Veterinary Medicine International 3 Table 1: Variation of the mean embryonation and hatching rates of Heligmosomoides bakeri eggs according to the concentration (mg·mL−1) of aqueous and ethanolic extract of leaves of Ageratum conyzoides. Embryonation hatching NA: not applicable. Treatment Aqueous extract Ethanolic extract Aqueous extract Ethanolic extract Negative controls Tested concentrations (mg·mL−1) Distilled water 100.0 ± 0.0 97.9 ± 2.6 5% tween 100.0 ± 0.0 100.0 ± 0.0 0.625 94.5 ± 7.8 96.1 ± 2.9 97.0 ± 6.1 61.4 ± 8.4 1.25 85.1 ± 6.2 91.5 ± 6.0 85.2 ± 13.8 47.5 ± 9.6 2.5 75.7 ± 5.7 77.7 ± 13.3 59.1 ± 26.2 26.4 ± 12.5 3.75 53.3 ± 10.9 39.6 ± 2.9 48.7 ± 27.2 26.7 ± 7.3 each of 12 Petri dishes (35 mm Ø × 10 mm) and mixed with the same volume of a speciﬁc concentration of each extract. The dishes were covered and the larvae incubated at room temperature for 24 hours, after which the number of dead or immobilised larvae was counted under a microscope (at 4x magniﬁcation). The percent mortality (Mc%) was determined using Abbott’s formula for corrected mortality [7]: Mce − Mt Mc(%) = 100 − Mt × 100, (3) where Mce is the mortality obtained during the test and Mt the mortality registered in the negative control dishes. It is considered that when the mortality rate in the leter dishes is less than 5%, Mc = Mce [17]. 2.7. Data Analysis. At equal concentration, the mean embry- onation rates, hatching rates, and larval mortality rates due to the two types of extracts were compared using the chi- square at the P < 0.05 signiﬁcance level. The 50 per cent eﬀective concentration (EC50) was determined using the regression lines of the probit according to the decimal logarithm of the concentration. All tests were repeated four times for each treatment and control. 3. Results The variation of mean embryonation rate of H. bakeri eggs according to the concentration of extracts of A. conyzoides leaves is shown in Table 1. Overall, the eﬀect was dose dependent. At a concentration of 2.5 mg·mL−l, the mean embryonation rates were 75.7 ± 5.7% and 77.7 ± 13.3% for aqueous and ethanolic extract, respectively. At 3.75 mg.mL−1, the embryonation rates were moderate and similar in solution containing both extracts. The mean embryonation rate was maximum (100 ± 0.0%) in distilled water and 5% tween. The variation of the mean hatching rate of L1 larvae of H. bakeri according to the concentration of extract is illustrated in Table 1. The aqueous extracts did not aﬀect egg hatching. At a concentration of 3.75 mg·mL−1, mean hatching rate was 48.7 ± 27.2%. The negative controls did not aﬀect the hatching rate (97.9 ± 2.6 and 100% hatching rate for 5% tween and DW, resp.). The eﬀects of diﬀerent extracts and Mebendazole (MBZ) on L1 larvae of H. bakeri after 24 h of contact are shown in Table 2. Larval mortality rate was highest at 2.5 and 3.75 mg.mL−1. The mean mortality rate due to ethanolic extract was 96.3 ± 4.8 and 99.4 ± 1.2% and MBZ (89.4 ± 7.4 and 84.35 ± 3.83%) was similar (P > 0.05) and higher (P < 0.05) than that attributed to aqueous extract (32.3 ± 12.4 and 55.0 ± 22.3%) with the same concentrations. Distilled water and 5% tween did not aﬀect the survival of the larvae with mortality rate of 3.5 ± 5.0% and 3.0 ± 4.8%, respectively. The EC50 obtained were 2.14 mg·mL−1, 0·66 mg.mL−1, and 0.37 mg.mL−1for aqueous, ethanolic extracts, and mebenda- zole respectively. Twenty-four (24) hours after incubation of L2 larvae in three treatments, the larval mortality increases with that of the concentrations (Table 2). With the three ﬁrst concentration, the mortality due to MBZ (77.0 ± 3.5%, 86.7 ± 5.2%, 96.0 ± 0.8%) was higher (P > 0.05) than that due to aqueous extract (32.6 ± 20.3%, 40.8 ± 15.0%, 50.1 ± 13.1%) and to ethanolic extract (13.6 ± 7.0%, 32.5 ± 4.2%, 35.4 ± 29.0%). With the highest concentration, the mortalities were similar (P > 0.05) and higher (P < 0.05) in ethanolic extract (95.48 ± 5.2%) and MBZ (100 ± 0.0%) than in aqueous extract (58.2 ± 20.0%). Distilled water and 5% tween did not aﬀect H. bakeri larval survival with a mortality rate of 3.5 ± 5.0% and 3.0 ± 4.8% for DW and 5% tween, respectively. Regression analysis indicates that there was a dose-dependent relationship and the EC50 obtained were 2.29 mg·mL−1, 1.51 mg·mL−1, and 0.32 mg·ml−1 for aqueous, ethanolic extracts, and mebendazole, respectively. 4. Discussion Generally, the extracts of A. conyzoides aﬀect embryonic development and hatching rate of H. bakeri. Similar ﬁndings were shown by Wabo Pone´ et al [5] with the extracts of Canthium mannii. The ovicidal activities of the extracts of A. conyzoides could be due to the fact that the active compounds penetrated the egg shell and stopped the segmentation of blastomeres or paralysed the larvae inside embryonated egg. The fact that aqueous solution seems to be more eﬃcient against embryonation of eggs than ethanolic could be due to the composition of each extract. In fact, Ciulei [10] stated that aqueous extract contained hydro-soluble compounds compared to ethanolic extract which possesses, in addition to hydrosoluble substances, lipid substances, alkaloids, and polyphenols. However, since the layers of the egg shell are hydrophobic, the aqueous extract has the ability to penetrate the layers than the ethanolic extract which has an