Anticoccidia presence in slurries/manures and agricultural soils in Galicia (NW Spain)

Coccidiosis is one of the most important parasitic diseases, responsible for significant damage affecting animal production worldwide. It is caused by different protozoan species belonging to the genera Eimeria and Isospora. To treat and prevent this disease ionophore antibiotics are widely used in veterinary medicine especially in food-producing animals as food additives. Ionophore coccidiostats, such as monensin, salinomycin, lasalocid or narasin have been a key tool in the fight against coccidiosis for more than 40 years. Non-ionophore coccidiostats, such as robenidine, toltrazuril and decoquinate are also widely used to treat coccidiosis. All these compounds are toxic to humans, which explains why they are not used as pharmaceuticals in human medicine and are only used in veterinary medicine. Release of these anticoccidiostat in agricultural soils, through the application of manures and slurry from treated animals, poses a risk as crops could uptake coccidiostats and start entering the food chain, risking human health. The objective of this study was to perform a survey of the presence of anticoccidial in slurries from medicated animals and the soils where these manures were applied, to assess the risk of soil pollution.

A total of 66 slurries/manures from different animals were collected: poultry (16), veal (17), cow (10), pig (10), rabbit (12), and one sample which was a mixture of cow and pig slurry. Likewise, the soils that were amended with those slurries (76 in total) were also sampled by collecting samples at two different depths: 0-5 cm and 5-20 cm. The presence of ionophore antibiotics, non-ionophore and compounds from various therapeutic groups were analysed in all the samples (slurries/manures and soils) by HPLC-MS/MS. The results showed that 53% of the slurry/manure samples and 25% of the soil samples presented some pharmaceutical product. Focusing on ionophore antibiotics in slurry/manure, 21% and 4.5% of the samples presented narasin and salinomycin, respectively; these two antibiotics were not detected in the soils, but other ionophore, such as monensin, was detected in 4% of the soil samples in the 0-5 cm soil depth. Ionophore antibiotics were not detected in the soil depth of 5-20 cm, indicating a low mobility of these compounds, possibly related to a strong adsorption by soil components. The non-ionophore anticoccidial robenidine and decoquinate were present in 8% of manure/slurry and 1% and 11% of soil samples respectively; meanwhile toltrazuril appeared in 2% of manures/slurries. Moreover, 15 other pharmaceutical compounds were detected:  one corticosteroid (dexamethasone), one anti-inflammatory (diclofenac), one antifungal (griseofulvin) and 12 antibiotics from different groups (tylosin, trimethoprim, sulfadiazine, sulfamethazine, sulfachloropyridazine, enrofloxacin, ciprofloxacin, levofloxacin, lincomycin, doxycycline, oxytetracycline, tetracycline). In summary, narasin was the most frequent present in slurries/manures and the decoquinate in soils.

Even though the focus of our project was the anticoccidial compounds, the fact that we detected a wide array of other pharmaceutical products highlight the risk that suppose the overuse of these compounds in animal farms for both environmental and human health.