Environmental Contamination with Sulfadiazine Powder Given to Pigs

A study recently published in BMC Veterinary Research found that sulfadiazine given to pigs in powder form contaminated the environment to a greater degree than did sulfadiazine given in pelleted or granular forms. Researchers also detected sulfadiazine in the plasma and urine of sentinel pigs housed in an area that had previously contained pigs treated with sulfadiazine powder.

Antibiotic residues in the environment increase the risk of bacterial resistance, and traces of antibiotics have previously been reported in pig barns. The purpose of this German study was to determine whether different pharmaceutical formulations of sulfadiazine cause the same degree of environmental contamination.

Researchers gave sulfadiazine formulated as powder, pellets, or granules to 24 pigs (4 groups of 6 pigs each). The powder group received sulfadiazine powder mixed into the feed in 2 different subtherapeutic dosages, followed by 1 therapeutic dosage. Pigs received each dosage for 4 consecutive days, with washout periods separating the dosages. The pen was cleaned between dosages [personal communication with the lead author]. After the final therapeutic dose was given, the pen was dry-cleaned and a group of untreated pigs (sentinel group) was moved into the area for 6 days. Pigs in the pellet and granule groups received therapeutic dosages of sulfadiazine for 4 consecutive days.

The researchers measured sulfadiazine concentrations in the treated pigs’ blood before and 3 hours after sulfadiazine administration each day. Blood samples from sentinel pigs and urine samples from all pigs were collected once a day. Environmental contamination was assessed from samples of sedimentation (surface) dust and aerosolized dust collected from various locations within the barn.

Plasma and urine levels of sulfadiazine were similar in pigs given therapeutic doses of sulfadiazine in all 3 pharmaceutical formulations. Traces of sulfadiazine were also detected in the plasma and urine of pigs in the sentinel group (urine levels were higher than plasma levels).

Sulfadiazine residues were detected in all tested locations in the pen housing the powder group. Environmental residues were significantly lower in areas housing the pellet and granule groups. In some locations, environmental sulfadiazine levels were higher after subtherapeutic dosages were given in powder form than after therapeutic dosages were given in pelleted or granular forms.

According to the researchers, the distribution of sulfadiazine residue in the environment suggested that the antibiotic was spread by air currents, possibly linked to air conditioning and pig activity. The authors also inferred from the data that the sentinel pigs absorbed sulfadiazine mostly by oral ingestion, with perhaps a small amount absorbed through the lungs by inhalation. The authors concluded that the pharmaceutical formulation of antibiotics given orally to pigs affects the degree of environmental antibiotic contamination.

The study was supported by the Deutsche Bundesstiftung Umwelt DBU (German Federal Environmental Foundation).

Dr. Laurie Anne Walden received her doctorate in veterinary medicine from North Carolina State University in 1994. After an internship at Auburn University College of Veterinary Medicine, she returned to North Carolina, where she has been in companion animal general practice for over 20 years. Dr. Walden is also a board-certified Editor in the Life Sciences and owner of Walden Medical Writing.