Anguillicola crassus in the Baltic Sea: field data supporting transmission in brackish waters

The effect of salinity on hatching, larval survival and infectivity of Anguillicola crassus was studied under experimental conditions using eggs obtained from naturally infected eels. Egg hatching rate, second-stage larval survival and larval infectivity were maximal in fresh water and declined with increase in salinity. Larvae survived up to 100 d in fresh water, 70 d in 50% sea water and 40 d in 100% sea water. Infectivity experiments demonstrated that salinity influenced transmission success throughout the life cycle by decreasing total infectivity of the larval population in utero within female A , crassus and when larvae were free-living in the aquatic environment. Infectivity was agedependent in relation to salinity. Larvae were infective to intermediate and paratenic hosts for up to 80 d in fresh water, 21 d in 50% sea water and up to 8 d in 100% sea water. The data confirm field observations that infection levels decrease with an increase in salinity. The study contributes to experimental verification of the colonization abilities of A. crassus and supports the hypothesis that A. crassus can be disseminated and transmitted in brackish water. The importance of regular monitoring and stringent hygiene practices in the transportation of eels is emphasised.

Section: Discussionmentioning

confidence: 99%

Effect of salinity on hatching, survival and infectivity of Anguillicola crassus (Nematoda:Dracunculoidea) larvae

Kirk¹,

Kennedy²,

Lewis³

2000

“…The current range of A. crassus may be related to the movement and distribution of intermediate and paratenic hosts, which are believed to be the main mechanisms behind the parasite's rapid dispersal in European eels considering the extensive range of both types of transitional hosts (Moravec 1992, Moravec & Skoríková 1998. Deep snout pipefish and black goby have been naturally infected with nematodes in the Baltic Sea, confirming freshwater, estuarine, and marine infections (Reimer et al 1994). This supports the hypothesis that the parasite is not restricted to freshwater and can potentially be transferred to new locations through all salinity regimes and through many paratenic hosts (reviewed by Taraschewski 2006).…”

Section: Discussionmentioning

confidence: 99%

Distribution, prevalence, and intensity of the swim bladder parasite Anguillicola crassus in New England and eastern Canada

Aieta

Oliveira

2009

In the summer of 2005, yellow phase American eels Anguilla rostrata were examined for the swim bladder parasite Anguillicola crassus from 26 locations in New England, USA, ranging from the Pawcatuck River, Rhode Island, to the East Machias River, Maine. An additional 12 sites were sampled within Canada during the summers of 2006 and 2007: 7 sites in southern Nova Scotia and 5 sites within the St. Lawrence River system. In 2007, eels were also obtained from New Brunswick, northern Nova Scotia, Prince Edward Island, and Newfoundland through the commercial eel fishery. All locations in Rhode Island (n = 3) and Massachusetts (n = 10) and 7 in Maine (n = 13) had infected eels, with parasite prevalence ranging from 7 to 76%. No eels sampled from southern Nova Scotia or the St. Lawrence River system were infected with the parasite. New Brunswick and northern Nova Scotia had infected eels ranging from 3 to 30% parasite prevalence, with Cape Breton, Nova Scotia, being the furthest north the parasite has been reported in American eels. There was no significant relationship between parasite prevalence and latitude. The present study supports the hypothesis that the parasite is capable of expanding its range further into the Maritimes and could potentially reach the St. Lawrence River system.

“…The life cycle of A. crassus involves mainly cyclopid copepods as intermediate hosts (Egusa 1979, De Charleroy et al 1990, Kennedy & Fitch 1990, Bonneau et al 1991, Thomas 1993, Wiirtz et al 1996 as well as other crustaceans (Petter et al 1990, Bonneau et al 1991, Thomas 1993, Moravec & Konecny 1994. About 30 fish species are known to serve as paratenic hosts, which has further facilitated the spread of A. crassus (De Charleroy et al 1990, 1991, Thomas & Ollevier 1992a, Moravec & Konecny 1994, Pazooki & Szekely 1994, Reimer et al 1994, Szbkely 1994, 1995, Szkkely et al 1996. Additionally, at least one species of aquatic snails can act as paratenic host for A. crassus (Moravec 1996).…”

Section: Introductionmentioning

confidence: 99%

Distribution and prevalence of Anguillicola crassus (Nematoda) in eels Anguilla anguilla of the rivers Rhine and Naab, Germany

Würtz¹,

Knopf²,

Taraschewski³

1998

Over a period of 2 yr eels were collected at several sites along the river Rhine as well as from adjacent waters and examined for Anguillicola crassus in the swimbladder. Additionally eels were collected once from a site on the river Naab (Danube system). All eels were searched for both juvenile and adult stages of A. crassus, revealing prevalences of 80 % in eels from the river Rhine and 39% in eels from the river Naab. The mean intensities were 5.6 and 7.7, respectively. With respect to the prevalence and mean intensity of infection, no significant differences were observed between the different sampling sites in the Rhine system. Neither the prevalence nor the intenslty showed significant seasonal patterns. Further, no correlation between the condition factor of the eels and intensity of infection with A. crassus could be found. Of all eels examined, 28 O/o showed pathological alterations of the swimbladder.