Abstract
BackgroundChagas disease is a key health problem in Latin America and is caused and transmitted by Trypanosoma cruzi and triatomine bugs, respectively. Control of triatomines has largely relied on the use pyrethroids, which has proved to be ineffective in the long term. Alternatively, the use of entomopathogenic fungi has been implemented to control triatomine bugs. These fungi are highly efficient as they induce a reduction in immune response on insects. Meccus pallidipennis is the main triatomine vector of Chagas disease in Mexico. In this work we investigated the effects of two entomopathogenic fungi, Metarhizium anisopliae and Isaria fumosorosea, on M. pallidipennis nymphs in terms of insect survival and immune response.MethodsWe had an infected and a control group for each fungal species and assessed: a) insect survival during 30 days; and, b) phenoloxidase (PO) and prophenoloxidase (proPO; two key traits in insect immune response) at 24, 48, 96 and 144 h. For survival we used Kaplan-Meier survival analysis while for immune response we used factorial, repeated-measures ANOVA for each fungal species.ResultsAnimals treated with M. anisopliae died sooner than animals treated with I. fumosorosea. Infected animals showed lower PO and proPO values than sham individuals, with a clear decrease in these parameters at 24 h with no further changes after this time.ConclusionsOur study widens the possibility of entomopathogenic fungi being used for triatomine control. The negative effect on PO and proPO seems mediated by a down-regulation of the triatomine immune response.
Highlights
Chagas disease is a key health problem in Latin America and is caused and transmitted by Trypanosoma cruzi and triatomine bugs, respectively
We explored the use of two entomopathogenic fungi, Metarhizium anisopliae (Hypocreales: Clavicipitaceae) and Isaria fumosorosea (Hypocreales: Cordycipitaceae), against M. pallidipennis nymphs
A comparison of both fungal treatments indicated that individuals treated with M. anisopliae died sooner than those treated with I. fumosorosea (X2(1) = 11.49, P = 0.0007)
Summary
Chagas disease is a key health problem in Latin America and is caused and transmitted by Trypanosoma cruzi and triatomine bugs, respectively. The use of entomopathogenic fungi has been implemented to control triatomine bugs These fungi are highly efficient as they induce a reduction in immune response on insects. Given the risk that M. pallidipennis implies for T. cruzi transmission, there have been several efforts to control it One of these is the use of synthetic pyrethroids such as bifenthrin, cyfluthrin and deltamethrin insecticides. We explored the use of two entomopathogenic fungi, Metarhizium anisopliae (Hypocreales: Clavicipitaceae) and Isaria fumosorosea (Hypocreales: Cordycipitaceae), against M. pallidipennis nymphs Use of these fungi has been highly successful for controlling different insect pests and vectors such as Asian tiger mosquitoes Aedes albopictus [16], cattle ticks Rhipicephalus microplus [17], Asian citrus psyllids Diaphorina citri [18] and diamondback moth Plutella xylostella [19]. Entomopathogenic fungi seem a viable route for triatomine biological control [12, 23,24,25]
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