Carcass Decomposition Research Articles

An Insect Complex of Large Animal Carcasses and the Peculiarities of Their Decomposition in Northern European Russia

An insect complex decomposing large animal carcasses was studied in two habitat types in northern European Russia (the Republic of Karelia), with the domestic pig Sus scrofa domesticus L. used as a model. Altogether, 100 species of insects belonging to 25 families and 6 orders were revealed on or in the carcasses. The two biotopes differed in the species composition and relative abundance of necrobionts. The structure and succession of the insect complex in the process of carcass decomposition are analyzed.

Seasonality of Insect Succession and Dog Carcass Decomposition in Different Habitats

The different collected insect species were distributed on the carcasses according to the decomposition stages or postmortem intervals (PMI). In the winter season, the insect succession showed that carcasses placed outdoor attracted the greatest numbers and highest diversity of insect species. The calliphorid fly; Chrysomya albiceps was first attracted to the bloated and decay stages. In both habitats (outdoor and indoor), the numbers and diversity of insect species on carcasses were decreased during the advanced decay stage and then increased again during the dry stage. In the spring season, Chrysomya albiceps was the first fly attracted to the fresh or bloated stage of dog carcass in both habitats. Moreover, calliphorid flies were disappeared during the advanced decay stage in both habitats. While Coleopteran insects appeared during the decay and advanced decay stages. In the summer season, the forensic insect species showed nearly the same distribution of the different decomposition stages. Also, Chrysomya albiceps was the first fly attracted to the early stages of decomposition. In general, it appeared that the diversity and numbers of forensic insect species, which colonize dog carcass, were increased outdoor and decreased indoor. In the autumn season, carcasses placed outdoor attracted the greater numbers and higher diversity of forensic insects. The calliphorid fly, Chrysomya albiceps,and housefly, Musca domestica were first attracted to the fresh and bloated stages, especially of carcasses placed outdoor. The adult beetles, Dermestes maculatus, Necrobia rufipes and Hister sp.were early seen during bloated, decay and advanced decay stages.

Development and Field Evaluation of a Novel, Inexpensive Passive Trap for Monitoring Dispersal of Necrophagous Dipteran Larvae.

Techniques for the survey of necrophagous dipterans are frequently designed for adult flies and often neglect forensically important information, such as the postfeeding larval dispersal following carcass colonization. In this study, we propose and test a novel trap design for the collection of dipteran larvae at the postfeeding stage. The Trap for Dispersing Larvae (TDL) consists of two semiindependent parts: 1) a 2-liter PET bottle, containing the attractant (carcass); and 2) a plastic box, which selectively captures postfeeding dispersing larvae. Based on a field test in a dry forest fragment in Brazil, the TDL trap captured ca. 1,500 larvae of 13 species of Calliphoridae, Muscidae, Fanniidae, and Sarcophagidae. The species richness of dispersing larvae recorded in our study was ca. 60% of that previously recorded in this area. As the TDL trap can assess larval dispersal without interfering with carcass decomposition, we demonstrate that it can be used to assess temporal variation in the dynamics of colonization. In the present study, most larval dispersal occurred at 5-d postexposure, but the traps remained efficient until 7 d, by which time rat carcasses had skeletonized. We conclude that the TDL trap captures the dispersing dipteran larvae with little interference in carcass decomposition processes. The trap also provides a representative sample of species and is simple to use and of low cost.

Decomposition of Pig Carcasses at Varying Room Temperature

Decomposition of Pig Carcasses at Varying Room Temperature

Succession pattern of insects in relation to killing methods of <i>Rattus norvegicus</i> at Delta State University, Abraka, Nigeria

The succession pattern of insects associated with the strangling and slaughtering of rat (Rattus norvegicus) was conducted between March and June 2017. Four (4) Albino Wistar rats were killed using strangle and slaughter methods, one method for a pair. The rat carcasses were secured from scavengers and restricted from human interference in a way that did not necessarily restrict access to the carcasses and also enabled insect collection. Insects were collected daily by hand picking and with the aid of aerial net, forceps and fine paintbrush. Collection was done within short period while checking the physical condition of carcass to note the stages of decay. Six insect families of three orders were collected from the carcass killed by strangling namely the Muscidae (32%), Sarcophagidae (16%), Calliphoridae (16%), Dermestidae (16%), Chrysomelidae (4%) and Cleridae (5%). In the carcass killed by slaughtering method, the families obtained were Muscidae (50%), Sarcophagidae (18%) Calliphoridae (18%), Dermestidae (9%), Staphylindae (5%). There was no significant difference (P>0.05) in the succession pattern of the insects though more individuals were obtained in the strangled carcass (55%) compared to the slaughtered carcass (45%). This study shows the succession pattern may have no significant or obvious influence on the decomposition of carcasses. Therefore there is need to probe further into other killing methods.Keywords: Carcass; decomposition; forensic; strangled; slaughtered

Insect succession pattern on decomposing pig carcasses in Tasmania: a summer study'

Insect succession has been studied around the world using the predictable and mostly sequential arrival pattern of different insect species that are attracted to a decomposing carcass. In cases of suspicious death of humans and animals, carrion insects may be used to assist in crime scene reconstruction. The present research represents the first study in forensic entomology to be undertaken in Tasmania, investigating insect succession patterns on decomposing pig carcasses and providing a preliminary database of forensically important insects. Six pig carcasses were placed in two contrasting locations (rural and urban) in northern Tasmania. Insect successional waves were recorded over a 40-day study during the austral summer season. Results showed that decomposition rates and insect assemblages varied between each location. Eleven insect taxa, representing nine families, were identified in association with the decomposition of the pig carcasses at both localities. Blowflies present on the pig carcasses throughout the decomposition process were Calliphora stygia Malloch (Diptera: Calliphoridae) at both sites and Lucilia sericata (Meigen) at the urban site only. These preliminary results will provide useful information in any future casework involving human remains and associated insect material in Tasmania.

Changes in soil nutrients (ammonia, phosphate and nitrate) associated with rat carcass decomposition under tropical climatic conditions

Changes in soil nutrients have been applied in legal investigations of the time of death or to locate a clandestine grave. However, research on forensic soil chemistry under the tropical climate conditions in Malaysia is at its infancy, with few data available for forensic investigations. This study aims to study changes of soil nutrients (i.e. ammonia, phosphate and nitrate) as well as soil pH and electrical conductivity (EC), and the associated stages of decomposition of rat carcasses (n = 3) under controlled tropical climate conditions. The results showed differences in soil pH between control and carcass soils. Soil EC and concentrations of ammonia and phosphate increased during early decomposition stages, and declined thereafter. Nitrate concentration increased at the later stage of decomposition. We also found that the top layer of soil (i.e. 5 cm from surface) rendered a significant pattern of soil nutrient dynamics compared with soil at 10 cm from the surface, possibly due to a slower rate of vertical transfer and the washing-off effect. We suggest that the soil EC value and changes of soil nutrients in the top 5 cm of the soil layer have potential in forensic investigation to determine the minimum post-mortem interval and serve as an indicator for hidden graves and cadaver decomposition islands.

Assessment of Entomological Remains from Soil Samples Collected from a Pig (Sus scrofa domestica) Carcass Decomposition Site after 13 Years

Carrion insects inhabiting the soil play an important role in forensic investigations because they may help to solve both active and cold cases. The aim of this study was to examine the entomofauna of forensic importance in soil samples removed after 13 years from a pig carrion decomposition site. Soil samples were collected from an old carrion decomposition study site in Bâla, the Ankara Province. Four holes, approximately 40 cm deep and 35 cm width were excavated at the study site. The samples were collected and placed in ventilated cups. Each cup was labeled mentioning the excavation location, time, date, and name of the collector. Insects and their remains found in the soil were collected by sweeping the soil from the specimens using a brush. The insects were morphologically identified. A total of 635 specimens of Calliphoridae, Dermestidae, Cleridae, Staphylinidae, Histeridae, and Formicidae were identified. Flies such as Chrysomya albiceps (Wiedmann, 1819), and beetles such as Dermestes frischii (Kugelan, 1792), Necrobia rufipes (De Geer, 1775), and Creophilus maxillosus (Linnaeus, 1758), were identified as the species. Our results show that soil samples still harbor entomological specimens after 13 years. This study, to the best of our knowledge, was the first of its kind in Turkey. Forensically, important insects and their remains may be identified in the soil long time after the corpse is buried. Consequently, cold cases may be solved using insects.

Metabarcoding to investigate changes in soil microbial communities within forensic burial contexts

The estimation of the time elapsed since death (post-mortem interval, or PMI) is one of the key themes that forensic scientists have to address frequently. However, the estimation of PMI still suffers from poor accuracy and biases especially when decomposition stages are prolonged, so further improvements in methods for PMI estimation are desirable. Soil microbial communities associated with decomposing bodies have been shown to be good candidates for the estimation of the PMI of exposed bodies. Nevertheless, further research is required to better understand the bacterial succession associated with decomposition of buried carcasses in order to test its reliability and applicability for the estimation of PMI and to better understand the dynamics involved with decomposition within this particular scenario. Therefore we explored the succession of soil microbial communities associated with four decomposing pig carcasses (from one to six months PMI) using a metabarcoding approach. The sequencing of the bacterial 16S rRNA variable region 4 (V4) revealed trends linking particular microbial taxa with specific PMIs, and notably an increase in Proteobacteria, Firmicutes and Bacteroidetes at specific PMIs as well as a decrease in Acidobacteria. Our results, in accordance with previous studies conducted on exposed bodies of different mammalian species (including humans), also showed a general reduction of the taxonomic richness from two months PMI onwards, as well as an incomplete re-establishment of the starting soil microbial conditions after six months PMI. We also found specific mammal-derived taxa, such as Bacteroides spp., being still present in the soil after six months PMI. As such, this study serves as a baseline for additional research to allow the characterisation of biomarkers associated with specific PMIs. Due to the similarity between the results presented here and those reported in other types of decomposition studies we believe that the metabarcoding approach has considerable potential in the estimation of the PMI, particularly to clarify cases involving heavily skeletonised bodies or for the investigation of clandestine graves in which the carcass has been moved from its original place of deposition.

Effect of carbon and nitrogen mobilization from livestock mortalities on nitrogen dynamics in soil

Carcass decomposition in the soil can be an important source of nutrients such as nitrogen (N) by affecting N turnover in soils. The objective of this research was to estimate N input from decaying swine carcasses, thereby evaluating the impact of carrion decomposition on N dynamics in soil. Carcass decomposition using recently culled (<6 h) swine carcasses was carried out in a reactor filled with agricultural soil. Soil samples, collected four times (at 0, 10, 30 and 60 days after carcass placement) from the reactor were used in a tracer experiment to quantify the changes in soil nutrients and N dynamics. Tracer incubation experiments were carried out for seven days using 14C-labelled L-alanine (C3H7NO2) to investigate key N cycling processes in the soil. Mortalities were a significant source of N and carbon (C), providing an average of 42 and 236 g/kg, respectively, to the soil directly below the decomposing carcasses. There was also a significant and long-term input of amino acids (ca. 11 mg/kg) into the soil. The abundance of N increased the microbial turnover of labile N substances in the tracer experiment. Based on results from this study, it has been demonstrated that decaying carcasses provide a significant and long-lasting localized resource with the potential to contribute to soil N cycling. Therefore, it is important to develop guidelines on the management of carcass burial farmland using soil from burial pits as a nutrient supplement where biosecurity is assured.

A Preliminary Study of Carrion Insects and Their Succession in Luanda, Angola.

The study of the arthropod fauna involved in carcass decomposition is crucial for medicolegal forensic purposes. This knowledge is especially needed in countries with high levels of criminality and where the arthropod fauna is still under-recorded and not well known, such as Angola. We present data from the first survey on sarcosaprophagous flies and beetles in Angola, conducted in Luanda over a 17-d period, in the wet summer season. In total, 881 adult and immature specimens, belonging to 18 species, were collected from three pig carcasses that were sampled daily. Three species were not previously known from Angola. The dominant flies were Chrysomya albiceps (Wiedemann, 1819) (Diptera: Calliphoridae) and Chrysomya megacephala (Fabricius, 1794), but Chrysomya marginalis (Wiedemann, 1830), Chrysomya putoria (Wiedemann, 1830), and Liosarcophaga emmrichiana (Lehrer, 2002) (Diptera: Sarcophagidae) also bred on the carcasses. The dominant beetles were Dermestes maculatus De Geer, 1774 (Coleoptera: Dermestidae), Saprinus splendens (Paykull 1811) (Coleoptera: Histeridae), and Necrobia rufipes (De Geer, 1775) (Coleoptera: Cleridae). Because of the hot weather during the experimental period (~27°C), decomposition was extremely fast. Periods of insect activity on carcasses are presented and comparisons are made with other carrion communities reported from the Afrotropical region.

Temperature Influence on Prevailing Necrophagous Diptera and Bacterial Taxa With Forensic Implications for Postmortem Interval Estimation: A Review.

The decomposition process of human (and other mammalian) remains is influenced by numerous factors such as the environmental temperature, relative humidity, precipitation, geographical location of the remains, as well as the medical conditions of and any injuries sustained by the deceased person. The decomposition process generally follows a consistent pattern (fresh, bloat, active decomposition, advanced decomposition, and dry stage). Understanding the time-span of each stage of decomposition and the influence of the biotic and abiotic factors involved is imperative when trying to estimate the time elapsed since death (postmortem interval [PMI]). Over the course of decomposition, the tissues are gradually consumed by necrophagous insects and bacteria. The environmental temperature and its variations influence how insects colonize the remains, having a significant impact on their presence and developmental cycle. Additionally, the bacterial community colonizing decomposing tissues is also greatly affected by variations in environmental temperature. Because both the rate of decomposition of human remains and the relative abundance of certain insects and bacterial species are all temperature-dependent, insect and bacterial colonization data are useful as key points for the PMI estimation. This article reviews the current literature documenting the data collected on the occurrence and development cycles of predominant necrophagous Diptera (Calliphoridae, Muscidae, Sarcophagidae) and bacterial taxa involved in the decomposition of various carcasses at different temperatures. This review will impact the forensic community by providing an overview on the temperature, insect and bacterial records for the PMI estimation, seeking to aid forensic entomologists, microbiologists, pathologists, and the legal community.

Characterizing forensically important insect and microbial community colonization patterns in buried remains

During violent criminal actions in which the perpetrator disposes of the victim’s remains by burial, the analysis of insects and bacterial colonization patterns could be necessary for postmortem interval (PMI) estimation. Our research aimed to assess the decomposition process of buried rat carcasses from shallow graves (40 cm), the diversity and dynamics of insects and bacteria throughout the decomposition stages, and the environmental parameters’ influence on these variations. The results provide further insight on decomposition in soil and contribute to a broader understanding of the factors involved in decomposition by qualitatively and quantitatively analysing the decomposer community (bacteria and insects). Additionally, two bacterial taxa, Enterococcus faecalis and Clostridium paraputrificum that were investigated for the first time as PMI indicators using quantitative polymerase chain reaction (qPCR) showed differential abundance over time, promising data for PMI estimation. The current study on the decomposition of buried rat carcasses in a natural environment will strengthen the current knowledge on decomposed remains from shallow graves and represents an effort to quantify insect and bacterial taxa as PMI estimators.

The Diversity and Activity of Flies (Diptera: Cyclorrhapha) as Forensic Indicators at Outdoor and Indoor Rat Carccasses in Dramaga, Bogor

This study aims to identify the diversity of flies that were caught and interacted with carcasses at the day and night. Each of the three rat carcasses (Rattus norvegicus) was placed outdoor and indoor within the campus of IPB Dramaga. The carcasses were put into a screen cage. Observation of flies was begun at 06:00 am and so on every four hours until the skeletal stage of the carcasses reached. The flies that come to the carcasses and into the screen cage were collected and identified. The decomposition of the indoor carcasses is slower than at outdoor, with the longer fresh stage. Meanwhile, post-decay stage and skeletal stage were achieved at the same time at each location. Nine spesies captured flies which are forensic indicator were Chrysomya megacephala (Fabricius), Chrysomya bezziana Villeneuve, Chrysomya rufifacies (Macquart), Chrysomya saffranea, Chrysomya spp, Lucilia spp, Sarcophaga spp, Calliphora spp and Musca domestica. C. bezziana Villeneuve and C. megacephala (Fabricius) were the dominant flies at outdoor carcasses. Meanwhile, the indoor carcasses was dominated by Lucilia spp.

Likely locations of sea turtle stranding mortality using experimentally-calibrated, time and space-specific drift models

Sea turtle stranding events provide an opportunity to study drivers of mortality, but causes of strandings are poorly understood. A general sea turtle carcass oceanographic drift model was developed to estimate likely mortality locations from coastal sea turtle stranding records. Key model advancements include realistic direct wind forcing on carcasses, temperature driven carcass decomposition and the development of mortality location predictions for individual strandings. We applied this model to 2009–2014 stranding events within the Chesapeake Bay, Virginia. Predicted origin of vessel strike strandings were compared to commercial vessel data, and potential hazardous turtle-vessel interactions were identified in the southeastern Bay and James River. Commercial fishing activity of gear types with known sea turtle interactions were compared to predicted mortality locations for stranded turtles with suggested fisheries-induced mortality. Probable mortality locations for these strandings varied seasonally, with two distinct areas in the southwest and southeast portions of the lower Bay. Spatial overlap was noted between potential mortality locations and gillnet, seine, pot, and pound net fisheries, providing important information for focusing future research on mitigating conflict between sea turtles and human activities. Our ability to quantitatively assess spatial and temporal overlap between sea turtle mortality and human uses of the habitat were hindered by the low resolution of human use datasets, especially those for recreational vessel and commercial fishing gear distributions. This study highlights the importance of addressing these data gaps and provides a meaningful conservation tool that can be applied to stranding data of sea turtles and other marine megafauna worldwide.

Characterization and microbial analysis of first recorded observation of Conicera similis Haliday (Diptera: Phoridae) in forensic decomposition study in Romania

The identification of necrophagous insect diversity and dynamics has forensic significance for postmortem interval estimation specific to burial. Few studies regarding the necrophagous entomofauna from buried remains have been performed to date. In contrast to the exposed carcasses, the accessibility of soil to insects is limited due to burial depth and is dependent on soil type. This study highlights the colonization behavior of Conicera similis (Haliday 1833) (Diptera: Phoridae) during carcass decomposition, a previously unobserved taxon in Romania. Adult and larvae specimens were collected from rat (Rattus norvegicus) carcasses buried at 40 cm depth in an urban park environment in June 2016 during active decomposition and their presence and activity period was correlated with the environmental parameters variation. Bacterial diversity from C. similis female adult and larvae specimens was determined via 16S rRNA gene Illumina sequencing to further characterize these commonly encountered and forensically important necrophagous insects. This report signals the easternmost geographical location in Europe (Bucharest, Romania) of C. similis to date.

Lab-scale evaluation of aerated burial concept for treatment and emergency disposal of infectious animal carcasses

Nearly 55,000 outbreaks of animal disease were reported to the World Animal Health Information Database between 2005 and 2016. To suppress the spread of disease, large numbers of animal mortalities often must be disposed of quickly and are frequently buried on the farm where they were raised. While this method of emergency disposal is fast and relatively inexpensive, it also can have undesirable and lasting impacts (slow decay, concerns about groundwater contamination, pathogens re-emergence, and odor). Following the 2010 foot-and-mouth disease outbreak, the Republic of Korea's National Institute of Animal Science funded research on selected burial alternatives or modifications believed to have potential to reduce undesirable impacts of burial. One such modification involves the injection of air into the liquid degradation products from the 60–70% water from decomposing carcasses in lined burial trenches. Prior to prototype development in the field, a laboratory-scale study of aerated decomposition (AeD) of poultry carcasses was conducted to quantify improvements in time of carcass decomposition, reduction of potential groundwater pollutants in the liquid products of decomposition (since trench liners may ultimately leak), and reduction of odorous VOCs emitted during decomposition. Headspace gases also were monitored to determine the potential for using gaseous biomarkers in the aerated burial trench exhaust stream to monitor completion of the decomposition. Results of the lab-scale experiments show that the mass of chicken carcasses was reduced by 95.0 ± 0.9% within 3 months at mesophilic temperatures (vs. negligible reduction via mesophilic anaerobic digestion typical of trench burial) with concomitant reduction of biochemical oxygen demand (BOD; 99%), volatile suspended solids (VSS; 99%), total suspended solids (TSS; 99%), and total ammonia nitrogen (TAN; 98%) in the liquid digestate. At week #7 BOD and TSS in digestate met the U.S. EPA standards for treated wastewater discharge to surface water. Salmonella and Staphylococcus were inactivated by the AeD process after week #1 and #3, respectively. Five gaseous biomarkers: pyrimidine; p-cresol; phenol; dimethyl disulfide; and dimethyl trisulfide; were identified and correlated with digestate quality. Phenol was the best predictor of TAN (R = 0.96), BOD (R = 0.92), and dissolved oxygen (DO) (R = −0.91). Phenol was also the best predictor populations of Salmonella (R = 0.95) and aerobes (R = 0.88). P-cresol was the best predictor for anaerobes (R = 0.88). The off-gas from AeD will require biofiltration or other odor control measures for a much shorter time than anaerobic decomposition. The lab-scale studies indicate that AeD burial has the potential to make burial a faster, safer, and more environmentally friendly method for emergency disposal and treatment of infectious animal carcasses and that this method should be further developed via prototype-scale field studies.

Nesting strategies and disease risk in necrophagous beetles.

While the effects of carcass decomposition on microorganisms have been demonstrated in recent years, little is known of how this impacts necrophagous insects. A common assumption is that insects that exploit carcasses are exposed to a high density of potentially harmful microorganisms, but no field data have so far validated this. Necrophagous beetles such as the Scarabaeinae have complex nesting behaviors with elaborate parental care. So here, we begin to explore whether this conjunction of life history and nesting behavior represents an adaptive response to the threat posed by microbes in these environments, mainly by entomopathogens. We evaluated the density and distribution of fungi and bacteria from soil near the carcasses, and their ability to infect and kill insects that are in contact with this soil during the decomposition process. Our data showed an increase in the density and activity of opportunistic or facultative pathogens during the apex of decomposition, when there is a predominance of necrophagous insects. Meanwhile, the survivorship of bait insects decreased when in contact with soil from this period of decomposition, indicating a potential risk of infection. However, the density and activity of these microorganisms decreased with distance from the carcass, mainly with depth, which would benefit tunneller beetles in particular. We have thus provided the first field data to show that necrophagous insects are indeed exposed to high densities of potentially harmful microorganisms. Furthermore, we propose that some parental care strategies may have arisen not only as a response to competition, but also as adaptations that reduce the risks of disease. Although we have focused on carrion feeders, we suggest that the same occurs with coprophagous beetles, as both carrion and dung are nutrient‐rich resources.

The Influence of Carcass Microlocation on the Speed of Postmortem Changes and Carcass Decomposition

The Influence of Carcass Microlocation on the Speed of Postmortem Changes and Carcass Decomposition

Modeling the transmission dynamics of anthrax disease in cattle and humans

Anthrax is a zoonotic disease caused by bacillus anthraces. In this study a deterministic mathematical model for transmission dynamics of anthrax in humans and animals is presented and quantitatively analyzed. To understand the dynamics of anthrax, the basic reproduction number $R_0$ which measures average new infections is computed using next generation matrix operator and analyzed by normalized forward sensitivity index. Analysis shows that anthrax transmission rate to animals, animals' natural death rate, anthrax natural death rate and animal's birth rate are the most sensitive parameters to the disease transmission dynamics. When animal recruitment and anthrax transmission rates increase, the basic reproduction number $R_0$ also increase proportionally. However, when animal natural and anthrax induced death rates increase, basic reproduction number $R_0$ decreases. Numerical simulations using Runge-Kutta method show that animals drive the dynamics of anthrax. The study suggests control strategies such as vaccination, fumigation and decomposition of carcasses to eradicate the disease.