Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2010
Publication Date: 9/8/2010
Citation: Squires, J.M., Ferreira, J.F., Lindsay, D.S., Zajac, A.M. 2010. Effects of artemisinin and Artemisia annua extracts on Haemonchus contortus in gerbils (Meriones unguiculatus). Veterinary Parasitology. 175:103-108. Interpretive Summary: Blood-sucking gastrointestinal nematodes (GIN) are the major economic obstacle in meat production systems of sheep and goats raised under grazing conditions. These GIN have been continuously developing resistance to currently commercial anthelmintic drugs. Due to this growing drug resistance, and the expenses involved in control of GIN with these commercial drugs, there is a growing demand for affordable and natural anthelmintic products. The Annual Wormwood, or Sweet Annie, plant produces a natural compound (artemisinin) that is widely used to treat multi-drug resistant malaria and has recently shown to be effective against other internal parasites of humans and animals such as the one that causes Schistosomiasis, the second most important parasitic infection in the world after malaria. Sweet Annie and artemisinin-derived pharmaceuticals have also proved by others to be effective against coccidiosis in chickens and Fasciola infection in sheep. In this study, we used a gerbil model where the animals were infected with the blood-sucking GIN of interest and treated with artemisinin, Sweet Annie essential oil, and with aqueous and hydroalcoholic extracts of Sweet Annie and with the hydroalcoholic extract of Wormwood (a relative of Sweet Annie). Although a reduction in the number of adult worms from the stomachs of gerbils of 25% was obtained for the hydroalcoholic extract of Sweet Annie, it was not significantly different from the control (untreated animals). None of the other treatments showed any reduction in adult worms in gerbils. These results indicate that although there might be a potential anthelmintic effect provided by Sweet Annie hydroalcoholic extract, the gerbil system might not be an effective way to test crude plant extracts that are not effective in five days or less and that the extract need to be tested in the original sheep and goat hosts. A non-toxic solvent, believed to enhance the effects of non-water soluble compounds was very effective in dissolving the extracts and might prove useful to deliver these extracts orally in future studies with animals.
Technical Abstract: Haemonchus contortus is a blood-sucking abomasal parasite of small ruminants that is responsible for major losses to producers worldwide. Resistance of this nematode to commercial anthelmintics has produced a demand for alternative control methods. Artemisia annua is the sole commercial source of artemisinin, the raw material used to produce drugs that are effective against chloroquine-resistant Plasmodium falciparum, Schistosoma japonicum, and other gastrointestinalparasites that afflict humans and livestock. In this study, gerbils (Meriones unguiculatus) artificially-infected with Haemonchus contortus (H.C.) was used to test artemisinin, an essential oil of A. annua (AAEO), an aqueous extract (AAAE) and an ethanolic extract (AAEE) of A. annua, and an ethanolic extract of Artemisia absinthium (ABEE). In all experiments, gerbils were infected with 600 third-stage larvae. In experiment 1, gerbils were treated orally with 400 mg/kg artemisinin once or 200 mg/kg artemisinin daily for 5 days. In experiment 2, gerbils were treated daily for 5 days with 600 mg/kg of AAAE or AAEE. In Experiment 3, gerbils were treated with 1000 mg/kg of A. annua or A. absinthium ethanolic extract in 25% Labrasol or with 15mg/kg of A. annua essential oil daily for five consecutive days (days 4-8). No significant effects of treatment were seen with artemisinin or any of the Artemisia spp. extracts in this gerbil model, suggesting that five days might not be enough time to prove or disprove the anthelmintic potential of the plant products tested. Labrasol was non-toxic at the used dose and proved to be a useful solvent to deliver both hydrophilic and lipophilic plant products to test animals.