I’m currently attending the American College of Veterinary Internal Medicine (ACVIM) continuing education forum, followed by the Evidence-Based Veterinary Medicine Association (EBVMA) symposium, and between lectures, labs, and other events I’m going to try and post tidbits of interest I come across.
This morning I looked at the poster presentations. Posters at scientific meetings are like mini journal articles. They usually report on small studies, often with significant methodological limitations, and they are considered a lower level of evidence than peer-reviewed papers in the journals. This is not a criticism of them as they are a very important starting point for deciding whether to pursue new ideas. It is just important to recognize their limitations and to take a cautious approach to both positive and negative findings presented as posters.
Some researchers are looking at a possibility that leftover bits of feline kidney proteins in vaccines manufactured using cat kidney cells might be a risk factor for immune-mediated diseases which are relatively common in the cat, especially some types of kidney disease and inflammatory liver and intestinal diseases. A couple of papers (1, 2, 3) have shown that cats do form antibodies to some of these proteins after receiving vaccines, but no conclusive evidence has linked this to clinical disease. The concern is a significant one. If it is true, then changes need to be made in vaccine manufacture and use, and there is the potential to reduce significantly an important set of cat diseases. However, if it is not true, then suggestive but inconclusive research on the possibility will only serve to fuel anti-vaccine fears unnecessarily.
The same research group behind the previous papers presented a poster at the ACVIM forum looking for associations between bloodwork values and the presence of antibodies to several feline kidney proteins of concern.
Association Between Feline Antibody Responses to Crandell Rees Feline Kidney (CRFK) Cell Lysates, Alpha-Enolase, and Annexin A2 and Biochemical Abnormalities in 1,477 Privately-owned Cats. J.C. Whittemore; J.R. Hawley; S.V. Radecki; M.R. Lappin
In this project, blood submitted to a commercial laboratory from 1,477 cats was analyzed. No information about age, sex, vaccination or medical history, or health status was available for specific patients. 16 biochemical measures were compared with the presence of antibodies against 3 feline kidney proteins known to be present in some vaccinated cats. The results were fairly inconsistent and not supportive of the hypothesis that antibodies against feline kidney antigens in vaccines is a cause of disease. For one antigen (CRFK) there was a positive association with one of the 16 measured values, bilirubin (a measure of possible liver disease, among other things). There was also a significant negative association with 2 of the 16 values, creatinine (a measure of kidney function) and alkaline phsophatase (a measure of possible liver disease). The other two antibodies examined both had negative associations with blood sugar, a common blood protein and, for one of them, alkaline phosphatase.
In general, then, these results don’t suggest a strong association between chemistry abnormalities in the blood and the production of antibodies against feline kidney proteins found in vaccines. There was no association with most of the values measured, and most of the associations that were found were negative, which if they were clinically significant might suggest the antibodies somehow protected against liver and kidney diseases, which is highly unlikely. Given all the limitations of the study, especially the lack of any information about the cats the blood came from, this by no means rules out the possibility that the underlying theory is correct, it simply provides a tiny bit of low-level evidence against it. Undoubtedly, this group and others will continue investigating the problem and will hopefully eventually amass sufficient information for a strong conclusion one way or the other. In the meantime, though, it is appropriate to reassure cat owners that the hypothesis is a real but so far unproven concern, and it is not yet appropriate to alter vaccination practices on the basis of it.