Fasciolosis (Liver fluke) is one of the most important parasitic diseases throughout the world including, South Africa.

Liver fluke infections in livestock are responsible for economic losses such as:

• Liver condemnation
• Mortality
• Reduction in milk and meat production

• • Reduction in reproduction
  • Secondary bacterial infections

OVERVIEW OF THE PARASITE

Two types of liver fluke occur in South Africa:

Common liver fluke (Fasciola hepatica), their size is on average 2.5cm long and 1.5cm wide and they are commonly found all over South Africa where conditions are suitable

Giant liver fluke  (Fasciola gigantica), their size is on average 5.5cm long and 1.5cm wide. The Giant liver fluke are more found in the northern regions of South Africa

The life cycle of liver fluke is complex and has several stages of development inside and outside the livestock. Liver fluke populations are maintained with the presence of freshwater snails that act as intermediate hosts.

INTERMEDIATE HOST

Freshwater snails (Lymnaea spp.) is well known as the intermediate host of the liver fluke. They prefer habitats with a mean annual air temperature of 10–20 °C and a mean annual rainfall of 600 – 900 mm.

The shape of the shell is elongate ovoid and is colourless or light brown in colour. Size vary between species  (The width of the shell is about 5.75–7 mm and the height of the shell is 4.6–19.2mm)

HABITAT

The typical habitat of liver fluke is wet, marshy areas or ponds. It is the ideal habitat for the survival of the freshwater snail. The water must be still or slow moving

Areas where pastures are irrigated can also be conducive to the survival of the parasite

In some cases water reservoirs and troughs can also be a source of the infection

Liver fluke infections in cattle depend on a number of factors:

• The presence of Freshwater snails (intermediate host) on the farm.
• The presence of suitable wet, marshy areas or ponds. The water must be slow moving or still.
• Rainfall helps to wash the eggs out of faeces. Rainfall also maintains the water bodies where snails can survive.
• Temperature also plays a big role in influencing liver fluke infestations:

• • Both fluke and snails thrive over the warmer months of the year. When the average daily temperature drops below 10 ̊C, fluke eggs stop hatching and development of larval flukes in the snails slows down and the snails become inactive.
  • In the colder areas the liver fluke life cycle comes to a halt over the winter periods. In the warmer areas where the temperatures are mild, the fluke life cycle can continue throughout the year and fluke infection will continue and numbers will build up.

Successful liver fluke control can be challenging because the number of parasites in the host must be reduced and the fluke population present in the environment.

Effect on the liver

The liver ensures detoxification and excretion of endogenous and exogenous waste. It neutralizes toxic elements from the metabolism (bilirubin, ammonia, ketones) then transforms them into recycled nutrients and expels them via feces or urine

“The liver is an extremely important organ. It provides functions essential for: General health, Vitality, Production, Reproduction.” 

The Liver is the largest internal organ and has numerous functions including:

• Protein, fat and carbohydrate metabolism.
• Storage of water soluble vitamins, fat soluble vitamins, iron, triglyceride and glycogen.
• Fights infections and filters out toxins.
• Regulating and breaking down of hormones

Liver fluke infections cause severe damage in livestock from the time the animal  ingest metacercaria (Infectious stage) until it is controlled (or until the adult liver fluke dies and this can take up to two years)

In cattle, about ± 25% of the metacercaria ingested  reach the liver within 2 weeks to 85 days after ingestion.  In the case of sheep, up to as much as 80% of the metacercaria reach the liver during this time. The rest migrate through the body and cause damage to other organs until the animal eventually dies.

DAMAGE CAUSED BY LIVER FLUKE

Bleeding is caused in the small intestine due to liver fluke damage
The metacercaria are ingested by the animal when grazing and follow the digestive tract until they reach the small intestine. In the small intestine, they bore through the intestinal wall and end up in the body cavity. They migrate back and forth for around two weeks until they reach the liver.

Migrating liver fluke cause necrosis and bleeding spots in the liver
The migrating immature to adult liver fluke stadia in the liver cause haemorrhage and damage to liver tissue, leading to unproductive scar tissue.

Liver fluke infestations cause thickening, calcification and blocking of the bile ducts. 
The development from early immature to adult liver fluke stadia in the bile ducts causes irritation to which the body reacts. The bile ducts thicken and may even form a “panhandle” where the bile duct becomes closed off, no longer transporting bile.

Liver Fluke control strategy

There is no quick fix for liver fluke, effective liver fluke control can be a challenge and needs to be addressed throughout the year .

The control strategy should be aimed at both reducing the number of parasites in the host as well as reducing the liver fluke population in the environment.

Research and experience have shown that effective and sustainable control is based on an integrated control program that includes chemical treatment (deworming the animals), pasture/ grazing management, fencing of  contaminated areas (if possible) and repairing of leaking troughs.

“For optimal liver health use a STRATEGIC CONTROL STRATEGY throughout the year to LIMIT THE DAMAGE caused by liver fluke”

The Economic Impact

The economic impact of liver fluke can be very substantial. Liver fluke infection causes a reduction in growth rates (ADG), reduced milk production, reduced fertility, liver condemnation at the abattoir, mortalities (deaths) and secondary infections.

IMPACT ON MILK PRODUCTION

In high-risk fluke areas, liver fluke is a significant threat to optimal milk production. The effect of liver fluke on milk is well documented.² 

• Milk loss due to liver fluke infection can amount up to 1kg/day.  Over a lactation period of 300 days, it translates to a loss in milk production of up to 300 litres per cow³.  With a producer milk price of R5,15/lt, it translates to a possible loss of R1545 per cow per lactation!
• A high incidence of liver fluke infestation does not only reduce milk production, but also negatively affects the quality of the milk produced due to a reduction in the milk butterfat concentration¹.

IMPACT ON GROWTH IN CALVES

Liver fluke can affect weight gains (ADG) in all cattle, but especially in young and growing cattle. A heavy infestation of 200 fluke per calf, can cost up to 28,5% in reduced weight gain ^4,5 The graph below shows the reduction in body weight expressed as weight loss on calves – depending on the severity of liver fluke infestation²

A reduced growth rate could affect the general development of the calf and can lead to reduced weaning weights or a delay reaching puberty (breeding age). Both these conditions have a major economic impact. With the current weaner price of >R30/kg, a small reduction in weaning weight will mean a big loss in income.

IMPACT ON BODY WEIGHT OF SHEEP

Liver fluke infestations have a 15% impact on food intake that results in poor growth if not controlled.

In this trial : Liver fluke free sheep were dosed with F.hepatica metacercaria for 5 days each week for a period of 22 weeks, there was a tendency of poorer weight gain in the infected groups from week 20.

• Animals with the light infestation were dosed with 8 x F.hepatica metacercaria for 5 days a week for 22 weeks
• Animals with the heavy infestation were dosed with 14 x F.hepatica metacercaria for 5 days a week for 22 weeks

LIVER CONDEMNATION

The loss of income due to liver condemnations caused by liver fluke infestation, can exceed R100 per animal slaughtered!

CONTROL PROGRAM

Effective liver fluke control can be a challenge! The number of parasites in the host must be reduced as well as the fluke population present in the environment.

Effective, sustainable control must be based on an integrated parasite control program that includes, chemical control (dosing of animals), grazing management, fencing of infected areas (where possible) and the repair of leaking troughs (which reduces the habitat of the intermediate host).  The chemical control of freshwater snails through the application of copper sulphate is usually impractical and can be dangerous for the animals!

Timing of liver fluke treatments is one of two key factors for effective liver fluke control. It is based on the following:

• Curative treatment:
  Autumn (April / May). The autumn treatment is to control early immature, immature and adult liver flukes to reduce liver damage.
• Preventive treatment:
  Late Winter / Early Spring (Aug / Sept). This treatment is essential to remove remaining liver fluke and to reduce re-contamination of the pasture with liver fluke eggs.
• Optional treatment:
  Summer (Jan / Feb). In areas where the liver fluke infestation is very high, this treatment is necessary to ensure optimal control.

Product choice is the second key factor in effective liver fluke control.

By controlling liver fluke as effectively as possible, the damage can be limited. To this end, controlling the early-adult stadia that penetrate the liver and then migrate is critical! Therefore, timeous treatment and the use of effective remedies are of importance.

• Oral dosing: Triclabendazole is the active ingredient of choice to control the liver fluke in the liver. Keep in mind that no treatment can control the migrating stage from the small intestine to the liver! (< two weeks old) Oral dosing is the most effective way to control the early adult stage (≥ two weeks old), which is also the most damaging.
• Injectable treatments control only certain stadia in the liver. The most commonly used products contain clorsulon/ivermectin, as well as those containing closantel, only control the adult stages in the bile ducts. Injectable treatments containing closantel may assist in controlling the immature and mature liver fluke at the higher recommended dosage.

Use Flukazole C once or twice in the liver fluke control program, especially in areas where liver fluke infections are high. The synergistic combination of Flukazole C’s two active ingredients (triclabendazole and oxfendazole), offers broad-spectrum control that includes:

• Liver control – effective control of the first controllable 2-week-old immature stage (when it enters the liver), up to and including the adult stage,
• Roundworm control and
• Milk tapeworm control

The benefit of treating your livestock with Flukazole C is confirmed by local and overseas trials. Please contact your Virbac Technical Sales Advisor for more information regarding the confirmation of liver fluke infection on your farm, as well as an appropriate control program.

For more information, or if you have any concerns or need assistance with disease prevention, treatment protocols, or selecting the correct products, don’t hesitate to reach out to our resident livestock vet, Dr. Izak van Rensburg, at:

WhatsApp: 081 031 4694

Email: izakjvr@hotmail.com