What is fasciola hepatica infection and life cycle

Fasciolosis, also called fascioliasis, is a parasitosis caused by the parasite Fasciola hepatica, and more rarely Fasciola gigantica , which can be found in the bile ducts of mammals, such as sheep, cattle and pigs, for example.

Infection with Fasciola hepatica is rare, however it can happen through the ingestion of water and vegetables contaminated by the infectious form of this parasite, because the eggs released in the environment hatch when in contact with the water, the released miracide develops in the snail until the infectious form is released and then develop into the infectious form called metacercaria, leaving not only contaminated water, but also aquatic plants, such as watercress, for example.

It is important that diagnosis and treatment are made quickly, as the parasite is not adapted to the human body, the symptoms can be quite severe. Treatment should be done with Albendazole, Bithionol and Deidroemetina.

How the transmission and the cycle happens

Fasciola hepatica is transmitted to humans from the consumption of water or raw vegetables that contain metacercariae of this parasite. Another possible, but rarer, way is through the consumption of raw liver meat from infected animals and contact with the snail or its secretions.

This parasite has a life cycle that involves the infection of intermediate and definitive hosts, and it happens according to the following steps:

1. The worms' eggs are released by the host's feces, which can be people or animals such as cattle, goats and pigs; The eggs released on contact with the water hatch and release the miracide; The miracide present in the water meets a intermediate host, which is the freshwater snail of the genus Lymnaea sp.; inside the snail, the miracide grows into sporocysts, reds and reds containing cercariae; cercariae are released into the water and attach themselves to the surface of leaves and riverside plants either reach the surface of the water, lose the cause, become enthralled and stick to the vegetation or go to the bottom of the water, being called metacercaria; animals and people ingesting contaminated water or river plants are infected through the metacercariae, which are lost in the intestine, perforate the intestinal wall and reach the hepatic pathways, characterizing the acute phase of the disease;

After about 2 months, the parasite moves to the bile ducts, develop to the acute phase, multiply and lay eggs, which are released in the feces, and a new cycle can begin.

Fasciola hepatica larva

Fasciola hepatica miracide

Main symptoms

The symptoms that fasciolosis can cause may be different in each case, varying according to the stage and intensity of the infection. Thus, in the acute illness that occurs during the migration of the parasites, in the first 1 to 2 weeks after infection, symptoms such as fever, abdominal pain and swelling of the liver can be caused.

When the parasites are lodged in the bile ducts, the infection becomes chronic, inflammation of the liver may occur, causing signs and symptoms such as weight loss, recurrent fever, enlarged liver, accumulation of fluid in the abdomen, anemia, dizziness and shortness of breath.

In some cases, inflammation of the liver can lead to complications such as obstruction of the bile ducts or cirrhosis of the liver. Liver cancer is not a direct complication of Fasciola hepatica infection, however, it is known that liver cancer is more common in people with liver cirrhosis.

How to confirm

The diagnosis of fasciolosis is suspected by the doctor according to the clinical evaluation and observation of the affected person's habits, such as raising animals or eating raw vegetables. Tests that can confirm the infection include the identification of eggs in the stool and immunological blood tests.

In addition, ultrasound or tomography of the abdomen can help demonstrate parasites within the biliary tree, in addition to identifying areas of inflammation and fibrosis. Find out more about the liver tests.

How the treatment is done

The treatment of fascioliasis is guided by the doctor, and includes the use of antiparasitic drugs such as Bithionol for 10 days every other day, Deidroemetina for 10 days or Albendazole, although serious side effects associated with the use of this antiparasitic have been described.

If there are already complications in the liver, such as cirrhosis or obstruction of the ducts, it will be necessary to follow up with the hepatologist, who will indicate ways to prolong the health of the liver and, if necessary, indicate some type of surgery to correct obstructions.

How to prevent

To prevent infection with Fasciola hepatica , it is recommended to decontaminate raw vegetables well before eating, and always use clean water suitable for consumption. In addition, it is advisable to avoid the consumption of raw meats.

It is also important that caretakers of livestock and other animals are careful with feeding and carry out treatment, if they are infected, as a way to prevent the worms from persisting in the environment.