Prawns and shrimps (small prawns) are the world’s most popular shellfish. High demand for prawns leads to intensive farming, which can lead to bacterial disease problems. To prevent bacterial disease and promote growth, antibiotic drugs are frequently used. US Researchers in Louisiana took 56 prawn samples in late 2016 and early 2017 from a variety of local retail outlets, and all the prawns were raised by aquaculture and imported from India, Thailand, Indonesia, Vietnam, China, Bangladesh and Ecuador. The samples were analysed for the presence of veterinary drug residues (oxytetracycline, nitrofurantoin, chloramphenicol, fluoroquinolone and malachite green) using ELISA test kits. Additional screening with the Alert sulfite detection kit was used to determine if sulfite residue was over the US legal limit of 100 ppm.
Screening analysis revealed that samples were positive for nitrofurantoin (70 % of samples), malachite green (5 %), oxytetracycline (7 %), and fluoroquinolone (17 %). Malachite green, oxytetracycline and fluoroquinolone are all banned in the US, and nitrofurantoin, an antibiotic growth promoter, has been banned in the EU since 1995. No samples contained chloramphenicol residues. Using LC-MSMS validation, one sample tested positive for 60 ppm of oxytetracycline and 4 ppb of ciprofloxacin. Almost half the 51 samples tested positive for sulfite residue (45 %), but were within the US Food and Drug Administration (FDA) limit (10−100ppm, with one sample was greater than 100ppm).The rest were less than 10ppm of sulphite However, sulfites were not listed on any of labels of the 51 tested packages of imported prawns.