Renal trematode infection in wild birds: histopathological, morphological, and molecular aspects

Paratanaisia are eucotylidae digeneans that affect the upper urinary tract of birds. This genus contains three species (Paratanaisia bragai, P. robusta, and P. confusa) with similar morphological features. Macroscopic and microscopic damage caused by these parasites ranges from the irrelevant to significant lesions. This study aimed to describe the histological, morphological, and molecular features of the renal tissues and parasite specimens obtained from naturally infected free-ranging and captive wild birds in Brazil. Histopathological evaluations were performed on 103 slides containing kidney tissue sections from parasitized birds. Parasites were observed inside the collecting ducts, causing the dilation and destruction of the lining epithelial cells and alterations in other structures of the renal parenchyma. Such findings indicate that Paratanaisia have pathogenic potential in a wide range of hosts, suggesting low host specificity. The parasites recovered from the kidneys of 10 birds, including Columbiformes, Galliformes, Strigiformes, and Cuculiformes, were morphologically evaluated and identified as Paratanaisia sp. Formalin-fixed paraffin-embedded kidney fragments were subjected to conventional PCR assays targeting the 18S and 28S rDNA genes. A Bayesian inference analysis based on an 800-bp 18S rDNA gene fragment separated the trematode genus accurately, clustering all of the parasites tested with a previously described P. bragai specimen. Analyses on a small fragment of the 28S rDNA gene did not allow for accurately differentiating the Paratanaisia species. Therefore, further morphological studies with additional molecular markers are necessary to improve our understanding of the alpha-taxonomy of this group.