fungi is necessary to guide development of fungi beyond the ‘proof of concept’ stage and to design suitable intervention tools. Methods: Here we tested whether oil-formulations of the two fungi could be detected and avoided by adult Anopheles gambiae s.s., Anopheles arabiensis and Culex quinquefasciatus. The bioassays used a glass chamber divided into three compartments (each 250 × 250 × 250 mm): release, middle and stimulus compartments. Netting with or without fungus was fitted in front of the stimulus compartment. Mosquitoes were released and the proportion that entered the stimulus compartment was determined and compared between treatments. Treatments were untreated netting (control 1), netting with mineral oil (control 2) and fungal conidia formulated in mineral oil evaluated at three different dosages (2 × 1010, 4 × 1010 and 8 × 1010 conidia m-2). Results: Neither fungal strain was repellent as the mean proportion of mosquitoes collected in the stimulus compartment did not differ between experiments with surfaces treated with and without fungus regardless of the fungal isolate and mosquito species tested. Conclusion: Our results indicate that mineral-oil formulations of M. anisopliae and B. bassiana were not repellent against the mosquito species tested. Therefore, both fungi are suitable candidates for the further development of tools that aim to control host-seeking or resting mosquitoes using entomopathogenic fungi.Item Exploiting the behaviour of wild malaria vectors to achieve high infection with fungal biocontrol agents(BioMed Central, 2012) Mnyone, L. L.; Lyimo, I. N.; Lwetoijera, D. W.; Mpingwa, M. W.; Nchimbi, N.; Hancock, P. A.; Russell, T. L.; Kirby, M. J.; Takken, W.; Koenraadt, C. J. M.Control of mosquitoes that transmit malaria has been the mainstay in the fight against the disease, but alternative methods are required in view of emerging insecticide resistance. Entomopathogenic fungi are candidate alternatives, but to date, few trials have translated the use of these agents to field-based evaluations of their actual impact on mosquito survival and malaria risk. Mineral oil-formulations of the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana were applied using five different techniques that each exploited the behaviour of malaria mosquitoes when entering, host-seeking or resting in experimental huts in a malaria endemic area of rural Tanzania. Results: Survival of mosquitoes was reduced by 39-57% relative to controls after forcing upward house-entry of mosquitoes through fungus treated baffles attached to the eaves or after application of fungus-treated surfaces around an occupied bed net (bed net strip design). Moreover, 68 to 76% of the treatment mosquitoes showed fungal growth and thus had sufficient contact with fungus treated surfaces. A population dynamic model of malaria-mosquito interactions shows that these infection rates reduce malaria transmission by 75-80% due to the effect of fungal infection on adult mortality alone. The model also demonstrated that even if a high proportion of the mosquitoes exhibits outdoor biting behaviour, malaria transmission was still significantly reduced. Conclusions: Entomopathogenic fungi strongly affect mosquito survival and have a high predicted impact on malaria transmission. These entomopathogens represent a viable alternative for malaria control, especially if they are used as part of an integrated vector management strategy.Item Infection of Anopheles gambiae mosquitoes with entomopathogenic fungi: effect of host age and blood-feeding status(PMC / Springer, 2010-09) Mnyone, L. L.; Kirby, M. J.; Mpingwa, M. W.; Lwetoijera, D. W.; Knols, B. G. J.; Takken, W.; Koenraadt, C. J. M.; Russell, T. L.Physiological characteristics of insects can influence their susceptibility to fungal infection of which age and nutritional status are among the most important. An understanding of host–pathogen interaction with respect to these physiological characteristics of the host is essential if we are to develop fungal formulations capable of reducing malaria transmission under field conditions. Here, two independent bioassays were conducted to study the effect of age and blood-feeding status on fungal infection and survival of Anopheles gambiae s.s. Giles. Mosquitoes were exposed to 2×1010 conidia m−2 of oil-formulated Metarhizium anisopliae ICIPE-30 and of Beauveria bassiana I93-825, respectively, and their survival was monitored daily. Three age groups of mosquitoes were exposed, 2–4, 5–8, and 9–12 days since emergence. Five groups of different feeding status were exposed: non-blood-fed, 3, 12, 36, and 72 h post-blood feeding. Fungal infection reduced the survival of mosquitoes regardless of their age and blood-feeding status. Although older mosquitoes died relatively earlier than younger ones, age did not tend to affect mosquito susceptibility to fungal infection. Nonblood-fed mosquitoes were more susceptible to fungus infection compared to all categories of blood-fed mosquitoes, except for those exposed to B. bassiana 72 h postblood feeding. In conclusion, formulations of M. anisopliae and B. bassiana can equally affect mosquitoes of different age classes, with them being relatively more susceptible to fungus infection when non-blood-fed.