A particularly warm and wet start to Summer in 2017 may result in a greater risk of liver fluke disease this Autumn meaning UK farmers must be ready to take action.
Fascioliasis is the name given to the disease caused by the Liver fluke parasite and may be caused by:
- The migration of fluke through the liver tissue causing damage
- The present of the adult flukes in the bile duct
Adult fluke inside the bile duct lay eggs which are passed out in the faeces on to the pasture. From the moment the fluke releases the egg until it reaches the pasture can be up to 3 weeks due to the intermittent contraction of the bile duct.
Once environmental conditions are optimum the Miracidium will develop inside the egg and then hatch out. This Miracidium is only able to survive for a few hours after hatching out so must find a snail host very quickly- the mud snail.
If the Miracidium is able to find a snail host, it will bury through its muscular foot where it undergoes a further 2 stages of development and multiplies - eventually becoming the infective cercariae.
The cercariae burst out of the snail host after this period of development and migrate onto the herbage where they encyst as metacercariae. These metacercariae are hardy and can remain viable for some time.
The early immature fluke (1- 5 weeks old) tunnel through the liver tissue eventually developing into the immature fluke. The immature fluke (6-9 weeks old) continue tunnelling towards the bile duct. Eventually they reach the bile duct and if untreated at 10-12 weeks old will mature into adults, which produce eggs contaminating the pasture and continuing the life cycle.
When are Livestock Affected?
New infection occurs when the metacercariae are ingested from pasture. During very warm and wet summers this could be as early as August. In cooler, dryer summers which do not favour the mud snail there will be less metacercariae on the pasture and they will appear later.
Existing infection also known as chronic fluke disease occurs when animals are harbouring fluke which were not treated after the new infection period. These fluke are then able to complete their life cycle into adults and reside inside the bile duct producing eggs which contaminate the pasture. Chronic fluke disease is generally observed from January onwards.
In late Summer and early Autumn the risk period for acute fascioliasis begins. Acute fluke disease may result in the following:
- Sudden death
- Reduced feed intake
- Abdominal distension
- Abdominal pain
If any stock die suddenly always get a post mortem carried out to avoid further loss.
Impact on your Stock
Fascioliasis has a significant impact not only on the welfare of your stock but also on their productivity.
Production consequences of liver fluke infection:
- Reduced Weight Gain
- Reduced Food Conversion Ratio
- Drop in Milk Yield
- Drop in fertility
Liver fluke infection is estimated to cost UK farmers £300 million per year. 1
In sheep infection is estimated at £3-5 per animal which comprises not only of the cost of treatment but of the sub-clinical production losses such as reduced weight gain and liver condemnation. ¬¬¬2
Liver fluke is estimated to cost producers £20-25 per head of cattle3 resulting in a serious dent in profit margins.
Liver fluke can be a challenging parasite to treat as different life stages are susceptible to different active ingredients and a reservoir of infection persists in the mud snail population and in the environment.
Most importantly, in order to protect our flukicides from the development of resistance, you must select a product which targets only the life stages you are trying to kill and dose accurately.
Your vet or SQP can advise you on the most appropriate product for your herd or flock.
Key Treatment points:
- Use an active which targets only the life stages you are trying to kill
- Remember that no flukicides prevent reinfection - if they are returned to the same pasture reinfection will occur immediately
- Weigh animals and dose accurately- under-dosing increases the rate of development of resistance
Table 1: Active Ingredients licenced for Fluke Treatment in sheep and cattle
|Active Ingredient||Preparation||Age of Fluke Killed|
|Triclabendazole||Oral||2 days||2 weeks|
|Pour-on||6 weeks +|
|Closantel||Oral||5 weeks +|
|Injectable||7 weeks +||7 weeks +|
|Pour-on||7 weeks +|
|Nitroxynil||Injectable||7 weeks+||8 weeks+|
New animals entering the farm may act as a source of infection. Ensure that you have good biosecurity protocols in place.
Chronically infected animals will contaminate the pasture when let out to grazing in Spring - check if stock are affected in Spring with a faecal sample and treat if necessary.
Environmental controls such as drainage, fencing off wet areas and moving animals from high risk pasture at key times can greatly reduce the number of metacercariae ingested and subsequently the severity of disease.
Liver fluke control should also be incorporated into your herd and flock health plans.
This editorial is provided by Bimeda- makers of Endofluke
Date editorial Prepared: August 2017
Endofluke is a POM-VPS medicine containing 100mg/ml triclabendazole.
Use medicines responsibly- Noah.co.uk/responsible
Please consult your vet or SQP to determine which is the most appropriate treatment for your flock/herd. All SPC data sheets are available on the VMD website.