SAGE-Hindawi Access to Research Veterinary Medicine International Volume 2011, Article ID 140293, 5 pages doi:10.4061/2011/140293 Research Article The In Vitro Effects of Aqueous and Ethanolic Extracts of the Leaves of Ageratum conyzoides (Asteraceae) on Three Life Cycle Stages of the Parasitic Nematode Heligmosomoides bakeri (Nematoda: Heligmosomatidae) J. Wabo Pone´ ,1 Olivia Fossi Tankoua,1 Jeannette Yondo,1 Marie Claire Komtangi,1 Mpoame Mbida,1 and C. F. Bilong Bilong2 1 Department of Animal Biology, Faculty of Science, University of Dschang, P.O. Box 067, Dschang, Cameroon 2 Department of Animal Biology and Physiology, Faculty of Science, University of Yaounde I, P.O. Box 812, Yaounde, Cameroon Correspondence should be addressed to J. Wabo Pone´, waboponejosue@yahoo.fr Received 18 December 2010; Revised 27 March 2011; Accepted 16 May 2011 Academic Editor: David W. Horohov Copyright © 2011 J. Wabo Pone´ et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A comparative in vitro study was carried out to determine the ovicidal and larvicidal activity of aqueous and ethanolic extracts of Ageratum conyzoides (Asteraceae) leaves on the eggs (unembryonated and embryonated), ﬁrst and second larval stages of Heligmosomoides bakeri. Four diﬀerent concentrations (0.625, 1.25, 2.5, and 3.75 mg·mL−1) of both aqueous and ethanolic extracts were tested. Distilled water and 5% tween were used as negative controls in the bioassay. In fact, they did not aﬀect development of eggs, hatching, and larval survival. The extract activities were dose dependent. The ethanolic extract was more potent against embryonation (39.6 ± 2.9%) than the aqueous extract (53.3 ± 10.9%) at the highest concentration (3.75 mg·ml−1). Both types of extracts killed larvae. Mebendazole proved more lethal (EC50 of 0.745 and 0.323 mg·mL−1, resp., for L1 and L2 larvae). The aqueous extracts were the least lethal (EC50 of 4.76 and 2.29 mg·mL−1, resp., for L1 and L2 larvae). The ethanolic extracts showed intermediate activity (EC50 of 1.323 and 1.511 mg·mL−1, resp., for L1 and L2 larvae). It is concluded that the ovicidal and larvicidal properties of aqueous and ethanolic extracts of Ageratum conyzoides leaves are demonstrated in this work. 1. Introduction Helminthiases are worldwide and constitute a major health issue. More than 1 billion people are infected with gastro- intestinal helminths. Helminthiases are more common in the tropics where poor hygienic conditions and poverty increase the risk of infection. In addition, these diseases are respon- sible for mortality in human beings and aﬀect especially children of school age, thus, compromising their growth, intellectual, development and their school performance as well as increasing their vulnerability to other infections. On the other hand, in domesticated animals, helminth infections impair health, welfare, and productivity. Worm infections result in increased death rate and poor growth and reproduction. To control verminosis, patients and likewise farmers use synthetic anthelmintic drugs. Unfortunately, these substances are not only less available in the countries of the South but also their cost in local markets is relatively high. Moreover, for more than two decades now, new anthelmintic molecules have not been discovered. Also, the misuse of these drugs for many years had led to the development of resistant worm strains. Some side eﬀects are noted and the use of disinfectants to control free stage of parasites is harmful to the environment [1]. This has motivated investigation into alternative approaches. Phytotherapy based on the use of preparation of medicinal plant, with low cost and eﬃciency, remains the most serious alternative to modern anthelmintics drugs. The discovery of new natural, less expensive, and nontoxic products remains a continued quest in the control of helminths worldwide [2, 3]. Studies carried out in that direction include those of Alawa et al. [4], Wabo Pone´ et al. [5–7], Maciel et al. [8], and M.-M. Claire et al. [9] who assessed the in vitro anthelmintic activities of extracts of: Vernonia amygdalina and Annona senegalensis in