How does dichlorvos act on lice? - briefly
Dichlorvos, an organophosphate insecticide, irreversibly inhibits acetylcholinesterase in lice, leading to accumulation of acetylcholine, uncontrolled nerve firing, paralysis, and death. The effect manifests within minutes, providing rapid control of infestations.
How does dichlorvos act on lice? - in detail
Dichlorvos, an organophosphate insecticide, interferes with the nervous system of lice by inhibiting acetylcholinesterase, the enzyme responsible for hydrolyzing the neurotransmitter acetylcholine. Accumulation of acetylcholine at synaptic junctions leads to continuous stimulation of cholinergic receptors, causing paralysis and eventual death of the parasite.
The toxic action proceeds through several identifiable steps:
- Absorption through the cuticle or respiratory openings allows rapid entry into the hemolymph.
- Binding of the compound to the active site of acetylcholinesterase forms a stable phosphorylated complex, rendering the enzyme inactive.
- Elevated acetylcholine levels maintain depolarization of neuronal membranes, resulting in uncontrolled muscle contraction.
- Sustained contraction exhausts the insect’s energy reserves, leading to loss of motor control and cessation of feeding.
Metabolic degradation of dichlorvos in the host environment is limited, ensuring sufficient concentration to affect the target organism before rapid hydrolysis reduces toxicity. Resistance mechanisms, such as elevated detoxifying enzymes or mutations in acetylcholinesterase, can diminish efficacy, but susceptibility remains high in most head‑lice populations.