Identification and Characterization of Toxicity of Contaminants in Pet Food Leading to an Outbreak of Renal Toxicity in Cats and Dogs

Abstract

This paper describes research relating to the major recall of pet food that occurred in Spring 2007 in North America. Clinical observations of acute renal failure in cats and dogs were associated with consumption of wet pet food produced by a contract manufacturer producing for a large number of companies. The affected lots of food had been formulated with wheat gluten originating from China. Pet food and gluten were analyzed for contaminants using several configurations of high-performance liquid chromatography (HPLC) and mass spectrometry (MS), which revealed a number of simple triazine compounds, principally melamine and cyanuric acid, with lower concentrations of ammeline, ammelide, ureidomelamine, and N-methylmelamine. Melamine and cyanuric acid, have been tested and do not produce acute renal toxicity. Some of the triazines have poor solubility, as does the compound melamine cyanurate. Pathological evaluation of cats and dogs that had died from the acute renal failure indicated the presence of crystals in kidney tubules. We hypothesized that these crystals were composed of the poorly soluble triazines, a melamine-cyanuric acid complex, or a combination. Sprague dawley rats were given up to 100 mg/kg ammeline or ammelide alone, a mixture of melamine and cyanuric acid (400/400 mg/kg/day), or a mixture of all four compounds (400 mg/kg/day melamine, 40 mg/kg/day of the others). Neither ammeline nor ammelide alone produced any renal effects, but the mixtures produced significant renal damage and crystals in nephrons. HPLC-MS/MS confirmed the presence of melamine and cyanuric acid in the kidney. Infrared microspectroscopy on individual crystals from rat or cat (donated material from a veterinary clinic) kidneys confirmed that they were melamine-cyanuric acid cocrystals. Crystals from contaminated gluten produced comparable spectra. These results establish the causal link between the contaminated gluten and the adverse effects and provide a mechanistic explanation for how two apparently innocuous compounds could have adverse effects in combination, that is, by forming an insoluble precipitate in renal tubules leading to progressive tubular blockage and degeneration.

Melamine in eggs, plasma and tissues of hens fed contaminated diets

“…Melamine forms crystals in renal tubular and kidney tissues, and the contemporary presence of cyanuric acid in the diet increases the dimension and consistency of the crystals (Dobson et al, 2008). The FDA (2007) reported cases of renal diseases in dogs and cats fed melamine-contaminated pet food, with the deaths of some subjects.…”

Biodegradation of melamine and its hydroxy derivatives by a bacterial consortium containing a novel Nocardioides species

“…However, this opinion of melamine changed after a large outbreak of nephrotoxic renal failure of dogs and cats associated with the intake of melaminecontaminated pet foods occurred in 2007 in North America (Brown et al 2007), and four thousand dogs and cats died from acute renal failure. Melamine and its hydroxyl analogues such as ammeline (4,6-diamino-2-hydroxy-1,3,5-triazine), ammelide (6-amino-2,4-dihydroxy-1,3,5-triazine), and cyanuric acid (1,3,5-triazinane-2,4,6-trione) were detected in vegetable proteins in the contaminated pet foods (Dobson et al 2008). Chemical analysis of crystals found in the kidney tubules of the dead animals identified that they were mainly composed of co-crystallized melamine and cyanuric acid, both of which were present in extremely high concentrations (more than 3,000 mg kg −1 ) in vegetable proteins produced in China (Suchý et al 2009).…”

Melamine Toxicity

“…The pet food tested from this outbreak contained melamine and cyanuric acid [33,34]. The amounts of melamine found in some tested food ranged from 10 to 3,200 ppm (1 ppm is equivalent to 1 mg/kg food source); animals received an estimated dose of 360 to 430 mg kg −1 day −1 from the contaminated food [11,33]. Histological investigations showed that melamine and cyanuric acid were present in the tissues of animals fed these products [1,33,34].…”

“…However, the cats fed both compounds developed urinary stones at a dose of 32 mg/kg body weight of melamine and cyanuric acid [11]. Two other animal studies showed that melamine and cyanuric acid when administered together at 400 mg kg −1 day −1 produced renal stones, but when they were administered separately, no stones formed [10,33]. Based on these studies, melamine and cyanuric acid appeared to be relatively safe in low doses when administered individually, but when combined caused stone formation.…”

“…The feed was recalled and destroyed [2]. The pet food tested from this outbreak contained melamine and cyanuric acid [33,34]. The amounts of melamine found in some tested food ranged from 10 to 3,200 ppm (1 ppm is equivalent to 1 mg/kg food source); animals received an estimated dose of 360 to 430 mg kg −1 day −1 from the contaminated food [11,33].…”