Toxicological data and growth characteristics of single post-feeding larvae and puparia of Calliphora vicina (Diptera: Calliphoridae) obtained from a controlled nordiazepam study

Effects of aluminium phosphide on larval morphometry of two important Chrysomya species

Chrysomya megacephala and C. rufifacies are globally predominant species of blowflies that are amongst the primary colonisers of decomposing carcasses. The development of blowflies has been studied extensively to estimate the minimum postmortem interval (PMImin). This article evaluates the effect of aluminium phosphide (AlP) on the larval morphometry and life cycles of C. megacephala and C. rufifacies. The rabbits were given different dosages of AlP and their livers were excised to rear C. megacephala and C. rufifacies. Through multiple-regression analysis, we assessed the overall impact of varying dosages of AlP on larvae of both species. AlP accelerated development until pupation, whilst the time until emergence remained the same. At higher concentrations, AlP had a positive effect on the development of these species. Since both species are abundant, forensic entomology studies examining the effect of AlP on morphometry and developmental stages would provide valuable information to investigators assessing PMImin.

Effect of diazinon (organophosphate) on the composition and succession of Calliphoridae assemblages in rabbit carcasses in the Eastern Amazon

Fatal poisonings with diazinon may occur both accidentally or intentionally in suicide cases. Forensic entomotoxicology can aid in understanding these deaths by detecting and analyzing the interference of toxic substances in the biology of necrophagous insects. Hence, this study sought to evaluate diazinon's effect on the composition and succession of calliphorid species in the tropical savannas of the Amazon. Nine rabbit carcasses were divided into three groups: one control and two diazinon treatments (100 mg/kg and 300 mg/kg); each group had three replicates. Three fragments of the Amazon tropical savanna were selected for the experiments. Daily collections of adult and immature calliphorids were performed. Five decomposition stages were observed: fresh, bloated, active decay co-occurring, advanced decay, and dry. Eight species of Calliphoridae were identified among the collected adults: Chloroprocta idioidea (0.1%), Chrysomya albiceps (58.3%), Chrysomya megacephala (14.2%), Chrysomya putoria (2.6%), Cochliomyia hominivorax (1.3%), Cochliomyia macellaria (0.5%), Lucilia eximia (19.8%), and Paralucilia paraensis (3.3%). The adult specimens in the control group with the highest abundance were observed only from the advanced decay stage onward. In the dry stage, abundance was higher in control than in treated carcasses. From the sampled 941 Calliphorid immatures, three species were identified: C. albiceps (76,3%), C. putoria (1%), and L. eximia (22,7). The number of immatures was higher in control than in treated carcasses. Therefore, diazinon interferes with the putrefaction timeframe in carcasses, slowing the decomposition stages and affecting their colonization by immature forms of Calliphoridae.

Research Progress on Developmental Biology of Sarcosaprophagous Insects

Forensic entomology provides a feasible way to estimate postmortem interval (PMI), of which the growth and development of sarcosaprophagous insects is the most widely used indicator in forensic practice. Over the years, forensic entomologists have carried out a large number of studies on the development biology of sarcosaprophagous insects. This paper illustrates the main factors that affect the development of sarcosaprophagous insects, including temperature, humidity, light, food types and poisons. The development indicators of sarcosaprophagous insects were reviewed from the perspectives of morphology, differential gene expression and biochemical characteristics. It is emphasized that future research of development biology on sarcosaprophagous insects should fully absorb and integrate the methods of artificial intelligence and omics, and the research object also needs further expansion in order to establish a more objective and more accurate PMI estimation method.

Forensic Entomology in China and Its Challenges

Simple Summary

Forensic entomologists utilize sarcosaprophagous insect species to estimate the postmortem interval to aid death investigations. In this paper, we present the recent chronology of forensic entomology in China and illustrate how identification, development, and succession data are obtained and applied at the scale of such a large country. To overcome the difficulties and challenges forensic entomology faces in China, a number of countermeasures are provided.

Abstract

While the earliest record of forensic entomology originated in China, related research did not start in China until the 1990s. In this paper, we review the recent research progress on the species identification, temperature-dependent development, faunal succession, and entomological toxicology of sarcosaprophagous insects as well as common applications of forensic entomology in China. Furthermore, the difficulties and challenges forensic entomologists face in China are analyzed and possible countermeasures are presented.

The implication of morphometrics and growth rate of dipteran flies in forensic entomotoxicology research: a review

Forensic entomotoxicology integrates toxicology into forensic entomology to estimate minimum postmortem interval (PMI_min) and circumstances of death where toxicants and poisonous substances are the suspected cause of death. Forensic entomotoxicology not only confirms the presence of toxicants in insects feeding off a cadaver but also studies its effect on the bio-morphometry and growth rate of insects. This review article highlights the effects of various toxicants on forensically important species of dipteran flies. It also discusses the parameters that may affect accuracy in estimation of time since death. The bio-physical effects of toxicants (excluding the analytical approach for qualitative detection) would help understand the trends in forensic entomotoxicological research worldwide.

Detection of heroin metabolites at different developmental stages of Lucilia cuprina (Diptera: Calliphoridae) reared in heroin-treated meat: a preliminary analysis

Background

Blowfly larvae and pupae collected during post-mortem forensic investigation can be analysed to detect drugs or toxins in a dead body. Drug or toxin-contaminated tissues of human remains consumed by blowfly larvae are stored in the crop even after a body has decomposed to the point where no fluid or tissues are retrievable. Therefore, blowfly larva and pupa are favourable specimens under conditions in which host tissues or blood samples are not available.

Methodology

We carried out a study to detect heroin metabolites in Lucilia cuprina (Weidemann, 1830) immatures fed on different concentrations of heroin-treated meat: 500, 1000, 2500, 5000, and 10,000 ng/μl. Heroin metabolites detection was performed by a gas chromatography mass spectrophotometry (GCMS) analysis.

Results

This study indicates that L. cuprina can be utilized in a toxicological analysis to detect heroin in a host. However, the expected complete metabolites of heroin were not detected in the first instar larvae and pupa, while the second and third instar larvae contributed to a complete heroin metabolite which was morphine. This was subject to the heroin concentration given. Morphine was detected in the third instar larvae treated with 5000 and 10,000 ng/μl heroin, while in the second instar, it was detected only at 10,000 ng/μl. Heroin metabolites detected in the second and third instar larvae proves that biochemical conversions occur in the fly larvae.

Conclusion

The absence of heroin metabolites in the first instar larvae and pupa does not necessarily mean that the drug was not present in the host. Therefore, the limitations of heroin detection capability during these stages should be always kept in mind, as this could contribute to a false-negative result in a forensic analysis. If all stages are available during sample collection, it is crucial to prioritize the third instar larvae in a toxicological analysis.

Forensic entomotoxicology revisited-towards professional standardisation of study designs

Forensic entomotoxicology is the use of insects as evidence of whether a toxicant is present in an environment such as a corpse, river or landscape. The earliest overtly forensic study was published in 1977, and since then, at least 63 papers have been published, most of them focused on the detection of toxicants in insects or on effects of toxicants on diverse insect indicator taxa. A comprehensive review of the published literature revealed various inconsistencies between studies that could be addressed by introducing standard protocols for such studies. These protocols could include selecting widespread and common model organisms (such as Lucilia sericata, Calliphora vicina, Chrysomya megacephala and Dermestes maculatus) and model toxicants (e.g. morphine and amitriptyline) to build up comparative databases; developing a standard matrix for use as a feeding substrate; setting guidelines for statistically adequate sample sizes; and deploying more sophisticated analytical methods from the general field of toxicology. Future studies should then be aimed at refining standardised protocols to improve experimental results, and make these results more comparable between studies.

Helminthes and insects: maladies or therapies

By definition, parasites cause harm to their hosts. But, considerable evidence from ancient traditional medicine has supported the theory of using parasites and their products in treating many diseases. Maggots have been used successfully to treat chronic, long-standing, infected wounds which failed to respond to conventional treatment by many beneficial effects on the wound including debridement, disinfection, and healing enhancement. Maggots are also applied in forensic medicine to estimate time between the death and discovery of a corpse and in entomotoxicology involving the potential use of insects as alternative samples for detecting drugs and toxins in death investigations. Leeches are segmented invertebrates, famous by their blood-feeding habits and used in phlebotomy to treat various ailments since ancient times. Leech therapy is experiencing resurgence nowadays in health care principally in plastic and reconstructive surgery. Earthworms provide a source of medicinally useful products with potential antimicrobial, antiviral, and anticancer properties. Lumbrokinases are a group of fibrinolytic enzymes isolated and purified from earthworms capable of degrading plasminogen-rich and plasminogen-free fibrin and so can be used to treat various conditions associated with thrombotic diseases. Helminth infection has been proved to have therapeutic effects in both animal and human clinical trials with promising evidence in treating many allergic diseases and can block the induction of or reduce the severity of some autoimmune disorders as Crohn's disease or ulcerative colitis. What is more, venomous arthropods such as scorpions, bees, wasps, spiders, ants, centipedes, snail, beetles, and caterpillars. The venoms and toxins from these arthropods provide a promising source of natural bioactive compounds which can be employed in the development of new drugs to treat diseases as cancer. The possibility of using these active molecules in biotechnological processes can make these venoms and toxins a valuable and promising source of natural bioactive compounds. The therapeutic use of helminthes and insects will be of great value in biomedicine and further studies on insect toxins will contribute extensively to the development of Biomedical Sciences.

Standardization of histological procedures for the detection of toxic substances by immunohistochemistry in Dipteran larvae of forensic importance

Immunohistochemistry (IHC) technique is an alternative toxicological analysis to detect drugs in insects of forensic importance, but it requires thorough histological procedures. In this study, we tested different fixatives--phosphate-buffered paraformaldehyde 4% (PP), Carnoy's fluid (CF), Kahle's solution (KS), ethanol in different concentrations, and ethanol associated to PP and CF, time of fixation and histological processes for dipteran larvae's tissue, aiming to develop a sample preparation protocol for IHC application. A suitable fixation was achieved using PP for 12 and 24 h, CF for 3 h, 70% ethanol for 19 days, and 70% ethanol/CF for 2 h/3 h. Postfixation using negative pressure, two immersions in xylene for 30 min each, and one in xylene plus paraffin for 45 min increased tissue preservation. An immunohistochemical test for cocaine detection was performed using monoclonal benzoylecgonine antibody from mouse, peroxidase-conjugated anti-mouse IgG and visualized by 3,3'-diaminobenzidine method showed these histological procedures didn't compromise antigenicity.

Effect of ketamine on the development of Lucilia sericata (Meigen) (Diptera: Calliphoridae) and preliminary pathological observation of larvae

The estimation of postmortem interval (PMI) based on the growth patterns of necrophagous arthropods is the main mission of forensic entomology in practice. The larval development rates can be affected by various drugs or toxins, causing deviation in PMI estimate. Ketamine is a widely used anesthetic and recreational drug in Asia, which is rarely focused on in the previous entomotoxicological studies. The present work investigated the effect of ketamine on the development of Lucilia sericata (Meigen) (Diptera: Calliphoridae) by the measurement of body length and weight and the analysis of relationship between the ketamine effect and drug dosage or time interval, meanwhile the difference between ketamine effect on larval body length and weight was also analyzed. Additionally, the preliminary pathological observation of larvae was also employed for evaluating the drug effect in morphology. Significant differences were observed between control and treatment colonies of L. sericata at each life stage, and the effect of ketamine displayed a dosage-and-time-dependent manner, but no differences were noticed between the effects of ketamine on larval body length and weight, which provided a useful indication for larvae sample collection in practice. The pathological observation revealed that ketamine could promote the growth of trophocytes in fat body of L. sericata.

Entomotoxicology, experimental set-up and interpretation for forensic toxicologists

Forensic entomotoxicology studies the usefulness of insects as alternative toxicological samples. Use of insects as alternative matrix for drug detection is well documented and recommended when conventional matrices such as blood, urine or internal organs are no longer available. However, several limitations of entomotoxicology have been highlighted, especially concerning interpretation of the drug concentrations in insects on human forensic cases. In addition, the lack of knowledge in pharmacokinetic of drugs in insects, large variability of experimental set-up and toxicological analysis compromise the utility of this science. This review focuses on the current knowledge of factors influencing drug detection in insects. Reasons for the current limitations, but also recommendations for future research are discussed and proposed in this paper.

Effects of malathion on the insect succession and the development of Chrysomya megacephala (Diptera: Calliphoridae) in the field and implications for estimating postmortem interval

A field study on the effects of malathion on insect succession and the development of carrion flies on corpses, and its quantitative determination from the larvae on decomposing rabbit carrion was conducted. The rabbits were treated with malathion at concentrations of lethal, half-lethal and fourth-lethal doses. Malathion altered decomposition rates and species diversity: Chrysomya megacephala (Diptera: Calliphoridae) was the most abundant adult species in all the experiments; third instar larvae of Chrysomya rufifacies (Diptera: Calliphoridae) were not found on the toxic carcasses but were collected from the control; the appearance of beetles on the treated carcass was later by 1 to 3 days than on the control carcass. Development rate of the dominated species C. megacephala larvae and pupae was observed. Stepwise increases in the period of larval development, the maximum length of larvae, and weight of pupae were observed with increasing malathion concentrations. However, there was no significant difference in the duration of the pupal stage. The differences in development rate were sufficient to alter postmortem interval estimates based on larval development by 12 to 36 hours. The time of finding fresh pupae from the fourth-lethal carcass was 12 hours later than the control. Accumulations of the pesticide in larvae were observed, but no correlations were found between larvae concentrations and the initial quantity administered to rabbits.In conclusion, it is necessary to consider the effects of malathion present in decomposing bodies when estimating the postmortem interval based on entomological evidence. The results of this study have more practical implications for forensic investigations because it is under natural conditions.

Determination of malathion levels and its effect on the development of Chrysomya megacephala (Fabricius) in South China

The present study determines the concentration of Malathion in rabbit tissues and Dipteral larvae feeding on those tissues. Malathion was found in all muscle and liver samples of the test rabbit, as well as larvae fed on it. Samples from the control rabbit and pupae from all colonies were negative for Malathion. Correlations were found between administered dosage, tissue concentrations and younger or prepuparial larvae. Effects of Malathion on the development rate of Chrysomya megacephala (Fabricius) were also reported. C. megacephala is the most common fly species found on corpses in South China during the early stages of decomposition. Significant differences in larval growth rate were both observed among the colonies fed on muscle and liver. The presence of Malathion in both muscle and liver appears to retard the normal growth rate of C. megacephala in larval stage. Larvae from all colonies fed on tissues from rabbits treated with Malathion were smaller and attained maximum length later than those from the control colony. Duration of the larval and pupal stages was both significantly prolonged for larvae on tissues from rabbit receiving Malathion than those from the control colony. The difference of the duration of the larval and pupal stages together from the muscle colonies would alter the postmortem interval estimation by up to 36h. As for liver colonies, it would alter the postmortem interval estimation by up to 28h. A significantly different duration of the larval and pupal stages from the muscle colonies would alter a postmortem estimate by up to 28h relative to the liver colonies.

Recent applications of liquid chromatography–mass spectrometry in forensic science

Recent years have seen the development of powerful technologies that have provided forensic scientists with new analytical capabilities, unimaginable only a few years ago. With liquid chromatography-mass spectrometry (LC-MS) in particular, there has been an explosion in the range of new products available for solving many analytical problems, especially for those applications in which non-volatile, labile and/or high molecular weight compounds are being analysed. The aim of this article is to present an overview of some of the most recent applications of LC-MS (/MS) to forensic analysis. To this end, our survey encompasses the period from 2002 to 2005 and focuses on trace analysis (including chemical warfare agents, explosives and dyes), the use of alternative specimens for monitoring drugs of abuse, systematic toxicological analysis and high-throughput analysis. It is not the intention to provide an exhaustive review of the literature but rather to provide the reader with a 'flavour' of the versatility and utility of the technique within the forensic sciences.

Fly pupae and puparia as potential contaminants of forensic entomology samples from sites of body discovery

Fly pupae and puparia may contaminate forensic entomology samples at death scenes if they have originated not from human remains but from animal carcasses or other decomposing organic material. These contaminants may erroneously lengthen post-mortem interval estimates if no pupae or puparia are genuinely associated with the body. Three forensic entomology case studies are presented, in which contamination either occurred or was suspected. In the first case, blow fly puparia collected near the body were detected as contaminants because the species was inactive both when the body was found and when the deceased was last sighted reliably. The second case illustrates that contamination may be suspected at particularly squalid death scenes because of the likely presence of carcasses or organic material. The third case involves the presence at the body discovery site of numerous potentially contaminating animal carcasses. Soil samples were taken along transects to show that pupae and puparia were clustered around their probable sources.

Drug analysis in blowfly larvae and in human tissues: a comparative study

The present study investigates the correlation between concentrations of drugs in human tissues and Diptera larvae feeding on these tissues. Samples of liver were taken from 18 cases in which preliminary toxicological screening indicated the presence of drugs. Blowfly larvae (Diptera: Calliphoridae) were reared on these samples and subsequently analyzed for drug content. Toxicological analyses were carried out using ONLINE Abuscreen (Roche) and GC/MS for available body fluids (blood, urine and bile) as well as liver samples and maggots. All drugs detected in human tissues were also detected in insect specimens. Opiates, cocaine and barbiturates as well as some antidepressants (clomipramine, amitryptiline, nortryptiline, levomepromezine and tioridazine) were observed. Comparisons of drug concentrations between those in human tissues and blowfly larvae showed different patterns of distribution that may be attributed to differences in physiology. Results confirm the reliability of entomological specimens for qualitative analyses, although quantitative extrapolations are unreliable. All xenobiotics detected were in higher concentrations in human tissues than in maggots. Concentrations in post-feeding maggots were significantly lower than for feeding maggots, suggesting that the feeding state of maggots may affect toxicological analyses as they metabolize and eliminate drugs during development.