Anthelmintics or antihelminthics are drugs that are used to expel parasitic worms from the body, by either stunning or killing them. They may also be called vermifuges or vermicides. They are used to treat both flat worms as well as roundworms. Anthelmintics play a very important role in veterinary as well as human tropical medicine. According to the reports published by the World Health Organization, two billion people harbor these parasite worm infections. They are a nuisance as they infect livestock and crops, which in turn cause a loss in crops as well as an economic downturn. Infection in domestic pets is an area of concern today. A huge number of people rear pets at home and so animal health companies are taking huge steps in the research of drugs like anthelmintics.

People are infected in some period in life with parasitic worms, which may cause morbidity or even kill. Anthelmintics are generally used for the treatment and control of the human helminthiases. Although parasitic worms are prevalent today, the development of the anthelmintics drug is poor in comparison with other drugs in the pharmaceutical industry. This is because these infections are generally observed in tropical nations who are so poor that they do not have sufficient money to invest in drug research and therapy. Therefore there is a small repertoire of chemotherapeutic agents available for treatment. Anthelmintic drug discovery has taken a back burner because of the success of Ivermectin. Ivermectin is known as an anti-parasite medication. It causes the death of certain parasitic organisms present in the body.

Anthelmentic resistance
The resistance to anthemintic is causing widespread concern especially in nematode parasites of sheep, goats and horses. Drugs such as Benzimidazole, levamisole and ivermectin are showing resistance in nematodess such as sheep and goats. The worm count or egg count reduction after the anthemintic treatment helps us to detect the resistance level of the parasites. Economical and faster methods to detect anthelintic resistance are also being developed.

For specific classes of anthemenics egg hatch assay methods are used and for other remaining classes we use the larval development assay method. With the advancements of biochemistry and molecular genetics we can develop sensitive assays to detect anthelmintic resistance in individual parasites. It is observed that Ivermectin appears to act by binding itself to a glutamate receptor of a membrane chloride channel. So tests and research are being conducted to study the interaction of this receptor with ivermectin and find a feasible solution to ivermectin resistance.

Benzimidazole (BZ) resistance is causing concern as it appears in a variety of nematode parasites of animals. It is seen that there is a lack of efficacy of BZ anthelmintics against soil transmitted nematode parasites of humans. It is difficult to confirm this as tests cannot be performed on humans due to ethical reasons. Anthelmintic drugs are used for the control of helminth parasites in people so as to treat gastrointestinal nematode parasites in children. The need to monitor anthelmintic resistance is gaining importance and new tools are being developed make that monitoring sensitive, inexpensive and practical. Importance should be given for DNA-based markers and BZ resistance in nematode parasites of humans.

Development of resistance
It is seen that the treatment of infections caused by parasites especially on animals and the subsequent treatment with the anthelmentic drug kills worms that are susceptible to the drug. Some of the worms possess resistance power and pass on these strong genes. These worms that have the resistance power grow in number and the drug ceases to act.