Characterization of the development of Haemonchus contortus ZJ strain from gerbils.

BACKGROUND: Haemonchus contortus is a serious parasitic nematode in domestic ruminants around the world, including China. Haemonchus contortus has developed extensive resistance to commercial anthelmintics, which has produced a demand for new control methods, such as more effective drugs. Gerbils infected with H. contortus have previously been used as a model for anthelmintics selections, and the growth of H. contortus had been briefly examined. To enhance the model, this study provides an additional description of the development of H. contortus ZJ strain in gerbils.

RESULTS: Gerbils were infected with H. contortus ZJ strain at a dose of 2000 exsheathed infective larvae (xL3s) and sacrificed at 4, 7 and 18 days post-infection (dpi). Only fourth-stage larvae were found in the stomachs. About 2% of the inoculums were obtained at each of the three sampling time points. Larvae grew more slowly in gerbils than in sheep, but presented almost the same morphology. Rod-like crystalline inclusions were present in the intestinal cells of larvae, indicating that the metabolic rate of larvae was probably greatly reduced. Histological examination of stomach sections showed that larvae are located in the lumens or at the mucosal surfaces, with few inflammatory changes evident.

CONCLUSIONS: The development and features of H. contortus ZJ strain in gerbils were described. Our results provide supplementary information of H. contortus growth in gerbils, especially the presence of rod-like crystalline inclusions, and may contribute to improve the anthelmintic selection system.