Belt worm

Belt worm
Systematics
Class :	Tapeworms (Cestoda)
Subclass :	True tapeworms (Eucestoda)
Order :	Pseudophyllidea
Family :	Diphyllobothriidae
Genre :	Ligula
Type :	Belt worm
Scientific name
	Ligula intestinalis
	( Linnaeus , 1758)

The belt worm or belt tapeworm ( Ligula intestinalis ) is a parasite belonging to the Eucestoda (true tapeworms) , whose second larval stage (plerocercoid) lives in the body cavity of non-predatory fish, mostly Cyprinidae .

Life cycle

The eggs of the tapeworm get into the water with the droppings of water birds. The first larval stage ( Coracidium ) hatches from them and actively bores into a copepod swimming past. The small crab thus serves as the beltworm's first intermediate host and the second larval stage ( procercoid ) develops in it within a few days . If the copepods are eaten by a fish - usually a carp fish - the third larval stage ( plerozerkoid ) develops in the body cavity . The plerocercoid can become very large and possibly survive a whole fish life. Only when the fish is eaten by a definitive host (birds such as seagulls, gray herons or cormorants) does the parasite mature into an adult tapeworm in the host's intestine. In birds, the hermaphrodite parasite lays millions of eggs, which are released through the birds' droppings. The cycle is closed and starts all over again.

Plerocercoid morphology

The second larval stage of the beltworm can grow up to 20 cm in the fish. Tapeworms usually consist of three parts: the head, the zone of origin and the link chain. The beltworm, however, is not articulated, which is an important characteristic for identifying this species.

Pathogenicity

For the fish

Due to the extreme size of the parasite, the internal organs are displaced. In addition, the belt tapeworm suppresses the gonadal maturation of the fish by drawing energy from the fish and influencing the hormonal balance. So the cestode retains enough space in the body cavity to develop.

For the people

The belt tapeworm is harmless to humans. The parasite is killed from a temperature of 70 ° C. A cooked or fried fish is therefore not a transmission route to humans. Even if a live tapeworm were to get into the intestine of a person (via raw fish) it would be harmless and would die within a few hours, since the person is a false host. The only tapeworm found in Europe that can be transmitted to humans is the fish tapeworm ( Diphyllobothrium latum ).

Individual evidence

↑ ^a ^b Loot, G., Lek, S., Dejean, D., Guégan, JF (2001) Parasite-induced mortality in three host populations of the roach Rutilus rutilus (L.) by the tapeworm Ligula intestinalis (L.) . Annale de Limnologie 37 (2), 151-159
↑ Chubb, JC, Pooland, DW, Veltkamp, CJ (1987) A key to the species of cestodes (tapeworms) parasitic in British and Irish freshwater fishes. Journal of Fish Biology 31, 517-543.
^ Food chemistry by Werner Baltes at books.google.de (accessed December 10, 2009)
↑ Mehlhorn , H., Piekarski, G. (2002) Outline of parasite science: Parasites of humans and farm animals. 6th edition, Heidelberg, Spektrum Verlag.

[Loot151-159-1] Loot, G., Lek, S., Dejean, D., Guégan, JF (2001) Parasite-induced mortality in three host populations of the roach Rutilus rutilus (L.) by the tapeworm Ligula intestinalis (L.) . Annale de Limnologie 37 (2), 151-159

[2] Chubb, JC, Pooland, DW, Veltkamp, CJ (1987) A key to the species of cestodes (tapeworms) parasitic in British and Irish freshwater fishes. Journal of Fish Biology 31, 517-543.

[3] Food chemistry by Werner Baltes at books.google.de (accessed December 10, 2009)

[4] Mehlhorn , H., Piekarski, G. (2002) Outline of parasite science: Parasites of humans and farm animals. 6th edition, Heidelberg, Spektrum Verlag.