GENERAL CHARACTERISTICS
The adults of F. buski have an elongated shape and range from 20 to 75 mm long to approximately 8 to 20 mm wide (Figure 1). They have an oral sucker at the anterior end and a ventral sucker located about midway to the posterior end. The eggs, which are indistinguishable from those of Fasciola hepatica (Figure 2), are oval and elongated, transparent, and yellow-brown with an operculum (lid) at one end, and they range in size from 130 to 140 µm long to 80 to 85 µm wide and may be unembryonated.
Fig1. Whole mount of Fasciolopsis buski. (Courtesy Dr. Henry Travers, Sioux Falls, S.D.)
Fig2. Fasciola egg. The eggs of F. buski and F. hepatica are indistinguishable morphologically. (Courtesy Dr. Henry Travers, Sioux Falls, S.D.)
EPIDEMIOLOGY
Fasciolopsis buski is found in Bangladesh, Cambodia, China, India, Indonesia, Laos, Malaysia, Pakistan, Taiwan, Thailand, and Vietnam, and is prevalent in school-aged children. Contaminated feces drains into the water from farm lands, where feces is used for fertilization, and defecation occurs in or near water sources. Reservoir hosts include pigs, dogs, and rabbits.
F. buski is the largest of the intestinal trematodes, and infection is acquired by ingestion of raw water chestnuts or caltrop. The definitive host is the pig, and fish-eating wild and domestic animals may serve as reservoir hosts. The water vegetation may become contaminated when feces is used for fertilization or where disposal of farm animal feces is inadequate.
PATHOGENESIS AND SPECTRUM OF DISEASE
The intestinal attachment site of the adult worms often becomes locally inflamed and ulcerated, and may hemorrhage. Moderate to heavy infections may cause abdominal pain, diarrhea, intestinal obstruction, and edema of the abdomen and lower extremities, and may result in inadequate absorption of vitamin B12. Eosinophilia is commonly observed.
PREVENTION
Infection can be prevented by making sure that water plants and fish are properly cooked before eating. In addition, changes are needed in agricultural practices and health education in the endemic areas.
