Occurrence of Paratanaisia confusa Freitas , 1951 in free-living guira cuckoo ( Guira guira , Cuculiformes : Crotophagidae )

This report presents a description of natural infection of an adult free-living guira cuckoo with Paratanaisia confusa. Histological and morphological evaluations of renal and parasite samples were performed. The morphological analysis of the parasites revealed spiny tegument, characteristic of P. confusa helminthes. Although macroscopic alterations were absent in the kidneys, the histopathology revealed parasites inside the collecting ducts causing dilatation and destruction of the lining epithelial cells in addition to small focal inflammatory infiltrates in the renal parenchyma. However, as the bird was free-living and naturally infected it was not possible to confirm if all these alterations were directly caused by the parasite presence or if they were related to causes other than the parasitism. Nonetheless, such findings indicate that these trematodes may have pathogenic potential in this host.

This report presents a description of natural infection by P. confusa in a free-living guira cuckoo and describes the associated pathological alterations.
The bird was attended at the Veterinary Hospital "Governador Laudo Natel", from Universidade Estadual Paulista (Unesp), Faculdade de Ciências Agrárias e Veterinárias, Jaboticabal campus, SP, Brazil.The physical examination revealed poor body condition, apathy and hypothermia.Although the bird received clinical support therapy, it died the next day and was necropsied.A range of tissues samples were collected and fixed in 10% buffered formalin for 24h.Soon after, this material was embedded in paraffin, cut into 4-µm section, mounted on slides, stained with hematoxylin and eosin (JECKEL, 2007) and analyzed by light microscopy.Images were obtained with an Olympus BX-51 light microscope and processed with Image Pro Plus v. 4.0.
The remaining renal tissue was sliced and evaluated under stereoscopic microscope for parasite collection.The parasites were stored in vials with Railliet & Henry solution (92% deionized distilled water, 5% commercial formaldehyde and 3% glacial acetic acid) for latter chloridric carmine staining according to Travassos (1950) and identification according to Travassos et al. (1969).
At post mortem examination, all the internal organs including the kidneys showed normal appearance, coloration and size.The histopathological analysis of the renal tissue revealed the presence of several adult trematodes inside the collecting ducts (Figure 1A).
The affected ducts were dilated, compressing the adjacent tissue, showing flattening and destruction of the lining epithelial cells (Figure 1B).Still, moderate diffuse tubular degeneration and moderate multifocal congestion of the blood vessels were found.Discrete agranulocytic inflammatory reaction was observed in the parenchyma but without direct relation to the parasitized ducts.
The morphological evaluation of the parasite revealed tegument covered with spines, presence of well-developed sub-terminal oral sucker, with muscular wider than long pharynx.Sinuous ceca were fused in the caudal end.There was post-bifurcal pre-ovarian genital pore.Small acetabulum was seen on the first third of the body.Testes were lobed, pre-equatorial and post-ovarian, mostly intracecal and located in the same zone.Pre-testicular irregularly shaped ovary was observed laterally displaced.Vitelaria extended from the bifurcal zone to the body end.Uterus was well developed and covered most of the body from the genital pore to the caudal end.There were ellipsoid brownish eggs (Figures 2A and 2B).The parasites were characterized as P. confusa mainly because their typical spiny tegument, not seen in other congeneric species, which have scales covering the tegument (TRAVASSOS et al., 1969;BRANDOLINI & AMATO, 2007).
Most of the reports on avian natural infection by Paratanaisia refer to P. bragai or to undetermined species.Previously, P. confusa has been described in captive Rhynchotus rufescens (MAPELI et al., 2003;MOMO & WERTHER, 2013) and free-living Zenaida auriculata (TARODA et al., 2013).Therefore, this is the first report of this digenean in Guira guira.
The absence of macroscopic renal alterations, also mentioned in previous reports (MENEZES et al., 2001;MAPELI et al., 2003;TAVELA et al., 2014), indicate that these are not common on Paratanaisia infections, even though alterations with variable degree of relevance were described in some host species (UNWIN et al., 2012;MOMO & WERTHER, 2013).Microscopically, all the observed alterations in the morphology of the collecting ducts, leading to compression of adjacent tissue, as observed by other authors (PINTO et al., 2004;GOMES et al., 2005;UNWIN et al., 2012;TAVELA et al., 2014), were probably caused by direct action of the parasites because their relatively large body size may result in physical compression.
This compression may even lead to alterations in non-parasitized ducts, such as decrease in lumen diameter or replacement by connective tissue, as reported for Paradisaea rubra (UNWIN et al., 2012) and Estrilda astrild (TAVELA et al., 2014) infected by P. bragai.Therefore, the parasitism could play an important role in inducing secondary renal lesions.The partial or complete obstruction of the collecting ducts could occur due to the parasites presence or cellular debris.This would decrease urine formation and elimination, which might predispose the host to visceral gout, as described in Rhynchotus rufescens infected by P. confusa (MOMO & WERTHER, 2013;MOMO et al., 2016).In contrast, the dilation of the collecting ducts might be compensatory, therefore allowing the urine flow (PINTO et al., 2004).
While most previous studies indicate a relatively benign disease focused only in structures directly affected by the parasites (PINTO et al., 2004;BRENER et al., 2006;TAVELA et al., 2014), the bird from this report showed diffuse moderate tubular degeneration as well as discrete agranulocytic inflammatory reaction in the parenchyma of the cortical area of renal lobules.This indicates more severe kidney impairment and suggests that chronic infection could lead to renal deficiency.The relatively discrete alterations observed by other authors could be due to early onset of infection.However, as the bird was free-living and naturally infected it was not possible to confirm if all these alterations were directly caused by the parasite presence or if they were related to causes other than the parasitism, such as conditions of the host organism, nutritional state and concomitant infections.
In conclusion, the histopathological findings suggest that P. confusa might have pathogenic potential in Guira guira.
All applicable institutional guidelines for the care and use of animals were followed.