The eggs have a maximum length of 150 μm and width of 90 μm ( Figure 5).Įgg production starts 10–11 week after ingestion (prepatent period) of the metacercariae. The eggs that they produce are yellowish/brown gold in color with an operculum. Flukes are hermaphroditic (with male and female genital organs) and proterandric (male sexual maturity is reached first). In the larger bile ducts and gallbladder, they grow out in about 4 weeks to adult flukes of maximum length 5 cm and width 1.5 cm. However, most flukes penetrate the liver and wander through the parenchyma for a period of about 6 weeks to reach the bile ducts. If young flukes are wandering in pregnant cows, they may reach the fetus and cause intrauterine infection, which may even result in abortion. The majority of the young flukes migrate in 3–4 days toward the liver, but occasionally flukes may reach other organs such as lungs, brain, or other organs (ectopic flukes). It penetrates the wall of the small intestine with the help of proteolytic enzymes and reaches the peritoneal cavity. Part of the Life Cycle of Fasciola hepatica within the HostĪfter ingestion of the metacercariae, the outer cyst wall is removed under the influence of the digestive enzymes in abomasum and duodenum and the young fluke escapes actively from the cyst. In general where F. hepatica establishes itself its epidemiological pattern will adapt to the local situation within the limits given above. This infection becomes available on the herbage from July onward with a peak in late autumn. Fasciolosis is a seasonal diseases and, especially in temperate northern hemisphere climate, two waves of infection of the vegetation are possible: the winter infection in the period April–July, caused by the shedding of cercariae by infected snails that have survived the winter and the summer infection caused by snails that have been infected in the spring and summer due to overwintered eggs or eggs shed by cattle in the spring. Thus liver fluke can overwinter as egg, as sporocyst/redia in the snail, and as metacercaria on the vegetation. They can survive a few degrees below 0 ☌, but severe frost is also lethal. Metacercariae can survive for long periods of up to almost 1 year. During dry periods, the release of cercariae can stop and can be resumed when the conditions are more favorable again. Snails can shed cercariae for several weeks. The development from miracidium to metacercaria requires a minimum of 5 weeks. This stage is called metacercaria and is the infective stage for the mammalian final host. Cercariae leave the snail and swim around and settle on the vegetation. The cercariae have many characteristics of the adult fluke, but they have a distinct tail. Eventually, cercariae develop in the redia or daughter redia. The sporocyst develops into a redia and the redia may develop into daughter redia. On encountering a snail, it penetrates the snail with the help of proteolytic enzymes, and migrates as a young sporocyst to the hepatopancreas. The miracidium has to find a suitable snail intermediate host within a few hours after hatching. The miracidium leaves the egg after the ‘lid’ (operculum) of the egg is opened. The minimum time required to develop to the first larval stage, the miracidium, is about 10 days at 26 ☌ and extends to 6 weeks at 15 ☌. The developmental rate is dependent on the temperature.
Schematic representation of the life cycle of Fasciola hepatica: 1, adult fluke (within the mammalian definitive host) 2, egg 3, miracidium 4, redia (within the mollusk intermediate host) 5, cercaria 6, metacercaria (on vegeatation). Repeat treatment twice more, spaced 4 or 5 days apart.įigure 4. Remove carbon from the filter and add 1 g of praziquantel per 378 L of water. Treatment: A number of treatments are available for flukes, but those containing praziquantel are the most effective. When branchial infestations are present, respiratory signs (increased opercular rate, piping, and respiratory distress) may be seen. Symptoms: Flashing, tiny red spots or yellow dusting, excessive production of mucus, shedding of the slime coat, clumped fins. Flukes are usually introduced into the tank when new fish or plants that can carry eggs or the parasite itself are added.
Dactylogyrus predominantly affects the gills, whereas Gyrodactylus is more commonly found on the skin ( Mayer and Donnelly, 2013a). Freshwater fish, including goldfish, are commonly affected by monogeneans of the genera Dactylogyrus and Gyrodactylus. Blanco, Suraj Unniappan, in Laboratory Fish in Biomedical Research, 2022 Flukesįlukes are monogenean parasites.