Eicosanoid production by adult Fasciola hepatica and plasma eicosanoid patterns during fasciolosis in sheep

Fasciola hepatica infection in sheep is known to cause anaemia, fever and e levated levels of liver enzymes. It was hypothesised that eicosanoids play a role in these pathophysiological changes, so the pattern of plasma eicosa noids during the course of acute and chronic fasciolosis was studied in she ep infected with a single dose of 800 F. hepatica metacercariae. Blood plas ma was collected weekly until week 17 p.i. from infected sheep, and from un infected controls. Adult F. hepatica were then recovered from bile ducts an d incubated for production of ES products. Eicosanoids were determined by e nzyme immune-assay in blood plasma, fluke homogenates and ES products after chromatographic purification of the samples. Fever and anaemia a ere seen from 3 to 12 weeks p.i, and from 8 to 17 weeks p.i., respectively. Onset of fever was accompanied by elevated liver enzyme activities (aspartate amino transferase and gamma glutamyl transferase) in the plasma. In general, the plasma levels of prostaglandin E2 (PGE2), prostaglandin I2 (PGI2) and leuk otriene B4 (LTB4) were reduced during the acute and chronic stages of the i nfection, whereas thromboxane B2 (TXB2) was reduced only at 8 weeks p.i. Th e TXB2/PGI2 ratio was increased in favour of TSB2 at 3 and 11 weeks p.i. Ad ditionally, TXB2, PGI2, PGE2 and LTB4 were detected both in ES products and in homogenates of F. hepatica. It was concluded that eicosanoid depletion in the plasma is caused by parasite-induced liver damage. The changes in ei cosanoid levels are highly correlated to the clinical signs of the disease. Changes in the pattern of host plasma eicosanoids during fasciolosis, as w ell as parasite-derived eicosanoids, may reflect or contribute tn the patho logy of the disease. (C) 1999 Australian Society for Parasitology. Publishe d by Elsevier Science Ltd. All rights reserved.