Chronic kidney disease, a common killer of elderly cats, can only be managed, not treated. But U.S. researchers have invented a new genetic test that may help at-risk cats get the care they need before their kidneys start to fail.
Developed by researchers from Washington State University, the test detects the variant of a gene that helps manage waste removal in feline kidneys. By finding this variant before disease sets in, the inventors believe they can improve the lives of millions of cats and their owners. The researchers have applied to patent their technology with the World Intellectual Property Organization, which published the application March 18.
"Being able to bring a potential solution to people, veterinarians and cats is a plus," said Nicolas Villarino, one of the inventors of the test and an associate professor of veterinary clincal pharmacology at Washington State. "It's something unique for a scientist, where discovery doesn't end at publication, and, at least for me, it's difficult to explain in words how it feels."
Researchers estimate that as many as 35% to 81% of cats over 12 years old suffer from chronic kidney disease, according to the patent application. The range is wide because different studies of the disease use different experimental designs and criteria, according to Villarino. It also illustrates how this condition remains poorly understood.
This test, a cheek swab that can be performed by veterinarians or owners, looks for the 4-domain variant of the gene fAIM, a feline variant of the AIM gene, which creates a protein that helps remove waste from the kidneys. All cats possess this gene, and all are potentially at risk for chronic kidney disease. Cats that have the 4-domain variant of fAIM, however, may develop kidney disease faster.
In addition to felines' dry diets and general distaste for water, a number of threats to cats' kidneys can foster cumulative damage over time. For example, when any mammal becomes dehydrated or experiences low blood pressure, its body restricts blood flow to the kidneys, resulting in the death of a small amount of tissue. This lack of blood flow is called ischemia.
Cats, especially, can experience ischemia from typical events in their lives, either through not drinking water or by going under anesthesia when they are spayed or neutered. When that happens, dead cells build up in the tubules of their kidneys, and the protein governed by fAIM helps clean them out, maintaining homeostasis.
However, the kidneys of cats that have the 4-domain variant of fAIM have a harder time clearing debris, which, over time, can cause scarring and lead to the death of an afflicted cat. Their gene has an additional, "fourth," axon, so the protein it creates is larger and less water-soluble.
Current blood tests detect kidney disease only when about 75% of kidney function is gone, according to Katrina Mealey, director of Washington State's Veterinary Program in Individualized Medicine, who had an advisory role in the test's development. With this test, Mealey and Villarino hope to encourage feline hydration and promote earlier use of kidney supplements and changes in diet to stave off further collapse of kidney function.
"There are a lot of things that veterinarians will do to manage kidney disease," Mealey said. "We try to slow it down, but there's nothing that's a true treatment to reverse those changes and get you back a normal kidney."
The test differs from other tests commonly conducted at veterinary offices, such as the SNAP test for feline immunodeficiency virus and other diseases, because it examines DNA rather than protein. At first, all tests will be sent to the lab at WSU, though Villarino and his colleagues are interested in licensing their technology so other labs can run the test as well. Currently, unlike common tests for the feline leukemia virus and the feline immunodeficiency virus, which analyze protein and run in minutes, the technology for a DNA genotyping test performed bedside does not exist, according to Mealey.
Though Villarino and his colleagues are in contact with established medical companies about producing the new technology, they wish to confirm their findings within the scientific community before offering their test to the public. They believe it is the ethical choice, whereas other companies — they will not name names — offer expensive genetic tests with no scientific backing.
They now have three different research articles planned to undergo peer review, and the first will soon be submitted to the Journal of Veterinary Pharmacology and Therapeutics. Only then will they share this test that could change the lives of many of the U.S.'s 94 million domestic cats.
"This genetic test is a starting point for a new window of opportunity for further research to move the field forward," Villarino said. "There are many things that wait for us ahead."
The application for the patent, "Genetic test for identifying cats at a high risk for developing tubulointerstitial fibrosis," was filed on Sept. 17, 2019 with the World Intellectual Property Organization. It was published March 18 with the application number PCT/US2019/051495. The earliest priority date was Sept. 9, 2019. The inventors of the pending patent are Nicolas Villarino, Liam Broughton-Neiswanger, Michael Court and Neal Burke. The assignee is Washington State University.
Parola Analytics provided technical research for this story.