Macrocyclic lactones for parasite control in equids.

This research article discusses the use of macrocyclic lactones (MLs) for parasite control in horses and other animals. It details the potency and limitations of various MLs, including ivermectin and moxidectin.

Introduction to Macrocyclic Lactones

• The study focuses on drugs known as macrocyclic lactones (MLs), which have proven to be incredibly effective in managing and controlling parasites in horses and other animals.
• These drugs are unique because they are active against both arthropods and nematodes.

Ivermectin

• Ivermectin, the first widely used avermectin, was introduced to the market in 1983 as an injectable substance for horses.
• However, due to adverse effects, it was taken off the market in 1984, almost a year after its initial release.
• It was later reintroduced in a safer paste and oral/stomach tube liquid formulation.
• Ivermectin is effective against various parasites, such as bots, ascarids, large and small strongyles, pinworms, strongyloides, stomach worms, among others.

Moxidectin

• Moxidectin is another macrocyclic lactone that was introduced in 1997 as a gel formulation for oral administration.
• This compound exhibits similar parasiticidal activity as ivermectin. However, it is less effective against common bots (Gastrophilus intestinalis) but more active against encysted small strongyles.

Decreased Efficacy

• The study notes that recently, both ivermectin and moxidectin have demonstrated a reduced level of activity against ascarids and small strongyles.
• This indicates the potential development of resistance among these parasites, consequently leading to decreased efficacy of the drugs.