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An ectoparasiticide is an antiparasitic drug used in the treatment of ectoparasitic infestations. These drugs are used to kill the parasites that live on the body surface. Permethrin, sulfur, lindane, dicophane, benzyl benzoate, ivermectin and crotamiton are well known ectoparasiticides. Additionally, ectoparasiticides have been used to safely contaminate rhinoceros horns with hopes of it deterring the demand for these horns on the black market.

Variants

Permethrin

Broad-spectrum and potent pyrethroid insecticide and is most convenient for both scabies and lice. First choice drug. Permethrin exerts its therapeutic effect by disrupting sodium transport across neuronal membranes in arthropods, inducing depolarization. This mechanism ultimately leads to respiratory paralysis in the affected arthropod, establishing permethrin as a potent agent in managing scabies and pediculosis.

Additional information about treatment failure rates amongst medications used to treat ectoparasites:

https://www.dermatologyadvisor.com/news/scabies-treatment-failure-rates-increasing-among-children-and-adults/

The above research article, noted from current studies, shows that Permethrin is only 89.2% effective. There is noted resistance that has been increasing each year, as noted in the article.

Crotamiton

Second choice drug. Effective scabicide, pediculocide and antipruritic. Cure rate 60-88%.

Benzyl benzoate

2nd line drug for scabies and is seldom used for pediculosis. Cure rate 76-100%

Lindane

Effective in treating head lice (67-92%cure) and scabies (84-92% cure) with a single treatment. Penetrates through chitinous covers and affecting the nervous system.

Sulfur

Oldest scabicide and weak pediculocide, antiseptic, fungicide and keratolytic. Applied to skin, it is slowly reduced to H₂S and oxidized to SO₂ and pentathionic acid, which dissolve the cuticle of itch mites and kill it.

Ivermectin

Antihelminthic drug found highly effective in scabies and pediculosis. Acts through a glutamate-gated Cl ion channel found only in invertebrates.

Dicophan

Insecticide for mosquito, flies and other pests. Penetrates through the exoskeleton and acts as a neurotoxin.

Other Applications

Possible Poaching Deterrent

Ectoparasiticides have seen use as chemical agents in South Africa with the aim of devaluing rhinoceros horns and combating illegal poaching. Lorinda Hern, founder of the Rhino Rescue Project, devised a plan to infuse rhino horns with ectoparasiticides and mark the outer surface with a bright pink dye. This innovative approach seeks to deter poachers by creating health concerns amongst potential buyer communities. The procedure involves drilling into the rhinoceros horn, injecting it with an ectoparasiticide compound, and tagging it with a distinctive pink dye. The drill and inject procedure is considered harmless to the rhinoceros species due to the horn being isolated from both the nervous system and the bloodstream.

References

1. Taylor MA (May 2001). "Recent developments in ectoparasiticides". Vet. J. 161 (3): 253–68. doi:10.1053/tvjl.2000.0549. PMID 11352483.
2. Tripathi, J.D (2010). Textbook of Pharmacology. Jeypee Publications. pp. 862–863. ISBN 978-81-8448-085-6.
3. Henriques2016-01-13T00:00:00+00:00, Martha. "Ectoparasiticides". Chemistry World. Retrieved 2024-05-01.{{cite web}}: CS1 maint: numeric names: authors list (link)
4. Nanda, Japbani; Patel, Preeti; Juergens, Andrew L. (2024), "Permethrin", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 31985943, retrieved 2024-08-23
5. "Poisoning rhino horns doesn't hurt the rhinos, but it may keep poachers away". The World from PRX. Retrieved 2024-05-01.

• Antiparasitic agents