Liver fluke is a significant cause of disease and production loss in many areas of the North Coast of NSW. The map summarises what is known of the distribution and prevalence of liver fluke in cattle on the North Coast. It was compiled from disease information held at the three North Coast LHPA offices plus information kindly supplied by Virbac (Australia) Pty Ltd.
As can be seen, the Lismore area appears to have the highest prevalence the Grafton and Casino areas appear to have a lower prevalence. The prevalence estimates are based on data obtained by collecting all the results of liver fluke ELISA profiles done in the region.
However this map reflects only the incomplete and patchy data available. The investigation in this case study occurred around Murwillumbah where less liver fluke data has been collected.
In December 2010 a property near Murwillumbah reported severe, repeated ill-thrift in a small proportion of their steers. The majority of steers grew well but occasionally some steers would suffer severe weight loss. At the time of the investigation, one of 80 steers was in very poor condition. This steer had been well enough to be sent to the saleyards three weeks earlier but had become obviously sick in the saleyards and was sent back to the property. It progressively deteriorated and at the time of examination was not eating. The steers had been treated twice in the last 12 months with a pour-on drench containing ivermectin 15g/L and triclabendazole 240g/L. A drench containing both these actives was given 3 weeks before the steer was examined.
The 2-year-old steer was emaciated with pale mucous membranes, reduced rumen sounds, no faeces in rectum, small oral erosions and corneal ulcers and opacity in both eyes. The rectal temperature was normal. Samples were taken for haematology, biochemistry, faecal egg count and pestivirus testing. At the time of examination the owner elected to drench the steer and treat it with antibiotics (organised through a private veterinarian) rather than euthanase it.
The steer died a few days later. The carcass was emaciated and both eyes were ulcerated with corneal oedema. The liver had enlarged thickened bile ducts and approximately 10 mobile live adult liver fluke were found.
The steer had elevated liver, kidney and muscle enzymes. Haematology was normal. Antigen testing for pestivirus was negative. The faecal egg count was negative. Histopathology of the liver showed mild chronic fibrosis.
The steer is assumed to have had chronic damage from liver fluke and infectious bovine kerato-conjunctivitis (IBK). The IBK developed after being yarded at the saleyards. The presence of live liver fluke despite drenching is probably explained by the drench product chosen by the owner not being active against immature fluke or by the time taken for the product to kill the fluke. (Steve Love and Joe Boray, pers. comm.). It is also possible that triclabendazole resistance is developing on this property. Although oral triclabendazole is effective against immature fluke, in some pour on products triclabendazole is only registered against adult liver fluke. This can be confusing for both rural store staff and producers. The producer in this case study had been advised that his preventative program, especially the treatment in late April or early May, should target immature fluke.