The occurrence of semicarbazide in the meat and shell of Bangladeshi fresh-water shrimp.

There is evidence that semicarbazide (SEM), a marker for the banned nitrofuran nitrofurazone, can arise from other, unrelated sources. Recently, Belgium rejected 54 consignments of Bangladeshi freshwater shrimp (Macrobrachium rosenbergii), following a laboratory decision to test meat and exoskeleton combined. To study the possible natural occurrence of SEM in wild shrimp, samples were collected and analysed from 29 sites across Bangladesh. SEM (<1.0 µg/kg) was detected in ∼65% of meat samples. However, SEM concentrations were approximately 100 times higher in the exoskeleton, and were unrelated to sampling location, strongly suggesting natural occurrence. In meat, most SEM was surface-associated. When the shrimp was shelled, some of the epidermal layer (which synthesises new exoskeleton) remained with the shell and some remained with the meat--leading to differing levels of natural SEM on the shrimp surface. This has implications for the use of SEM and the analytical strategy used to control nitrofuran use.

Nitrofurazone accumulates in avian eyes--a replacement for semicarbazide as a marker of abuse.

Intact nitrofurazone is present in whole eyes of chickens fed varying levels of this banned antibiotic and may therefore be used as an alternative to the controversial marker residue, semicarbazide, to monitor for abuse of this drug in primary production.