Organophosphate
Definition
A class of synthetic pesticides that irreversibly inhibit acetylcholinesterase, causing cholinergic toxidrome: muscle paralysis, hypersecretion, seizures. Common agricultural compounds (e.g. dimethoate, chlorpyrifos) are misused in wildlife poisoning.
- Mechanism
- Irreversible acetylcholinesterase inhibition
- Toxidrome
- Cholinergic: paralysis, hypersecretion, seizures
- Examples
- Dimethoate, chlorpyrifos
- Forensic context
- Wildlife poisoning misuse
Common questions
Why is organophosphate inhibition of acetylcholinesterase described as irreversible?+
The compound binds and phosphorylates the enzyme's active site, and unless a reactivating antidote such as pralidoxime is given promptly, the bond ages into a permanent form, so the body must synthesise new enzyme rather than simply clearing the inhibitor to recover function.
How is organophosphate poisoning confirmed in a wildlife forensic case?+
Investigators typically measure depressed cholinesterase activity in blood or brain tissue alongside targeted chemical analysis, usually GC-MS, for the specific parent compound or its metabolites in stomach contents, tissue, or bait material recovered at the scene, since enzyme depression alone does not identify which compound was used.
Related terms
- Alpha-Chloralose
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- Carbofuran
- A carbamate insecticide (N-methyl carbamate group) that inhibits acetylcholinesterase. Marketed as Furadan; highly toxic at low doses; documented in large-scale raptor and...
- Cholinesterase Inhibition
- The biochemical mechanism of organophosphate and carbamate toxicity: inhibition of the enzyme acetylcholinesterase prevents breakdown of acetylcholine at synapses, producing overstimulation of...
- LC-MS
- Liquid chromatography-mass spectrometry: the confirmatory analytical method for pesticide residues in biological matrices. Separates compounds by chromatography, then identifies them by mass-to-charge...
- PAX Field Kit
- Poison Avoidance eXplorer immunoassay kit: a rapid colorimetric screening tool that detects compound groups (OPs, carbamates, rodenticides) in field extracts from bait...