RESUMEN
Renicolid digeneans are frequently observed in the renal tubules and ureters of seabirds, such Puffinus puffinus, a migratory species distributed along the Brazilian coast. However, few studies have focused on the relationship between renicolid infection and health status in P. puffinus. Thus, the aim of this study was to describe (i) renal and systemic alterations, (ii) the renicolids and (iii) the biological aspects associated with the presence of renicolids in P. puffinus. Gross and histological assays were performed in 93 P. puffinus stranded on the Paraná coast, southern Brazil, and renicolids were submitted to morphological and molecular assays. A high prevalence of renicolids in P. puffinus (71/93) was observed. In the kidney, the main microscopic findings were lymphocytic interstitial infiltrate, ductal ectasia and tubular necrosis. The renal lesions were significantly associated with the parasite infection. The morphological (n = 84) and molecular analyses (n = 2) confirmed the species as Renicola sloanei (100% and 95.9% of nucleotide identity with R. sloanei strains from P. puffinus and from Spheniscus demersus, respectively). In both parasitized and non-parasitized animals, cardiac and skeletal muscle degeneration and necrosis were the most frequent systemic changes. Therefore, the results suggest renicolids being a possible cause for the demonstrated renal alterations. A contribution of this parasite to a decreased health status of Puffinus puffinus along their migratory route is possible.