The collective term coccidiostatics covers various drugs used to prevent and treat coccidiosis, an intestinal disease caused by certain protozoa.

Eimeriosis, the most important coccidiosis, which occurs predominantly in poultry, manifests itself in bloody, watery diarrhea and reduced performance and, in cases of severe infestation, leads to death of the infected animals. In farm poultry, where many animals live in a confined space, the pathogens can spread through the feces (fecal-oral infection) over the entire flock within a few days, posing a serious threat to the flock. The higher the number of animals and the lower the hygiene status, the greater the risk of infection and the more likely it is that coccidiostats will be used.

Coccidiostats can accumulate in eggs to a greater or lesser extent. Therefore, to avoid residues in eggs, the use of coccidiostats is not allowed in laying hens. For coccidiostats approved as feed additives for poultry, the approval is limited to poultry for fattening and pullets during the rearing phase (16 weeks).

There is a second reason for the occurrence of coccidiostat residues in eggs, besides the improper treatment of laying hens, which is related to feed production. During the production of feed with permitted coccidiostat additives, contamination of the laying hen feed produced immediately afterwards can occur due to the so-called "carry over".

Regulation (EU) No. 37/2010 sets a maximum level for eggs for the group of coccidiostats only for the polyether antibiotic lasalocid. It amounts to 150 µg/kg. Lasalocid and four other coccidiostats are regulated for animal tissues.

The maximum levels of coccidiostats that may be present in feed for non-target species due to unavoidable carryover have been set by Directive 2009/8/EC since February 2009. The unavoidable carry-over in feed due to production processes can further lead to the presence of these substances in small amounts as contaminants in food of animal origin. Regulation (EC) 124/2009 sets maximum levels for carry-over residues of coccidiostats in food of animal origin to protect consumers.

The control of domestic eggs and animal tissues (liver) for coccidiostat residues is part of the National Residue Control Plan (NRKP) for food of animal origin. The egg samples are taken either directly from the producer or from the packing plants, so that the traceability of the samples to the farm of origin is guaranteed in the sense of preventive consumer protection. To clarify the cause of positive findings in eggs, the feed administered is also examined.

Further examinations of eggs for coccidiostat residues are carried out as part of actions by the official food control or in cases of suspicion.

Our Department of Veterinary Medicinal Products, Hormones and Contaminants of the Institute for Food Safety Vienna is entrusted with the analyses within the framework of the NRKP. The department is also the National Reference Laboratory for these investigations.

Regular participation in international interlaboratory comparisons and in workshops of the EU Reference Laboratory (EURL) in Berlin, which is responsible for coccidiostats, ensure the quality of the results and a continuous development of the analytical methods to the latest state of the art and research.

Investigation methods

An immunochemical method is used for rapid and cost-effective screening of coccidiostatics residues in eggs. In case of non-negative results, the samples in question are examined using a confirmatory method (LC-MSMS) to identify and quantify the substances.

Samples of animal tissues (mainly liver) are analyzed by HPLC coupled with mass spectrometric detection (LC-MSMS).

Legal basis

CommissionRegulation (EU) No. 37/2010 of 22 December 2009 on pharmacologically active substances and their classification with regard to maximum residue limits in food of animal origin (OJ EU No.L 15 of 20.1.2010).

CommissionDirective 2009/8/EC of 10 February 2009 amending Annex I to Directive 2002/32/EC of the European Parliament and of the Council as regards maximum levels for coccidiostats and histomonostats present in non-target feed due to unavoidable carry-over (OJ No. L 40, 11.02.2009).

CommissionRegulation (EC) No 124/2009 of 10 February 2009 setting maximum levels for coccidiostats and histomonostats present in foodstuffs due to unavoidable carry-over in non-target feed (OJ No L 40, 11.02.2009).