How does fipronil work against ticks? - briefly
Fipronil blocks GABA‑gated chloride channels in the tick’s nervous system, causing uncontrolled neuronal activity and paralysis. The resulting disruption leads to rapid death of the parasite.
How does fipronil work against ticks? - in detail
Fipronil belongs to the phenylpyrazole class of ectoparasiticides. Its primary action targets ligand‑gated ion channels of the tick nervous system. By binding to the γ‑aminobutyric acid (GABA)‑gated chloride channel, the compound blocks the flow of chloride ions that normally hyperpolarize neuronal membranes. The resulting loss of inhibitory signalling produces uncontrolled neuronal firing, leading to paralysis and death. A secondary target is the glutamate‑gated chloride channel, which is absent in mammals but present in many arthropods; inhibition of this channel reinforces the neurotoxic effect.
Key steps of the mode of action include:
- Penetration through the tick’s cuticle or ingestion during blood feeding.
- Conversion of fipronil to its sulfone metabolite, which exhibits greater affinity for the GABA receptor.
- Occupation of the receptor’s inhibitory binding site, preventing chloride ion influx.
- Disruption of synaptic transmission, causing sustained muscular contraction and eventual cessation of feeding.
Systemic application on a host animal distributes the chemical via the bloodstream, exposing attached ticks to lethal concentrations without direct contact. The compound remains active for several weeks, providing prolonged protection. Resistance mechanisms observed in some tick populations involve mutations in the GABA‑receptor subunits that reduce binding affinity, underscoring the need for integrated pest‑management strategies.