What is Fascioliasis?
Fascioliasis is a Liver Fluke Worm Disease caused by one of the parasitic worms known as Fasciola hepatica; hence the name Fascioliasis. There are various types of parasitic worms which plague the human body. Many of us are aware of the worms which reside in our gut and thrive on nutrients present in the food; however, not many of us aware that there are parasitic worms, which can also live inside the bloodstream or the organs in the body. Flatworms are one such type of parasitic worms which live in the human body and this worm is commonly known by the term ‘flukes.’
What is a Liver Fluke?
A liver fluke is a helminth, i.e. a type of parasitic worm which resides in the liver. Trematodes or flatworms are a type of parasitic worm which are also known by the term “Flukes.” Liver fluke is one type of flukes and there are more such types. Fasciola hepatica is one of the species of liver fluke, which commonly affects the humans. Fasciola hepatica also infects cattle and is therefore also known as the sheep liver fluke. Fasciola gigantica is another species of liver fluke, which can infect human beings.
One of the largest flatworms is the Fasciola hepatica fluke. It is around 30 mm long. Human beings get affected from this infection not only from meat consumption, but also through eating herbs and freshwater vegetables to which the larvae get attached. This parasite enters the body when the freshwater plants are eaten raw. The worm cannot spread from one individual to another. Patient can experience mild or non-specific symptoms of fascioliasis; however, this condition can also take form of a serious disease in some individuals. This worm can also migrate to other parts of body from the liver, such as skin, lungs, heart and brain; however, this is not common.
Stages of Fascioliasis
There are 4 stages of Fascioliasis in human beings:
Stage 1 of Fascioliasis: Incubation Period: This is the phase, which starts from the ingestion of the larvae to the initial appearance of the symptoms. The incubation period takes about a few days to 3 months and depends on the amount of number of ingested larvae and the immune status of the patient.
Stage 2 of Fascioliasis: Acute or Invasive Phase: There is migration of the fluke to the bile ducts. This stage occurs as a result of mechanical destruction of the peritoneum and hepatic tissue by the migration of the juvenile flukes, which causes localized/generalized allergic and toxic reactions.
Stage 3 of Fascioliasis: Latent Phase: This stage can be present from months to years. Patient can be asymptomatic in this stage and the disease is commonly discovered during a screening test.
Stage 4: Chronic or Obstructive Phase of Fascioliasis: This stage can develop months or years after the initial phase of infection. The adult flukes present in the bile ducts cause hyperplasia and inflammation of the epithelium, which results in cholecystitis and cholangitis. This along with the large body of the flukes causes mechanical obstruction of the biliary duct. In this stage, patient experiences epigastric pain, biliary colic, intolerance to fatty food, jaundice, nausea, pruritus, tenderness in the right upper-quadrant. There may be liver enlargement along with spleen enlargement or ascites. If there is an obstruction, then the gall bladder is often edematous and enlarged with thickening of its walls. Fibrous adhesions of the gall bladder are commonly found to the adjacent organs. Lithiasis of the gall bladder or bile duct occurs. The stones are usually multiple and small in size.
How Does the Liver Fluke Spreads to the Humans?
Both sheep and cattle get infected from Fasciola gigantica and Fasciola hepatica. However, this parasite need not necessarily get transmitted though these animals. Many people get accidentally infected by eating certain raw freshwater plants. A different type of fascioliasis can however be acquired when a person eats raw livers of goat, sheep, cattle etc. As this mode of transmission is rare, thus the primary mode of transmission is through consumption of plants like watercress, mint and lettuce.
Lifecycle of Liver Fluke
It is important to understand the life cycle of the liver fluke when looking at the spread of these worms. The eggs of the liver fluke are present in the stool of the animal and gets in contact with the water. Miracidia, which are the larvae of Fasciola hepatica fluke, hatch within 9 days to 2 weeks providing that the water is tepid to warm. These larvae then enter the freshwater snails, where they mature and exit as a different larvae known as cercaria. These free-swimming larvae then get attached to freshwater plants. A cyst encloses these larvae and after consumption of the freshwater plants by the humans, they come out of the cyst and travel to the duodenum (small intestine) where they then penetrate the wall of the bowel wall and ultimately reach the liver. The larvae then move through the liver and mature which takes about 3 to 4 months. Then the larvae finally lodge in the common bile duct and the hepatic duct. It can sometimes get lodged in the gallbladder also. After about 4 to 6 months, the adult fluke worms lay eggs that travel out into the intestine. The adult fluke worms have the ability to live within the hepatic and common bile ducts for many years. These larvae survive by feeding on the hepatocytes, which are the host liver cells and the epithelium of the duct wall. Tens of thousands of eggs can be produced by these larvae in its lifetime.
Signs & Symptoms of Fascioliasis
The symptoms of fascioliasis can be mild and non-specific in nature. In about 50% of cases, these symptoms are not definitive of fascioliasis. Majority of the cases of chronic fascioliasis patients are asymptomatic. The diagnosis of infection is made from the presence of ova (eggs) in the stool. Blood tests cannot give conclusive results for diagnosing fascioliasis. Imaging tests, such as CT scan and abdominal ultrasound, can help in revealing the burrow tracks in the liver tissue made by the worms. Common signs and symptoms of fascioliasis are:
- Pain in the right upper quadrant of the abdomen.
- Intermittent fever.
- Malaise where the patient has a general feeling of not being well.
- Pallor of the skin.
- Unintentional weight loss.
- Hepatomegaly, which is liver enlargement. Patient may or may not experience tenderness.
- Dizziness and sweating can also occur; however, this is more often seen in children.
- Urticaria or hives can be seen in about 20% of patients.
- Subcutaneous nodules and wheezing can occur if the worms are lodged in other organs.
- Patient can experience swelling of the voice box and acute sore throat if they have had contracted the infection through consuming infected animals or raw liver.
- Patients who develop complications, such as cholangitis, which is the infection of the bile duct, experience severe pain in the abdomen with persistent fever and jaundice.
- If the patient has developed pancreatitis as a complication, then patient develops severe symptoms, such as fever, acute abdominal pain, nausea and vomiting. This is primarily seen in children.
Treatment of Fascioliasis
There are many medicines which can be used for treating fascioliasis in humans and as well as domestic animals. Triclabendazole is the main drug of choice for treating Fascioliasis. Triclabendazole belongs to the benzimidazole family of anthelmintics. Treatment with praziquantel is not effective. Nitazoxanide and bithionol have been reported to be effective in treatment of fascioliasis. A short course of Corticosteroids can be prescribed for acute stages in patients having severe symptoms.
Mirazid is an Egyptian drug which is under research for treatment of trematode-caused infections including fascioliasis.
Surgery may be needed in patients who are suffering from complications such as cholangitis.
Prevention of Fascioliasis
Fascioliasis or liver fluke infection can be prevented easily and treated effectively. Given below are some steps in how to prevent Fascioliasis:
- Never eat raw liver from goats, sheep, cattle etc.
- Avoid eating raw vegetables and ground fruit that have been grown near grazing pastures.
- Care should be taken that the water, which is used for preparing food and drinking is clean.
- Fresh water plants should always be cooked well before eating.
- If the fresh water plants are being eaten raw, then they should be soaked for 5 to 10 minutes in a 6% acetic acid solution.
- Centers for Disease Control and Prevention. Fasciola (Liver Fluke) Infection. Accessed from: https://www.cdc.gov/parasites/fasciola/index.html
- Mas-Coma S, Bargues MD, Valero MA. Fascioliasis and other plant-borne trematode zoonoses. Int J Parasitol. 2005;35(11-12):1255-1278. doi:10.1016/j.ijpara.2005.07.010
- Keiser J, Engels D, Buscher G, Utzinger J. Triclabendazole for the treatment of fascioliasis and paragonimiasis. Expert Opin Investig Drugs. 2005;14(12):1513-1526. doi:10.1517/13543722.214.171.1243
- Carnevale S, Rodríguez MI, Santillán G, Labbe JH, Cabrera MG, Bellegarde E. Fascioliasis: The tropical disease of temperate countries. Acta Gastroenterol Latinoam. 2017;47(4):288-295. PMID: 29745908.