Fascioliasis (Liver Fluke Disease)

Fascioliasis (Liver Fluke Disease) is also called liver rot and pipe stem liver disease in animals.

Fascioliasis (Liver Fluke Disease) is one of the widespread causes of mortality in sheep and cattle characterized by weight loss, anaemia and hypoproteinaemia.

Etiology

• Fascioliasis (Liver Fluke Disease) is caused by Fasciola hepatica and Fasciola gigantica.
• The Fasciola hepatica found in temperate areas and in cooler areas of high altitude in the tropics and subtropics.
• The F. gigantica which predominates in tropical areas. Fascioliasis (Liver Fluke Disease) rarely fatal in cattle, but often fatal in sheep.

Host affected

Definitive host

• Most mammals, sheep and cattle are the most commonly affected than other ruminant animals.
• Unusual host: Horse & Man.

Intermediate hosts (Amphibious snail)

• Fasciola hepatica: Lymnea truncatula is most commonamphibious snail is found throughout the world.
• Fasciola gigantica: L.auricularia, L.accuminata and L.rufescens (India & Pakistan).

Location of parasite in host

• Adult fluke- Bile ducts.
• Immature fluke-liver parenchyma.
• Occasionally aberrant encapsulated fluke found in other organ such as lungs.

Epidemiology

• Snail habitats: L.truncatula found in wet mud to free water, banks of ditches or streams and edge of small ponds. Temporary habitat in hoof marks of animals (clay soil).
• Temperature: A mean day/night temperature >10°C is necessary both for snail to breed and development of F. hepatica with moist environmental condition.
• Summer infection of snails, in which metacercariae appear on pasture from August to October.
• Winter infection of snails in which metacercariae appear on the pasture in May to June.

Life cycle

• The minimum period for completion of entire life cycle is 17-18 weeks.
• Prepatent period: 10-12 weeks.

Pathogenesis

Acute

Acute fascioliasis occur in two phases:

• First phase: Migration of  immature fluke in liver parenchyma results in liver damage and haemorrhage
• Second phase: Presence of adult fluke in bile duct causes damage to biliary mucosa by cuticular spine leads to cholangitis

Chronic

Clinical manifestation

It occur as acute, subacute and chronic form.

Acute ovine fascioliasis

• ‘The acute disease occurs 2-6 weeks after the ingestion of  large numbers of metacercariae, usually over 2000.
• Outbreak of acute fascioliasis is generally presented as sudden death during autumn and early winter.
•  On examination of remaining flock one may find some sheep are weak and pale mucous membrane, dyspnoeic, some instances have palpable enlarged liver associated with abdominal pain and ascites and weight loss due to liver damage.
• Outbreak of disease is complicated by concurrent infection with clostridium novyi resulting in black disease.

Subacute ovine fascioliasis

• This form of  the disease occurring  6-10 weeks after ingestion of approximately 500-1500 metacercariae.
• It is presented as a rapid and severe haemorrhagic anaemia with hypoalbuminea, and if untreated, can result in a high mortality rate.
• Marked  pale mucous membrane, enlarged and palpable liver.
• Submandibular and facial edema.
• Ascities.

Chronic fascioliasis

• It is seen  mainly in late winter/early spring  season  this is most common form of the disease
• It occurs 4-5 months after the ingestion of moderate numbers of metacercariae 200-500.  Chronic infection may be asymptomatic or lead to intermittent abdominal pain, cholelithiasis, cholangitis, obstructive jaundice, or pancreatitis.
• The main pathogenic effect is anemia and hypoalbuminemia and more than 0.5 ml blood/fluke can be lost in bile duct each day.
• Additional loss of plasma proteins occurs by leakage through the hyperplastic biliary mucosa.
• Pharyngeal fascioliasis has been reported in human after consumption of infected raw liver in the Middle East.

Bovine fascioliasis

• Clinical signs same as that of sheep.
• Acute and subacute fascioliasis may occasionally occur especially in young calves.
• Chronic form is most common in cattle.

Necropsy Finding

Acute fascioliasis

• Severe haemorrhage in liver parenchyma due to rupture of  blood vessels by migrating  liver flukes.
• Subcapsular haemorrhage are common.
• Blood-stained fluid is often present in the abdominal cavity and natural orifices. These symptoms and lesions are differentiated with anthrax.

Chronic fascioliasis

• Hepatic fibrosis and hyperplastic cholangitis.
• Liver has irregular outline, pale and firm and ventral lobe become atrophied.
• Heavy infection can cause sclerosing cholangitis and biliary cirrhosis. Ectopic lesions may occur in the intestinal wall, lungs, or other organs.

Diagnosis

• Microscopic examination of stool or duodenal or biliary material for eggs (oval brown colour operculated egg. Which is distinguished from rumen flukes.
• Antibody assays is useful in early stage of infection before eggs are produced.
• Computerized tomography (CT) frequently shows hypo dense lesions in the liver during the acute stage of infection.
• Ultrasonography, CT, MRI, ERCP, or cholangiography can detect biliary tract abnormalities in chronic disease.
• Increased plasma concentration of γ-glutamyl transpeptidase, which is due to bile duct damage, and also helpful during the late maturation period.
• Copro antigen ELISA is used for detection of Fasciola hepatica in cattle and sheep.

Treatment

• Several drugs are available to treat infected ruminants, including triclabendazole, clorsulon (cattle and sheep only), albendazole, netobimin, closantel, rafoxanide, and oxyclozanide.

Older drug (mostly effective against mature flukes)

• Carbon tetrachloride (oldest – 50 years)
  • Recommended for adult fluke of sheep only (not for Cattle)
• Hexachlorethane – 90% Effective against mature flukes
  • Cattle – 220 to 400 mg/kg in divided doses (3-4)
  • Sheep – 20 to 30 grams / animal
• Hexachlorophene – 90% Effective against mature flukes
  • Cattle – 10 to 20 mg / kg
  • Sheep – 15 to 20 mg / kg
• Hetol – against adult flukes
  • Cattle – 125mg / kg
  • Sheep – 150 mg / kg
• Bithionol
  • Cattle – 30 –35 mg / kg ( 66 to 68%)
  • Sheep – 40 mg / kg (90 to 100% -chronic fasioliasis)

Recent drugs (Active against mature & immature flukes)

• Diamphenethide – 100 to 150 mg / kg (90 to 100 % for Adult)
• Oxyclozanide
  • Cattle – 10 to 15 mg / kg (mature -100%)
  • Sheep – mature – 15 to 20 mg / kg & Immature – 45 mg /kg
• Rafoxanide
  • Sheep & Cattle – 7.5 mg / kg
  • Mature – more than 90 % & Immature – 50 to 90%
• Nitroxynil
  • Sheep & Cattle
  • Mature (100%)- 10 mg / kg & Immature (90%) – 15 mg / kg
• Benzimidazole (Albendazole & Oxfendazole)

Latest drug (Active against mature and highly effective against immature flukes)

• Triclabendazole – 10 mg/kg body.
  • Highly effective against immature flukes
  • Sheep – single dose remove all stages (over one week old)
  • Cattle – two doses remove over 4 weeks aged flukes
  • Movement of stock from the infected pasture
• Closantel – 7.5 mg/ kg.
• Rafoxanide , Nitroxynil  and Oxyclozanide most commonly used for subacute and chronic fascioliasis.
• Anthelmintic resistance by F hepatica to various compounds, including albendazole, clorsulon, and triclabendazole, has been demonstrated.
• The timing of treatment is also important so that the pharmacokinetics of the drug used will result in the optimal removal of flukes. Each flukicide has varying efficacy against different ages of fluke.
• In areas where heavy infections are expected, sheep may require treatment in September or October, January or February, and again in April or May to reduce both the chances of acute or chronic infections and the output of fluke eggs for development of future disease.
• Cattle-antihelmintics should be given every December and May to prevent pasture contamination on spring and winter season.

Immunization

Natural immunity

• Cattle – Reinfection of F. hepatica  induce moderate to high immunity.
• Sheep – fails to develop protective immunity.

Active immunity

• Cattle – Three doses of irradiated metacercariae of F. Hepatica.
• Age – 6 – 9 months.
• Sheep – Not effective.
• Sheep infected with Taenia hydatigena give immunity to F. hepatica but reverse not possible.

Control

• Reduction of pasture contamination:
  • Reduction of pasture contamination with parasitic egg at most suitable time for development i.e April to August with suitable antihelmintic drugs.
  • Late April to early May- treat the adult sheep with drug effective for immature and mature flukes.
  • In June- 4-6 weeks after April/May treatment again treat the adult sheep with drug effective for both immature and mature flukes.
  • October- treat entire flock with drug effective for immature stage.
  • January- treat entire flock with drug effective for mature stage.
• Snail control:
  • Survey of snail habitat to implement control measures.
  • Drainage of water stagnation area to reduce snail population.
  • Fencing of snail habitat and treat with mollusicide (Copper sulphate 1 in 100000 solution for water reservoir and N-Trityl Morpholine 0.45 kg/680 litre/hectare.
  • Copper sulphate is most commonly used mollusicide.
  • Application of copper sulphate on pasture10-35 kg/hectare.  It should be applied along with sand for easy application. Avoid grazing of sheep on treated pasture for 6 weeks after application because copper sulphate is toxic to sheep.
  • Rearing of ducks, geese and frog in infected water reservoir.
• Computerized prediction systems based on rainfall, evapotranspiration, number of wet days per month, and/or prevalence is used to predict the timing and severity of disease.