Fasciolopsis buski

Geographic Range

Fasciolopsis buski is found mainly in Asia and the Indian subcontinent, occurring in Taiwan, Thailand, Laos, Bangladesh, India, and Vietnam. This trematode is especially prevalent in areas where pigs are raised, or where underwater vegetables such as water chestnut, water caltrop, lotus, and bamboo are often consumed. It has a prevalence of up to 60% in India and mainland China. ("DPDx - Fasciolopsis", 2009; Le, et al., 2004)


Fasciolopsis buski occurs in places with warm, moist, weather. This species is found in aquatic environments, where aquatic plants grow. Once consumed by the definitive host, the adult stage of Fasciolopsis buski adheres to the small intestine of its host, remaining until it dies or is removed. ("DPDx - Fasciolopsis", 2009; Le, et al., 2004; Raymondo, 1999)

  • Aquatic Biomes
  • lakes and ponds
  • temporary pools

Physical Description

The eggs of Fasciolopsis buski vary in length from 130 to 150 micrometers and vary in width from 60 to 90 micrometers.

An adult Fasciolopsis buski is shaped like an elongated oval. The adult's length ranges from 20 mm to 75 mm, and has a width up to 20 mm, making it the largest human intestinal fluke. This species has poorly developed ventral and oral suckers, lacks "shoulders" present in other members of the family, and contains unbranched ceca. The adult is hermaphroditic. ("DPDx - Fasciolopsis", 2009; Le, et al., 2004; Liu and Harhasuta, 1996; Raymondo, 1999)

  • Range length
    20 to 75 mm
    0.79 to 2.95 in


The life cycle of Fasciolopsis buski begins when unembryonated eggs are released from the mammal host through the feces. An adult F. buski produces up to 26,000 eggs daily. To continue development, the eggs must reach fresh water. Once these eggs are released into water, they become embryonated and take up to 7 weeks to hatch at temperatures of 27 to 32 degrees Celsius.

The embryonated eggs release miracidia which invade snails and use them as an intermediate host. In the snail, the parasite undergoes several developmental stages, from miracidia to sporocyst to rediae to cercariae. The cercariae are released from the snail back into the aquatic environment. This is fatal to the snail host. The cercariae then encyst on aquatic plants (such as water chestnut, water caltrop, lotus, and bamboo) as metacercariae.

Mammalian hosts (humans and pigs) become infected when they ingest the plants that contain the parasite's metacercariae. Once ingested, the metacercariae excyst in the duodenum and attach to the intestinal wall. After 3 months, the parasites develop into adults and begin producing eggs. ("DPDx - Fasciolopsis", 2009; Mas-Coma, et al., 2005; Raymondo, 1999)


Fasciolopsis buski is hermaphroditic. Dendritic testes are in the posterior half of the worm, and branched ovaries are anterior to the testes. Fasciolopsis buski has extensive vitelline follicles, and a short uterus. Sexual reproduction occurs in the definitive mammal hosts (humans and pigs), and asexual reproduction occurs in the snail intermediate host. (Liu and Harhasuta, 1996)

There is no set time of the year that reproduction occurs. Once Fasciolopsis buski has matured in its definitive host, it produces eggs for the remainder of its life. Fasciolopsis buski can either self-fertilize or cross-fertilize.

Asexual reproduction and development occurs in snail hosts. (Liu and Harhasuta, 1996; Mas-Coma, et al., 2005)

  • Breeding interval
    Fasciolopsis buski breeds continuously, producing about 16,000 eggs per day.
  • Breeding season
    Breeding occurs throughout the year.
  • Range number of offspring
    13000 to 26000
  • Average number of offspring
  • Average gestation period
    7 weeks
  • Average age at sexual or reproductive maturity (female or asexual)
    3 months
  • Average age at sexual or reproductive maturity (male)
    3 months

There is no parental investment with Fasciolopsis buski. Once eggs are produced, they are released from the host body with the feces, and develop by themselves. ("DPDx - Fasciolopsis", 2009; Mas-Coma, et al., 2005)

  • Parental Investment
  • no parental involvement


The lifespan of the adult Fasciolopsis buski is one year. Factors that contribute to the lifespan and development of Fasciolopsis buski include being released into the proper environment for development (freshwater) and the ability to find an intermediate host. If this does not occur, Fasciolopsis buski will fail to develop and reach adulthood. ("DPDx - Fasciolopsis", 2009; Liu and Harhasuta, 1996)

  • Average lifespan
    Status: wild
    1 years


Fasciolopsis buski does not move around very much. This parasite encysts on aquatic vegetation and remains there until it is picked up by a host. Once in a host, F. buski remains there for the rest of its life. This species is not particularly social. Although multiple worms can be present in a host, they do not communicate with each other. ("DPDx - Fasciolopsis", 2009; Le, et al., 2004; Liu and Harhasuta, 1996; Mas-Coma, et al., 2005; Raymondo, 1999)

Communication and Perception

For a great part of its lifecycle, there is no communication or movement. Once leaving a snail host, Fasciolopsis buski encysts on aquatic vegetation until it is consumed by the definitive host.

However, perception is important in locating a snail host. When placed near susceptible snail hosts, the miracidia rapidly locate and penetrate the host, but the mechanism of recognition is unknown. Upon leaving the host, the cercariae swim freely before finding and encysting on aquatic plants. (Graczyk, et al., 2000; Nakagawa, 1922)

Food Habits

Fasciolopsis buski is a parasite that resides and feeds in human and pig hosts. The adult stage is the only feeding stage, and it eats blood cells and mucus. (Nakagawa, 1922)

  • Animal Foods
  • mammals
  • body fluids


There are no known predators to Fasciolopsis buski. It needs to be ingested by mammalian hosts in order to mature to its adult stage, and no information was found about predators in other stages of development.

  • Known Predators
    • no known predators

Ecosystem Roles

Fasciolopsis buski is parasitic, using snails as an intermediate host to undergo development (this is fatal to the snail). This parasite reaches adulthood and produces eggs in mammal hosts, usually humans and pigs, but also equines, bovines, caprines, and ovines. Fasciolopsis buski can make its hosts very sick, and is very problematic in developing countries.

Fasciolopsis buski snail hosts that have been identified in Thailand include Segmentina hemisphaerula and Segmentina trochoideus. Plants identified to be important in transmission include water morning glory, Ipomoea aquatica; water caltrop Trapa bicornis; lotus, Nymphaea lotus; water cress, Neptunia oleracea; and water hyacinth, Eichhornia speciosa. ("DPDx - Fasciolopsis", 2009; Le, et al., 2004; Manning and Ratanarat, 1970)

Species Used as Host
Mutualist Species
  • none
Commensal/Parasitic Species
  • none

Economic Importance for Humans: Positive

There was no information of any benefits that Fasciolopsis buski provides to humans. It is possible that further research may reveal ways that Fasciolopsis buski could be beneficial.

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

Fasciolopsis buski negatively impacts humans by causing disease, although most cases of this parasite are asymptomatic. Disease symptoms include ulceration, hemorrhage and abscess of the intestinal wall, diarrhea, and even death. ("DPDx - Fasciolopsis", 2009)

Conservation Status

There is no information about conservation efforts concerning Fasciolopsis buski, and Fasciolopsis buski does not seem to be in danger of disappearing.

Other Comments

Fasciolopsis buski is unique because it is the only member of its family (Fasciolidae) to invade the small intestine. Other members of Fascioloidae invade the liver of their host.

Disease caused by Fasciolopsis buski is most prevalent in areas with extreme poverty, or places which lack sanitation or hygienic dietary practices. It is easy to prevent invasion of a host by Fasciolopsis buski, simply by immersing vegetables in boiling water for a few seconds prior to eating them. (Le, et al., 2004; Liu and Harhasuta, 1996; Mas-Coma, et al., 2005)


Lindsey Greiner (author), University of Michigan-Ann Arbor, Heidi Liere (editor), University of Michigan-Ann Arbor, John Marino (editor), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor, Renee Mulcrone (editor), Special Projects.



living in landscapes dominated by human agriculture.


reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).


uses smells or other chemicals to communicate


a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


mainly lives in water that is not salty.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


marshes are wetland areas often dominated by grasses and reeds.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


found in the oriental region of the world. In other words, India and southeast Asia.

World Map


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death


an animal that mainly eats blood


remains in the same area


non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa


reproduction that includes combining the genetic contribution of two individuals, a male and a female


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

year-round breeding

breeding takes place throughout the year


CDC. 2009. "DPDx - Fasciolopsis" (On-line). Laboratory Identification of Parasites of Public Health Concern. Accessed March 24, 2011 at http://www.dpd.cdc.gov/dpdx/HTML/Fasciolopsiasis.htm.

Graczyk, T., K. Alam, R. Gilman, G. Mondal, S. Ali. 2000. Development of Fasciolopsis buski (Trematoda: Fasciolidae) in Hippeutis umbilicalis and Segmentina trochoideus (Gastropoda: Pulmonata). Parasitology Research, 86/4: 324-326.

Le, T., V. Nguyen, B. Phan, D. Blair, D. McManus. 2004. Case report: unusual presentation of Fasciolopsis buski in a Viet Namese child. Transactions of the Royal Society of Tropical Medicine and Hygiene, 98/3: 193-194.

Liu, L., K. Harhasuta. 1996. Liver and intestinal flukes. Gastrenterology Clinics of North America, 25/3: 627-636.

Manning, G., C. Ratanarat. 1970. Fasciolopsis buski (Lankester, 1857) in Thailand. Am. J. Trop. Med. Hyg., 19 (4): 613-619. Accessed March 25, 2011 at http://www.ajtmh.org/cgi/content/abstract/19/4/613.

Mas-Coma, S., M. Bargues, M. Valero. 2005. Fascioliasis and other plant-borne trematode zoonoses. International Journal for Parasitology, 35/11-12: 1255-1278.

Nakagawa, K. 1922. The development of Fasciolopsis buski Lankester. The Journal of Parasitology, 8/4: 161-166. Accessed March 26, 2011 at http://www.jstor.org/stable/3271232?seq=1.

Raymondo, D. 1999. "Parasitology Training Manual - Fasciolopsis buski" (On-line). Fasciolopsis buski. Accessed March 24, 2011 at http://www.practicalscience.com/fb.html.