Parasite problems in organic livestock and options for control

Summary

ABSTRACT: Organic livestock production has increased dramatically in recent years in Europe and other parts of the world. The aim of producing livestock under more natural conditions has led to a reversion to primarily outdoor production systems and less intensive housing when indoor, more forage-based diets, and a reduced reliance on external inputs like antiparasiticides. These major changes in livestock production systems may potentially result in re-emergence (or emergence) of parasitic infections. The basic objective of this paper is to give an overview of the available information on parasitic problems in organic livestock production with a focus on northern temperate regions. Furthermore, options for control that target these problems and are acceptable within the framework of organic farming will be discussed. The large majority of conventional pigs and poultry are raised in highly intensive production systems which differ dramatically from organic housing systems and especially outdoor runs and pastures. A comparably pronounced difference between conventional and organic systems is not found for ruminants. Thus, organic rearing may be a higher risk factor for pigs and poultry than for ruminants, however this may partly be counteracted by the fact that pigs and poultry never rely on pasture vegetation for feeding, while ruminants do so with associated potential problems of insufficient nutritional status and increased parasite transmission. Several studies have indicated higher parasite infections rates in organic herds vs. and conventional herds, and many of these differences may be explained by environmental factors favourable to the development of parasite oocysts/eggs/larvae and perhaps for intermediate hosts, while fewer differences may be due to the lack of chemical intervention. However, parasite species have to overcome many very diverse constraints in their attempts to complete their life cycles and it may therefore be risky to generalize. Thus, helminths and Eimeria sp. infections are most prevalent in organic swine herds whereas infections with Isospora suis seems less common than in intensive herds. A higher risk of helminth infections has also been documented in organic poultry. In organic dairy production, gastrointestinal parasites may pose a problem, and lungworm infection remains a major problem, not only in grazing heifers and steers but also in adult milking cows. This is not different from conventional herds but control measures are restricted. Many problems can be controlled by appropriate management routines, e.g. pasture management. However, avoiding chemotherapeutics for control in certain regions, e.g. in relation to ectoparasitic infections, remains a major challenge. Future research has to actively exploit new, promising avenues for control like forages or diets with anti-parasitic activities, biological control and selection for resistance, using approaches compatible with organic farming principles.