Pathology of illness: Common symptoms are nausea, abdominal pain, diarrhoea and weakness, but infection may also cause pernicious anaemia and vitamin B12 deficiency if the worm attaches to the jejunum. D. denderiticum and Ligula intestinalis (tapeworms of fish eating birds) and D. pacificum (tapeworm of seals) have also been found in humans. The infection is usually mild, or even asymptomatic, and often of long duration. Massive infections may be associated with diarrhoea and obstruction of the intestinal tract, because the mature worm may be up to 10 metres long in the human host (FDA 2003; Goldsmid & Speare 1997).
People are universally susceptible to cestode infection, and there appears to be no induction of immunity (Benenson 1995). People of Scandinavian heritage may be genetically more susceptible to developing severe anaemia due to the tapeworm’s great requirement for and absorption of Vitamin B12 (FDA 2003). Victims may harbour more than one worm and multiple worms can amplify the symptoms of infection (M&S Food Consultants 2001).
Epidemiological data: Infection is related to dietary and culinary practices. As with nematodes, human infections have been linked to consumption of raw or minimally processed fish. Freezing and cooking temperatures lethal for anisakids will kill the infective stage of D. latum.
