The adult nematode Anguillicola crassus is covered by a soft wrinkled outer cuticle with males measuring 20-60mm and females measuring 47-71.5 mm. The mouth has a circular opening surrounded by 4 cephalic papillae and 2 lateral amphids. Males have 6 pairs of caudal papillae. Females posses a cone-shaped vuvla on the posterior end of the body and a white uterus which occupies most of the body housing copious amounts of eggs.
Symptoms: Infection from A. crassu can occur as early as the glass eel stage resulting in acute inflammatory reactions such as fibrosis and fibrotic conglomerates in the swimbladder. Scar tissue build up causes constriction of the intestine and can lead to rupture of the swimbladder. This emaciation from the swimbladder rupture can increase risk of bacterial infection resulting in increased mortality rate. Further vulnerability to bacterial infection results from increased cortisol levels when infected with this nematode.
Host(s): European eel (Anguilla anguilla), American eel (Anguilla rostrata), and the Japanese eel (Anguilla japonica)
Ecological Threat: Anguillicola crassus is hearty and aggressive colonizer resulting from a large egg production and low intermediate host specificity. Reports of infestation in 1989 went from 10% to 50% within a one year time period. With the American eel population already declining, the introduction of this nematode may have a large negative impact on survival of this species. This is a result of reduced swimming ability from infection rendering the eel vulnerable to predators such as the cormorant. Moralities have been reported in eel farms in addition to reduced growth rate, which has a large impact on economic output of the eel farm.
History: It is believed that A. crassus was transported to Europe from Taiwan in the 1980's within a shipment of eels. By the late 90's the nematode was seen throughout Europe and had become established with high prevalence in the European eel.
Native Origin: Southeast Asia
U.S. Present: New York, Delaware, Maryland, North Carolina, South Carolina, and Florida.
Not yet reported
Other nematodes due to overall body shape.
The main vector of dispersal has been identified as humans. It is important to monitor and quarantine eel farms to prevent further spread of this nematode. Providing information and awareness is the only management method currently. If an infection is suspected it is important to notify local authorities and prevent uncontrolled migration when possible.
Ashworth, S. T., and Blanc, G., 1997. Anguillicola crassus, a recently introduced aggressive colonizer of European eel stocks. Bulletin Francais de la Peche et de la Pisciculture 344/345: 335-342.
Barse, Ann M., Scott A. McGuire, Melissa A Vinores, Laura E. Eierman, and Julie A. Weeder. 2001. The swimbladder nematode Anguillicola crassus in American Eels (Anguilla rostrata) from middle and upper regions on Chesapeake Bay. Journal of Parasitology 87(6): 1366-1370.
Belpaire, C., De Charleroy, D., Thomas, K., van Damme, P. and Ollevier, F. 1989. Effects of eel restocking on the distribution of the nematode Anguillicola crassus in Flanders, Belgium. Journal of Applied Ecolology 5: 151-153.
Evans, D. W., and M. A. Matthews. 1999. Anguillicola crassus (Nematoda, Dracunculoidea); first documented record of this swimbladder parasite of eels in Ireland. Journal of Fish Biology 55: 665-668.
Kennedy, C. R., and Fitch, D. J., 1990. Colonization, larval survival and epidemiology of the nematode Anguillicola crassus, parasitic in the eel, Anguilla anguilla, in Britain. Journal of Fish Biology 36: 117-131.
Koops, H., & Hartmann, F., 1989. Anguillicola infestations in Germany and in German eel imports. Journal of Applied Ichthyology 1: 41-45.