What is Liver Fluke?
Liver fluke is a trematode parasite that doesn’t just cause problems for cattle; it can also affect sheep, goats and horses. Flat, oval shaped and just 25mm in length (Figure 1), it makes its home in the bile duct of its host.
Liver Fluke complete what is called an indirect life cycle. It is quite complicated and precise, requiring the right conditions and a special intermediate host.
The adult fluke lays its eggs, where they reside, inside the liver bile ducts of the cow. The eggs are expelled from the body through the cow’s manure. Once free of the dung, eggs hatch into free-swimming miracidium when mean daily temperatures are above 10˚C. The miracidium then has 24-30 hours to locate their intermediate host. At least three species of snail occur in Australia that are known to be intermediate hosts for liver fluke. The most important is the freshwater snail, Lymnaea tomentosa (Figure 2).
Once inside the snail, miracidium multiply and develop for 4-7 weeks, leaving the snail as tadpole-like cercariae to attach to vegetation and form cysts. Cattle and other livestock then eat these cysts while grazing. The cysts hatch immature flukes in the small intestine which make their way to the liver tissue, taking 6-7 weeks before arriving at the bile ducts as adults. 3-6 weeks after arriving at the bile ducts, adult Liver Flukes will begin laying eggs. Resulting in a total life cycle length of 10 – 17 weeks.
What regions in Australia is it present?
Liver Fluke can be present in all areas where its intermediate host, the freshwater snail, has a suitable habitat. This habitat includes springs, marshy areas, water courses, water troughs and irrigated pastures.
These conditions favour southeastern Australia, especially the tablelands, coastal regions and irrigation areas of New South Wales, Victoria and Queensland (Figure 4).
If you are unsure if you have Liver Fluke on your property, and are seeing potential signs of infection in your livestock, infection can be identified using faecal samples. The two types of tests can tell you a) if liver fluke eggs are present, or b) how many eggs are present, which can indicate the severity of the overall infection.
Clinical signs of Liver Fluke
Young cattle are most vulnerable to severe effects of Liver Fluke infections. However, any age group of stock is susceptible if they are moved into a heavily infested area.
Signs of a Liver Fluke infection can include:
- a reduction in the production and quality of milk
- lower growth rates
- anaemia (pale gums and membranes around the eyes)
- gums and eyes may take on a yellow colour to jaundice
- signs of abdominal pain
- weight loss and general ill-thrift among other symptoms.
- bottle jaw
The most commonly observed sign of Liver Fluke in cattle and sheep is a ‘bottle jaw’ (Figure 5). This is the name for a ‘fluidy’ swelling below the jaw. This comes about because the fluke has ‘sucked protein’ from the host animal leaving the blood low in protein content. As such, the blood lacks the power to keep fluid within the blood and the circulatory system and so is lost to the tissues. Which, in cattle, accumulates under the jaw giving this characteristic ‘fluidy’ swelling.
Treating Liver Fluke
Flukicide drenches are chemicals used to treat infections of Liver Fluke. Liver Fluke specific active ingredients include clorsulon and triclabendazole.
Products containing triclabendazole will treat all stages of susceptible Liver Fluke (immature and adults). They often come in oral or pour-on delivery forms. Where this active ingredient still remains effective, the optimal time for use is in autumn or tactical summer treatments.
Clorsulon treats adult Liver Fluke and is present in many injectable flukicides, including our very own Vetmec F. As it only kills the most parasitic/important stage of the parasite, the timing of treatment(s) is critical to ensuring drench and labour isn’t wasted.
The following program outlines a strategic Liver Fluke treatment and control program. It involves two compulsory treatment times that can be implemented in all Liver Fluke areas, as well as two tactical/optional treatment times for specific regions or environmental conditions.
Compulsory Treatments:
Autumn Treatment – April/May
7 – 10 days following the first frost. Designed to clean out the fluke prior to the stresses of winter.
Spring Treatment – August/September
Break the liver fluke lifecycle by removing any fluke that have survived winter. Prevents the contamination of pasture with fluke eggs as temperatures warm up. This treatment should occur prior to the spring break.
Tactical Treatments
Summer Treatment
Recommended for areas with extended periods of warm conditions. The ideal timing is January or February to suppress Liver Fluke numbers.
Mid-Winter Treatment
For areas where Liver Fluke infections can continue all through the year, such as warm coastal areas, a mid-winter treatment may also be necessary.
Prevention
Preventing Liver Fluke infection primarily involves breaking its life cycle. The easiest way to do this is to restrict grazing access to snail-ridden areas during times of the year when environmental conditions are favourable to the stages of the Liver Fluke life cycle that occur outside the animal.
Other prevention measures can include:
- Drenching any new stock that come from a liver fluke or wet area with an effective Liver Fluke drench, keeping them in a safe paddock away from other cattle for at least two days. Better still, avoid introducing any cattle to our property that might have had a history of fluke.
- Fence off any wet/marshy areas where snails are present (if possible).
- Keep water troughs free of snails and clean/clear.
- Ensure that you are aware of the Liver Fluke status of your livestock. You can do this with blood tests, faecal sample checks or reports on liver status of animals sent for slaughter.
- If an animal does die on farm – check the liver for signs of Liver Fluke infection (Figure 6).
The information above is written for properties that reside in Liver Fluke regions. If you do not reside in a Liver Fluke/freshwater snail area, and are introducing cattle with Liver Fluke, one or two quarantine treatments will be required, but after that, the cattle should be cured. There are nuances to this situation, so it can also be helpful to have a conversation with a parasite management advisor.
Other Considerations – Black Disease
Black Disease is a fatal liver disease of cattle, sheep and goats. It is caused by a bacterium called Clostridium novyi, which can be carried in with immature flukes migrating through the liver. Prevent Black Disease by ensuring livestock are up to date with their clostridial vaccinations, e.g., ‘5-in-1’.
Resources
Liver Fluke | Meat & Livestock Australia
Fasciolosis in cattle | Improve Veterinary Practice