May 30, 2016

Risk Factors for Chronic Kidney Disease in Cats

Researchers in the United Kingdom identified frequent vaccination and moderate to severe dental disease as risk factors for the development of chronic kidney disease in cats, according to a recent study.
By Laurie Anne Walden, DVM, ELS
Researchers in the United Kingdom identified frequent vaccination and moderate to severe dental disease as risk factors for the development of chronic kidney disease in cats, according to a study recently published in the Journal of Veterinary Internal Medicine.
The longitudinal study followed 148 client-owned cats between 2005 and 2009. Cats included in the study were over 9 years old and not azotemic when the study began. Cats that developed nonrenal diseases, such as hyperthyroidism, were excluded from the analysis. Physical examinations and blood and urine tests were performed at 2 primary-care practices at intervals of 6 months or less. Information about breed, diet, vaccination status, environment, exposure to tobacco smoke, and history of dental disease was compiled from questionnaires completed by cat owners.
Azotemic chronic kidney disease was defined as either a plasma creatinine level above the reference range and a urine specific gravity below 1.035 or 2 successive plasma creatinine levels above the reference range (usually measured 6 to 8 weeks apart). Over the course of the study, 27 (18%) of the 148 cats included in the final analysis developed azotemic chronic kidney disease. This number does not include 36 cats who developed hyperthyroidism and were excluded from the final analysis; the incidence of chronic kidney disease among the hyperthyroid cats was not calculated.
Vaccination categories included in the owner questionnaire were no vaccination, initial vaccination only, occasional vaccination (intervals of more than 2 years), frequent/annual vaccination (intervals of 1 to 2 years), and unknown. Frequent/annual vaccination, which was reported by 26% of participating cat owners, was an independent risk factor for the development of azotemia.
The specific vaccines given to cats in the study population were not reported. Core vaccines for UK cats, as listed by the Royal Society for the Prevention of Cruelty to Animals, are those against feline panleukopenia, herpesvirus-1, calicivirus, and (for at-risk cats only) feline leukemia virus. Rabies vaccines are not core feline vaccines in the United Kingdom.
According to the authors, vaccines against feline panleukopenia, herpesvirus-1, and calicivirus are produced using Crandell-Rees feline kidney cells. Antigens from these cells may become incorporated into vaccines and provoke an immune response against kidney tissue. The authors suggest further research into the possible association of vaccination and renal disease, noting that a limitation of this study was the potential inaccuracy of the owner-reported vaccine histories.
Dental disease categories were based on examination records and calculus and gingivitis scores. Moderate and severe dental disease were independent risk factors for developing azotemia. “Periodontal disease has been identified as a risk factor for CKD [chronic kidney disease] in human patients,” write the authors, noting that periodontal disease may cause kidney damage via chronic inflammatory processes. The study did not exclude potential confounding factors (such as infectious causes of gingivitis) that might influence the development of kidney disease. A history of treatment for dental disease was not significantly associated with development of azotemia. Therefore, the authors concluded that the risk of azotemia is associated more with dental disease itself than with its treatment, which might include antibiotics, nonsteroidal anti-inflammatory drugs, and general anesthesia. The authors recommend more studies to confirm their results and investigate the connections between inflammation, dental disease, and chronic kidney disease in cats.
“Results of our study suggest there is no single risk factor, exposure, or predictor that can explain development of CKD in cats,” they write. “Epidemiological studies, as conducted in our study, do not necessarily imply causality, but simply suggest associations.” They conclude that avoiding vaccine overuse and maintaining good oral health might minimize lifelong risk and help preserve kidney function in cats.
Dr. Laurie Anne Walden received her doctorate in veterinary medicine from North Carolina State University in 1994. After an internship at Auburn University College of Veterinary Medicine, she returned to North Carolina, where she has been in companion animal general practice for over 20 years. Dr. Walden is also a board-certified Editor in the Life Sciences and owner of Walden Medical Writing. 

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