Case reports of melamine-induced pathology in penaeid shrimp fed adulterated feeds

Shrimp (Penaeus monodon and P. vannamei) specimens were submitted to the University of Arizona's Aquaculture Pathology Laboratory (UAZAPL) and to the Texas Veterinary Medical Diagnostic Laboratory (TVMDL) in 2007 and 2008 from shrimp-rearing facilities in India and Indonesia for histological testing. These were found to present prominent golden to greenish-brown needle-and plate-like birefringent crystals within multifocal hemocytic granulomas in the antennal gland tubules and peritubular hemal sinuses. Their appearance was very similar to melamine-cyanuric acid-induced crystals previously described from cat and dog kidneys with melamine-associated renal failure (MARF). Significant chronic mortalities were reported from the affected P. vannamei farms in Indonesia, but were not observed in the affected P. monodon facility in India. Shrimp feed was suspected as the source of melamine due to the similarity of the shrimp antennal gland lesions to those present in MARF. 'Normal' and 'suspect' feed samples from the facilities in Indonesia and India were sent to regional laboratories for analysis. Melamine was detected in 2 of 4 feed samples from an affected Indonesian farm. Melamine was not detected in 'normal' feed from the Indian facility, but it was found in 2 'suspect' samples (Feeds A and B) at levels of 183.39 and 112.50 ppm, respectively. A bioassay of Feed A with P. vannamei at UAZAPL confirmed that the melamine-contaminated feed induced prominent granulomas in the antennal gland with the characteristic crystals within 10 d of the first feeding, experimentally confirming the direct relationship of melamine-adulterated feed to the unique pathology observed.