Anisakis pegreffii experimental challenge in Dicentrarchus labrax: An endoscopic study

To validate the use of imaging techniques to evaluate tissue damage in vivo, ten European sea bass (Dicentrarchus labrax) were anesthetized with MS-222 and experimentally infected with nematode larvae collected from three Lepidopus caudatus. Live nematode larvae were introduced by gastroscopy into the stomach of ten fish. Another challenge was performed 15 days later. After a 60 day period, an explorative celioscopy was carried out. Fish were examined for Anisakis larvae and biopsy samples were collected. Parasites sampled from L. caudatus and D. labrax were morphologically identified at genus level. Biopsy samples were routinely processed for histopathology. Some larvae were sampled for PCR. At gastroscopic exam 15 days after the first challenge some live nematode larvae were found within the lumen of the stomach in four fish. Two months later, at celioscopy, four sea bass showed hemorrhages and/or irregular neoformations within the celomic cavity. Within each of these changes a single nematode larva was detected. Histopathology showed hemorrhagic lesions with a cystic aspect. Parasite larvae were identified as L3 stages Anisakis Type I. PCR-RFLP analysis has allowed the identification of larvae isolated as Anisakis pegreffii. Endoscopy is a suitable noninvasive procedure for evaluation of experimental challenges in sea bass using live Anisakis larvae. The evidence of tissue change is an unusual occurrence in fish parasitized by Anisakis. The paper sets out to assess the damage anisakid nematodes induce in infected fish by imaging techniques.