How does dichlorvos work against fleas? - briefly
Dichlorvos is an organophosphate that blocks acetylcholinesterase, disrupting nerve transmission and causing paralysis in fleas. The neurotoxic action results in rapid death, typically within minutes of exposure.
How does dichlorvos work against fleas? - in detail
Dichlorvos is an organophosphate insecticide that targets the nervous system of fleas. After contact or ingestion, the compound penetrates the cuticle and is distributed through the hemolymph. Inside the nervous tissue, dichlorvos binds to the active site of acetylcholinesterase (AChE), an enzyme responsible for hydrolyzing the neurotransmitter acetylcholine. The binding is covalent and irreversible, preventing the breakdown of acetylcholine in synaptic clefts.
The resulting accumulation of acetylcholine continuously stimulates cholinergic receptors. Overstimulation produces uncontrolled muscle contraction, loss of coordination, and paralysis of the parasite. Paralysis progresses to respiratory failure and death within minutes to hours, depending on dose and flea life stage.
Key steps in the toxic action are:
- Absorption: rapid diffusion through the exoskeleton into the hemolymph.
- Enzyme inhibition: irreversible phosphorylation of AChE active site.
- Neurotransmitter buildup: excess acetylcholine in synaptic gaps.
- Physiological disruption: sustained stimulation of nicotinic and muscarinic receptors leads to spastic paralysis.
- Mortality: failure of neuromuscular transmission causes cessation of vital functions.
Formulations for flea control typically contain dichlorvos dissolved in a volatile solvent, allowing quick evaporation and widespread distribution on treated surfaces. The vapor phase enhances penetration into flea habitats, reaching hidden stages such as eggs and larvae. Residual activity persists for several days, providing ongoing control.
Resistance mechanisms reported in some flea populations involve elevated levels of detoxifying enzymes (e.g., esterases) that hydrolyze organophosphates before they reach AChE. Monitoring for reduced susceptibility is necessary when using this compound repeatedly.
Safety considerations include strict adherence to label concentrations, avoidance of direct skin contact, and proper ventilation during application. Dichlorvos is toxic to mammals and non‑target insects; protective equipment and containment measures reduce accidental exposure.