Post-mortem implications of suicidal organophosphate on the rate of decomposition and necrophagous dipteran signatures on Sus scrofa L. carrions

Abstract Background Necrophagous insects, particularly species belonging to the order Diptera, have been utilized in forensic entomology for the estimation of the minimum post-mortem interval germane to the establishment of guilt or innocence during medicolegal investigations. However, the knowledge of these carrion insects and the succession patterns have remained undocumented in the study area, Uburu, Ebonyi State, Nigeria. This study examined the influence of dichlorvos — an organophosphate commonly associated with suicide — on the rate of carrion decomposition and the necrophagous dipterans associated with pig carrions treated with dichlorvos for forensic investigations. Six domestic pigs were used, which consisted of three treated with dichlorvos and three untreated. The length of days taken for each decomposition stage of the carrions was calculated, and the insects’ successions were documented using detailed taxonomic keys. In addition, cytochrome oxidase subunit I (COI) gene of selected insects was amplified and sequenced for species confirmation. Results Carrion decomposition occurred more rapidly in the dichlorvos-treated carrions, while a greater number of dipteran flies were found on the control carrions. The dichlorvos-treated group decomposed in 51 days ( t = 1.568; p < 0.05), while the controls took 65 days ( t = 1.308; p < 0.05). A total of 869 dipterans was collected from the dichlorvos-treated carrions, while 1167 were collected from the control carrions. Morphologically, 12 fly species from 4 families — Calliphoridae, Sarcophagidae, Muscidae, and Stratiomyidae — were identified. Molecular analysis carried out via BLAST search against GenBank confirmed species which included Chrysomya marginalis , Chrysomya putoria , Lucilia cuprina , Sarcophaga tibialis , Musca domestica , and Hermetia illucens . Conclusions The study demonstrated that dichlorvos significantly influences both the decomposition rate and the makeup of necrophagous fly communities on carrions. It also establishes foundational and essential morphological and genetic data on key dipteran species relevant to forensic investigations in this region — an area previously lacking such entomological records. These findings can support future entomo-toxicological research in forensic entomology, both in Uburu, Ebonyi State, Nigeria, and globally.