Macracanthorhynchus hirudinaceus: Thorny-headed worm.

General Description: The adult worms are 10 to 35 cm long, with reddish transversely wrinkled bodies. An extended, spiny proboscis anchors each worm to the intestinal wall.

Life Cycle: Eggs passed in the faeces contain acanthor larvae surrounded by several-layered walls. The spiny-coated acanthors hatch only after being ingested by the grub larvae of dung beetles or water beetles. The uneaten eggs may be viable in soil for several years. The immature worms develop and encyst within the body cavities of the beetles. Pigs become infected by eating grubs or beetles harbouring the infective stage of the parasite. Development within the insect takes 2 to 3 months. The larvae mature in 2 to 3 months in the small intestine of the pig. The adult Macracanthorhynchus lies attached to the intestinal wall by its proboscis and absorbs nutrients from the intestinal contents. Adult females can lay about 260,000 eggs daily for 10 months.

Location: Small intestine.

Geographical Distribution: Widely distributed in temperate and tropical climates.

Significance: Mild infections cause little damage, but heavy infections can produce losses by slowing growth of swine.

Effect on Host: Attachment sites of these worms become nodular scars. Occasionally a worm proboscis may penetrate the intestinal wall, resulting in peritonitis and death. Heavy worm burdens can cause diarrhoea, slow weight gain, and emaciation. Usually this parasite causes only minor damage, by competing with swine for nutrients from intestinal contents.

Diagnostic Information: Eggs in faeces.

Control: Management practices to prevent pigs from eating beetles are essential in the control of this parasite. Effective practices include good sanitation, housing on concrete, nose-ringing, and pasture rotation.

Macracanthorhynchus adult showing spiny proboscis		Section of small intestine showing Macracanthorhynchus attached
Adult M.hirudinaceus showing nodular attachment site		Macracanthorhynchus – egg