Quantitative and qualitative morphologic, cytochemical and ultrastructural characteristics of blood cells in the Crested Serpent eagle and Shikra

The Crested Serpent eagle (Spilornis cheela) is a bird of prey found in the tropical rain forest in Thailand. The Shikra (Accipiter badius) is a sparrow hawk and common resident in Thailand. Blood samples from 9 Crested Serpent eagles and 12 Shikras were obtained from September 2010 to November 2014. They were clinically healthy and negative for blood parasites detectable by light microscopy and molecular techniques (partial cytochrome b gene for avian malaria and partial 18S rRNA gene for trypanosome). Cytochemical staining (Sudan black B, peroxidase, a-naphthyl acetate esterase, and beta-glucuronidase) and transmission electron microscopy were performed. Hematological results were reported as the mean standard deviation and median. Heterophils were the most prevalent leukocytes in the Crested Serpent eagle, but in the Shikra, lymphocytes were the most prevalent leukocytes. In the Shikra, some vacuoles were observed in the cytoplasm of the eosinophils. All blood cells in both types of raptors stained positively for beta-glucuronidase but negatively for peroxidase. The ultrastructure of heterophils showed more clearly differentiate long rod granules in Crested Serpent eagle and spindle-shaped granules in Shikra. The ultrastructure of the eosinophils in the Crested Serpent eagle revealed varied electron-dense, round-shaped granules with round, different electron-dense areas in the centers of some granules, which differed from the structure reported for other raptors. These quantitative results may be useful for clinical evaluations of Crested Serpent eagles and Shikras that are undergoing rehabilitation for release.