Liver flukes are flat, parasitic worms of the class Trematoda, and they reside in the human bile ducts. These bile ducts are an integral part of the Liver parenchyma. Liver flukes can infect humans, which will cause liver and bile duct disease.
The Opisthorchiidae and Fasciolidae families of liver flukes cause disease in humans. The Opisthorchiidae comprises the Clonorchis and Opisthorchis species. The Fasciolidae includes species of Fasciola. These two liver flukes have different geographic distributions, life cycles, and long-term outcomes after clinical infection.
Fasciola hepatica is a waterborne and foodborne zoonotic disease. It’s sometimes known as “the common liver fluke” or “the sheep liver fluke.” Fasciola hepatica is a parasitic infection that is responsible for fascioliasis. Fascioliasis is present in over 50 nations, primarily in areas where sheep or cattle are raised. Fasciola hepatica can be found on every continent except Antarctica, and it is significantly more frequent in underdeveloped countries.
Life cycle & mode of transmission of the Liver Fluke
One of the largest digeneans infecting people is Fasciola hepatica, sometimes known as the (sheep liver fluke). It is 30 mm long and 13 mm wide. They are found primarily in domestic and wild cattle. Most commonly, it’s sheep that becomes the definitive host. The definitive host is a creature infected with the adult parasite and can reproduce sexually. The intermediate host is the one that attains the parasite’s larval stage or asexual forms.
Immature eggs are expelled and passed in the stool picture in the biliary ducts. In freshwater, eggs become embryos for two weeks. These eggs release miracidia, which enter a suitable snail intermediate host. Miracidia are encysted versions of the parasite. The parasites in the snail go through numerous stages of development. The cercariae encyst metacercariae on aquatic plants or other substrates after being released from the snail. Ingestion of metacercariae-contaminated vegetation infects humans and other mammals.
After ingestion, the exocyst in the duodenum passes through the intestinal wall into the peritoneal cavity. The immature flukes then travel through the parenchyma of the liver to the biliary ducts, where they mature into adult flukes and lay eggs. The transition from metacercariae to adult flukes normally takes 3–4 months in humans.
People become infected by inadvertently swallowing the parasite. The most typical way to happen is by eating raw watercress or other polluted freshwater plants. People can also become infected by drinking polluted water or eating vegetables washed or irrigated with contaminated water. By consuming undercooked sheep or goat liver that contained immature forms of the parasite under unusual circumstances, people become sick.
Fasciola is not a disease that can spread from one person to another. To be able to infect someone else, the eggs discharged in the stool of infected individuals (and animals) must develop (mature) in certain types of freshwater snails under optimal environmental conditions.
(Next lets look closer at the signs and symptoms)