Studies on cardiovascular fluke (Digenea: Spirorchiidae) infections in sea turtles from the Great Barrier Reef, Queensland, Australia.

Twenty-seven sea turtles (23 Chelonia mydas and four Eretmochelys imbricata) from northeast Queensland were found to be infected with cardiovascular flukes and/or their eggs. Five had originated from turtle farms in the Torres Strait, five from an oceanarium on Magnetic Island (146 degrees 56'E, 19 degrees S) and the remainder from coral reefs in the Torres Strait or near Townsville. The incidence of flukes and/or eggs in the groups was 4.8 per cent (5 of 104), 33.3 per cent (5 of 15) and 72.2 per cent (17 of 22), respectively. Affected animals ranged in size from 18 to 108 cm (curved carapace length) and weighed between 0.5 and 77 kg. The average number of flukes per host was 47. Flukes were recovered from the three chambers of the heart and major vessels (right aortic arch and brachiocephalic artery), where they were attached to the walls or free in the lumen. They were subsequently identified as Haplotrema spp. and/or Learedius spp. In 59.2 per cent (16 of 27) of turtles, flukes were not found, although their eggs were detected microscopically. Gross pathological changes associated with the presence of flukes included thickening and hardening of arterial walls (four turtles), thrombus formation (three), chronic pneumonia (two) and an excess of pericardial or peritoneal fluid (four). Microscopically, the essential changes was that of chronic inflammation, as evidenced by the proliferation of epithelial cells, reticulo-endothelial cells and fibroblasts in areas accessible to flukes and/or eggs. Multiple diffuse egg granulomas were a prominent feature of most organs, the spleen and lungs being predilection sites. Proliferative changes had occurred in the endocardium and in the endothelium of vessels supplying the spleen, stomach, intestine and pancreas (18 turtles). The walls of major arteries, lungs, liver, brain, crop and stomach were also acutely inflamed (eight turtles). Haemorrhage was recorded in the lungs and/or brain of eight turtles with heavy fluke infestations. Other vascular changes, viz. congestion, oedema and hypertrophy of arterial/arteriolar walls, resulted from the inhibition of blood flow by parasitic emboli.