Browsing by Author "Mnyone, L. L."

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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.
Does cattle milieu provide a potential point to target wild exophilic anopheles arabiensis (diptera: culicidae) with entomopathogenic fungus? a bioinsecticide zooprophylaxis strategy for vector control.
(Hindawi Publishing Corporation, 2012) Lyimo, I. N.; Ng'habi, K. R.; Mpingwa, M. W.; Daraja, A. A.; Mwasheshe, D. D.; Nchimbi, N. S.; Lwetoijera, D. W.; Mnyone, L. L.
Background. Anopheles arabiensis is increasingly dominating malaria transmission in Africa. The exophagy in mosquitoes threatens the effectiveness of indoor vector control strategies. This study aimed to evaluate the effectiveness of fungus against An. arabiensis when applied on cattle and their environments. Methods. Experiments were conducted under semi-field and small-scale field conditions within Kilombero valley. The semi-field reared females of 5-7 days old An. arabiensis were exposed to fungus-treated and untreated calf. Further, wild An. arabiensis were exposed to fungus-treated calves, mud-huts, and their controls. Mosquitoes were recaptured the next morning and proportion fed, infected, and survived were evaluated. Experiments were replicated three times using different individuals of calves. Results. A high proportion of An. arabiensis was fed on calves (>0.90) and become infected (0.94) while resting on fungus-treated mud walls than on other surfaces. However, fungus treatments reduced fecundity and survival of mosquitoes. Conclusion. This study demonstrates for the first time the potential of cattle and their milieu for controlling An. arabiensis. Most of An. arabiensis were fed and infected while resting on fungus-treated mud walls than on other surfaces. Fungus treatments reduced fecundity and survival of mosquitoes. These results suggest deployment of bioinsecticide zooprophylaxis against exophilic An. arabiensis.
Does cattle milieu provide a potential point to target wild exophilic anopheles arabiensis (Diptera: Culicidae) with entomopathogenic fungus? a bioinsecticide zooprophylaxis strategy for vector control.
(Hindawi Publishing Corporation, 2012) Lyimo, I. N.; Ng'habi, K. R.; Mpingwa, M. W.; Daraja, A. A.; Mwasheshe, D. D.; Nchimbi, N. S.; Lwetoijera, D. W.; Mnyone, L. L.
Background.Anophelesarabiensis isincreasinglydominatingmalariatransmissioninAfrica.Theexophagyinmosquitoesthreatens the eﬀectiveness of indoor vector control strategies. This study aimed to evaluate the eﬀectiveness of fungus against An. arabiensis when applied on cattle and their environments. Methods. Experiments were conducted under semi-ﬁeld and small-scale ﬁeld conditions within Kilombero valley. The semi-ﬁeld reared females of 5–7 days old An. arabiensis were exposed to fungus-treated and untreated calf. Further, wild An. arabiensis were exposed to fungus-treated calves, mud-huts, and their controls. Mosquitoes were recaptured the next morning and proportion fed, infected, and survived were evaluated. Experiments were replicated three times using diﬀerent individuals of calves. Results. A high proportion of An. arabiensis was fed on calves (>0.90) and become infected (0.94) while resting on fungus-treated mud walls than on other surfaces. However, fungus treatments reduced fecundity and survival of mosquitoes. Conclusion. This study demonstrates for the ﬁrst time the potential of cattle and their milieu for controlling An. arabiensis. Most ofAn. arabiensis were fed and infected while resting on fungus-treated mud walls than on other surfaces. Fungus treatments reduced fecundity and survival of mosquitoes. These results suggest deployment of bioinsecticide zooprophylaxis against exophilic An. arabiensis.
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.
An extra-domiciliary method of delivering entomopathogenic fungus, Metharizium anisopliae IP 46 for controlling adult populations of the malaria vector, Anopheles arabiensis
(BioMed Central, 2010-03-16) Lwetoijera, D. W; Sumaye, R. D.; Madumla, E. P.; Kavishe, D. R.; Mnyone, L. L.; Russell, T. L.; Okumu, F. O.
Fungal biopesticides have the potential to significantly reduce densities of malaria vectors as well as associated malaria transmission. In previous field trials, entomopathogenic fungus was delivered from within human dwellings, where its efficacy was limited by low infection rates of target mosquitoes, high costs of spraying fungus inside houses, and potential public health concerns associated with introducing fungal conidia inside houses. Here we have demonstrated that Metarhizium anisopliae IP 46, delivered within an extra-domiciliary odor-baited station (OBS), can infect and slowly-kill a high proportion of the wild adult malaria vector, Anopheles arabiensis which entered and exited the OBS. This study, carried out in rural Tanzania, showed that by using a concentration of 3.9 × 1010 conidia/m2, more than 95% of mosquitoes that flew in and out of the OBS died within 14 days postexposure. At least 86% infection of mosquito cadavers was recorded with a significant reduction in the probability of daily survival of exposed An. arabiensis in both treatments tested: low quantity of conidia (eave baffles plus one cotton panel; HR = 2.65, P < 0.0001) and high quantity of conidia (eave baffles plus two cotton panels; HR = 2.32, P < 0.0001). We conclude that high infection rates of entomopathogenic fungi on wild malaria vectors and possibly significant disruption of malaria transmission can be achieved if the fungus is delivered using optimally located outdoor odor-baited stations.
An extra-domiciliary method of delivering entomopathogenic fungus, Metharizium anisopliae IP 46 for controlling adult populations of the malaria vector, Anopheles arabiensis
(BioMed Central, 2010-03-16) Lwetoijera, D. W; Sumaye, R. D; Madumla, E. P.; Kavishe, D. R.; Mnyone, L. L.; Okumu, F. O.
Fungal biopesticides have the potential to significantly reduce densities of malaria vectors as well as associated malaria transmission. In previous field trials, entomopathogenic fungus was delivered from within human dwellings, where its efficacy was limited by low infection rates of target mosquitoes, high costs of spraying fungus inside houses, and potential public health concerns associated with introducing fungal conidia inside houses. Here we have demonstrated that Metarhizium anisopliae IP 46, delivered within an extra-domiciliary odor-baited station (OBS), can infect and slowly-kill a high proportion of the wild adult malaria vector, Anopheles arabiensis which entered and exited the OBS. This study, carried out in rural Tanzania, showed that by using a concentration of 3.9 × 1010 conidia/m2, more than 95% of mosquitoes that flew in and out of the OBS died within 14 days post-exposure. At least 86% infection of mosquito cadavers was recorded with a significant reduction in the probability of daily survival of exposed An. arabiensis in both treatments tested: low quantity of conidia (eave baffles plus one cotton panel; HR = 2.65, P < 0.0001) and high quantity of conidia (eave baffles plus two cotton panels; HR = 2.32, P < 0.0001). We conclude that high infection rates of entomopathogenic fungi on wild malaria vectors and possibly significant disruption of malaria transmission can be achieved if the fungus is delivered using optimally located outdoor odor-baited stations.
First report of Metarhizium anisopliae IP 46 pathogenicity in adult Anopheles gambiae s.s. and An. arabiensis (Diptera; Culicidae)
(BioMed Central, 2009-12-01) Mnyone, L. L.; Russell, T. L.; Lyimo, I. N.; Lwetoijera, D. W.; Kirby, M. J.; Luz, C.
The entomopathogenic fungus Metarhizium anisopliae isolate IP 46, originating from a soil sample collected in 2001 in the Cerrado of Central Brazil, was tested for its ability to reduce the survival of adult male and female Anopheles gambiae s.s. and An. arabiensis mosquitoes. A 6-h exposure to the fungus coated on test paper at a concentration of 3.3 × 106 conidia cm-2 reduced the daily survival of both mosquito species (HR = 3.14, p < 0.001), with higher risk of dying in An. gambiae s.s relative to An. arabiensis (HR = 1.38, p < 0.001). Fungal sporulation was observed in >95% of mosquito cadavers in the treatment groups. The results indicate that M. anisopliae IP 46 has the potential to be a bio-control agent for African malaria vector species, and is a suitable candidate for further research and development.
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.
Infection of the malaria mosquito, Anopheles gambiae, with two species of entomopathogenic fungi: effects of concentration, co-formulation, exposure time and persistence
(BioMed Central, 2009-12-23) Mnyone, L. L.; Kirby, M. J.; Lwetoijera, D. W.; Mpingwa, M. W.; Takken, W.; Russell, T. L.; Knols, B. G.
Entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana isolates have been shown to infect and reduce the survival of mosquito vectors. Methods Here four different bioassays were conducted to study the effect of conidia concentration, co-formulation, exposure time and persistence of the isolates M. anisopliae ICIPE-30 and B. bassiana I93-925 on infection and survival rates of female Anopheles gambiae sensu stricto. Test concentrations and exposure times ranged between 1 × 107 - 4 × 1010 conidia m-2 and 15 min - 6 h. In co-formulations, 2 × 1010 conidia m-2 of both fungus isolates were mixed at ratios of 4:1, 2:1, 1:1,1:0, 0:1, 1:2 and 1:4. To determine persistence, mosquitoes were exposed to surfaces treated 1, 14 or 28 d previously, with conidia concentrations of 2 × 109, 2 × 1010 or 4 × 1010. Results Mosquito survival varied with conidia concentration; 2 × 1010 conidia m-2 was the concentration above which no further reductions in survival were detectable for both isolates of fungus. The survival of mosquitoes exposed to single and co-formulated treatments was similar and no synergistic or additive effects were observed. Mosquitoes were infected within 30 min and longer exposure times did not result in a more rapid killing effect. Fifteen min exposure still achieved considerable mortality rates (100% mortality by 14 d) of mosquitoes, but at lower speed than with 30 min exposure (100% mortality by 9 d). Conidia remained infective up to 28 d post-application but higher concentrations did not increase persistence. Conclusion Both fungus isolates are effective and persistent at low concentrations and short exposure times.
Tools for delivering entomopathogenic fungi to malaria mosquitoes: effects of delivery surfaces on fungal efficacy and persistence
(BioMed Central, 2010) Mnyone, L. L.; Kirby, M. J.; Lwetoijera, D. W.; Mpingwa, M. W.; Simfukwe, E. T.; Knols, B. G. J.; Takken, W.; Russell, T. L.
To eliminate malaria, vector control programmes will need to incorporate novel tools to complement the use of insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS). Both ITNs and IRS are highly effective against anthropophagic and endophilic species, but their efficacy is threatened by emergence of resistance to synthetic insecticides [1,2]. Therefore, the growing demand of the global community for non-chemical control tools has refocused research objectives to address the practical aspects of biological control tools that have previously had limited uptake. Biological control tools have several advantages over chemical-insecticides. The most important ones include reduced risk of host resistance and minimal risk to the environment and living organisms [3,4]. Currently, a number of novel tools based on biological interactions are undergoing development including fungal, bacterial, viral and protozoan pathogens [5]. Of these, entomopathogenic fungi show considerable promise for development as biopesticides [6-10]. Fungus production and application all involve relatively simple infrastructure and processes