Drug resistance is a problem wherever livestock are raised under intensive conditions and drugs are used to combat
parasitic infections. This is particularly true for the
anticoccidial agents used for the prevention of
coccidiosis caused by protozoa of the apicomplexan genus Eimeria in poultry. Resistance has been documented for all the dozen or so drugs approved for use in chickens and varying levels of resistance is present for those currently employed. A possible
solution may be the introduction of
drug-sensitive parasites into the houses where poultry are raised so that they may replace such
drug-resistant organisms. This can be achieved by utilizing live
vaccines that contain strains of Eimeria that were isolated before most anticoccidial compounds were introduced. Such strains are inherently
drug-sensitive. Practical proposals to achieve this objective involve the alternation of vaccination with medication (known as rotation programs) in successive flocks reared in the same poultry house. A proposal for a yearly broiler production cycle involving
chemotherapy and vaccination is presented. There are few, if any, examples in veterinary parasitology where it has proved possible to restore sensitivity to drugs used to control a widespread parasite. Further research is necessary to ascertain whether this can result in sustainable and long-term control of Eimeria
infections in poultry.