Anguillicolosis: dynamics of the infection over two decades

Abstract

The dynamics of the infection of the European eel Anguilla anguilla L. by the Asian nematode Anguillicola crassus Kuwahara, Niimi and Itagaki, 1974 (i.e. anguillicolosis) was monitored over 2 decades in an oligohaline canal in southern France (Camargue, Mediterranean coast). Since the first mention of the parasite in this canal in 1985, which was also the first record in France, prevalence of pre-adult and adult forms has risen from 32 to 73%. However, during the last 7 yr (1997 to 2003), prevalence seems to have stabilized around values of 60 to 70% and parasite load, though inter-annual variation is substantial, shows no sign of increase (intensity for the last 5 yr: min. = 3.70, max. = 9.66, mean = 6.01). Our results thus confirm the dynamic pattern observed elsewhere in Europe, i.e. a rapid spread following the introduction of the parasite in a water system and then stabilization around ceiling levels. We review possible mechanisms that may explain such a leveling off in the infection spread. We particularly document the possibility that repetitive infections may render the infected organ, i.e. the swimbladder, unsuitable for further A. crassus establishment. In support of this hypothesis, we showed that the infection rate is lower among eels with severely damaged swimbladders.

Contamination, parasitism and condition of Anguilla anguilla in three Italian stocks

“…In the case of France, Spain and Italy, only few works have been recently published about the status of local eel stocks (Bordajandi et al 2003;Buet et al 2006;Ferrante et al 2010) and little is known about the past decades (Bressa et al 1997). A. crassus has been extensively monitored in the Camargue Lagoon and in other Mediterranean inland and coastal waters (Lefebvre et al 2002(Lefebvre et al , 2003Lefebvre and Crivelli 2004;Maillo et al 2005;Genc et al 2005;Esteve and Alcaide 2009). Other than a few notable exceptions, the quality of eels fished and farmed in the coastal areas of the rest of the Southern Europe and Northern Africa is almost unknown (Maamouria et al 1999;Rahhou et al 2001;Gargouri Ben Abdallah and Maamouria 2006).…”

Impact of Tide Gates on the Migration of Adult European Eels, Anguilla anguilla

“…Delay extends the migratory period, while avoidance and exploration uses energy that might be otherwise allocated to gamete development (Van den Thillart and Dufour 2009) or the 5000 to 6000 km oceanic migration to spawning grounds in the Sargasso Sea (Tesch 2003). The impact of delay, acting through increased energetic expense, may be exacerbated for those eels already compromised through infection with the invasive parasite Anguillicoloides crassus (Höglund et al 1992) which may be present in up to 90% of the eel population in most European systems (Lefebvre and Crivelli 2004). Further, due to accumulation of fish delayed at structures, the potential for parasite disease transfer is also enhanced (Garcia de Leaniz 2008), as is the risk of predation by species such as cormorants, Phalacrocorax carbo, Keller 1995) and otters, Lutra lutra, (Jenkins and Harper 1980) both of which are known to frequent the study site.…”

Biogeographical Relationships of the Eel Parasite Anguillicola Crassus Revealed by Random Amplified Polymorphic Dna Markers (Rapds)

“…However, only one recent work (LEFEBVRE and CRIVELLI, 2004) present a long term series of epidemiological data. However, there is still a need in long term studies to have a better estimation of the virulence evolution.…”