Storage stability of nucleic acids in the body louse, Pediculus humanus

Abstract

Stability of nucleic acids in the body louse preserved under several conditions was investigated in order to explore the ideal stock method of the human louse for molecular diagnosis. The partial DNA sequence of the para-orthologous sodium channel, which is the target site of pyrethroid insecticide, was amplified by utilizing the polymerase chain reaction (PCR) and the stability of genomic DNA and poly (A)^+ RNA in dead insects was evaluated. Overall, poly (A)^+ RNA was less stable than the genomic DNA even if lice were stored in 70% or in absolute ethanol. Stability of genomic DNA lasted for at least two months when the lice were fixed in 99.5% ethanol or even in the lice which died of starvation at room temperature without any treatment. On the contrary, apparent degradation of genomic DNA and poly(A)^+ RNA was observed for lice, which were killed with vapor of diethyl ether, suggesting that the moisture or blood in the body of louse needs to be dried out or digested naturally before storing insects for molecular analysis.