Ichthyophthirius multifiliis

Ichthyophthirius multifiliis
Cichlid showing the white spots characteristic of Ich
Scientific classification Edit this classification
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Alveolata
Phylum: Ciliophora
Class: Oligohymenophorea
Order: Hymenostomatida
Family: Ichthyophthiriidae
Genus: Ichthyophthirius
Species:
I. multifiliis
Binomial name
Ichthyophthirius multifiliis
Fouquet, 1876

Ichthyophthirius multifiliis, often termed "Ich",[1][2] is a parasitic ciliate described by the French parasitologist Fouquet[who?] in 1876. Only one species is found in the genus which also gave name to the family. The name literally translates as "the fish louse with many children". The parasite can infect most freshwater fish species and, in contrast to many other parasites, shows low host specificity. It penetrates gill epithelia, skin and fins of the fish host and resides as a feeding stage (the trophont) inside the epidermis. It is visible as a white spot on the surface of the fish but, due to its internal microhabitat, it is a true endoparasite and not an ectoparasite.[3]

It causes a disease commonly referred to as white spot disease due to the macroscopically visible trophonts (up to 1 mm in diameter) in the skin and fins. The trophont, continuously rotating, is surrounded by host cells (epidermal cells and leukocytes), producing a minute elevation of the skin. These light-reflecting nodules are recognized as white spots.[4][5]

If strict bio-security rules are violated, the parasite may be introduced into a fish rearing unit by transfer of fish or equipment from infected systems. When the organism gets into a large fish culture facility, it is difficult to control due to its fast-reproductive cycle. If not controlled, the infection may lead to 100% mortality in the tank.

Strict management measures including mechanical and chemical methods are generally applied and can keep the infection at an acceptable level at farms. However, these measures are costly in terms of labour, chemicals and lost fish.[6]

Research within the Horizon2020 project ParaFishControl pointed to a range of new approaches for control. For example, the fish immune system has an ability to combat invading parasites and a vaccine may be developed in the future.[7][8] In addition, novel bacterial products (surfactants from Pseudomonas) can directly kill the external stages of the parasite without harming the host.[9]

Ichthyophthirius multifiliis inflicts considerable damage to gills and skin in two ways. Firstly, the theronts penetrate the host epithelia and, when the number of parasites is high in relation to the fish size, the penetration may directly kill the fish by destroying the integrity of the fish surface. Secondly, if the invasion is successful, the invading theronts transform into the trophont stage in the fish epidermis where they develop and expand their volume manifold.[10][11] When the trophonts burst out from their epidermal residence, severe ulceration follows, leading to high host mortality. The osmoregulation of the fish is challenged both by penetration and by trophont escape. Damage to the host's gills also reduces the respiratory efficiency of the fish, reducing its oxygen intake from the water.

  1. ^ "'Ich' discovery could yield new ways to treat devastating freshwater fish parasite". ScienceDaily. Retrieved 2021-10-23.
  2. ^ "Ich | fish disease". Encyclopedia Britannica. Retrieved 2021-10-23.
  3. ^ Noga, Edward (2000). Fish disease: diagnosis and treatment. Wiley-Blackwell. pp. 95–97. ISBN 978-0-8138-2558-8.
  4. ^ Buchmann, Kurt (2019). "Immune response to Ichthyophthirius multifiliis and role of IgT". Parasite Immunology. 42 (8): e12675. doi:10.1111/pim.12675. ISSN 1365-3024. PMC 7507210. PMID 31587318.
  5. ^ Olsen, Moonika M.; Kania, Per W.; Heinecke, Rasmus D.; Skjoedt, Karsten; Rasmussen, Karina J.; Buchmann, Kurt (2011-03-01). "Cellular and humoral factors involved in the response of rainbow trout gills to Ichthyophthirius multifiliis infections: Molecular and immunohistochemical studies". Fish & Shellfish Immunology. 30 (3): 859–869. Bibcode:2011FSI....30..859O. doi:10.1016/j.fsi.2011.01.010. ISSN 1050-4648. PMID 21272651.
  6. ^ Heinecke, Rasmus D.; Buchmann, Kurt (2009-03-02). "Control of Ichthyophthirius multifiliis using a combination of water filtration and sodium percarbonate: Dose-response studies". Aquaculture. 288 (1): 32–35. Bibcode:2009Aquac.288...32H. doi:10.1016/j.aquaculture.2008.11.017. ISSN 0044-8486.
  7. ^ von Gersdorff Jørgensen, Louise; Sigh, Jens; Kania, Per Walter; Holten-Andersen, Lars; Buchmann, Kurt; Clark, Theodore; Rasmussen, Jesper Skou; Einer-Jensen, Katja; Lorenzen, Niels (2012-11-07). "Approaches towards DNA Vaccination against a Skin Ciliate Parasite in Fish". PLOS ONE. 7 (11): e48129. Bibcode:2012PLoSO...748129V. doi:10.1371/journal.pone.0048129. ISSN 1932-6203. PMC 3492342. PMID 23144852.
  8. ^ Jørgensen, L. von Gersdorff; Kania, P. W.; Rasmussen, K. J.; Mattsson, A. H.; Schmidt, J.; Al-Jubury, A.; Sander, A.; Salanti, A.; Buchmann, K. (2017). "Rainbow trout (Oncorhynchus mykiss) immune response towards a recombinant vaccine targeting the parasitic ciliate Ichthyophthirius multifiliis". Journal of Fish Diseases. 40 (12): 1815–1821. Bibcode:2017JFDis..40.1815V. doi:10.1111/jfd.12653. hdl:10261/177214. ISSN 1365-2761. PMID 28548690. S2CID 29544998.
  9. ^ Al-Jubury, A; Lu, C; Kania, P W; von Gersdorff Jørgensen, L; Liu, Y; de Bruijn, I; Raaijmakers, J; Buchmann, K (July 2018). "Impact of Pseudomonas H6 surfactant on all external life cycle stages of the fish parasitic ciliate Ichthyophthirius multifiliis". Journal of Fish Diseases. 41 (7): 1147–1152. Bibcode:2018JFDis..41.1147A. doi:10.1111/jfd.12810. hdl:20.500.11755/42488b43-5220-4527-be1b-e192631f991d. PMID 29671884.
  10. ^ Burgess, P (2016). "The essential guide to whitespot". Practical Fishkeeping. 7: 60–63.
  11. ^ Andrews, Chris, 1953- (2010). Manual of fish health : everything you need to know about aquarium fish, their environment and disease prevention. Carrington, Neville., Exell, Adrian. (Rev. 2nd ed.). Richmond Hill, Ont.: Firefly Books. ISBN 978-1-55407-691-8. OCLC 578105245.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)