Salinity effects on anguillicolosis in Atlantic eels: a natural tool for disease control

Abstract

Anguillicolosis, the disease caused by the invasive nematode Anguillicoloides crassus, is one of the many threats facing the already endangered Atlantic eel species. We conducted a systematic review of literature data linking water salinity and prevalence of the infection during the continental phase of Anguilla anguilla and A. rostrata. Overall, we showed a significant negative relationship across all sites (r S = −0.42, n = 77). In order to limit the effect of confounding factors (e.g. variable latitudes and parasite introduction dates), we performed a meta-analysis on the correlation coefficients calculated from data within studies (restricted period and area) and revealed a stronger negative relationship ( -r = −0.75, n = 13). Finally, using our long-term monitoring in a French Mediterranean lagoon, we documented a step decrease in both parasite prevalence and induced swimbladder pathologies in response to increased salinity values. Salinity effects manifested with an apparent threshold value around 15 ‰ and are readily appreciable in young-of-the-year eels. To date, managing around water salinity parameters remains one of the best options to control the ever-expanding infection (both in aquaculture and in the wild) and to improve the quality of future spawners en route to the Sargasso Sea.

The Influence of Sex, Parasitism, and Ontogeny on the Physiological Response of European Eels (Anguilla anguilla) to an Abiotic Stressor

“…Although we have not analyzed the life stage of A. crassus infecting the tested specimens, it is possible that the tested eels could have been in an early onset of infection. The environmental characteristics of the system where eels lived (water temperature, water salinity) also played an important role on the results obtained as it is known that the spread, extent and intensity of infestation by A. crassus is dependent on water salinity and the age and size of the fish (Sures et al 2001;Lefebvre and Crivelli 2012). Differences in plasma cortisol levels between nonparasitized and parasitized specimens was strongly evident on female silver eels, even if overall there were no significant differences were found between the two life-stages.…”

Experimental immunology Influence of nematode Anguillicoloides crassus infestation on the cellular and humoral innate immunity in European eel ( Anguilla anguilla L.)

“…The extent and intensity of infestation is dependent on water salinity and the age and size of the fish. The nematode was noticed in brackish water and freshwater breeding farms [ 25 – 27 ]. The infestation prevalence in the European eel may be as high as 90-100% with a very high intensity of 30 nematodes in a single fish [ 28 – 30 ].…”

Climate change and aquaculture: considering biological response and resources

“…(Chen et al 2006) and to decrease infection with the parasitic nematode Anguillicoloides (= Anguillicola) crassus in Atlantic eels (Anguilla spp.) (Lefebvre & Crivelli 2012). Saltwater intrusion and storm surge-based flooding may also increase disease susceptibility of coastal freshwater species.…”