Epidemiology of blood flukes (Digenea: Spirorchiidae) in sea turtles from Tyrrhenian and Adriatic Seas, off Italy

Abstract

Background: The Spirorchiidae is a family of blood flukes parasitizing turtles. Spirorchiids may cause a wide range of inflammatory reactions in the vascular system of their host being frequently implicated with stranding and death of sea turtles worldwide. Recent studies revealed the presence of two spirorchiid species in the Mediterranean basin. Our study presents comparative epidemiological data of spirorchiid infections in loggerhead turtles (Caretta caretta) stranded during an eight-year period from Adriatic and Tyrrhenian Seas, and the first report of Neospirorchis Neogen-11 in a green turtle (Chelonia mydas). Methods:We screened a total of 319 carcasses of loggerhead turtles stranded from January 2011 to December 2018 along the Tyrrhenian coast (n = 111) and the north-western Adriatic coast (n = 208) of Italy using traditional (copromicroscopy and histopathology) and molecular assays. Three green turtles from the Tyrrhenian coast were also included in the study. Results:A total of 56 (17.5%) loggerhead turtles and one green turtle (33.3%) were found to be infected with spirorchiid flukes. Amplification, sequencing of the ITS2 region of the ribosomal RNA gene cluster and BLAST analysis confirmed the presence of Hapalotrema mistroides and Neospirorchis Neogen-11 in 51 (16.0%) and 24 (7.5%) loggerhead turtles, respectively, and Neospirorchis Neogen-11 in an infected green turtle. Differences in prevalence of infection between the two sampling areas were found. Conclusions:The risk of spirorchiid infection in the Tyrrhenian Sea is lower than in the Adriatic Sea and in general the risk of infection in the Mediterranean is lower than in other geographical locations. Differences in the prevalence of infection between the two sampling areas were related to the differences of regional habitats supporting different abundance of spirorchiid intermediate hosts. A systematic monitoring to evaluate the progress of the infection is recommended, as well as studies on the occurrence and distribution of spirorchiid species from other Mediterranean areas.

Serious lesions in Green turtles (Chelonia mydas) afflicted by fatal Spirorchiidiasis found stranded in south and southeastern Brazil

“…Spirorchiidiasis infections are high in marine turtles, globally affecting endangered sea turtle populations, as the Spirorchiidae family is near cosmopolitan in its distribution ( Chen et al, 2012 ; Chapman et al, 2017 , 2019 ; Santoro et al, 2020 ). This parasitic infection has, in fact, been significantly associated to sea turtle stranding and mortality events worldwide ( Santoro et al, 2007 ; Stacy et al, 2010 ; Werneck et al, 2015 ; Jerdy et al, 2020 ).…”

“…Spirorchiidiasis causes a wide range of inflammatory vascular reactions ( Santoro et al, 2020 ). The lesions associated with this disease are caused by spirorchiids inhabiting the blood and lymphatic vessels of infected animals and by their egg deposition, known to affect most sea turtle organs ( Santoro et al, 2007 ; Stacy et al, 2010 ).…”

Helminth Infection of the Loggerhead Sea Turtle Caretta caretta along the Coasts of Sicily and the North West Adriatic Sea

“…Digenean flukes require hosts to complete their life cycle [ 9 ] and sea turtles are definitive hosts of the adult parasites, localized in the alimentary tract, in the bile ducts or more rarely in the urinary bladder and vascular system. Among the parasites with the greatest pathogenic potential bloodflukes of the Spirorchiidae family whose infections have in some cases been related to mortality episodes [ 10 , 11 ]. The pathogenic effect of the adult stage of these parasites is closely related to their localization, mainly the circulatory system, and to the severe inflammatory reactions caused in various organs and tissues by their eggs eliminated through the bloodstream.…”

“…The pathogenic effect of the adult stage of these parasites is closely related to their localization, mainly the circulatory system, and to the severe inflammatory reactions caused in various organs and tissues by their eggs eliminated through the bloodstream. Cases of Spirorchidiasis have been recorded in different parts of the world and in particular in the north-western and central Atlantic Ocean [ 11 , 12 , 13 ], in the Indian Ocean and in the north-eastern Pacific Ocean [ 14 , 15 , 16 ], while in the Mediterranean Sea infections by Spirorchiidae have been reported by Monticelli [ 17 ], Marchiori et al [ 18 ] and Santoro et al [ 10 ].…”

“…Over the past 10 years several studies have been conducted on helminths present in stranded and free-living individuals of C. caretta in different areas of the Mediterranean Sea [ 19 , 20 ]. Most of these studies refer mainly to the Central Tyrrhenian Sea, Adriatic and Ionian Sea [ 10 , 19 , 20 , 21 ], while knowledge about the Sicilian coasts is still very limited [ 20 ].…”