RESUMEN
BACKGROUND: Entomopathogenic fungi, particularly those belonging to the genera Metarhizium and Beauveria have shown great promise as arthropod vector control tools. These agents, however, have not been evaluated against flea vectors of plague. FINDINGS: A 3-h exposure to the fungi coated paper at a concentration of 2 × 108 conidia m-2 infected >90% of flea larvae cadavers in the treatment groups. The infection reduced the survival of larvae that had been exposed to fungus relative to controls. The daily risk of dying was four- and over three-fold greater in larvae exposed to M. anisopliae (HR = 4, p<0.001) and B. bassiana (HR = 3.5, p<0.001) respectively. Both fungi can successfully infect and kill larvae of X. brasiliensis with a pooled median survival time (MST±SE) of 2 ± 0.31 days post-exposure. CONCLUSION: These findings justify further research to investigate the bio-control potential of entomopathogenic fungi against fleas.
Asunto(s)
Beauveria/fisiología , Metarhizium/fisiología , Control Biológico de Vectores/métodos , Xenopsylla/microbiología , Animales , Larva/microbiología , Peste/prevención & control , Peste/transmisión , Esporas Fúngicas , Análisis de SupervivenciaRESUMEN
The viability of Anopheles gambiae sensu stricto and Anopheles arabiensis (Diptera: Culicidae) eggs over time and the ovicidal activity of Beauveria bassiana (Ascomycota: Cordycipitaceae) and Metarhizium anisopliae (Ascomycota: Clavicipitaceae) were investigated. Eggs were incubated in soil or leaf litter for up to 12 weeks at 26°C and 75%, 86% or >98% relative humidity (RH). Eggs were treated topically with M. anisopliae ICIPE-30 or B. bassiana I93-825 conidia in either water or oil-in-water formulations. Survival of eggs whether treated or not with fungus was similar, and untreated eggs generally did not survive longer than 2 weeks regardless of the substrate or humidity tested. After a minimal 5-day exposure, M. anisopliae at 5 × 10(6) conidia/cm(2) clearly reduced the number of larvae. The efficacy of the fungus increased when it was oil-in-water formulated, and eclosion was completely prevented regardless of the conidial concentration (10(5)-10(7) conidia/cm(2)) after a 10-day exposure in soils at >98% RH. Treatment of eggs with B. bassiana, however, failed to reduce the number of eclosing larvae. This is the first demonstration of the ovicidal activity by M. anisopliae against either A. gambiae s. s. or A. arabiensis and the results underline the potential of this fungus against anopheline mosquitoes.
Asunto(s)
Anopheles/microbiología , Beauveria/crecimiento & desarrollo , Metarhizium/crecimiento & desarrollo , Animales , Beauveria/patogenicidad , Metarhizium/patogenicidad , Óvulo/efectos de los fármacos , Control Biológico de Vectores/métodos , Análisis de SupervivenciaRESUMEN
Some soil-dwelling entomopathogenic fungi that are widely used in pest control are also able to reduce the survival of adult mosquito vectors under laboratory conditions. However, there is still little information about the naturally occurring fungal pathogens affecting culicid mosquitoes. As such, we hypothesized that fungi that already kill mosquitoes in realistic domestic environments could be effective against these vectors in human habitations. A simple, inexpensive, handmade, cylindrical kiln-fired clay pot (30 cm height, 24 cm inner diameter, 0.8-1cm wall thickness) was modified into a trapping device for resting adult mosquitoes and to sample fungus-infected moribund and dead individuals. The entomopathogenic fungus Lecanicillium muscarium was isolated from a dead culicid mosquito collected with this trap in southeastern Tanzania. This isolate is the first L. muscarium reported to occur naturally on adult culicids in Tanzania and was found to be pathogenic also to adults of Aedes aegypti, Anopheles arabiensis and Culex quinquefasciatus under laboratory conditions. The trapping device confirmed its efficacy to sample mosquito-specific fungi in domestic locations and that the isolated fungus might have potential for mosquito control.