SOURCE:

Faculty: Biosences
Department: Zoology

CONTRIBUTORS:

Abajue, M.C;
Ewuim, S.C;

ABSTRACT:

Forensic entomology is geared towards using insects recovered from decomposing cadavers to estimate the time of questionable death as well as ascertaining whether the victim died of poison (entomotoxicology) when the body fluids have dried out. However, there is paucity of information about the use of insects in forensic investigation and toxicology in Nigeria, despite incessant homicides reported or witnessed regularly in our neighbourhoods. Therefore, there is need to cue in cadaveric insects from Southeastern Nigeria into the global data base of forensic entomology as well as toxicologically analyse the cadaveric insect larvae as alternative to body fluids, to assist coronary investigators unravel mysteries surrounding questionable deaths in Nigeria. The study investigated decomposition processes of poisoned and asphyxiated pig cadavers at a forest and in a building in Awka, Nigeria in relation to their forensic and toxicological importance. Sixteen pig cadavers (Sus scrofa Linn.) were used as model to study the decomposition process of human being in Awka, Nigeria. Eight pigs were sacrificed with zinc phosphide (rodenticide) as food poison and another eight pigs were strangled to mimic asphyxiation. Two poisoned and two asphyxiated pig cadavers were deposited in a building (6°15′18.06″N and 7°06′41.37″E) and another replicate deposited in a forest (6°15′15.32″N and 7°06′40.22″E). They were simultaneously studied during the rainy season till they were skeletonized. The same process was repeated during dry season. Different stages of insects attracted to the decomposing cadavers were collected with entomological techniques. Samples of insect eggs and larvae were reared in the laboratory to ascertain the identity of the adults. The larval and the pupal samples of insects recovered from the decomposing cadavers were chemically digested to assess zinc and phosphorus on them with atomic absorption spectrophotometer (AAS). Adult insects collected from the cadavers were preserved in Kahle’s solution. The decomposition stages of the cadavers took ten and fourteen days during the rainy and dry seasons respectively. The insects collected on the cadavers were classified into seven orders, twenty families and thirty-eight species in twenty-nine genera. The community composition, the guild structure and the community dynamics of the insects did not change between the two seasons and between the two environments, irrespective of the killing methods. Insects of forensic importance collected from the study were only depicted in two insect orders; coleopterans and dipterans. Atomic absorption spectrophotometer detected excess zinc and negligible quantity of phosphorus which were the active ingredients of the rodenticide on the larval and pupal samples of the insects. This showed that the rodenticide that killed the pigs, bio accumulated in the larval and pupal tissues of insects that fed on the poisoned cadavers. Statistically, the decomposition rates of the cadavers as well as the temperature and relative humidity between the two seasons were significant (P < 0.05). Interestingly, the growth rates of the insect larvae recovered from the poisoned and asphyxiated pig cadavers were not significant (P>0.05). The study showed that the insects collected from the cadavers estimated the time the pigs died at the contrasting environments. More so, season and killing methods do not affect the insect fauna and their succession. The larval and the pupal samples also proved to be valuable for toxicological study. Evidently, forensic entomology and entomotoxicology should be part of coronary investigation in cases related to questionable deaths in Nigeria.