Coccidiosis in poultry: anticoccidial products, vaccines and other prevention strategies.

Coccidiosis in chickens is a parasitic disease with great economic significance, which has been controlled successfully for decades using mainly anticoccidial products. However, large-scale and long-term use of anticoccidial drugs has led to the worldwide development of resistance against all these drugs. In order to minimize the occurrence of resistance, the rotation of various anticoccidial drugs in single and/or shuttle programmes is used. Unfortunately, this has not solved the anticoccidial resistance problem. Recently, live anticoccidial vaccines have been incorporated into rotation programmes, resulting in an increasing incidence of anticoccidial drug-sensitive Eimeria spp. field isolates, which may ameliorate the efficacy of anticoccidial drugs. Nevertheless, possible upcoming bans restricting the use of anticoccidials as feed additives, consumer concerns on residues and increasing regulations have prompted the quest for alternative coccidiosis control strategies. Although management and biosecurity measures could halt the introduction of Eimeria spp. to a farm, in practice they do not suffice to prevent coccidiosis outbreaks. Phytotherapy, aromatherapy and pre- and probiotics either show conflicting, non-consistent or non-convincing results, and have therefore not been applied at a large scale in the field. So far, live attenuated and non-attenuated anticoccidial vaccines have proved to be the most solid and successful coccidiosis prevention and control strategy. Despite the drawbacks associated with their production and use, their popularity is increasing. If with time, the immunogenicity of subunit vaccines can be improved, they could represent the next generation of highly efficient and low-cost anticoccidial strategies.