Diphyllobothriasis B70.0

Diphyllobothriasis refers to an infection (parasitosis) caused by the fish tapeworm (Diphyllobothrium latum) also known as pit head. Diphyllobothrium latum belongs to the group of tapeworms (Cestoda) that parasitise mainly in domestic dogs, less frequently in cats or in humans.

Infection in humans occurs through consumption of raw fish.

Diphyllobothrium latum (cestode, fish tapeworm).

The worms parasitize in the anterior small intestine of humans, various fish-eating animals can become infected.

The adult worms are 8-20 m long and consist of 3000-4000 tapeworm members (proglottids).

The eggs enter suitable stagnant waters with the faeces of the final host (humans, dogs, cats), where they develop into a first larva (hexacanth larva; in the case of the fish tapeworm called Coracidium). They are taken up by copepods of the genera Diaptomus and Cyclops. In these crustaceans, the first larvae develop into prozecoids.

The rudder crabs are still eaten by carp fish. As a result, the parasites penetrate the intestinal wall of the fish and further develop into plerocercoids. It can happen that the fish is taken up by another predatory fish, whereby the latter serves as a paratenic host (e.g. pike).

The final host (human, dog, cat) becomes infected by the intake of the intermediate host (carp) or the paratenic host (false host) pike.

In humans, the consumption of raw fish meat leads to the ingestion of the plerocercoids, which develop into adult worms in the intestine. The worm grows in the intestine 9 to 15 cm/day. After 3 to 5 weeks the worms become sexually mature and start producing eggs. The parasite can remain unnoticed in the intestine for up to 25 years.

Microscopy of the stool for detection (after enrichment by sedimentation) and detection of tapeworm members.

Vitamin B12 level in serum.

Praziquantel (Biltricide) 10 mg/kg bw p.o. as a single dose.

Alternatively: Niclosamide (Yomesan) 2 mg p.o. as single dose p.o.

Substitution of vitamin B12.

Avoid raw freshwater fish.

1. Grasbeck R et al: Lognormal distribution of serum vitamin B12 levels and dependence of blood values on the B12 level in a large population heavily infected with Diphyllobothrium latum. In: The Journal of laboratory and clinical medicine 59: 419-429
2. Henricson J (1977): The abundance and distribution of Diphyllobothrium dendriticum (Nitzsch) and D. ditremum (Creplin) in the char Salvelinus alpinus (L.) in Sweden. Journal of Fish Biology 11: 231-248.
3. Vindigni SM et al (2017) Intermittent obstructive symptoms in a patient with diphyllobothriasis. Gastrointest Endosc 86:1185-1186.