Head Louse Feces: Chemical Analysis and Behavioral Activity

PICOLLO, M I; GALASSI, F G; GONZALEZ-AUDINO, P

JOURNAL OF MEDICAL ENTOMOLOGY

ENTOMOLOGICAL SOC AMER

Año: 2019

0022-2585

">Human head lice Pediculus humanus capitis (De Geer) (Phthiraptera: Pediculidae) are insect parasites closelyassociated with humans, feeding on the blood of their hosts and causing them skin irritation and probablesecondary infections. Despite being a severe nuisance, very few studies have reported on intraspecific chemical communication in head lice. Here, we evaluated the attractive response of head lice to the volatile compounds and solvent extracts from their feces. We also chemically analyzed the main volatile components ofthese feces and those of the feces? extracts. Head lice were attracted to the methanol extract of their feces butnot to the hexane or dichloromethane extracts, suggesting the polar nature of bioactive chemicals present inhead louse feces. Follow-up chemical identifications, in fact, showed the presence of hypoxanthine, uric acid,and another purine tentatively identified as either guanine or iso-guanine. Additionally, head lice were significantly attracted by volatiles emitted from samples containing feces. The volatiles emanated from feces alonecontained 19 identified substances: 2-pentanone, hexanal, heptanal, 3-methyl-3-buten-1-ol, octanal, sulcatone,nonanal, acetic acid, 2-ethyl-1-hexanol, decanal, 1-octanol, butyric acid, 1-nonanol, hexanoic acid, octanoicacid, 2,6-dimethyl-7-octen-2-ol, 2-undecanone, geranylacetone, and hexadecane. The major compounds foundwere decanal, nonanal, hexanal, and acetic acid, together representing approximately 60% of the identifiedcompounds. This work represents the first chemical evidence of intraspecies communication among head lice.The results support the existence of active substances present in the feces of P. humanus capitis that may beinvolved in its aggregation behavior.