Diphyllobothriasis B70.0

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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Diphyllobothrium infection; Fish tapeworm infection

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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.

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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.

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Distribution in Europe and West Asia, the Baltic States and Northwest Russia, rarely also in Canada and Alaska, related species in Africa, East Asia, Papua New Guinea, Australia, South America (e.g. D. pacificum in Peru and Chile). Reservoir hosts are numerous fish-eating animals like dogs, cats and bears.

Clinical features
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Most infections are asymptomatic. Uncharacteristic abdominal pain. Vitamin B12 deficiency with megaloblastic anemia and encephalomyeloneuropathy. In most cases no skin changes occur. Occasionally generalized pruritus is described; not infrequently there are rhagades of the corner of the mouth. More rarely, a discreet, more straw-yellow than brown, jaundice is more pronounced. In severe cases tongue burning; atrophic, highly red, mirror-smooth tongue surface with loss of the papillae; lack of coating on the tongue. Occurrence of white anemia areas (Arndt's sign) when the tongue is stuck out. S.u. Glossitis Möller-Hunter.

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

Vitamin B12 level in serum.

Differential diagnosis
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Vitamin B12 deficiency of another origin.

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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.

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Avoid raw freshwater fish.

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  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.

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Paratenic host;


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Last updated on: 29.10.2020