Acanthocephalosis of the fish
The Acanthocephalose of fish is a parasitic disease in fish by infestation with different types of acanthocephala is triggered (Acanthocephala).
The causative agent
A number of types of scratchworms can be used as the causative agent of acanthocephalosis in fish, all of which can attack fresh and saltwater fish in a more or less species-specific manner. These are small to medium-sized species of the Palaeacanthocephala and Eoacanthocephala , which settle as endoparasites in the intestine of the infected fish and, with the help of the hooked proboscis, hook into the muscle tissue or the mucous membrane of the intestinal lumen .
Some well-known scratchworms that cause infections in domestic fish are for example
- Acanthocephalus anguillae ; The intermediate host is the water louse; Cyprinidae, trout fish, perch, pike and eels in particular are infected.
- Acanthocephalus lucii ; The intermediate host is the water louse ( Asellus aquaticus ); Cyprinidae and various predatory fish such as pike , eel or various perch as well as flatfish and herring in seawaterare infected.
- Echinorhynchis truttae ; The intermediate hosts are amphipods ( Gammarus spec. ), Trout fish in particular are infected.
- Echinorhynchis gadi ; Intermediate hosts are marine amphipods, mainly sea fish, especially haddock , are infected.
- Neoechinorhynchus rutili ; The intermediate hosts are mussel crabs (Ostracoda); Cyprinidae, trout fish and eels in particular are infected.
- Pomphorhynchus laevis ; The intermediate hosts are amphipods; Cyprinidae, barbel , perch and eelsare mainly infected.
Depending on the types of scratching worms that cause the infection, it is referred to as pomphorhynchosis , echinorhynchosis , neoechinorhynchosis or acanthocephalosis .
Development and infection
Infection with the infectious larval stages, the cystacanthene , occurs through the ingestion of small crustaceans infected with the larvae as food (oral-alimentary infection). Above all, the amphipods ( Gammarus spec. ) And the water louse ( Asellus aquaticus ) play an important role as intermediate hosts and carriers. These take up the eggs from the free water, whereupon the larva, the acanthor , hatch in them and develop into the infectious acanthella. If the intermediate host is eaten, the larva develops into a fully grown adult animal and hooks itself into the intestinal wall of the midgut or rectum.
Symptoms
The symptoms caused by the scratchworm infestation vary widely and depend on the infected species, their age and constitution, and the number and type of parasites. An infection with a few worms can be harmless, but development and eating disorders, emaciation or even fish deaths can occur when the parasites occur on a large scale. Some species, including, for example, Acanthocephalus lucii , Echinorhynchis truttae or Neoechinorhynchus rutili found in native fish , only dig into the intestinal mucosa, others such as Acanthocephalus anguillae or Pomphorhynchus laevis get caught in the muscle layer or penetrate the intestine completely with their proboscis. There is pronounced local necrosis around the injury , which is formed by newly formed connective tissue from eosinophilic and heterophilic granulocytes .
Diagnosis and treatment
Diagnosis of the infected fish is usually only made after they have been killed by a thorough inspection of the intestines. Scratchworms with a proboscis that penetrate far into the muscle layer can already be recognized on the outside of the intestine through the connective tissue capsules. In the case of severe infestation, the eyes protrude in some fish, especially trout fish with severe infestation with Echinorhynchis truttae .
In the case of mass infestation in pond farming , especially in trout farming, medication is mixed into the dry food to drive out the scratching worms. This is di-n-butyltin oxide, which is given over several days in doses of 25 g per 100 g of feed. Infested fish can be fished as a preventive measure to reduce parasite infestation. In addition, very heavily infested waters are drained and limed in order to kill the intermediate hosts and thus the larvae of the parasites.
Lead indicator in the water
Due to their parasitic way of life in fish , scratchworms and other endoparasites of limnic and marine fish, especially heavy metals, accumulate much more intensely than their hosts. For this reason, the scratchworms living in the fish are examined primarily as an indicator of the lead content in water.
supporting documents
Evidence cited
Most of the information in this article has been taken from the sources given under literature; the following sources are also cited:
- ↑ Experimental Studies on Lead Accumulation in the Eel-Specific Endoparasites Anguillicola crassus (Nematoda) and Paratenuisentis ambiguus (Acanthocephala) as Compared with Their Host, Anguilla anguilla. Archives of Environmental Contamination and Toxicology 37 (2), 1999; Pages 190–195 ( doi: 10.1007 / s002449900505 )
literature
- Theodor Hiepe, Renate Buchwalder, Siegfried Nickel: Textbook of Parasitology. Volume 3: Veterinary Helminthology. Gustav Fischer Verlag, Jena 1985; Pages 395-403.
- Michel Rommel, Johannes Eckert, Erich Kutzer, Wolfgang Körting, Thomas Schnieder: Veterinary Parasitology. 5th edition, Parey Buchverlag, Berlin 2000; Pages 850-851.