Abstract
Three cases of metabolic bone disease (MBD) were identified in young Humboldt penguin (Spheniscus humboldti) chicks. Diagnosis, monitoring, and treatment of these cases were very challenging, in part because radiographs and traditional serum biochemistries could not provide adequate information for appropriate clinical management. Evaluation of ionized calcium (iCa), 25-hydroxyvitamin D3 (25-[OH]D3), and parathyroid hormone (PTH) levels may have provided valuable diagnostic information about these chicks, but access to these tests was not available at the time of clinical presentation. Additionally, normal values for these parameters have not been reported for any Sphenisciformes species. This study aimed to establish normal reference ranges for the tests to provide an important method for assessing clinical cases of MBD and other diseases.
Blood samples were collected from birds considered to be in normal health in conjunction with standard annual physical examinations. Ionized calcium was measured immediately after sample collection using an i-STAT portable chemical analyzer with an EG7+ cartridge (i-STAT Corporation, East Windsor, NJ, USA) and also by shipment to a commercial laboratory (Diagnostic Center for Population and Animal Health, Michigan State University, Lansing, MI, USA). The same commercial laboratory was used for analysis of PTH and 25-[OH]D3. Not all measurements were obtained from every animal when collected quantities of blood were insufficient. Ionized calcium results were consistent with other avian species, and this test should provide a useful clinical parameter for diagnosing and monitoring MBD cases, as well as other diseases. Obtained values for PTH were clustered in the low end of the detectable assay, raising uncertainties about the validity of the assays in this species. Results of the 25-[OH]D3 test were also near the limit of detection for the assay (4–5 nmol/L), which questions the validity and clinical usefulness of the assay in this species.
No additional cases of MBD have occurred in the penguin collection, and three additional chicks have been successfully hand reared. The ability to closely monitor future cases with these tests, especially iCa, allows for close monitoring of neonates and provides rapid results to immediately adjust therapy with only a very small sample of blood. The tests are also a valuable alternative to radiography, as newly hatched chicks are difficult to evaluate due to minimal bone calcification.