Anthelmintic resistance in gastrointestinal nematodes of sheep: Current situation and novel strategies

Abstract

Gastrointestinal nematodes nowadays represent a major obstacle to sustainable sheep farming due to their negative effect on animal health, welfare and productivity. Commercial drugs such as benzimidazoles, macrocyclic lactones and imidazothiazoles have been used with success in previous decades to control these parasites. However, their irrational application has led to the development of anthelmintic resistance and large economic losses, while the situation is expected to further deteriorate in the future due to the spread of resistance and the emergence of multi-resistant nematode strains. Thus, monitoring is of key importance, which involves the application of various in vitro and in vivo tests, as well as modern molecular methods in order to early detect the development of resistance and monitor the situation in a certain area. In addition, the problem of the exclusive application of chemical preparations is also reflected in the residues in meat and milk, as well as in the environment. This poses a risk to various organisms, including humans. For these reasons, it is necessary to define new strategies, which are based on the rational application of anthelmintics in terms of targeted treatments, targeted selective treatments, but also combination and rotation of preparations. The introduction of alternative methods into practice, such as phytotherapy, i.e. the use of plant preparations such as extracts and essential oils, direct and indirect biological control, development of vaccines, genetic selection of naturally resistant animals with appropriate management of pastures and nutritional status of animals are also needed, all with the aim of reducing application of commercial drugs. This implies an integrated approach to the control of gastrointestinal nematodes, which is the basis of future treatments.