Anthelmintic

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Anthelmintics or antihelminthics are drugs that expel parasitic worms (helminths) from the body, by either stunning or killing them. They may also be called vermifuges (stunning) or vermicides (killing).

Classes

Examples of drugs used as anthelmintics include:

• Albendazole – effective against threadworms, roundworms, whipworms, tapeworms, hookworms
• Diethylcarbamazine – effective against Wuchereria bancrofti, Brugia malayi, Brugia timori, tropical pulmonary eosinophilia, loiasis
• Mebendazole – effective against pinworms, roundworms and hookworms
• Niclosamide – effective against tapeworms
• Ivermectin – effective against most common intestinal worms (except tapeworms)
• Suramin
• Thiabendazole – effective against roundworms, hookworms
• Pyrantel pamoate – effective against most nematode infections
• Levamisole
• Piperazine family
• Praziquantel – effective against nematodes, some trematodes
• Triclabendazole – effective against liver flukes
• Octadepsipeptides (eg: Emodepside) – effective against a variety of gastrointestinal helminths

Natural anthelmintics include black walnut (Juglans nigra), wormwood (Artemisia absynthium), clove (Syzygium aromaticum), tansy tea (Tanacetum vulgare), Hagenia (Hagenia abyssinica), kalonji (Nigella sativa) seeds, and the male fern (Dryopteris filix-mas). In Brazilian folk medicine, Plumeria (P. acutifolia or P. rubra) is also an anthelmintic. Peganum harmala is used as an anthelmintic. Please note that many natural vermifuges or anthelmintics are poisonous and, in improper dosages, dangerous to humans as well as parasites.

Anthelmintic resistance

The ability of worms to survive treatments that are generally effective at the recommended dose rate. It is considered a major threat to the current future control of worm parasites of small ruminants and horses.

The clinical definition of resistance is a 95% or less reduction in a "Fecal Egg Count" test.

Development of resistance

Treatment eliminates worms whose genotype renders them susceptible. Worms that are resistant survive and pass on their "resistance" genes. Resistant worms accumulate and finally treatment failure occurs.

Causes of resistance

1. Treatment at frequent intervals
• Greater than 3 treatments per year
• Many farms apply greater than 6 treatments per year
2. Treating all animals at same time
• No refugia for non-resistant worms
3. Treating and moving to clean pasture
• No dilution
4. Under dosing
• Worms with low-level resistance survive. Worms can develop resistance a little at a time.

References

Footnotes

General references

• Department of the Army Headquarters (2004). U.S. Army Survival Manual Fm 21-76. Barns & Noble Inc.

External links

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Last updated on Monday March 10, 2008 at 13:03:33 PDT (GMT -0700)
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