In vitro testing of alternative synthetic and natural antiparasitic compounds against the monogenean sparicotyle chrysophrii

Gill monogenean Sparicotyle chrysophrii is considered the most detrimental fish parasite to the Mediterranean aquaculture. Treatment of sparicotylosis relies on frequent gill inspections correlated with the seasonal increase in seawater temperature, application of functional feeds, and treatments with formalin baths where permitted. While the latter is bound to be banned in Europe, other synthetic anthelminthics, such as praziquantel and ivermectin, are prone to induce resistance in the parasites. Therefore, we investigated, in vitro, 14 synthetic and natural compounds against adult S. chrysophrii, developing dose–response modelsm and estimated toxicity levels at 20%, 50%, and 80% parasite mortality. Bactericidal activity of target compounds was also tested in two important aquaculture bacteria; Vibrio harveyi and V. anguillarum, while their potential host toxicity was evaluated in gilthead seabream SAF-1 cell line. Synthetic compound bithionate sodium exerted the most potent toxicity against the monogenean, no host cytotoxicity, and a medium and high potency against two bacterial pathogens. In comparison, target natural compounds were approximately 20 (cedrol) or up to 154 times (camphor) less toxic for the monogenean. Rather than completely dismissing natural compounds, we suggest that their application in combination with synthetic drugs, especially if administered in the feed, might be useful in sparicotylosis treatment

Transfer of Sparicotyle chrysophrii and Ceratothoa oestroides between wild and aquaculture fish inferred by ddRAD sequencing

Comunicación presentada en la 19th International Conference on Diseases of Fish and Shellfish, celebrada en Oporto (Portugal) del 9 al 12 de septiembre de 2019.[Introduction]: The monogenean Sparicotyle chrysophrii and the cymothoid isopod Ceratothoa oestroides are among the most devastating ectoparasites in Mediterranean aquaculture, causing losses in gilthead sea bream (Sparus aurata) and European sea bass (Dicentrarchus labrax) production. Their life cycles and modes of transmission have not been fully elucidated and molecular resources for their investigation are extremely scarce. Being attracted by signals from conspecifics in aquaculture installations, the food and shelter availability in the farms, wild fish are generally recognised as reservoirs for parasite transmission to farmed fish. Viceversa, cultured stocks may also act as reservoirs of infectious stages, as they are present in concentrated numbers and density, and potentially more susceptible to disease than wild fish.[Methodology]: The potential extent of transmission of these two ectoparasites between wild and farmed fish populations has been evaluated by genotyping-by-sequencing approach, double digest Restriction-site Associated DNA sequencing (ddRAD-Seq), to generate a genome-wide SNP marker dataset. Parasites sampling was done across four large Mediterranean farming areas in Spain, Italy, Croatia and Greece, representing the largest collection of genotypes obtained from aquaculture and wild fish populations (n = 600).[Results]: Expectedly, a considerable variability in number of reads, polymorphic loci and SNPs between individuals for both species was observed, while transfer between wild and reared parasite population was more enhanced in case of the isopod. [Conclusion]: The results provide a baseline for the development of new ecological and epidemiological measures for mitigation of two parasites, as the observed transfer seems to be highly conditioned by parasite and environment traits

Mediterranean-wide SNPs of two aquaculture-important ectoparasites, Sparicotyle chrysophrii and Ceratothoa oestroides, developed by ddRAD sequencing

Trabajo presentado en la conferencia Molecular Helminthology: An Integrated Approach, celebrada en San Antonio (Estados Unidos) del 7 al 10 de abril de 2019.Parasite transmission between wild and farmed fish is poorly understood and controversial, although it has important implications for the reliable and sustainable use of aquatic resources. Wild fish are usually attracted by signals from conspecifics, the food and shelter availability in the farms, and general understanding is that they act as reservoirs for parasite transmission. In addition, cultured stocks may also act as reservoirs of infectious stages in the environment, as they are present in concentrated numbers and density, and potentially more susceptible to disease than wild fish. The monogenean Sparicotyle chrysophrii and the cymothoid isopod Ceratothoa oestroides are recognised as the most devastating ectoparasites in Mediterranean aquaculture, causing losses in gilthead sea bream (Sparus aurata) and European sea bass (Dicentrarchus labrax) production. Their life cycles and modes of transmission for both ectoparasites have not been fully elucidated and molecular resources for their investigation are extremely scarce. In order to analyse the potential extent of transmission of these two ectoparasites between wild and farmed fish populations, we have used a genotyping-bysequencing approach, double digest Restriction-site Associated DNA sequencing (ddRAD-Seq), to generate a genome-wide SNP marker dataset. Parasites sampling was done across four large Mediterranean farming areas in Spain, Italy, Croatia and Greece, representing the largest collection of genotypes obtained from aquaculture and wild fish populations. Expectedly, we observed a considerable variability in number of reads, polymorphic loci and SNPs between individuals for both species. The results provide a baseline for the development of new ecological and biological studies of these species, using new genomic tools and resources