A survey aimed at mapping the 'Anisakis risk' in anchovies (Engraulis encrasicolus) and sardines (Sardina pilchardus) caught off the Ligurian and north-western Adriatic coasts

AIM. According to EFSA Scientific Opinion on Risk Assessment of Parasites in Fishery Products (2010), all wild fish should be considered at risk of containing any viable zoonotic parasites if these products are to be eaten raw or almost raw, pointing out the need to carry out epidemiological surveys on presence/diffusion of zoonotic parasites in all fishery grounds. Therefore surveys aimed at mapping the presence of zoonotic anisakids, i.e. Anisakis spp., in commercially important fish are strongly encouraged. Since most of the cases of human Anisakiasis reported till now in Italy have been referred mainly to consumption of marinated/pickled anchovies and/or sardines, a quali-quantitative parasitological survey has been carried out on these two species from different Italian fishing areas. MATERIALS AND METHODS. From October 2010 to February 2012 a total of 3808 anchovies (Engraulis encrasicolus) and 2636 sardines (Sardina pilchardus) caught off the Ligurian and north-western Adriatic coasts were examined for the presence of anisakid larvae (see Table 1). Fishing areas were identified by geographic coordinates. All the anisakids recovered during the survey were fixed in 70% ethanol, cleared and identified at genus level by light microscope. A representative pool of larvae was subjected to molecular identification by PCR-RFLP of ITS rRNA using restriction enzymes HinfI e HaeIII. Data on localization, viability and number of anisakid larvae were recorded. Prevalence and mean intensity MI) were calculated as suggested by Bush AO et al. (1997, J Parasitol, 83: 575-583). RESULTS. Anisakid larvae have been detected in 791 (20.8%) anchovies and 531 (20.1%) sardines. Among anisakids, Anisakis sp. larvae were detected in 111 (2.9%) anchovies and 5 (0.2%) sardines, while Hysterothylacium sp. larvae, considered nonpathogenic to humans, were found in 703 (18.5%) anchovies and 526 (20%) sardines. Striking differences in prevalence values were observed among fishing areas and fish species. Sardines showed very low infection rates by Anisakis larvae (0-0.3%) from all fishing areas, while anchovies from Ligurian sea showed Anisakis prevalence values higher than those from northern Adriatic sea (0.9-9.8 vs. 0-0.8%). Hysterothylacium larvae were found in all the batches examined, with prevalence ranging from 2.3 to 46.3%. MI of Anisakis larvae was generally around 1, except for anchovies from Imperia (2.5), and MI of Hysterothylacium between 1 and 2.9, with highest values in Adriatic fish. Larvae were always viable and located in body cavity. Molecular analyses allowed to identify all the Anisakis larvae as owing to the species A. pegreffii, except for a specimen identified as an A. pegreffii/A. simplex hybrid, and all the Hysterothylacium larvae as H. aduncum. CONCLUSIONS. The results of this survey showed a very low Anisakis risk in anchovies caught off north-western Adriatic coast and in sardines from all the fishing areas under study. However, it should be stressed that prevalence values observed in anchovies from Ligurian sea (0.9-9.8%) were strongly lower than those reported by Rello FJ et al. (2009, Int J Food Microbiol, 129: 277-281) who found Anisakis sp. larvae in 21.88% of anchovies from Ligurian sea, but examining just 64 fish “landed at La Spezia and Piombino”. Influence of fish population structuring and dynamics, host ecological/trophic attitude and hydrogeographical factors are discussed in relation to the parasitological findings.