Objective—To determine whether renal crystals can be experimentally induced in animals fed melamine or the related triazine compound cyanuric acid, separately or in combination, and to compare experimentally induced crystals with those from a cat with triazine-related renal failure.
Animals—75 fish (21 tilapia, 24 rainbow trout, 15 channel catfish, and 15 Atlantic salmon), 4 pigs, and 1 cat that was euthanatized because of renal failure.
Procedures—Fish and pigs were fed a target dosage of melamine (400 mg/kg), cyanuric acid (400 mg/kg), or melamine and cyanuric acid (400 mg of each compound/kg) daily for 3 days and were euthanatized 1, 3, 6, 10, or 14 days after administration ceased. Fresh, frozen, and formalin-fixed kidneys were examined for crystals. Edible tissues were collected for residue analysis. Crystals were examined for composition via Raman spectroscopy and hydrophilic-interaction liquid chromatography–tandem mass spectrometry.
Results—All animals fed the combination of melamine and cyanuric acid developed goldbrown renal crystals arranged in radial spheres (spherulites), similar to those detected in the cat. Spectral analyses of crystals from the cat, pigs, and fish were consistent with melamine-cyanurate complex crystals. Melamine and cyanuric acid residues were identified in edible tissues of fish.
Conclusions and Clinical Relevance—Although melamine and cyanuric acid appeared to have low toxicity when administered separately, they induced extensive renal crystal formation when administered together. The subsequent renal failure may be similar to acute uric acid nephropathy in humans, in which crystal spherulites obstruct renal tubules.
OBJECTIVE To investigate risk factors for the development of pasture- and endocrinopathy-associated laminitis (PEAL) in horses and ponies in North America.
DESIGN Case-control study.
ANIMALS 199 horses with incident cases of PEAL and 351 horses from 2 control populations (healthy horses [n = 198] and horses with lameness not caused by laminitis ) that were evaluated in North America between January 2012 and December 2015 by veterinarian members of the American Association of Equine Practitioners.
PROCEDURES North American members of the American Association of Equine Practitioners were contacted to participate in the study, and participating veterinarians provided historical data on incident cases of PEAL, each matched with a healthy control and a lameness control. Conditional logistic regression analysis was used to compare data on PEAL-affected horses with data on horses from each set of controls.
RESULTS Horses with an obese body condition (ie, body condition score ≥ 7), generalized or regional adiposity (alone or in combination), preexisting endocrinopathy, or recent (within 30 days) glucocorticoid administration had increased odds of developing PEAL, compared with horses that did not have these findings.
CONCLUSIONS AND CLINICAL RELEVANCE The present study identified several risk factors for PEAL that may assist not only in managing and preventing this form of laminitis, but also in guiding future research into its pathogenesis.