Adaptation of Haemonchus contortus to condensed tannins: can it be possible?

The in vitro anthelmintic (AH) effect of Acacia pennatula, Lysiloma latisiliquum, Piscidia piscipula and Leucaena leucocephala tannin rich extracts on three Mexican strains of Haemonchus conforms L-3, larvae was evaluated. Water/acetone extracts were obtained from the fodder of A. pennatula, L. latisiliquum, P. piscipula and L. leucocephala collected in the vegetation of Yucatan, Mexico. Increasing concentrations of lyophilized extracts (300, 600, 1,200, 1,800 and 2,400 mu g/ml PBS) were screened for their in vitro AH effect using the larval migration inhibition (LMI) assay. Three unrelated H. conforms' Mexican strains were used (CENID-INIFAP, UADY and UNAM). The role of tannins on the AH effect was confirmed by means of polyvinyl polypyrrolidone (PVPP), an inhibitor of tannins. The different H. conforms strains showed different responses to the extracts. Only one plant extract (L. latisiliquum) affected the larval migration of the H. conforms strain obtained from Yucatan (UADY). Two plants extracts (A. pennatula and L. latisiliquum) inhibited the larval migration of the CENID-INIFAP strain. Meanwhile, three plant extracts affected larval migration of UNAM strain (A. pennatula, L. latisiliquum, P piscipula). Furthermore, UNAM strain was affected by extracts at lower doses than CENID-INIFAP and UADY strains. These results indicated that the larvae obtained from Yucatan, Mexico, were less sensitive to extracts of TRP from the same region suggesting a possible adaptation to tannins.