Triclabendazole-resistant liver fluke in cattle on the NSW South Coast

To: WormMail list (recip. undisclosed). WormMail 201007121300

Readers of WormMail will be aware that there are a relatively small number of strains or isolates of Fasciola hepatica (liver fluke) resistant to closantel or to triclabendazole in south eastern Australia, although there is a cluster of triclabendazole resistance in the Goulburn Valley, a dairying and fruit growing area centred on Shepparton, Victoria.

In a NSW DPI – RLPB (LHPA) fluke survey several years ago, we also picked up an extra case of triclabendazole resistance in NSW (in sheep in the Monaro district of southern NSW (District Veterinarian: Chris Haylock).

More recently District Veterinarian Ian Lugton (South East LHPA – Bega) in collaboration with CSU-Wagga researchers and Virbac have uncovered triclabendazole-resistant fluke on a south coast cattle property at  Numbugga (near Bega).

For further details, see the media release of 18 June 2010 below:

Resistant Liver Fluke Found on the Coast    (Media Release 18/6/10)

A recent collaborative effort between a local beef producer, the South East Livestock Health and Pest Authority, researchers from Charles Sturt University (Wagga Wagga) and Virbac, has identified resistant liver fluke on a Numbugga property.  Fluke eggs were recovered from cattle after treatment with triclabendazole (TCBZ) used under controlled conditions.  This suggests that adult liver fluke have survived the treatment and that the flukes may be resistant to this drench class.  It represents a treatment failure.  This is the first local property, and the first to show resistance, when investigated for a poor response to the use of TCBZ.  This chemical is the active ingredient found in most of the commonly used fluke treatments, both oral and backline.  Alternative injectable flukicides for cattle contain unrelated actives, such as nitroxynil, and clorsulon.

Liver fluke are a common and debilitating parasite on the coast resulting in lost profits for farmers.  This parasite may be gaining an advantage from the warmer winters and the increased activity of the water snail intermediate hosts.  Cattle blood and protein is lost to these parasites: they have a cumulative and adverse effect on liver function causing significant depression of appetite, loss of production, anaemia, bottle jaw and possibly death.  Flock and herd burdens will increase if stock are not treated for a number of years.  In particular problems arise where small ruminants are run with cattle or where drenching has been ineffective.

Resistance to TCBZ use in sheep was first reported in Australia in 1995.  TCBZ has been used to treat liver fluke since the release of Fasinex® several decades ago.  TCBZ is heavily relied upon for its ability to kill immature fluke down to 2 weeks of age.  Since 1995, it was only a matter of time before resistance became more widespread in Australia and was recorded in other countries.  Less effective forms of dosing, such as backlines, may have also contributed to the development of resistance on cattle properties.

If you have treated your cattle with TCBZ, and believe it was not fully effective please contact Dr Ian Lugton at the Authority on 64921283 if you want this further investigated.  There are other alternative strategies and products that can be recommended.  Charles Sturt University researchers can be involved free-of-charge in this investigation.  If resistance is identified an alternative effective drench will be supplied free to treat trial cattle.

MEDIA CONTACT:  Ian Lugton  mobile: 0417296739; 34 Auckland Street, (PO Box 16) Bega NSW 2550; Phone: 02 6492 1283        Fax: 02 6492 3516




Veterinarian, State Coordinator-Internal Parasites
Industry & Investment NSW – Primary Industries
University of New England – Armidale NSW 2351