Henneguya ictaluri
| Henneguya ictaluri | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Myxosporea |
| Order: | Bivalvulida |
| Family: | Myxobolidae |
| Genus: | Henneguya |
| Species: | H. ictaluri |
| Binomial name | |
| Henneguya ictaluri Pote, Hanson, & Shivaji, 2000 | |
Henneguya ictalyuri is a species of myxozoan parasite in the family Myxobolidae. It infects the channel catfish (Ictalurus punctatus) and is the primary causative agent of proliferative gill disease (PGD), an important parasitic disease of farmed catfish in the southeastern United States.
Discovery and taxonomy
Prior to the formal description of Henneguya ictaluri, the identity of the parasite responsible for proliferative gill disease (PGD) in farmed catfish was uncertain. The disease was suspected to have a myxozoan origin, because parasites that resembled Henneguya sp. were observed in histological samples from catfish with PGD.[1][2] Later studies instead associated PGD with an actinospore from the genus Aurantiactinomyxon, which was subsequently described as Aurantiactinomyxon ictaluri.[3][4]
In 2000, researchers found that inoculation of channel catfish with A. ictaluri actinospores resulted in the formation of typical PGD lesions followed by development of Henneguya myxospoers in the gills. Analysis of small-subunit ribosomal RNA sequences demonstrated that the actinospore and myxospore represented different stages of the same organism.[5]
Description
The mature myxospore, or spore, of H. ictaluri is similar to other members of the genus Henneguya, with an elongated spore body, two polar capsules, and two long caudal processes.[5]
Relationship to other cnidarians
Despite its microscopic parasitic form, H. ictaluri is an animal belonging to the phylum Cnidaria, which also contains jellyfish, corals, and sea anemones. Myxozoans are highly reduced cnidarians whose transition to obligate parasitism was accompanied by extensive reduction of their ancestral body plan and genome. Their relationship with other cnidarians is supported by molecular and phylogenomic studies and by the polar capsule, a distinctive structure that closely resembles the nematocyst, or stinging capsule, of other cnidarians.[6]
Life cycle
Henneguya ictaluri has a two-host life cycle involving the channel catfish and the freshwater oligochaete, Dero digitata.[5][7] The annelid worm, Dero digitata, serves as the definitive host of H. ictaluri. Within the worm, the parasite undergoes asexual reproduction before developing into actinospores, which are shed in the feces. Mature actinospores have three winglike processes that provide buoyancy, allowing them to float in the water to eventually infect catfish.[7] The actinospore stage has a brief infectious window, with infectivity decreasing substantially after one day.[8]
Actinospores enter channel catfish through several portals of entry, including the stomach, buccal cavity, and gills.[9] Following the initial infection, H. ictaluri spreads systemically throughout the catfish; however, developmental progression appears to only occur in parasites localized to the gills. At 24 hours, parasites are found primarily in the gastric mucosa and submucosa, but are also present in several other tissues and in the circulatory system. By 48 to 72 hours, parasite numbers begin decreasing in most organs and the remaining organisms appear to degenerate, while those in the gills continue to develop. By 96 hours post infection, parasites are found only in the gills, indicating the gills are the preferred site of development.[10]
In the gills, H. ictaluri undergoes further development and eventually forms plasmodia containing mature myxospores. Mature myxospores are released from infected fish, eventually infecting D. digitata, completing the two-host life cycle.[5]
Proliferative gill disease
Henneguya ictaluri is the primary etiologic agent of proliferative gill disease (PGD) in farm-raised channel catfish.[11] PGD is a significant cause for economic loss in the aquaculture industry in the southeastern United States. The characteristic swelling and hemorrhage give affected gills the appearance of raw hamburger meat, from which the name "hamburger gill disease" is derived.[12][11] Damaged gills cannot efficiently extract oxygen from the water, causing affected fish to exhibit severe respiratory distress or die, even when dissolved oxygen concentrations would normally be sufficient.[12] Mortality of as high as 100% has been reported in severe PGD outbreaks.[13]
PGD differs from most myxozoan diseases of fish in that clinical disease occurs as a result of initial parasite penetration and proliferation rather than during maturation of the myxospore stage.[8] The severity of PGD is influenced by continued exposure to the parasite, as fish transferred from infectious to parasite-free water showed a substantial recovery of damaged gill tissue.[8]
A real-time qPCR assay has been developed to detect H. ictaluri.[14]
References
- ↑ Kent, Michael L.; Duhamel, G.E.; Foott, J.S.; Hedrick, Ronald P. (1987). "Chronic branchitis (Hamburger gill disease) of channel catfish in California and its possible myxosporean etiology". California Fish and Game. 73: 99–105.
- ↑ Bowser, P.R.; Munson, A.D.; Jarboe, H.H.; Stiles, F.N. (1985). "In Transmission trials of proliferative gill disease in channel catfish (Ictalurus punctatus)". Mississippi Agricultural and Forestry Experiment Station Research Report. 10 (8).
- ↑ Burtle, G. J.; Harrison, L. R.; Styer, E. L. (1991). "Detection of a Triactinomyxid Myxozoan in an Oligochaete from Ponds with Proliferative Gill Disease in Channel Catfish". Journal of Aquatic Animal Health. 3 (4): 281–287. doi:10.1577/1548-8667(1991)003<0281:DOATMI>2.3.CO;2. ISSN 0899-7659.
- ↑ Bellerud, B. L.; Pote, L. M.; Lin, T. L.; Johnson, M. J.; Boyle, C. R. (1995). "Etiological and Epizootological Factors Associated with Outbreaks of Proliferative Gill Disease in Channel Catfish". Journal of Aquatic Animal Health. 7 (2): 124–131. doi:10.1577/1548-8667(1995)007<0124:EAEFAW>2.3.CO;2. ISSN 0899-7659.
- 1 2 3 4 Pote, L. M.; Hanson, L. A.; Shivaji, R. (2000-09-01). "Small Subunit Ribosomal RNA Sequences Link the Cause of Proliferative Gill Disease in Channel Catfish to Henneguya n. sp. (Myxozoa: Myxosporea)". Journal of Aquatic Animal Health. 12 (3): 230–240. doi:10.1577/1548-8667(2000)012<0230:SSRRSL>2.0.CO;2. ISSN 0899-7659.
- ↑ Chang, E. Sally; Neuhof, Moran; Rubinstein, Nimrod D.; Diamant, Arik; Philippe, Hervé; Huchon, Dorothée; Cartwright, Paulyn (2015-12-01). "Genomic insights into the evolutionary origin of Myxozoa within Cnidaria". Proceedings of the National Academy of Sciences of the United States of America. 112 (48): 14912–14917. doi:10.1073/pnas.1511468112. ISSN 1091-6490. PMC 4672818. PMID 26627241.
- 1 2 Tiwari, Ambika; Woodyard, Ethan T.; Rosser, T. Graham; Griffin, Matt J.; Mischke, Charles C. (2021-10-01). "Temperature Modulation and Feed Supplementation Significantly Improve Population Growth of Laboratory-Reared Dero digitata (Annelida: Naididae)". North American Journal of Aquaculture. 83 (4): 327–335. doi:10.1002/naaq.10201. ISSN 1522-2055.
- 1 2 3 Wise, David J.; Griffin, Matt J.; Terhune, Jeffrey S.; Pote, Linda M.; Khoo, Lester H. (2008). "Induction and evaluation of proliferative gill disease in channel catfish fingerlings". Journal of Aquatic Animal Health. 20 (4): 236–244. doi:10.1577/H08-023.1. ISSN 0899-7659. PMID 19306613.
- ↑ Gómez, Daniela; Bartholomew, Jerri; Sunyer, J. Oriol (2014). "Biology and mucosal immunity to myxozoans". Developmental and Comparative Immunology. 43 (2): 243–256. doi:10.1016/j.dci.2013.08.014. ISSN 1879-0089. PMC 4216934. PMID 23994774.
- ↑ Belem, A. M.; Pote, L. M. (2001-12-20). "Portals of entry and systemic localization of proliferative gill disease organisms in channel catfish Ictalurus punctatus". Diseases of Aquatic Organisms. 48 (1): 37–42. doi:10.3354/dao048037. ISSN 0177-5103. PMID 11843138.
- 1 2 Kelly, Anita M. (2020-04-07). "Proliferative Gill Disease". Alabama Cooperative Extension System. Retrieved 2026-08-17.
- 1 2 Mitchell, A.J.; Durborrow, R.M.; Crosby, M.D. (1998). "Proliferative Gill Disease (Hamburger Gill Disease)" (PDF). Southern Regional Aquaculture Center. Retrieved 2026-08-21.
- ↑ Beecham, Rachel V; Griffin, Matt J; LaBarre, Susan B; Wise, David; Mauel, Michael; Pote, Linda M W; Minchew, C Douglas (2010-07-01). "The Effects of Proliferative Gill Disease on the Blood Physiology of Channel Catfish, Blue Catfish, and Channel Catfish × Blue Catfish Hybrid Fingerlings". North American Journal of Aquaculture. 72 (3): 213–218. doi:10.1577/A09-034.1. ISSN 1522-2055.
- ↑ Griffin, Matt J.; Pote, Linda M.; Camus, Alvin C.; Mauel, Michael J.; Greenway, Terrence E.; Wise, David J. (2009-11-09). "Application of a real-time PCR assay for the detection of Henneguya ictaluri in commercial channel catfish ponds". Diseases of Aquatic Organisms. 86 (3): 223–233. doi:10.3354/dao02079. ISSN 0177-5103. PMID 20066957.