Serum iron analytes in healthy and diseased Florida manatees (Trichechus manatus latirostris)

Abstract

Serum iron concentration is usually decreased in true iron deficiency and with inflammatory disease in man and domestic animals. Serum total iron binding capacity (TIBC) may be increased in true iron deficiency and decreased with inflammatory disease. This prospective study was designed to measure serum iron analytes in healthy free-ranging and housed Florida manatees (Trichechus manatus latirostris) of both sexes and various ages and to evaluate the effects of diseases common to manatees on these analytes. Blood samples were collected without anticoagulant from 137 healthy free-ranging manatees, 90 healthy housed manatees and 74 free-ranging diseased manatees, and serum was prepared by centrifugation. Serum iron concentration and unsaturated iron binding capacity were measured colourimetrically, and TIBC and percent transferrin saturation with iron were calculated. Serum amyloid A (SAA) was measured to assist in the health assessment of manatees and provide evidence of inflammation in diseased manatees. Based on the serum iron analytes, iron availability was lower in immature manatees compared with adults, and it was lower in housed manatees compared with free-ranging manatees. In contrast to other mammals studied, serum iron concentration was elevated rather than depressed in late pregnancy. Serum iron concentrations and transferrin saturation with iron percentages were significantly lower, and SAA concentrations were significantly higher, in diseased (ill and injured) manatees compared with healthy manatees. Serum iron concentration and transferrin saturation with iron values were negatively correlated with SAA concentrations, and manatees with the highest SAA concentrations had lower serum TIBC values. These findings indicate that inflammation is the major factor responsible for alterations in iron analytes in diseased manatees. Consequently, hypoferraemia may be used as supportive evidence of inflammatory disease in manatees (unless haemorrhage is also present). A decision threshold of ≤13.8 μmol/l was determined for hypoferraemia using receiver operating curve analysis. Based on studies in man and domestic animals, iron therapy is unnecessary for manatees with hypoferraemia associated with inflammation and has the potential for causing tissue damage and increased susceptibility to bacterial infections.