Investigating and tackling possible liver fluke

Bottlejaw is one of the tell-tale signs of a bad dose of liver fluke, writes large animal vet Hazell Mullins.

A case of Bottlejaw.

Over the past few weeks, spring has certainly been in the air, the daffodils are out, and this always reminds me of my days lambing in Knockraha as a green vet student. 

It may be said by some that I have a certain dairy bias, however, but I really do enjoy flock health and especially the complex topic of sheep parasites.

At Nottingham Vet School, I was taught by one of the best sheep experts in the world, Fiona Lovett. 

For those who don’t know of her, she is well worth looking up. I remember her passion for flock health and especially parasite control and her sense of urgency about reducing the spread of anti-parasitic resistance.

Since Animal Health Ireland has commenced its parasite workshops, it has reminded me how interesting the world of sheep parasites can be and how vital it is that resistance is kept to a minimum so that sheep farming in Ireland can continue the way we know it in Ireland today. 

I have met super sheep farmers who are on top of all things resistance management, knowing their faecal egg sampling timing, monitoring weights and clinical signs of parasites. 

The future is looking positive for parasite control; however, they do need to keep up good practices and also keep updated on the latest recommendations.

It's an issue that came up while I was on a sheep farm a few weeks ago. Fluke seemed confined to a group of hoggets grazed away from the home farm on naturally wetter land. 

Fluke burdens are so dependent on weather, as their weak life cycle involves a developmental stage within a mud snail, which - as the name suggests - loves our damp Irish weather.

The snail lives prominently in poorly drained, wetland and muddy areas, for example, around water troughs. An interesting fact is this snail is extremely prolific, having the capacity to have over 100,000 offspring per snail over four months. 

This is why, unfortunately, Ireland ranks as one of the best countries in the world for parasite production - a ranking I won’t personally be boasting about around the dinner table.

The group of hoggets in question were in good condition, however, a couple were presenting with “Bottle Jaw”, a swelling under the chin which is caused to low protein in the blood due to liver damage. 

When the larval stages of the fluke invade the liver they prevent essential proteins from being synthesised, then, through osmosis, the fluid moves from the blood to the surrounding tissues and accumulates under the jaw via gravity.

This farm wouldn’t traditionally have high fluke burdens, however, something as simple as an outside farm can complicate matters and very quickly cause clinical disease. Other clinical signs of fluke include scouring, poor thrift and anaemia.

When treating, it is important to take the fluke’s long 12-week life cycle into consideration when choosing a suitable flukicide. A narrow spectrum product can be useful to target fluke alone to reduce unnecessary worm treatments and subsequent resistance. 

In winter, a product with efficacy against immature fluke should be chosen, whereas in spring, a product that kills the mature adult fluke can be used. In this particular case, a triclabendazole drench was used, which covers the fluke’s early larval stages.

Triclabendazole may sound like the gold standard, however, it is not without its problems, as resistance is appearing in Ireland and elsewhere in the world, so we need to monitor its use going forward. 

Another complicating issue with it is that the liver is required to metabolise the product meaning a compromised liver may not be able to activate it correctly, causing suboptimal results. 

The use in rotation of other products, such as Closantel for later larval stages in Autumn or Oxyclozamide in the winter for adult fluke, can be useful. Discuss with your vet the best choice of product for the time of year and history of your flock.

All the same, practical advice applies for fluke dosing; check the date of the product, calibrate your dosing equipment before use and dose to the heaviest animal in the group or the gold standard would be to weigh individually.

Remember that no flukicide has any persistent action, so it only kills what flukes are present on the day.

Diagnostic tests

For this farm, I recommended that faecal samples were taken from all groups as a precaution.

At this stage in the year, fluke eggs should be present as adult fluke will have had time to mature; however, there is another test called a coproantigen test which can detect fluke secretions in faeces at five to six weeks post infections, more useful in autumn before adult’s eggs are present. 

For the dairy farmers reading, of course, you have the bulk milk sampling to aid detection also. Abattoir feedback can be very valuable also, so always look at those multi-coloured feedback forms - and not just the cheque!

The Animal Health Ireland parasite Targeted Advisory Service on Animal Health (TASAH) consults are available for all sheep farmers again this year, and they are well worth contacting your vet to partake. 

It is a fantastic opportunity to get funded diagnostic samples to gain information of parasite burden, including fluke on your farm. For more information on parasite TASAHs, check out their website – animalhealthireland.ie.

• Hazell Mullins BVM BVS, is a large animal vet based in Carrignavar, Co Cork.