Common name: Asian tapeworm
Synonyms and Other Names: Bothriocephalus aegyptiacus, Bothriocephalus gowkongensis, Bothriocephalus kivuensis, Bothriocephalus opsariichthydis, Bothriocephalus phoxini, Schyzocotyle fluviatilis, Schyzocotyle acheilognathi
available through www.itis.gov
Identification: Schyzocotyle acheilognathi is a cestode which parasitizes freshwater fish, particularly cyprinids (Marcogliese, 2008). It can be identified by a unique fleshy, arrow-head or heart shaped scolex (head region) with a relatively undeveloped terminal disc, and two anterolaterally directed bothria (slit-like openings) which are short and deep (Scholz, 1997). It has no neck; instead, proglottids (body segments) begin directly behind the scolex. The proglottids are relatively elongate and much narrower than the scolex (Scholz, 1997).
Native Range: Native to East Asia and China, Schyzocotyle acheilognathi was first described by S. Yamaguti in 1934 from Ogura Lake, Japan (Scholz, 1997).
Hydrologic Unit Codes (HUCs) Explained
Puerto Rico &
Interactive maps: Point Distribution Maps
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Schyzocotyle acheilognathi are found here.
Table last updated 7/27/2018
† Populations may not be currently present.
Ecology: Schyzocotyle acheilognathi has a less complex life cycle than many tapeworm species, requiring only one intermediate host before reaching its final host (Hansen et. al, 2007). The adult worm is an intestinal parasite in fish. It absorbs nutrients directly across the tegument (body covering), competing with the host animal for nutrition (Hansen et al., 2006).
Adult worms are hermaphroditic; each proglottid has a complete set of both male and female reproductive organs and produces eggs through self-fertilization. The eggs are shed into the water with the host's fecal material, where they hatch into free-swimming hexacanth (six-hooked) larvae. Eggs require water temperatures between 12ºC and 37ºC to hatch. Within this range, the amount of time required for hatching varies with water temperature. Eggs tend to hatch within 1-5 days at 28-30ºC, and within 10-28 days at 14-15ºC (Marcogliese, 2008).
The free-swimming larvae, called coracidia, are consumed by cyclopoid copepods (tiny crustaceans). They then burrow into the copepod's haemocoel (body cavity), where they develop into a second larval stage called a procercoid. This process also depends upon water temperature; larvae become able to infect their final host in 11-18 days at 29-31ºC, and in 49 days at 20ºC (Marcogliese, 2008). Schyzocotyle acheilognathi is a true generalist, infecting a wide vareity of hosts, which contributes to its invasiveness (Choudhury and Cole 2012, Scholz et al. 2012).
While fish are normally infected by consuming infected copepods, there is some evidence that adult worms can be transmitted directly to piscivorous fish that prey on infected fish (Hansen et al., 2007). Once within the host fish's intestine, the larvae mature into adult worms over the course of 21-23 days at 28-29ºC (Marcogliese, 2008).
Common Carp (Cyprinus carpio) and Grass Carp (Ctenopharyngodon idella) are the principle native hosts for the Asian tapeworm, but it has an extremely low degree of host specificity, and has been found in fish species from 12 families and 6 orders worldwide (Dove and Fletcher, 2000).
Means of Introduction: Schyzocotyle acheilognathi acheilognathi is likely to have been accidentally introduced with Grass Carp, one of its native hosts, and subsequently spread through the translocation of bait fish (Choudhury et al., 2006; Heckmann et al., 1993). For example, Heckmann et al. (1993) found infected minnows in four bait shops near Las Vegas, NV, that had originated from commercial ponds outside the state.
Status: This parasite has become widespread, and is known in several areas of the United States. It appears to be well established in the lower Colorado River and the Hawaiian islands (Choudhury et al., 2006), and has been reported in the Great Lakes (Marcogliese, 2008).
Impact of Introduction: Infection with Schyzocotyle acheilognathi acheilognathi has been shown to reduce a fish's ability to cope with stressors such as reduced food availability (Hansen, et al., 2006). Competing with intestinal parasites for nutrients may lead to reduced body condition, anemia, reduced growth and temperature-dependent mortality, especially in juvenile fish. Other known pathogenic effects include intestinal inflammation, protein depletion and altered digestive enzyme activity (Marcogliese, 2008).
S. acheilognathi is known to infect wild populations of the federally endangered Humpback Chub (Gila cypha), Mojave Tui Chub (Siphateles bicolor mohavensis), Virgin Roundtail Chub (Gila robusta seminuda), and Woundfin Minnow (Plagopterus argentissimus), as well as several other rare and/or endemic fishes in the western United States, including Virgin Spinedace (Lepidomeda mollispinis mollispinis), Roundtail Chub (Gila robusta), Arroyo Chub (Gila orcutta), and Tamaulipas Shiner (Notropis braytoni) (Bean et al., 2007; Clarkson et al. 1997; Heckmann et al., 1986; Warburton et al., 2002; Ward, 2005). The federally endangered bonytail chub (Gila elegans) has also been shown experimentally to be a suitable host (Hansen et al., 2006). The increased stress of tapeworm infection may severely complicate efforts at conservation and recovery for these species. In Hawaii, at least two of the five native freshwater fish species have been found to be infected (Font and Tate, 1994). This is concerning because geographic isolation makes Hawaiian species inherently vulnerable.
References: (click for full references)
Alexander, J. 2008. New tapeworm found in Great Lakes fish. LaCrosse Fish Health Center. http://www.fws.gov/midwest/LaCrosseFishHealthCenter/Documents/MskegonAsianTW.pdf
. Accessed 19 June 2012.
Bean, M. G. 2008. Occurrence and impact of the Asian fish tapeworm Bothriocephalus acheilognathi in the Rio Grande (Rio Bravo del Norte). MS Thesis. Texas State University, San Marcos.
Bean, M. G., A. Skerikova, T. H. Bonner, T. Scholz, and D. G. Huffman. 2007. First record of Bothriocephalus acheilognathi in the Rio Grande with comparative analysis of ITS2 and V4-18S rRNA gene sequences. Journal of Aquatic Animal Health 19: 71-76.
Brandt, F.W., J.G. Van As, H.J. Schoombee, and V.L. Hamilton-Attwell. 1981. The occurrence and treatment of bothriocephalosis in the common carp, Cyprinus carpio in fish ponds with notes on its presence in the largemouth yellowfish Barbus kimberleyensis from the Vaal Dam, Transvaal. Water SA 7:35-42.
Brouder, M. J., and T. L. Hoffnagle. 1997. Distribution and prevalence of the Asian fish tapeworm, Bothriocephalus acheilognathi, in the Colorado River and tributaries, Grand Canyon, Arizona, including two new host records. Journal of the Helminthological Society of Washington 64(2): 219-226.
Brouder, M. 1999. Relationship between length of roundtail chub and infection intensity of Asian fish tapeworm Bothriocephalus acheilognathi. Journal of Aquatic Animal Health 11(3):302-304.
Carpenter, S.R., J.J. Cole, J.R. Hodgson, J.F. Kitchell, M.L. Pace, D. Bade, K.L. Cottingham, T.E. Essington, J.N. Houser, and D.E. Schindler. 2001. Trophic cascades, nutrient, and lake productivity: Experimental enrichment of lakes with contrasting food webs. Ecological Monographs 71:163-186.
Choudhury, A., T.L. Hoffnagle, and R.A. Cole. 2004. Parasites of native and nonnative fishes in the Little Colorado River, Grand Canyon, Arizona. Journal of Parasitology 90:1042-1052.
Choudhury, A., E. Charipar, P. Nelson, J. R. Hodgson, S. Bonar, and R. A. Cole. 2006. Update on the distribution of the invasive Asian fish tapeworm, Bothriocephalus acheilognathi, in the U.S. and Canada. Comparative Parasitology 73(2): 269-273.
Choudury, A., R. Cole. 2012. Bothriocephalus acheilognathi Yamaguti (Asian tapeworm). Pages 389-404 in Francis, R.A. (Ed.), A Handbook of Global Freshwater Invasive Species. Earthscan, London.
Clarkson, R. W., A. T. Robinson, and T. L. Hoffnagle. 1997. Asian tapeworm (Bothriocephalus acheilognathi) in native fishes from the Little Colorado River, Grand Canyon, Arizona. Great Basin Naturalist 57(1): 66-69.
Dove, A. D. M., and A. S. Fletcher. 2000. The distribution of the introduced tapeworm Bothriocephalus acheilognathi in Australian freshwater fishes. Journal of Helminthology 74: 121-127.
Font, W. F., and D. C. Tate. 1994. Helminth parasites of native Hawaiian freshwater fishes: an example of extreme ecological isolation. Journal of Parasitology 80(5): 682-688.
Hansen, S. P., A. Choudhury, and R. A. Cole. 2007. Evidence of experimental postcyclic transmission of Bothriocephalus acheilognathi in bonytail chub (Gila elegans). Journal of Parasitology 93(1): 202-204.
Hansen, S. P., A. Choudury, D. M. Heisey, J. A. Ahumada, T. L. Hoffnagle, and R. A. Cole. 2006. Experimental infection of the endangered bonytail chub (Gila elegens) with the Asian fish tapeworm (Bothriocephalus acheilognathi): impacts on survival, growth and condition. Canadian Journal of Zoology 84: 1383-1394.
Heckmann, R. A., and J. E. Deacon. 1987. New host records for the Asian fish tapeworm, Bothriocephalus acheilognathi, in endangered fish species from the Virgin River, Utah, Nevada, and Arizona. Journal of Parasitology 73(1): 226-227.
Heckmann, R. A., J. E. Deacon, and P. D. Greger. 1986. Parasites of the woundfin minnow, Plagopterus argentissimus, and other endemic fishes from the Virgin River, Utah. Great Basin Naturalist 46(4): 662-676.
Heckmann, R. A., P. D. Greger, and R. C. Furtek. 1993. The Asian fish tapeworm, Bothriocephalus acheilognathi, in fishes from Nevada. Journal of the Helminthological Society of Washington 60(1): 127-128.
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Lafferty, K.D., and A.K. Morris. 1996. Altered behavior of parasitized killifish increases susceptibility to predation by bird final hosts. Ecology 77(5):1390-1397.
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Vincent, A. G., and W. F. Font. 2003. Host specificity and population structure of two exotic helminths, Camallanus cotti (Nematoda) and Bothriocephalus acheilognathi (Cestoda), parasitizing exotic fishes in Waianu Stream, O'ahu, Hawai'i. Journal of Parasitology 89(3): 540-544.
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Hejna, M. A.K. Bogdanoff, A. Fusaro, S. Iott and R. Sturtevant
Revision Date: 8/17/2018
Hejna, M. A.K. Bogdanoff, A. Fusaro, S. Iott and R. Sturtevant, 2019, Schyzocotyle acheilognathi (Yamaguti, 1934): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=2798, Revision Date: 8/17/2018, Access Date: 1/21/2019
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.