Seasonal Dynamics of Gastrointestinal Nematode Infections of Goats and Emergence of Ivermectin Resistance in Haemonchus contortus in Hubei Province, China.

Introduction: Gastrointestinal nematodes (GINs) are a major constraint to the survival and productivity of animals. In southern China, goats are the most important small domestic ruminants.

Methods: From May 2013 to May 2017, we conducted a longitudinal study of hircine GIN infections in Huangshantou Town, Gongan County, Hubei Province, China, using fecal egg counts.

Results: Our investigation revealed that the GINs of goats in Hubei Province have changed significantly. Over 90% of eggs detected in the first month of investigation, May 2013, belonged to the species Haemonchus contortus and Chabertia sp. There was no seasonal variation in positive rates (PRs) of GINs, but the mean eggs per gram (EPG) of GINs were higher between April and July than between September and November (P < 0.05). The gradual increase in the percentage of H. contortus eggs among all detected eggs during our research and the low cure rate of IVM mass treatment revealed the emergence of IVM resistance in H. contortus. After the implementation of an integrated GIN control strategy, which included two mass treatments (one in April/May with ABZ and another in September/October with IVM + ABZ), in 2016 and 2017, both the PRs and EPG of GINs were significantly reduced.

Conclusion: The results presented here reveal that controlling GINs of small ruminants in small farms in southern China requires an integrated control strategy that should include monitoring of infection and anthelmintic resistance, and increased farmer education on the importance of using the appropriate drugs at the correct dose.