Cattle nematodes resistant to anthelmintics: why so few cases?

Abstract

-The apparent lack of anthelmintic resistant nematodes in cattle is due to the management systems used with most cattle and the lack of surveys for resistance. With extensive beef grazing or with beef suckler herds a large percentage of worms are in refugia (not exposed to anthelmintic) and few anthelmintic treatments are used. With dairy replacement heifers resistance can become a problem unless only first year animals are treated and different fields are used for grazing the animals each year. Intensive beef production on grass is unsustainable and in New Zealand resistance is already becoming a serious problem. Individual farms require monitoring for resistance and steps taken to avoid the introduction of resistance. New validated tests and surveys for resistance are required as the extent of anthelmintic resistant bovine nematodes is not known.anthelmintic / cattle / Cooperia / ivermectin / nematodes / refugia / resistance Résumé -Les nématodes des bovins résistants aux anthelmintiques : pourquoi si peu de cas sont-ils recensés ? L'absence apparente de nématodes résistants aux anthelmintiques chez les bovins est liée aux systèmes d'élevage pratiqués pour la majorité des bovins et à la rareté des enquêtes sur la résistance. Chez les bovins menés en troupeaux extensifs ou chez les bovins allaitants, un pourcentage important d'helminthes est en zone de refuge sur les pâtures (non exposé aux anthelmintiques) et les traitements anthelmintiques sont peu nombreux. Dans les systèmes avec des génisses de remplacement, la résistance peut devenir un problème, à moins que seuls les animaux dans leur première année soient traités et que chaque année des parcelles différentes soient affectées à la pâture des animaux. La production intensive de bétail à viande à l'herbe n'est pas durable et en Nouvelle Zélande la résistance commence à devenir un problème sérieux. Les exploitations devraient avoir recours à une surveillance de la résistance et mettre en place des dispositifs pour éviter l'introduction de nématodes résistants. De nouveaux tests diagnostics et des enquêtes complémentaires sur la résis-tance sont nécessaires car l'étendue de la résistance des nématodes de bovins n'est pas connue.anthelmintique / bovin / Cooperia / ivermectine / nematode / refuge / résistance

Sheep and goat nematode resistance to anthelmintics: pro and cons among breeding management factors

“…It corresponds to the fraction of the nematode population that is not submitted to selection pressure by a control measure [26,94]. The concept presents a spatial and temporal component when digestive-tract nematodes are considered: the part of the population in refugia corresponds to the free-living stages, located on pastures and not submitted to the anthelmintic treatment given to the hosts.…”

“…resistance against more than one anthelmintic family) has appeared in field strains [44]. The same species can be prone to develop anthelmintic resistance in a particular host and not in another one, for instance in goats versus sheep [10] or in sheep versus cattle [26]. In a community of nematodes (several species of nematodes), one species can be resistant to an anthelmintic family and a second species to another drug.…”

“…Cases of anthelmintic resistance have been recorded more and more often, threatening small ruminant breeding [30,77] and cases are also emerging in cattle [26,29,73,90,97]. Although many studies have enlightened the molecular basis for resistance to diverse anthelmintic families, reviewed by Sangster [81], few literature data are available concerning the factors responsible for anthelmintic resistance.…”

Immunoprotection in goats against Haemonchus contortus after immunization with cysteine protease enriched protein fractions

“…The control of H. contortus is largely based on pasture management and the use of anthelmintics. Clean pastures are not, however, readily available under intensive grazing conditions and there is an increasing occurrence of parasites resistant to anthelmintics [4,11,15,28,30,31]. Therefore, increasing attention has been given to the development of alternative control methods such as the use of vaccines.…”

Multispecies and multiple anthelmintic resistance on cattle nematodes in a farm in Argentina: the beginning of high resistance?

“…The resistance in small ruminants has mainly been directed against benzimidazoles (43% of cases) and then against levamisole or macrocyclic lactones (23% each). The apparent lack of anthelmintic resistant nematodes in cattle is probably due to the management systems used with most cattle and the lack of surveys for resistance [6]. With extensive beef grazing or with beef suckler herds a large percentage of the worms are in refugia (not exposed to anthelmintics) [26] and few anthelmintic treatments are used in most parts of the world.…”