Liver fluke

At a clinic a couple of weeks ago one rider informed me that her horse was recovering from liver fluke so when she needed to have a breather, they would.

It occurred to me that if I’m really honest, I don’t know that much about liver fluke. So I did some reading and thought I’d share it with you all.

Put basically, liver fluke is a collective name for flat parasitic worms that live in the livers of numerous mammals, including horses and humans.

Liver fluke has become more prevalent in recent years due to wet summers and mild winters. So whilst horse owners don’t need to  routinely check and treat for liver fluke, it’s important to be aware that horses grazing on heavy, poor draining land with other species (sheep in particular) are at a higher risk of liver fluke.

The liver is one of the most resilient organs, so symptoms of liver fluke can be hard to spot until the horse is very unwell. The most common sign of liver fluke is chronic anaemia, but soft dung, a dry coat, oedema, weight loss and jaundice can all be observed. Unlike sheep and cattle, liver fluke in horses s rarely fatal.

You can detect liver fluke through a faecal worm egg count done between February and May, and a blood test. Unlike sheep and cattle, there aren’t any licensed medications to treat liver fluke in horses; the only way is to use medication that is prescribed off license by the vet. This means that the vet will tell you to use the medicine in a different way to the instructions on the label or for what the medicine has be licensed for.

I looked up the life cycle of liver fluke, and here is Farmers Weekly’s description. I can’t really improve on this explanation so you might as well hear it from source.

It’s flat, leaf-shaped and a pale brown colour, with tiny sharp spines that irritate the liver tissue of animals. The adult, which is usually about 2cm to 3cm long, lays its eggs in the bile ducts of the liver.

The egg passes into the intestine and is excreted via the manure. If the eggs enter water, they hatch into small larvae known as miracidia.
These swim around until they find a small water snail on a leaf near the riverbank. After entering the snail they encyst (enclose themselves in a sac) and become dormant.
After about six weeks, they hatch into tiny tadpole-shaped cercariae. These attach themselves to water plants, usually grass, where they encyst again into metacercariae.
When the plant is eaten by the animal, the metacercariae penetrate the intestinal wall, enter the abdominal cavity and start eating their way into the liver.
After another six weeks or so, they make their way to a bile duct to reproduce.

In all, liver fluke is usually not too serious in equines due to their natural resistance, but it is tricky to treat and could take a couple of months for them to regain full health. So if your grazing is with cattle and sheep, near rivers and on heavy ground, it’s worth bearing liver fluke in mind and testing for it annually.

3 thoughts on “Liver fluke

  1. sueonmull May 14, 2017 / 8:30 am

    Good article, liver fluke is a not uncommon (and I think often overlooked) problem in horses. Even specific fluke egg counts are not reliable (no eggs seen does not mean no fluke present), our vet used to prescribe treatment with a cattle wormer. We also have a few sheep and they are regularly dosed too. Issues of resistance, as with all worming programmes, are increasingly of concern.

    • therubbercurrycomb May 14, 2017 / 9:18 am

      I think you’re right, it’s definitely overlooked. I had heard of it but it was very much taught as a “you don’t need to worry about this one” sort of approach

      • sueonmull May 14, 2017 / 10:28 am

        There were a few interesting threads a while back re fluke on the Horse and Hound Forum worth a read.

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