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Carrion Fly and Disease Vector Activity Associated with a Decomposing Corpse LTJG David England,MSC,USN Medicolegal Entomology Navy Entomology Center of Excellence Naval Air Station Jacksonville, FL
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Objectives 1.Basic Methods For Estimating Postmortem Interval 2.Oregon Decomposition And Insect Succession Model 3.Current Forensic Entomology Endeavors
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AccumulatedDegreeDayHours Post Mortem Interval(PMI)
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Estimation of PMI Insect succession patterns Insect life cycles Influential variables Life Cycle Variables SuccessionPMI
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Variables that influence PMI Temperature Season Species Death Scenario Toxicology Parasitoids & Predators
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Insect Succession Succession of insects generally follows a similar pattern at the family level, but there are variations at the genus and species levels with respect to differing geographical locations Forensic entomology ‘works’ because succession is a very predictable and consistent event
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Site Location Soap Creek Ranch, 18km NW of Corvallis
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Animal Model 36 kg domestic pigs Euthanasia method Clothed Caged Human homicide scenario
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Sampling Methods: Onsite & Laboratory Temperature readings: ambient, carcass and maggot mass Insect Sampling Sticky, Pitfall, Hand Sample and Net One Pig Weighed Daily (Change in Mass) Growth Chambers 22°C and 12 hours controlled light 22°C and 12 hours controlled light Identifications - OSU Insect Collection
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Stages Of Decomposition* Fresh Bloated Active Decay Advanced Decay Dry Remains * Catts and Haskell, 1990
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Fresh Stage 10 minutes PMI Calliphoridae, species Lucilia illustris (Meigen) Egg clusters: six hours PMI Reared and identified
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Calliphoridae Green bottle fly (Lucillia illustris) Photo: http://bugguide.net
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Bloated Stage Eight hours - Bloating 12 hours, bald-faced hornets (Dolichovespula maculata) (Linnaeus) 33 hours PMI: the green bottle fly eggs hatched 48 hrs: Staphylinidae appear
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Staphylinidae Brown and gold rove (Ontholestes cingulatus) Hairy rove (Creopilus maxillosus Photo: http://bugguide.net
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Active Decay Stage 72 hour PMI Red-tailed flesh fly (Sarcophaga haemorrhoidalis) Terrestrial isopods Adult green bottle fly decreasing Dermestidae, Silphidae, Histeridae
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Advanced Decay Stage 120 hours: carcass began to desiccate 132 hours: third instar/post feeding maggots 147 hours: maggot mass exited carcass Large predator/scavenger activity
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Post Feeding Activities
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Green bottle fly pupae
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Dry Remains Stage 288 hrs PMI Desiccated Beetle Activity No odor Seasonal rain mid- October 25 days: scavengers November: cages removed
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November, 2005 Cage removed Cage removed April, 2006 6 months after cage removal
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Decomposition Summary Green bottle fly within 10 min Ovipositing/egg cluster 6 hrs 33 hrs: first hatch 12 hrs: predators (hornet) 72 hrs: predators (beetles) 168 hrs: green bottle maggots left carcass Jan. 1 st little evidence left; dead vegetation
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Temperature Summary Ambient temperatures (°C): Mean 20.8; Min. 9.03; Max. 34.9 Maggot mass temperature (°C): Mean 30.9; Max. 50.7 (128 hrs.PMI) Mean RH: 50% Precipitation: none until Oct.
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Rate of Decomposition % mass
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Decomposition Rates Log of % mass
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Linearized Regression Analysis _______________________________________________________________ Studies R² Slope (estimated) _______________________________________________________________ Grassberger: European Urban Habitat 1) May 0.907-0.0786 2) Aug. 0.9677-0.0586 Richards: Hawaiian Islands 1) 1877 m 0.9338-0.1075 2) 1169 m 0.8651-0.1104 3) 646 m 0.8834-0.1204 Anderson: SW British Columbia 1) Carcass 10.9253-0.0372 2) Carcass 2 0.9781-0.0303 England: Corvallis, Oregon 1) Carcass 10.9517-0.2378
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Summary Regional Model Standardized Analysis * * All slope values produced consistent results *Exponential decomposition rate that can be evaluated with linearization Utilized In Further Research (geography, seasons, scenarios, etc.)
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Current Forensic Entomology Endeavors Provide Entomological Training For Naval Criminal Investigation Service Georgia Research With Naval Criminal Investigation Service Iraq Fly Samples
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Acknowledgements Dr. Phil Rossignol Dr. Anne Rossignol Dr. Brian Croft Dr. Paul Jespersen CDR Szumlas Joyce Takyasu Clint Sexton
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Questions and Discussion
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