The in vitro exsheathment kinetics of Trichostrongylus colubriformis L3 in ruminal, abomasal, and two-stage incubation protocols

Abstract

This study investigated the in vitro exsheathment kinetics of Trichostrongylus colubriformis L₃ using three protocols: ruminal medium (RM), abomasal medium (AM), and a two-stage incubation (RM+AM). The characteristics of L₃ exsheathment at various incubation times in each medium were described. For the RM, T. colubriformis L₃ were incubated for 0, 1, 3, 6, 9, and 24 h. Separate incubations with Haemonchus contortus L₃ were used as controls for the RM conditions. For the incubation in AM, the L₃ were incubated for 0, 1, 2, 3, and 4 h. In the two-stage incubation (RM+AM), the L₃ were first incubated in RM (0, 2, and 4 h), and then transferred to AM (5, 6, 7, and 8 h). Linear and nonlinear models were used to describe the L₃ exsheathment kinetics in T. colubriformis and H. contortus in RM, AM, and RM+AM. During the RM incubation, the exsheathment kinetics for T. colubriformis followed a log-logistic function, with a slower exsheathment rate at 24 h (63.84 %, T₅₀=8.88 h) compared to H. contortus (74.36 %, T₅₀=4.67 h). After 9 h of RM incubation, 52 % of the T. colubriformis L₃ completed its exsheathment, while 90 % of H. contortus larvae had fully exsheathed from 6 h onward. Incubation in AM without prior exposure to RM resulted in < 5 % exsheathment. The incubation in RM+AM resulted in linear kinetics, with 50 % exsheathment at 7.6 h. After 8 h of incubation in RM+AM, 90 % of the exsheathed T. colubriformis L₃ completed the process. The exsheathment of T. colubriformis L₃ began in the RM following a Log-Logistic function. Exposure to RM was necessary to induce T. colubriformis exsheathment in the AM.