No abstract

Infection of sheep by gastrointestinal nematodes (GIN) in pastoral systems such as those found in the South Western area of France, the Pyrénées Atlantiques, is one of the main reasons for economic loss and degradation of their welfare. In the present study, the efficacy of eprinomectin (EPN) was monitored on farms from this area following suspicion of lack of anthelmintic efficacy. Suspicions were raised by veterinarians, based on clinical signs ranging from milk and body condition loss, to anaemia, and mortality. Resistance was evaluated according to the World Association for the Advancement for Veterinary Parasitology (WAAVP) guidelines using fecal egg count reduction tests reinforced by individual analysis of drug concentration in the serum of all treated ewes by high-performance liquid chromatography (HPLC). EPN was administered by subcutaneous (SC) and topical (T) route according to manufacturer's requirements, as well as by the oral route (O) with the topical solution according to off-labelled practices in the field. For the first time in France, the presence of resistant isolates of Haemonchus contortus to EPN was observed in 5 dairy sheep farms. The HPLC dosages showed exposure of worms to concentrations compatible with anthelmintic activity for animals treated by the SC and O routes. By contrast, they showed under exposure to the drug of most individuals treated by the T route. EPN is the only null milk withdrawal anthelmintic molecule currently available. The presence of resistant isolates of the pathogenic H. contortus to EPN in this important dairy region requires an urgent change in grazing, and sometimes production, systems.

Background: Lamb coccidiosis, caused by intestinal parasites of the Eimeria genus, has pronounced health and economic impacts throughout the world. Eimeria ovinoidalis and Eimeria crandallis are the most pathogenic species in sheep. Control of these parasites requires the use of anticoccidial drugs such as sulfonamides, diclazuril, and toltrazuril. In this study, resistance to anticoccidial drugs was suspected in two farms as clinical signs (diarrhea) persisted after treatment. Method: On each farm, 4.5-month-old rams were divided into three groups so that they were either (i) left untreated (Control group), (ii) treated with diclazuril (1 mg/kg body weight), or (iii) treated with toltrazuril (20 mg/kg body weight). Animals were treated at day 0 (D0) and fecal samples were collected at D0 and eight days later (D8) to evaluate the reduction in intensity of Eimeria oocyst excretion. Oocyst morphology and morphometry were used to identify Eimeria species at both sampling dates. Results: Reduction of oocyst shedding was incomplete in both farms (92.44% and 93.58%) after diclazuril treatment. More specifically, the efficacy was reduced in both farms for E. ovinoidalis/Eimeria marsica (92.59% and 91.87%) and E. crandallis/Eimeria weybridgensis (75.34% and 80.10%). The general efficacy of toltrazuril was high in both farms (97.6% and 97.96%). However, a slightly reduced efficacy was noted in farm 1 for E. crandallis/E. weybridgensis (93.26%) while this efficacy was high in farm 2 (98.88%). Conclusions: We suggest a simple protocol to investigate the efficacy of anticoccidial treatments in sheep and to rapidly identify potentially resistant species. In these two farms, treating animals with diclazuril will select pathogenic species, and toltrazuril could favor resistant E. crandallis/E. weybridgensis in one of them.

Background: Lamb coccidiosis, caused by intestinal parasites of the Eimeria genus, has pronounced health and economic impacts throughout the world. Eimeria ovinoidalis and Eimeria crandallis are the most pathogenic species in sheep. Control of these parasites requires the use of anticoccidial drugs such as sulfonamides, diclazuril, and toltrazuril. In this study, resistance to anticoccidial drugs was suspected in two farms as clinical signs (diarrhea) persisted after treatment. Method: On each farm, 4.5-month-old rams were divided into three groups so that they were either (i) left untreated (Control group), (ii) treated with diclazuril (1 mg/kg body weight), or (iii) treated with toltrazuril (20 mg/kg body weight). Animals were treated at day 0 (D0) and fecal samples were collected at D0 and eight days later (D8) to evaluate the reduction in intensity of Eimeria oocyst excretion. Oocyst morphology and morphometry were used to identify Eimeria species at both sampling dates. Results: Reduction of oocyst shedding was incomplete in both farms (92.44% and 93.58%) after diclazuril treatment. More specifically, the efficacy was reduced in both farms for E. ovinoidalis/Eimeria marsica (92.59% and 91.87%) and E. crandallis/Eimeria weybridgensis (75.34% and 80.10%). The general efficacy of toltrazuril was high in both farms (97.6% and 97.96%). However, a slightly reduced efficacy was noted in farm 1 for E. crandallis/E. weybridgensis (93.26%) while this efficacy was high in farm 2 (98.88%). Conclusions: We suggest a simple protocol to investigate the efficacy of anticoccidial treatments in sheep and to rapidly identify potentially resistant species. In these two farms, treating animals with diclazuril will select pathogenic species, and toltrazuril could favor resistant E. crandallis/E. weybridgensis in one of them.