Advances in Entomotoxicology. Weaknesses and Strengths.

Medical forensic entomotoxicology currently deals mainly with the potential use of carrion-feeding insects as indirect proxy samples for detecting toxicants (e.g., drugs, poisons and other xenobiotic chemicals) when poisoning is suspected. Insects can provide a reliable biological source of proxy samples of xenobiotics where no body fluids or tissues traditionally sampled for toxicological analysis are available, especially in badly decomposed bodies such as pre-skeletonized, mummified and/or burnt bodies. Insects feeding on human tissues can ingest all of the substances taken by living humans, including common pharmaceuticals, illicit drugs, poisons, and heavy metals. Environmental forensic entomotoxicology seeks similar sources of evidence of toxicants in the environment in general. The detection of toxicants in different types of entomological remnants (including puparial cases and fecal material) through various analytical techniques has been demonstrated in many experimental and case studies. Forensic entomotoxicology also investigates the effects of toxicants on arthropod development, survival, and morphology and their implications for estimating post-mortem intervals (PMIs). This is crucial for forensic entomologists because the estimation of the minimum time since death is their most frequently requested task. A PMI estimate based on the estimated age of immature insects, without considering the effects of common toxicants on the rate of development, could easily be in error by hours and even days, depending on the toxicant, the insect species, and how long development has already progressed. Like toxicology in general, entomotoxicology is still in the process of developing validated protocol standards, commonly requested by courts internationally and is addressing the shortage of reliable pharmacokinetic information about toxicants in arthropods. Limitations in the application of quantitative toxicological results are related to several entomological and toxicological phenomena that affect analytical findings, particularly the affinity of toxicants to certain tissues (tropism) because of their basic molecular structure; inter-stadial variability arising from the feeding stage of larvae, the tissues they ate, and site-to-site variability; post mortem re-distribution of toxicants from tissues; post mortem and bacterial degradation of toxicants. There is a strong need of further research in these matters. These phenomena mean that insects are very useful as qualitative toxicological proxy specimens and less useful as quantitative evidence. All experts involved in a death investigation should be aware of how useful a drug screen on entomological specimens can be, and of the caveats due in the interpretation of quantitative toxicant concentrations. When poisoning is suspected in bodies colonized by insects, it is recommended that investigators undertake all reasonable methods and techniques to support a reliable diagnosis of the cause and time of death, including a toxicological screen on insect specimens. The role and applicability of entomotoxicology in court trials is likely to increase when validated protocols and methods can be systematically applied to the toxicological analysis of entomological samples.