Validation of mollies and gilthead seabreams as new model organisms for the study of anisakids: Experimental infection and histological analysis of the infective process in sailfin molly

This study aims to propose new fish model organisms for experimental studies on anisakis and other fish pathogens as alternatives to the commonly used fish model Danio rerio (Hamilton, 1822). For this purpose, the sailfin molly ( Poecilia latipinna (Lesueur, 1821)) and the gilthead seabream ( Sparus aurata Linnaeus, 1758) were tested by experimental infections with Anisakis simplex s.l. larvae. Preliminary susceptibility challenges on mollies showed successful infections, with larvae observed up to 384 h post-infection (hpi). Histological analysis showed encapsulation of larvae and mild tissue damage in the infected fish, providing insight into the infection process. Two infection methods, oral ingestion and orogastric inoculation, were tested in both fish species. The results indicate successful infections with both methods, with higher prevalence and recovery rates observed with orogastric inoculation (especially in gilthead seabream). In addition, the study examined the chronology of the infective process, histological changes, and encapsulation patterns in infected fish. This comprehensive study highlights the suitability of sailfin molly as a model organism for experimental studies on anisakid infections and provides valuable insights into infection dynamics and host-parasite interactions. Further research in this area could contribute to the development of effective prevention and control measures for anisakid infections, and thus reduce the health risks associated with fish consumption.