Survival and immune response of the Chagas vector Meccus pallidipennis (Hemiptera: Reduviidae) against two entomopathogenic fungi, Metarhizium anisopliae and Isaria fumosorosea

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.

The role of a novel Wo l b a c h i a (Rickettsiales: Anaplasmataceae) synthetic peptide, WolFar, in regulating prostaglandin levels in the hemolymph of Acheta domesticus (Orthoptera: Gryllidae)

“…For example, a study by Ebrahimi et al (2014) showed that the level of PO activity in the Colorado potato beetle, Leptinotarsa decemlineata, when treated against entomopathogenic nematode, Steinernema carpocapsae, also took the form of a zigzag pattern, with several upregulations and downregulations during the experiments. The same situation was also shown in a study by Flores-Villegas (2016), who recorded a zigzag pattern in proPO activity over time in the Chagas vector Meccus pallidipennis against two entomopathogenic fungi, Metarhizium anisopliae and Isaria fumosorosea.…”

Effects of Trypanosoma cruzi on the phenoloxidase and prophenoloxidase activity in the vector Meccus pallidipennis (Hemiptera: Reduviidae)

“…PO activity in the hemolymph was determined by spectrophotometry through the catalytic conversion of L-DOPA (3, 4-dihydroxy-L-phenylalanine, which is colorless) to dopachrome (brownish-red), employing the molar extinction coefficient (3.715/M/cm) of the latter [ 28 , 29 ]. Protein concentrations were quantified in the samples by utilizing the Pierce method with the BCA commercial kit (Thermo Fisher Scientific, Rockford, Illinois, USA) [ 30 ]. Hemolymph containing 10 μg of protein was placed in each well of a 96-well microplate (Costar 96; Corning, USA).…”

Coinfection by Trypanosoma cruzi and a fungal pathogen increases survival of Chagasic bugs: advice against a fungal control strategy

“…The absorbance was determined in an ELX 800 ELISA reader (Biotek Instruments, Winooski, VT, USA) at 562 nm. Protein content was adjusted to 10 µg of protein to measure PO activity (Flores-Villegas et al ., 2016).…”

“…On one hand, T. cruzi develops its life cycle in the intestine where PO may not necessarily participate directly, yet it is expressed as a bug's systemic response (Favila-Ruiz et al ., 2018). On the other hand, M. anisopliae triggers melanization processes, where PO is involved (reviewed by Flores-Villegas et al ., 2016). Thus, for the parasite and fungus, PO can be used as a reliable way to assess pathogen attacks as a bug's systemic and defense response, respectively (González-Santoyo and Córdoba-Aguilar, 2012).…”

“…Several studies have been conducted with different pathogen agents for the biological control of bugs (de Fuentes-Vicente et al ., 2018). One of such pathogens is the fungus Metarhizium anisopliae , which penetrates the insect cuticle, suppressing its immune response and causing a high mortality (Flores-Villegas et al ., 2016, 2018). Only one study has considered the combined effects of co-infection by T. cruzi and other pathogens used as control agents (Garcia et al ., 2016).…”