Effect of Pithecellobium dulce extract on vector competence of Aedes aegypti to chikungunya virus

Abstract

Chikungunya virus (CHIKV) is among re-emerging arboviruses that affect human health globally. The spread has been associated with lack of sustainable vector control and viral preventive measures. Studies of the biology and ecology of the key vector, Aedes aegypti can open avenues for control of this virus. Despite the increasing evidence linking plant feeding to the survival and pathogen transmission dynamics as observed in the Anopheles-malaria parasite system, little is known as to whether plant feeding can influence pathogen-Ae. aegypti interaction. This study aimed to determine the effect of Pithecellobium dulce, a host plant for this vector, on the competence of Ae. aegypti to CHIKV. Adult Ae. aegypti females fed orally on dimethyl sulfoxide (DMSO) extracts of P. dulce, reduced female survival in a dose-dependent manner (P<0.0001). Chemical analysis of pools of midgut content after ingestion of the plant extract detected by coupled liquid chromatography triple quadrupole tandem mass spectrometry (LC-QqQ-MS) and coupled gas chromatography-mass spectrometry (GC-MS) identified several plant metabolites namely the amino acid proline, the flavonoid glycoside kaempferol 3-O-rhamnoside, the sterol β sitosterol and the fatty acid linoleic acid. Further, the females were orally exposed to a CHIKV infectious blood using a membrane-feeding assay before and after feeding on an optimal survival dose of the plant extract. Virus infection in the mosquito vector was determined by plaque assays. Highly significant infection and dissemination rates and respective mean titers were observed in the control and post-exposed (mosquitoes fed on glucose solution then the plant extract) treatment (P<0.001). No significant effect was observed in mean titers of the control and the pre-exposed (mosquitoes fed on plant extract then glucose solution) cohort (P<0.001). Although there was no observed significant difference while using either frozen or freshly cultured virus, transmission, which is a measure of vector competence, was only observed in the freshly cultured virus type. The pre-exposed, control and pre + post-exposed treatments recorded transmission although with significantly reduced titer in the latter. The post-exposed treatment recorded no transmission further suggesting possibility of P. dulce activity. These results demonstrate that Ae. aegypti feeding on this plant i) influences its survival, ii) leads to ingestion of secondary metabolites and iii) modulates infection success to chikungunya virus. The known anti-pathogenic effect of the identified metabolites suggests the potential impact on virus transmission occurs through reduced virus titers, thus these findings open a novel avenue towards the development of antiviral strategies targeting vector plant feeding behavior.