Title: The effects of different doses of paracetamol on the development and morphometry of insects with forensic value
Abstract:
Postmortem interval (PMI) estimation is an important factor in forensic investigations. In forensic entomology, the time of death is estimated by analyzing the age of the oldest insects found on a decomposing carcass, examining the development and succession pattern of insects. However, the presence of drugs and/or toxins in a cadaver can influence and alter insect development and potentially affect the accurate PMI estimations. Paracetamol (acetaminophen) is one of the most abused over-the-counter drugs in Southern Africa and is frequently implicated in both intentional and accidental poisoning cases. Given the high incidences of paracetamol poisoning in the southern Africa region, this study investigated the effects of various doses of paracetamol on the development of insects feeding on spiked carcasses and results are aimed at contributing new knowledge to the currently limited research in the area of forensic entomotoxicology. Four pigs were used as models to mimic paracetamol overdose in humans and three doses of paracetamol were used:75 mg/kg (toxic), 150 mg/kg (lethal), and 300 mg/kg (double lethal). Results showed that abundance of insect species varied in different pig carcasses, with Chrysomya albiceps (112) and Chrysomya putoria (57) being the most abundant and the least abundant respectively, in both control and paracetamol groups. Oviposition was delayed by 24 hours in dipteran species from the spiked carcasses compared to species from the control carcass. Effects of paracetamol on the development of insects were dose-dependent and species-specific. Chrysomya putoria and Chrysomya megacephala exhibited an increased larval length, width, and weight at double lethal doses. Lucilia sericata showed significant reductions in weight at all paracetamol doses, highlighting the negative impact of the drug to the fly development. This response variation between species indicate that different paracetamol doses have different effects on different insect species which in turn can affect PMI estimations in investigation cases involving paracetamol. Furthermore, morphological abnormalities were observed in newly emerged adults where Ch. putoria and L. sericata exhibited progressive wing deformities and discoloration at higher paracetamol doses while Ch. albiceps exhibited no observable deformities across all doses. These findings indicate that paracetamol interrupts critical developmental processes in certain species, in a dose-dependent manner. Results showed that these species can serve as toxicological indicators of paracetamol in paracetamol related deaths. The results of this study contribute towards enhancing the PMI precision and advancing forensic entomotoxicology in the region, and generate a baseline data for KwaZulu Natal province. The observed interspecies variations and dose-dependent responses in this study suggest the need for studies on the effects of paracetamol and similar drugs on the development of other forensically important insects as the effect of different drugs vary with species.
