SAA in Birds

Serum Amyloid A in Birds

Serum amyloid A (SAA) was reported to serve as a good assessor of the health status of falcons (Journal of Avian Medicine and Surgery, 27(2):83-89, 2013). SAA is a highly conserved acute phase protein (APP) across many species. It is an critical APP produced by the liver during the systemic response made after an inflammatory insult. It has been described in many species varying from fish to elephants. This speaks to its conserved and important role in the innate immune response.

SAA is thought to migrate in the beta fraction which is resolved in standard plasma protein electrophoresis. While beta globulin increases are perhaps the most common electrophoretic abnormality observed in avian species, it is important to understand that assays for specific APP can afford an increased sensitivity for inflammation if the particular APP is involved in the response to an insult.

In the recent article by Caliendo et al., a significant increase in SAA concentration was observed in falcons with inflammatory based disease versus clinically normal birds. The mean value in the latter group was 3.4mg/L. This is hallmark of major APP across many species where near neglible levels are found in normal animals. A fourteen-fold higher value was observed in the clincially abnormal group with a mean value of 47.7mg/L and a maximum value of 137.5mg/L.

In birds with elevated SAA levels, it would be expected that SAA would serve as a prognostic indicator as has been well described in mammalian species. As the half life of the APP is 24 hours, significant decreases would be expected with a positive response to treatment. Another key use of APP testing is as part of routine health screens. While the test will not provide a specific diagnosis, the sensitivity for inflammation will have high value in health assessment. In mammalian species, APP testing has been shown to have much higher sensitivity and specificity versus total white blood cell counts, neutrophil counts, and band neutrophil counts.

It should be noted that normal APP levels can be observed in clinically abnormal animals. In the falcon study, normal values were found in cases of amyloidosis. In other species, it has been shown that chronic diseases may also promote different inflammatory patterns. In ongoing studies from our laboratory, we have observed elevated SAA in many different avian species. However, it should be noted that in some cases, SAA levels were normal when a significantly abnormal electrophoretic pattern was observed. At this time, we do not recommend requesting SAA testing alone. It should be used, at least initially, in conjunction with plasma protein electrophoresis (EPH). EPH can provide a full picture of the acute phase response throughout the globulin fractions as well as an accurate quantitation of albumin levels. If SAA levels are found to be elevated, repeated measures during treatment will provide high prognostic value.

EPH and SAA testing are available through the Avian & Wildlife Laboratory. For more information, call (800)596-7390 or email.