Fasciolopsis () is a genus of . They are also known as giant intestinal flukes.
Only one species is recognised: Fasciolopsis buski. It is a notable parasite of medical importance in humans and veterinary importance in pigs. It is prevalent in Southern and Eastern Asia. The term for infestation with Fasciolopsis is fasciolopsiasis.
Fasciolopsis buski
Fasciolopsis buski is commonly called the giant intestinal
trematoda, because it is an exceptionally large parasitic fluke, and the largest known to parasitise humans. Its size is variable and a mature specimen might be as little as 2 cm long, but the body may grow to a length of 7.5 cm and a width of 2.5 cm. It is a common
parasite of humans and pigs and is most prevalent in
South Asia and
Southeast Asia. It is a member of the family
Fasciolidae in the order
Plagiorchiida. The Echinostomida are members of the class
Trematoda, the flukes. The fluke differs from most species that parasitise large mammals, in that they inhabit the gut rather than the liver as
Fasciola species do.
Fasciolopsis buski generally occupies the upper region of the
small intestine, but in heavy infestations can also be found in the
stomach and lower regions of the intestine.
Fasciolopsis buski is the cause of the pathological condition
fasciolopsiasis.
[Roberts LS, Janovy, J, Jr. (2009). "Foundations of Parasitology." McGraw Hill, New York, USA, pp. 272–273. ]
In London, George Busk first described Fasciolopsis buski in 1843 after finding it in the duodenum of a sailor. After years of careful study and self experimentation, in 1925, Claude Heman Barlow determined its life cycle in humans.[ Dr. Claude Heman Barlow . Barlowgenealogy.com. Retrieved on 2012-12-18.]
Morphology
Fasciolopsis buski is a large, dorsoventrally flattened fluke characterized by a blunt anterior end, undulating, unbranched
cecum (sac-like cavities with single openings), tandem
Testicle, branched
ovaries, and ventral suckers to attach itself to the host. The acetabulum is larger than the oral sucker. The fluke has extensive follicles. It can be distinguished from other fasciolids by a lack of
cephalic cone or "shoulders" and the unbranched ceca.
Life cycle
Adults produce over 25,000 eggs every day; these take up to seven weeks to mature and hatch at 27–32 °C. Immature, un
embryonated eggs are discharged into the intestine and
feces. In two weeks, eggs become embryonated in water, and after about seven weeks, tiny parasitic organisms called
miracidia hatch from the eggs, which then go on to invade a suitable
snail intermediate host. Several species in the genera
Segmentina and
Hippeutis serve as intermediate hosts. In the snail the parasite undergoes several developmental stages (sporocysts, rediae, and cercariae). The
cercariae are released from the snail and encyst as
metacercariae on aquatic plants such as water chestnut,
water caltrop,
Lotus Flower,
bamboo, and other edible plants. The
mammalian final host becomes infected by ingesting
metacercariae on the aquatic plants. After ingestion, the metacercariae encyst in the
duodenum in about three months and attach to the intestinal wall. There they develop into adults (20 to 75 mm by 8 to 20 mm) in approximately three months, remaining attached to the intestinal wall of the mammalian hosts (humans and pigs). The adults have a
life expectancy of about one year.
Pathogenesis
Humans become infected by ingesting metacercariae present on contaminated
, like water chestnuts and watercress, or by consuming water contaminated with the parasite. Once ingested, the metacercariae
Microbial cyst in the
duodenum and attach to the
jejunum and
ileum of the intestinal wall. The flukes then use their oral sucker to stick to the intestinal mucosa- in which can cause mechanical damage and irritation to the lining of the intestine. This attachment can lead to ulcerations, inflammation, and local tissue damage. The pathogenesis results in various symptoms including, but not limited to:
In severe cases or with prolonged infections, there can be nutritional deficiencies due to malabsorption caused by the intestinal damage. In other cases, secondary bacterial infections might occur due to the disruption of the intestinal barrier by the fluke, leading to further opportunistic infections. Adult flukes reside in the small intestine, where they mature and produce eggs. These eggs are then passed into the host's feces where they will continue the life cycle of the parasite. Treatment involves anthelmintic medications to rid the flukes from the intestines. Early diagnosis and treatment are essential in preventing further complications an progression of the disease.
Diagnosis
Examination of stool samples microscopically to identify parasite eggs can aid in the diagnosis of this parasite. However, due to intermittent egg shedding, multiple stool samples may be necessary for an accurate diagnosis. The WHO recommends the Kato-Katz technique as the method of choice for fascioliasis diagnosis attending to its ease of use and reproducibility, and its enhanced sensitivity compared with the observation of eggs in fresh faeces. Enzyme-linked immunosorbent assay (
ELISA) or other
can also help identify specific
Antibody against Fasciolopsis buski antigens in the blood. In some cases, imaging techniques like
ultrasound or
endoscopy might also be used to visualize the flukes within the intestines.
Control
Promoting proper hygiene, clean water sources, and safe food practices to prevent contamination by infective stages of the parasite. Thoroughly cooking aquatic plants and ensuring proper washing and cleaning of vegetables and fruits to remove potential infective stages. Educating communities about the risks of consuming contaminated water, raw or undercooked plants, and promoting awareness of the disease can also play a huge role in containing the spread of this parasite. If contracted, another way to help control is the use of anthelmintic medications.
Praziquantel is the type of medication currently used to treat such infections. These are to be prescribed by healthcare professionals for infected individuals to eradicate the parasites from the body.
Vaccination
Vaccination against
Trematoda infections like
Fasciolosis and
fasciolopsiasis is still an area of ongoing research. Development of effective vaccines for these parasites remains a challenge due to the complex life cycles and various stages of the parasites involved. Researchers continue to explore different approaches and antigens for potential vaccine candidates.
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