Insect recovery of environmental human DNA

We tested the hypotheses that foraging adult insects could acquire human DNA from an indoor environment and that insect-delivered human DNA would be of sufficient quantity and adequate quality to permit standard forensic analyses. Insects used in this study included the common house fly (Musca domestica L.), German cockroach (Blattella germanica L.) and a camel cricket (Ceuthophilus sp.). Groups of five individuals of the same species were permitted to forage in an enclosed arena on a dusty surface for ~ 1 hour. Insects were then analyzed individually for human DNA using conventional and quantitative PCR methods for nuclear and mitochondrial loci, and by multiplex STR amplification followed by ultrathin and capillary electrophoresis. All of the groups over two experiments (n=24, n=12 groups per species) tested positive for human DNA, as did 2/3 of all individual house flies and cockroaches (n=180 per species over two experiments), and >1/3 of camel crickets (n=60), compared to 94% of all control surface swabs taken from an adjacent and equivalent surface area of each foraging arena. Of 177 individual insect samples, >1/3 tested positive for quantifiable human nuclear DNA. When submitted to STR analysis with the AmpFℓSTR® Profiler Plus™ kit, four of these samples had at least one positive allele call for one or more loci, and eight other samples showed multiple overlapping peaks at some loci. All negative control insects and PCR reactions tested negative. Results demonstrate the feasibility of using insects to assess human habitation of inaccessible locations.