Epidemiology and Multidrug Resistance of Strongyle Nematodes in Ordos Merino Sheep

Abstract

Background: Regular whole-flock treatments and long-term use of similar anthelmintics have led to the development of anthelmintic resistance and widespread epidemics of nematodiasis in sheep. This study was performed to understand the prevalence of gastrointestinal nematodes in Ordos Merino sheep and evaluate the efficacy of currently used anthelmintics. Results: Between March 2017 and April 2019, a total of 4014 fresh fecal samples were collected from sheep, and fecal nematode eggs were qualitatively and quantitatively analyzed to understand the prevalence of sheep nematodiasis. The anthelmintic efficacy of currently used drugs was evaluated in naturally infected sheep. Severe infection by gastrointestinal nematodes was observed in the Ordos Merino sheep. The infection rates of the nematodes in 3 consecutive years were 84.3%, 36.9%, and 42.3%. Haemonchus contortus and Nematodirus sp. were the predominant nematode species, with infection rates of 84.3% and 65.6%, respectively, in 2017. Moreover, these species had acquired high resistance to ivermectin, doramectin, albendazole, and levamisole; the fecal egg count reduction percentages were 6.9%, 1.7%, 3.5%, and 79.0%, respectively, after a single administration. Nitroxynil and closantel showed strong anthelmintic efficacy against the predominant species Haemonchus contortus and other nematodes, but they had almost no effect on Nematodirus sp. Conclusions: The prevalence of gastrointestinal nematodes in Ordos Merino sheep and their resistance to commonly used anthelmintics were comprehensively evaluated, and the drugs with high efficacy against the predominant species were identified. The findings of this study will provide a good foundation for the appropriate use of anthelmintics.

Positivity Rate Investigation and Anthelmintic Resistance Analysis of Gastrointestinal Nematodes in Sheep and Cattle in Ordos, China

“…Regarding different pasture types, we can see that the infection levels of sandy pastures, hilly pastures and low-lying pastures were similar, and there was no significant difference, but the infection intensity of nematodes in the pen-fed pastures was very low. The level of pen-fed management was high, and the prevention and control of parasites were also effectively performed, which is also consistent with the results reported by the frontal Eye L in 2018 [ 21 ]. There are also reports that, in captive areas, dung-burying beetles, coprophagous beetles and earthworms can greatly reduce the larvae of some trichostrongylids in pastures.…”

“…Because herdsmen in Ordos often report that their deworming drugs are ineffective, Professor Hasisurong started focusing on local parasitic studies in 2017, discovered the anthelmintics resistance of local GINs in the Wushen Banner, and screened for appropriate anthelmintics. Compared with the initial data from 2017, the infection rate of GINs has decreased from 84.3% to 32.16% [ 21 ]. However, the Hangjin Banner and Ejin Horo Banner lack relevant professional training, and herders have little awareness of parasite control.…”