Currently there are three different classes on anthelmintic drugs, although there is also monepantel which is a drug used against G.I. nematodes in sheep.
Benzimidazoles
- Fenbendazole, triclabendazole (mainly used against liver fluke) etc.
- Prodrug-> febantel.
- Tubulin binding-> inhibition of nutrition & starvation.
- Oral.
- Not well absorbed systemically (cannot be used against migrating larvae such as lungworms).
- Primarily targets nematodes.
- Ovicidal.
- Effective at targeting hypobiosed larvae (such as with horse cyathostomins & ostertagia).
- Levimasole, pyrantel or morantel.
- Neuromuscular blockage-> paralysis (nicotinic agonists at ACh receptors).
- Rapid distribution & excretion.
- Nematodes- gut dwelling stages only.
- Short acting.
- Can target lungworms.
- Oral, injectable or pour on.
- Double douse pyrantel is very effective against horse tapeworms.
Macrocyclic Lactones
- Ivermectin, moxidection.
- Paralysis- affects inter-neurone transmission and is active on glutamate gated Cl channels.
- Nematodes/athropods. No ovicidal.
- Injectable/pour on/oral/spot on.
- Migrating and hypobiotic larvae.
- Ivermectin- 2 weeks residual activity.
- Moxidectin 2+ weeks (4 weeks or 42 days) residual activity.
Interval dosing-> treat at regular intervals based on egg reappearence period.
Strategic dosing-> treat when the parasite numbers are highest to disrupt the seasonal cycle of transmission.
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