Scuticociliatosis

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Scuticociliatosis is a severe and often fatal parasitic infection of several groups of marine organisms. Species known to be susceptible include a broad range of teleosts, seahorses, sharks, and some crustaceans. The disease can be caused by any one of about 20 distinct species of unicellular eukaryotes known as scuticociliates, which are free-living marine microorganisms that are opportunistic or facultative parasites. Scuticociliatosis has been described in the wild, in captive animals in aquariums, and in aquaculture. It is best studied in fish species that are commonly farmed, in which typical effects of infection include skin ulceration, hemorrhage, and necrosis, with post-mortem examination identifying ciliates in the skin, gills, blood, and internal organs including the brain. [1] [2]

Contents

Host range

Scuticociliatosis has been reported in a broad range of teleosts; it is best studied in those teleost fish commonly raised in aquaculture, where the disease is of significant economic impact. It has also been reported in seahorses, sharks, and crustaceans. The mortality rate is particularly high among flatfish, possibly due to their sedentary lifestyle involving skin-to-skin contact between individuals. [1]

Disease mechanism

Scuticociliatosis consists of overwhelming infection of an animal's body by any one of around 20 species of scuticociliate. These unicellular organisms are free-living in marine environments but are opportunistic parasites with a diverse host range. It is unclear what triggers infection, although infection rates are known to be higher, in both experimental and aquaculture conditions, in warmer water. [1] Low salinity has also been reported to reduce disease rates. [3] Under some conditions, ciliates have been reported to successfully infect healthy fish, likely through the gills; [2] other reports suggest abrasions or skin damage may be required. [4] Scuticociliates are histophagous (tissue-eating) and extensively degrade body tissues. Histological postmortem examination of affected fish usually reveals ciliates in the skin and gills, blood, and internal organs, with significant damage to the brain and nervous system, which is likely responsible for behaviors such as abnormal swimming in infected individuals. [1]

Causative agents

The exact species of scuticociliate responsible for a given outbreak is often not identified. As a result, differences in virulence and disease course among different scuticociliates are not well characterized. In one study, infection by Miamiensis avidus was reported to have a higher mortality rate than Pseudocohnilembus persalinus , Pseudocohnilembus hargisi and Uronema marinum . [5] Infections by U. marinum show a less severe disease course, possibly restricted to the skin surface; it has been suggested that this ciliate may be only a secondary pathogen. [1] M. avidus, P. persalinus, U. marinum, and U. nigricans have all been reported in aquaculture settings. [3]

Outbreaks

Scuticociliatosis outbreaks are recurring problems in fisheries, especially of olive flounder. Outbreaks in both aquaculture and natural settings are more common in the spring and summer, when water temperature is higher. [1] Outbreaks have also been identified in captive settings; in one aquarium an outbreak of M. avidus was responsible for the deaths of six sharks. [6]

Scuticociliatosis due to Miamiensis avidus infection is believed to be responsible for a 2017 die-off of fish and leopard sharks found in the San Francisco Bay. [7]

Treatment and prevention

There is no treatment for scuticociliatosis once parasites have infected an animal's internal organs. In aquaculture settings, chemical treatment of the water to kill ciliates can be used in conjunction with antibiotics. [1]

Related Research Articles

<i>Ichthyophthirius multifiliis</i> Parasitic species of protozoan

Ichthyophthirius multifiliis, often termed "Ich", is a parasitic ciliate described by the French parasitologist Fouquet 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 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.

Perkinsus marinus is a species of alveolate belonging to the phylum Perkinsozoa. It is similar to a dinoflagellate. It is known as a prevalent pathogen of oysters, causing massive mortality in oyster populations. The disease it causes is known as dermo or perkinsosis, and is characterized by the degradation of oyster tissues. The genome of this species has been sequenced.

<i>Myxobolus cerebralis</i> Species of parasite

Myxobolus cerebralis is a myxosporean parasite of salmonids that causes whirling disease in farmed salmon and trout and also in wild fish populations. It was first described in rainbow trout in Germany in 1893, but its range has spread and it has appeared in most of Europe, the United States, South Africa, Canada and other countries from shipments of cultured and wild fish. In the 1980s, M. cerebralis was found to require a tubificid oligochaete to complete its life cycle. The parasite infects its hosts with its cells after piercing them with polar filaments ejected from nematocyst-like capsules. This infects the cartilage and possibly the nervous tissue of salmonids, causing a potentially lethal infection in which the host develops a black tail, spinal deformities, and possibly more deformities in the anterior part of the fish.

<span class="mw-page-title-main">Velvet (fish disease)</span> Parasitic disease of fish

Velvet disease is a fish disease caused by dinoflagellate parasites of the genera Amyloodinium in marine fish, and Oodinium in freshwater fish. The disease gives infected organisms a dusty, brownish-gold color. The disease occurs most commonly in tropical fish, and to a lesser extent, marine aquaria. Periodic use of preventive treatments like aquarium salt can further deter parasites. Regular monitoring, attentive care, and preventive measures collectively contribute to keeping fish healthy and velvet-free.

<span class="mw-page-title-main">Sea louse</span> Family of copepods

Sea lice are copepods of the family Caligidae within the order Siphonostomatoida. They are marine ectoparasites that feed on the mucus, epidermal tissue, and blood of host fish. The roughly 559 species in 37 genera include around 162 Lepeophtheirus and 268 Caligus species.

<span class="mw-page-title-main">Xenoma</span> Growth caused by various species of protists and fungi

A xenoma is a growth caused by various protists and fungi, most notably microsporidia. It can occur on numerous organisms; however is predominantly found on fish.

<i>Cryptocaryon</i> Genus of single-celled organisms

Cryptocaryon irritans is a species of ciliates that parasitizes marine fish, causing marine white spot disease or marine ich. It is one of the most common causes of disease in marine aquaria.

Brooklynella hostilis is a parasite of marine fish, found in wild fish, farmed fish and aquariums. It is kidney-bean shaped, and approximately 60–80 μm long, with bands of cilia. B. hostilis is the only species in the monotypic taxon Brooklynella, a genus in the order Hartmannulidae. It reproduces by binary fission.

<span class="mw-page-title-main">Protozoan infection</span> Parasitic disease caused by a protozoan

Protozoan infections are parasitic diseases caused by organisms formerly classified in the kingdom Protozoa. These organisms are now classified in the supergroups Excavata, Amoebozoa, Harosa, and Archaeplastida. They are usually contracted by either an insect vector or by contact with an infected substance or surface.

Dermocystidium is a genus of cyst-forming, eukaryotic fish parasites, the causative agents of dermocystidiosis.

<span class="mw-page-title-main">Fish diseases and parasites</span> Disease that affects fish

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Megalocytivirus is a genus of viruses in the family Iridoviridae and one of three genera within this family which infect teleost fishes, along with Lymphocystivirus and Ranavirus. Megalocytiviruses are an emerging group of closely related dsDNA viruses which cause systemic infections in a wide variety of wild and cultured fresh and saltwater fishes. Megalocytivirus outbreaks are of considerable economic importance in aquaculture, as epizootics can result in moderate fish loss or mass mortality events of cultured fishes.

Amyloodinium ocellatum is a cosmopolitan ectoparasite dinoflagellate of numerous aquatic organisms living in brackish and seawater environments. The dinoflagellate is endemic in temperate and tropical areas, and is capable of successfully adapting to a variety of different environments and to a great number of hosts, having been identified in four phyla of aquatic organisms: Chordata, Arthropoda, Mollusca and Platyhelminthes. Moreover, it is the only dinoflagellate capable of infecting teleosts and elasmobranchs.

Scuticociliatia is a subclass of ciliates in the class Oligohymenophorea. Its members are called scuticociliates. These unicellular eukaryotes are microorganisms that are usually free-living and can be found in freshwater, marine, and soil habitats. Around 20 members of the group have been identified as causative agents of the disease scuticociliatosis, in which the ciliates are parasites of other marine organisms. Species known to be susceptible include a broad range of teleosts, seahorses, sharks, and some crustaceans.

<span class="mw-page-title-main">Uronematidae</span> Family of single-celled organisms

Uronematidae is a family of ciliates in the order Philasterida.

Miamiensis avidus is a species of unicellular marine eukaryote that is a parasite of many different types of fish. It is one of several organisms known to cause the fish disease scuticociliatosis and is considered an economically significant pathogen of farmed fish. M. avidus is believed to be the cause of a 2017 die-off of fish and sharks in the San Francisco Bay.

<i>Philasterides dicentrarchi</i> Species of single-celled organism

Philasterides dicentrarchi is a marine protozoan ciliate that was first identified in 1995 after being isolated from infected European sea bass reared in France. The species was also identified as the causative agent of outbreaks of scuticociliatosis that occurred between summer 1999 and spring 2000 in turbot cultivated in the Atlantic Ocean. Infections caused by P. dicentrarchi have since been observed in turbot reared in both open flow and recirculating production systems. In addition, the ciliate has also been reported to cause infections in other flatfishes, such as the olive flounder in Korea and the fine flounder in Peru, as well as in seadragons, seahorses, and several species of sharks in other parts of the world.

Cyvirus anguillidallo1, also known as Anguillid herpesvirus 1 (AngHV-1) is a species of virus in the genus Cyprinivirus, family Alloherpesviridae, and order Herpesvirales.

Philasteridae is a family of ciliates in the order Philasterida.

Philasterides is a genus of ciliates in the order Philasteridae.

References

  1. 1 2 3 4 5 6 7 Jung, Sung-Ju; Woo, Patrick T.K. (2012). "Chapter 5: Miamiensis avidus and related species". In Woo, Patrick T.K.; Buchmann, Kurt (eds.). Fish parasites: pathobiology and protection . Wallingford, Oxfordshire: CABI. pp.  73-91. ISBN   9781845938062.
  2. 1 2 Jung, SJ; Kitamura, SI; Song, JY; Oh, MJ (18 January 2007). "Miamiensis avidus (Ciliophora: Scuticociliatida) causes systemic infection of olive flounder Paralichthys olivaceus and is a senior synonym of Philasterides dicentrarchi". Diseases of Aquatic Organisms. 73 (3): 227–234. doi: 10.3354/dao073227 . PMID   17330742.
  3. 1 2 Yokoyama, Hiroshi; Itoh, Naoki; Ogawa, Kazuo (2015). "Fish and Shellfish Diseases Caused by Marine Protists". In Ohtsuka, Susumu; Suzaki, Toshinobu; Horiguchi, Takeo; Suzuki, Noritoshi; Not, Fabrice (eds.). Marine Protists: Diversity and Dynamics. Springer. pp. 533–550. ISBN   9784431551300.
  4. ↑ Paramá, A; Iglesias, R; Álvarez, M.F; Leiro, J; Aja, C; Sanmartı́n, M.L (March 2003). "Philasterides dicentrarchi (Ciliophora, Scuticociliatida): experimental infection and possible routes of entry in farmed turbot (Scophthalmus maximus)". Aquaculture. 217 (1–4): 73–80. Bibcode:2003Aquac.217...73P. doi:10.1016/S0044-8486(02)00523-9.
  5. ↑ Song, JY; Kitamura, SI; Oh, MJ; Kang, HS; Lee, JH; Tanaka, SJ; Jung, SJ (12 February 2009). "Pathogenicity of Miamiensis avidus (syn. Philasterides dicentrarchi), Pseudocohnilembus persalinus, Pseudocohnilembus hargisi and Uronema marinum (Ciliophora, Scuticociliatida)". Diseases of Aquatic Organisms. 83 (2): 133–143. doi: 10.3354/dao02017 . PMID   19326794.
  6. ↑ Stidworthy, M. F.; Garner, M. M.; Bradway, D. S.; Westfall, B. D.; Joseph, B.; Repetto, S.; Guglielmi, E.; Schmidt-Posthaus, H.; Thornton, S. M. (17 June 2013). "Systemic Scuticociliatosis (Philasterides dicentrarchi) in Sharks". Veterinary Pathology. 51 (3): 628–632. doi: 10.1177/0300985813492800 . PMID   23774745.
  7. ↑ Shaban, Bigad; Witte, Rachel; Horn, Michael. "Thousands of Sharks, Other Sea Life Mysteriously Die in San Francisco Bay". NBC Bay Area. Retrieved 25 November 2017.
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