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

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.