MOLECULAR FORENSICS OF HUMAN BLOOD ISOLATED FROM BED BUGS

Identifying an individual based on blood or tissue isolated from insects can be used to implicate a suspect in the time and place of a crime. However, human DNA isolated from an insect would have to be stable and intact long enough to be useful in a forensic investigation and unambiguously identifiable to an individual host. Human DNA has been extracted and identified from mosquitoes, crab and body lice, fly larvae, and beetles. Bed bugs (Cimex lectularius) are globally resurgent pests that feed exclusively on vertebrate blood. Both males and females feed on blood, and juveniles require blood to molt to the next instar. In our field studies, we found population densities of hundreds per square foot in lower-income housing. Because of their obligate blood-feeding behavior and high population densities, bed bugs would be a valuable source of human DNA for forensic analysis. A proof-of-concept paper demonstrated that human DNA can be isolated from bed bugs, although the host genotype and time elapsed since feeding were not noted. Therefore, the goals of our study were (a) to assess the stability of human DNA in bed bugs over time, using validated polymorphic autosomal short tandem repeat (STR) markers commonly employed in forensic investigations and (b) to correlate blood isolated from bed bugs to the genotype of an individual human host. The results of our study showed that human DNA extracted from blood-fed bed bugs can be positively identified for up to 72 hours. Above 96 hours, human DNA was degraded, and was therefore unable to be amplified with the STR markers. Upon comparing DNA isolated from two human volunteers, one of which blood-fed the bed-bug samples, to the DNA isolated from the fed bed bugs, we were able to successfully identify an individual based on their unique STR banding patterns. These procedures will assist in the field of forensic entomology.

Additional Abstract Information

Student(s): Jennifer L. Raffaele, Brittany B. McCarthy, Rajeev Vaidyanathan

Department: Integrated Science and Technology (ISAT), Biology

Faculty Advisor: Dr. Ron Raab

Type: Oral

Year: 2014