When are ticks poisoned? - briefly
Ticks are poisoned when they ingest acaricides applied to hosts, vegetation, or bait stations, or when they feed on animals treated with systemic insecticides. These chemicals cause rapid paralysis and death within minutes to hours after exposure.
When are ticks poisoned? - in detail
Ticks become toxic to themselves under several well‑defined conditions.
Chemical control agents applied to the environment or directly onto hosts are the most common source of mortality. Acaricides such as permethrin, pyrethroids, organophosphates, carbamates, and amidines (e.g., amitraz) penetrate the cuticle or are ingested with blood, disrupting neural transmission or metabolic pathways. Laboratory data show lethal concentration (LC50) values ranging from 0.1 µg cm⁻² for permethrin to 5 µg cm⁻² for amitraz in adult Ixodes ricinus. Sub‑lethal exposure produces paralysis, reduced questing activity, and impaired attachment.
Veterinary pharmaceuticals administered to mammals can be transferred to feeding ticks. Ivermectin, moxidectin, and selamectin reach concentrations in blood that exceed the toxic threshold for many ixodid species. Ticks ingesting treated blood display rapid loss of motor coordination, cessation of feeding, and death within 24 h.
Environmental contaminants also induce toxicity. Heavy metals (lead, cadmium, mercury) accumulate in vegetation and soil, entering ticks through contact or through hosts that have bio‑accumulated the metals. Chronic exposure leads to enzymatic inhibition, oxidative stress, and mortality.
Biological control measures introduce pathogenic organisms that act as toxins for ticks. Entomopathogenic fungi (Metarhizium anisopliae, Beauveria bassiana) colonize the cuticle, producing cuticle‑degrading enzymes and secondary metabolites that cause rapid death. Bacterial agents such as Bacillus thuringiensis produce Cry toxins that, when ingested, disrupt gut epithelium.
Laboratory experiments sometimes use synthetic toxins to study tick physiology. For instance, injection of the neurotoxin tetrodotoxin blocks voltage‑gated sodium channels, resulting in immediate paralysis and death.
Key scenarios in which ticks are poisoned:
- Direct application of acaricides on vegetation or host fur/skin.
- Feeding on hosts that have received systemic antiparasitic drugs.
- Exposure to soils or plants contaminated with heavy metals.
- Infection by entomopathogenic fungi or bacteria producing lethal metabolites.
- Experimental administration of neurotoxins or metabolic inhibitors.
Each scenario involves a specific mode of action—neuroexcitation, enzyme inhibition, cuticle degradation, or metabolic disruption—leading to loss of motility, feeding cessation, and eventual death. Monitoring LC50 or LD50 values, exposure duration, and environmental conditions allows precise prediction of tick mortality under these toxic influences.