The control of gastrointestinal nematodes in livestock is becoming increasingly difficult due to the limited number of available drugs and the rapid development of anthelmintic resistance. Therefore, it is imperative to develop new anthelmintics that are effective against nematodes. Under this context, we tested the potential toxicity of three compounds in mice and their potential anthelmintic efficacy in Mongolian gerbils infected with Haemonchus contortus. The compounds were selected from previous in vitro experiments: two diamine (AAD-1 and AAD-2) and one benzimidazole (2aBZ) derivatives. 2aBZ was also selected to test its efficacy in sheep. In Mongolian gerbils, the benzimidazole reduced the percentage of pre-adults present in the stomach of gerbils by 95% at a dose of 200 mg/kg. In sheep, there was a 99% reduction in the number of eggs shed in faeces after 7 days at a dose of 120 mg/kg and a 95% reduction in the number of worm adults present in the abomasum. In conclusion, 2aBZ could be considered a promising candidate for the treatment of helminth infections in small ruminants.
Background
Infections by gastrointestinal nematodes cause significant economic losses and disease in both humans and animals worldwide. The discovery of novel anthelmintic drugs is crucial for maintaining control of these parasitic infections.
Methods
For this purpose, the aim of the present study was to evaluate the potential anthelmintic activity of three series of compounds against the gastrointestinal nematodes Trichuris muris and Heligmosomoides polygyrus in vitro. The compounds tested were derivatives of benzimidazole, lipidic aminoalcohols and diamines. A primary screening was performed to select those compounds with an ability to inhibit T. muris L1 motility by > 90% at a single concentration of 100 µM; then, their respective IC50 values were calculated. Those compounds with IC50 < 10 µM were also tested against the adult stage of T. muris and H. polygyrus at a single concentration of 10 µM.
Results
Of the 41 initial compounds screened, only compounds AO14, BZ6 and BZ12 had IC50 values < 10 µM on T. muris L1 assay, showing IC50 values of 3.30, 8.89 and 4.17 µM, respectively. However, only two of them displayed activity against the adult stage of the parasites: BZ12 killed 81% of adults of T. muris (IC50 of 8.1 µM) and 53% of H. polygyrus while BZ6 killed 100% of H. polygyrus adults (IC50 of 5.3 µM) but only 17% of T. muris.
Conclusions
BZ6 and BZ12 could be considered as a starting point for the synthesis of further structurally related compounds.
Graphical Abstract
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