monepantel and Trichostrongylosis

Monepantel resistance was diagnosed during routine monitoring of the effectiveness of a farm's roundworm control strategy. Weaned lambs had become ill thrifty and developed diarrhoea, despite the routine use of monepantel. This clinical presentation was caused by trichostrongylosis. The faecal egg count reduction was 76.7% (95% CI: 55.1-82.2%) following treatment with 2.5 mg/kg monepantel. Predominantly Trichostrongylus vitrinus along with small proportions of Oesophagostomum venulosum and Trichostrongylus vitrinus were identified by deep amplicon sequencing of pools of larvae recovered from pre and post monepantel treatment coprocultures and on postmortem examinations. The undifferentiated FECRT showed resistance to monepantel, but not to levamisole, ivermectin, or moxidectin. Examination of farm anthelmintic treatment and animal movement records suggested that treatments before movement onto silage aftermaths, putatively with low numbers of susceptible nematodes in refugia, may have placed a high selection pressure on monepantel resistance. Effective control of parasitic gastroenteritis using anthelmintic drugs is a prerequisite for sustainable sheep production. This case reiterates the need for care when combining anthelmintic treatments with movements to safe grazing, and the value of monitoring of anthelmintic efficacy as part of iterative planned animal health management.

Topics: Aminoacetonitrile; Animals; Anthelmintics; Drug Resistance; Female; Male; Oesophagostomiasis; Oesophagostomum; Parasite Egg Count; Sheep; Sheep Diseases; Trichostrongylosis; Trichostrongylus; United Kingdom

In a farm where Trichostrongylus colubriformis in sheep had been found resistant to monepantel (MNP), we aimed to evaluate the efficacy against gastrointestinal nematodes in a controlled efficacy test (CT) and a fecal egg count reduction test (FECRT) in goats. We used 15 (CT) and 30 goats (FECRT), naturally infected, and equally divided into control and treated groups. The efficacy of MNP in the CT against Haemonchus contortus, Trichostrongylus axei and Cooperia curticei was 100%. For T. colubriformis, the efficacy was 90.5% in goats treated with 2.5mg/kg, and 88.1% in goats treated with 3.5mg/kg. In the FECRT, the overall reduction was 91% (2.5mg/kg) and 90% (3.75mg/kg). In the fecal cultures, Trichostrongylus spp. larvae represented 25% (pre-treatment) and 15% (post-treatment) of the larvae in the control group, but they were 75% (2.5mg/kg) and 98% (3.75mg/kg) of the recovered larvae after MNP treatment. In accordance with published standards, and based on FECRT and CT, MNP was considered ineffective against T. colubriformis in the studied flock.

Topics: Aminoacetonitrile; Animals; Anthelmintics; Brazil; Drug Resistance; Feces; Goat Diseases; Goats; Haemonchus; Parasite Egg Count; Sheep; Trichostrongylosis; Trichostrongylus

Multiple drug resistance of nematodes against anthelmintics has become one of the most important economic problems in sheep production worldwide. The aim of this experiment was to evaluate the efficacy of monepantel (2.5mg/kg) against gastrointestinal nematodes in fecal egg count reduction test (FECRT) and controlled efficacy test (CT) in naturally infected sheep. We used 30 sheep for the FECRT and 20 sheep for the CT, equally divided into control and treated groups. In the FECRT, the reduction was 98%. Larval identification of pre-treatment coprocultures revealed 100% Haemonchus spp. for both control and treated groups. Post-treatment culture of treated sheep was 100% Oesophagostomum spp., but only few larvae were recovered. In the control group, they were 99% Haemonchus spp and 1% Oesophagostomum spp. larvae. Based on the FECRT, Haemonchus spp. was considered susceptible to monepantel. The efficacy of monepantel in the CT against Haemonchus contortus and Trichostrongylus axei was 100% and against Cooperia curticei was 99.7%. For Trichostrongylus colubriformis, the efficacy was -21.5%. In both treated and untreated animals, Oesophagostomum columbianum was recovered from the large intestines. Based on FECRT and CT and in accordance with WAAVP standards, monepantel was ineffective against T. colubriformis and O. columbianum, but effective against H. contortus, T. axei and C. curticei in the studied flock.

Topics: Abomasum; Administration, Oral; Aminoacetonitrile; Animals; Antinematodal Agents; Brazil; Drug Resistance; Feces; Female; Haemonchus; Intestines; Male; Oesophagostomum; Sheep; Sheep Diseases; Trichostrongyloidea; Trichostrongylosis; Trichostrongylus