CASE NOTES
Chronic fasciolosis with aberrant mature fluke
Bruce Watt (Tablelands Livestock Health and Pest Authority) and Patrick Staples (State Veterinary Diagnostic Laboratory, Elizabeth MacArthur Agricultural Institute, Menangle)
Posted Flock & Herd April 2013
Introduction
Fasciolosis is an important disease of sheep and cattle on the central tablelands of NSW but is much less of a problem on the central west slopes and plains (Barger et al. 1978). Fasciolosis occurs as either an acute, sub-acute or chronic disease in sheep (Boray 1973). This paper describes a case of chronic fasciolosis affecting only the ram flock on a mixed farming property at Woodstock, east of Cowra and just west of the known distribution of Fasciola hepatica (Figure 1).
Figure 1. Pre-1967 distribution of Fasciola hepatica and Lymnea tomentosa in South East Australia (Seddon HR 1967)
History
Over the past three months, two of five mature White Suffolk rams died after losing weight. Most of the cohorts had also lost weight and appeared lethargic. They had grazed low-lying wet paddocks during joining in the summer of 2011-12 but since then grazed only pasture paddocks without wet country until six weeks previously when they were run in a small paddock with some swampy country.
Clinical findings
A mature Suffolk ram was examined prior to euthanasia. The ram was lethargic, in poor body condition with pale mucous membranes.
Background
The lungs were normal except for white, chronic pleural adhesions. Small, firm (1mm) white foci were visible under the pleural surface of the mediastinum. The pericardium was adherent to the heart and firm, discrete to coalescing, chalky, white lumps were noted within the epicardial surface (Figure 3). The liver was enlarged with dimples and stellate depressions on the diaphragmatic surface (Figure 1). On the caudal surface of the liver, thick white bile ducts up to 10 mm in diameter, packed with mature fluke were seen (Figure 2). Mature fluke were also found within nodules in the mesentery (Figure 4).
Figure 1. Fluke damage to the diaphragmatic surface of the liver
Figure 2. Bile ducts opened to reveal massive mature fluke infestation
Figure 3. Heart showing pericardial adhesions and chalky white lesions within the myocardium
Figure 4. Mature fluke within lumps in the mesentery
Laboratory Findings
Haematology
Platelet clumping was observed. The platelets appeared adequate on blood film, with no reticulocytes observed on NMB stained blood film.
The main finding is of a moderate, non-regenerative anaemia, consistent with chronic liver damage, inflammation and blood loss.
Histopathology
There is moderate, diffuse, fibrous thickening of the epicardium with mild scattered infiltrates of lymphocytes. A few liver fluke eggs are present on the epicardial surface and within epicardial venules. The epicardium contains a few focal areas of fat necrosis surrounded by a rim of moderate numbers of macrophages, multinucleate giant cells and lymphocytes. Morphological diagnosis: Mild, chronic pericarditis with scattered epicardial necrogranulomas and the presence of low numbers of Fasciola hepatica eggs.
The mesentery contained scattered areas of fibrosis surrounding moderate to severe infiltrates of mixed neutrophils, eosinophils, macrophages, haemorrhage and moderate numbers of yellow-brown, liver fluke eggs. The mesenteric lymph node contains numerous plasma cells within medullary cords and moderate numbers of eosinophils within medullary sinuses. Morphological diagnosis: Moderate, multifocal, chronic peritonitis with the presence of moderate numbers of Fasciola hepatica eggs.
Histopathology confirms the presence of chronic peritonitis associated with the presence of mature liver fluke. The heart lesion may have been caused by migrating fluke but is not specific for fluke infection.
Subsequent management
The remaining rams were immediately drenched with triclabendazole. One died despite treatment. Faecal samples from three mobs of ewes were checked for fluke and strongyle eggs. Two mobs, including the ewes joined to the rams in the wet paddock in 2011-12 had low levels of fluke (1-2 epg) and were therefore drenched for fluke as well as strongyles. The remaining mob was not drenched for fluke.
Discussion
Gordon (1957) suggested that helminthiasis (and therefore fascioliasis and ostertagiasis for example) is the widespread, sub-clinical parasitism affecting almost all livestock (and perhaps almost all animals) whereas helminthosis is the more sporadic disease seen when parasites cause clinical disease. This then is a case of fasciolosis.
This case is of interest because it occurred in the Woodstock area, west of the known high fluke prevalence central tablelands of NSW. Of interest, the map of the distribution of Fasciola hepatica (and Lymnea tomentosa), published by Seddon, (1967) also shows Cowra to be just west of the distribution of Fasciola, suggesting a reasonably stable distribution over time.
The owners recall that fluke were seen 50 years ago but not since. Therefore, no routine fluke control was practiced. This problem appeared as chronic ill thrift and mortality in the ram flock with no discernible signs in any of the other livestock (sheep or cattle) on the property.
This case is also of interest in that the massive fluke infestation included aberrant fluke in tissues beyond the liver.
References
- Barger IA, Dash KM and Southcott WH (1978) Epidemiology and Control of Liver Fluke in sheep in The Epidemiology and Control of Gastrointestinal Parasites of sheep in Australia edited by Donald AD, Southcott WH and Dineen JK, p 66
- Boray J (1973) Epidemiological control of fasciolosis and paramphistomosis in sheep and cattle University of Sydney Post-Graduate Committee in Veterinary Science Proceedings 19, p 238
- Gordon H McL (1957) Advances in Veterinary Science 3:287 cited by Cole VG (1986) Animal Health Australia volume 8, Helminth Parasites of Sheep and Cattle p 5
- Seddon HR (1967) Diseases of Domestic Livestock Part 1, Helminth Infestations, revised by Albiston HE, p 17