The Efficacy of Trichlorphon and Naphthalophos against Multiple Anthelmintic-Resistant Nematodes of Naturally Infected Sheep in Argentina

Abstract

An anthelmintic efficacy trial was conducted in sheep harbouring anthelmintic-resistant worms in Argentina. Seventy lambs were selected from a flock that had been grazed on pastures infected with trichostrongyles previously shown to be resistant to the main anthelmintic groups. Lambs were allocated to comparable groups of ten animals each and treated with trichlorphon (50 mg/kg body weight (b.w.) orally); naphthalophos (50 mg/kg b.w. orally); ivermectin (0.2 mg/kg b.w. subcutaneously); fenbendazole (5 mg/kg b.w. orally); levamisole (8 mg/kg b.w. subcutaneously) and closantel (10 mg/kg b.w. orally). There was also an untreated group. The dose selection was based on manufacturer's recommendations.Faecal samples were collected 0 and 10 days post treatment to estimate efficacy (faecal egg count reduction). Six animals from each group were necropsied at day 10 for enumeration/identification of worms from the abomasum, small and large intestines to determine the absolute efficacy of each agent (controlled efficacy test). Trichlorphon and naphthalophos were effective (> 99 %) against Haemonchus contortus (p < 0.05).Naphthalophos also showed efficacy against Trichostrongylus axei (99.3 %), Teladorsagia circumcincta (97.8 %), Trichostrongylus colubriformis (99.2 %), Cooperia punctata/curticei/pectinata (90.4 %), Nematodirus spathiger (89.2 %) and Oesophagostomum venulosum/columbianum (93.7 %). Fenbendazole and levamisole showed efficacy (> 95 %) against all nematodes except T. colubriformis. The efficacy of ivermectin was low against H. contortus (23 %) and Cooperia spp. (46.3 %). Closantel showed low efficacy against T. axei (64.4 %), H. contortus (80.6 %) and T. colubriformis (59.5 %).When anthelmintic resistance is widespread, trichlorphon treatment is appropriate if H. contortus is present; however, naphthalophos represents an effective therapeutic alternative for incorporation into worm control programmes.

Multiple anthelmintic resistance in gastrointestinal nematodes of Caprines on Mountain Research Centre for Sheep and Goat at Kashmir Valley, India

“…Moderate resistance on 7 th and 14 th day post treatment was observed for closantel. The moderate resistance in H. contortus to closantel has also been reported by Wooster et al (2001) in New South Wales and Fiel et al (2011) in Argentina. Uppal et al (1992) and Kadam et al (2009) reported 100% efficacy of closantel against strongyle worms in UP, India and in Akola region of India, respectively.…”

Evaluation of an FDA approved library against laboratory models of human intestinal nematode infections

“…However, it is also known for its antischistosomal properties [trichlorfon (metrifonate) was marketed for the treatment of S. haematobium prior to the advent of praziquantel] [ 19 ] and is applied for the control of intestinal nematode parasites of cattle and sheep. Trichlorfon is particularly used for nematodes that have developed resistance to other commonly-used anthelmintics [ 20 ]. In the past years, it was investigated for the treatment of Alzheimer’s disease.…”

Phenobarbital Induction and Chemical Synergism Demonstrate the Role of UDP-Glucuronosyltransferases in Detoxification of Naphthalophos by Haemonchus contortus Larvae

“…The usefulness of the compound was demonstrated recently by Baker et al (7), who showed that the addition of NAP to a combination of chemicals from the three major drug groups increased efficacy against a population of H. contortus isolated from the field in New South Wales (NSW), Australia, from 40% to 100%. This role for organophosphate compounds in combination drenches to combat resistance to the other chemical groups has also been demonstrated in cattle and sheep in South America (8,9).…”