Can kidney bioaccumulation of arsenic cause chronic kidney disease in older cats

What is it about?

Domestic cats, as they age, have a much higher prevalence of chronic kidney disease (CKD) compared to other species. For example, 1-3% of the total domestic cat population may have CKD. This rises to around 50% for cats over the age of 15 years. In dogs over the age of 15 years, prevalence of CKD has been estimated at only 10%. Long-term inflammation and oxidative stress are involved in the progression of the disease. A healthy diet, rich in micronutrients, is usually abundant in natural antioxidant substances including many trace elements, which protect tissues, such as the kidney, against damaging reactive oxygen species (ROS) that cause oxidative stress. Some foods, for example fish, can be high in pro-oxidant trace elements, such as arsenic, which has very little known biological function but can increase the formation of ROS and induce mild inflammation.

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Why is it important?

Previous work in The School of Veterinary Medicine and Science, University of Nottingham had discovered that many pet foods with a high fish content were also relatively high in arsenic (Davies et al, 2017; | 7: 17107 | DOI: 10.1038/s41598-017-17159-7). The research and that manuscript in particular became the basis for the BBC2 program, “Trust Me I’m a Vet” to ask the question, “Why do we feed cats fish?”. Although such foods are not usually consumed exclusively, they are fed to cats more often than to dogs. Cats would never ordinarily consume fish, being animals evolved from the dry savannah. Could higher fish intake in our domestic cat population contribute toward their high incidence of CKD through accumulation of non-essential, toxic mineral elements such as arsenic in their kidneys? In a new study, the same researchers from Nottingham Vet School have followed up on their previous work to answer that question. They have now analysed the mineral content of domestic cat and dog kidneys, and urine, obtained from cadavers that were sent to The University of Nottingham Pathology service in order to determine the cause of death. Rather uniquely, and working with cadavers obtained by National Museums Scotland, they have also included a comparator population of cats that have never been exposed to either a domestic environment nor a commercial diet – the feral Scottish Wildcat. The study confirms high rates of renal disease in domestic cats versus dogs, and complete absence of renal disease in Scottish Wildcats. Whilst the data supports their original hypothesis in that tissue and urinary (corrected for creatinine) arsenic content was higher in domestic cats, relative to domestic dogs and Scottish Wildcats, the absolute levels were very low and were no higher in cats with renal disease. Moreover, the type of arsenic found in pet foods was discovered to be a non-toxic, organic form called arsenobetaine. These data do not suggest that higher arsenic intake from eating food with high fish content, is associated with the high rates of kidney disease seen in our domestic cat population.

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