Capillaria philippinensis

Infection with Capillaria philippinensis, a hairworm, first occurred in the Philippines and later in Thailand, Japan, Iran, Egypt and Taiwan, with most infections reported in the Philippines and Thailand. It is a zoonotic disease of migratory fish-eating birds. The eggs are spread along the flyways and infect the fish, which can infect humans if eaten raw (intestinal capillariasis).

The life cycle of Capillaria philippinensis includes freshwater fish as intermediate hosts and piscivorous birds as final hosts.

Embryonated eggs from bird feces ingested by fish hatch and grow as larvae in the fish gut. Infective larvae fed to monkeys, Mongolian gerbils, and fish-eating birds develop into adult hairworms. The larvae become adults in 10 to 11 days. First generation females produce larvae. These larvae develop into male and egg-producing female worms. The eggs are excreted in the feces, enter the water, embryonate, and infect fish. Autoinfection is part of the life cycle and results in hyperinfection.

Humans acquire the infection by eating small freshwater fish raw. The parasite multiplies, and symptoms such as diarrhea, abdominal pain, and edema develop. Chronic intestinal infections lead to malabsorption with protein and electrolyte losses.

Treatment consists of electrolyte replacement and administration of mebendazole or albendazole.

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