By Robert Sheridan, Chemist, New York State Department of Agriculture & Markets Food Laboratory
In 2007, dogs that had eaten chicken jerky treats imported from China were getting very sick with symptoms of decreased appetite, vomiting, diarrhea and increased urination – some were even dying. While an initial link was made to treats coming from China, doctors and scientists weren’t sure exactly what was harming the dogs. Robert Sheridan, a chemist with the New York State Department of Agriculture & Markets Food Laboratory, explains how testing began in 2007 and where it stands now.
A Needle in a Field of Haystacks
Before we received the chicken jerky treats for testing, veterinarians had diagnosed many of the ill dogs with acquired Fanconi syndrome. Known causes of this condition include chemical assault on the kidneys by heavy metals, certain antibiotics or some antiviral drugs. This diagnosis was rather telling, but there was still a lot of work to be done.
We began evaluating the treats for chemical contaminants including toxic elements and antibiotics. In chemical analysis, identifying an unknown contaminant is akin to finding a needle in a haystack. Adding to the difficulty was the fact that not every dog that consumed these treats became ill. Why was this? Did animals vary in sensitivity to the unknown contaminant? Was the contaminant present in some treats but not others? Or was some other factor at play? These questions made the investigation more like finding a needle in a field of haystacks.
In chemical analysis of food products, sample preparation typically begins with homogenizing a representative portion of the product before attempting to extract the suspected contaminant. This is done so that the measurement of the contaminant represents the average concentration present within a given sample. This procedure is not useful, however, when searching for a contaminant that may not be present in uniform concentrations throughout the product.
The Investigation and Findings
During our investigation we used the following logic: The implicated chicken jerky dog treats were sold in bags of 10-60 pieces. Our thinking was that if potential hot spots of contamination were present in just a few of these treats, homogenizing all treats from a bag could dilute the contaminant making it undetectable. We decided to look into the composition of each individual chicken jerky treat, one treat being the single serving size for most dogs.
Using this approach, we found a variety of antibiotics that were not approved by the FDA for use in poultry and an additional antibiotic that in some samples exceeded the FDA maximum allowable concentration. Though most of the antibiotics we found were at fairly low concentrations, in a number of samples the concentrations were quite high.
In all we found six antibiotics including Sulfaclozine, Sulfaquinoxaline, Sulfamethoxazole, Tilmicosin, Trimethoprim and Enrofloxacin. The concentrations of these drugs ranged from 1.0 to 2000 ng/g (ppb). Not every jerky treat contained one of these drugs and many contained more than one. Almost every bag had several pieces that contained at least one of the six drugs. (Sulfaquinoxaline is approved by FDA to be used in chickens bound for consumption as long as residues in chicken meat are below a set level. Several jerky treats with that antibiotic exceeded the FDA maximum allowable level. The other drugs are not allowed by FDA at any concentration in chicken.)
A Successful Recall
On January 7, 2013, New York State initiated a recall of several brands of chicken jerky treats based on the findings of the New York State Food Laboratory. Subsequently the manufacturers voluntarily recalled several brands of chicken jerky treats from US stores. FDA announced in a recent press release that the incidence of dog illnesses and deaths has decreased since these products were recalled.
Still Many Unknowns
The antibiotics detected in these products seem unlikely to be the underlying cause of the reported illnesses, and the investigation into other contaminants is ongoing.
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