Abstract
Anisakiasis is a problematic zoonotic infection associated with the consumption of raw or undercooked fish. Atlantic mackerel (Scomber colias) is of high commercial interest in Portugal and has been reported as a common host of Anisakisspp. In this study, the occurrence of anisakids is evaluated in S. colias and also Scomber scombrus, and the potential zoonotic risk associated with consumption of these two fishes is evaluated according to the recorded infection levels. These were found to be high for both fish species: a mean intensity and prevalence of 21.7 worms/fish and 85% for S. colias, and 16.4 worms/fish and 83.3% for S. scombrus, respectively. No correlation was detected between anisakid intensity and host total length, total weight, condition factor, and hepatosomatic and gonadosomatic indices for both fish species, but significantly higher intensity values were detected for more mature S. scombrus, i.e. fish recording a higher gonadosomatic index. Molecular tools allowed the identification of two species of Anisakis, A. simplex (s.s.) and A. pegreffii. They differed in their occurrence: in S. colias the prevalence of A. simplex (s.s.) was 18% and that of A. pegreffii was 82%, whereas in S. scombrus the prevalence of A. simplex (s.s.) was 73% and that of A. pegreffii was 27%. Occasionally, worms of Hysterothylacium aduncum were identified for both fish. The different infection levels of the two Anisakisspecies in both hosts off the Portuguese coast raise the hypothesis of a different life cycle at the level of the invertebrate intermediate host. S. colias lives in deeper waters than S. scombrus, and the differences found in infection levels suggest that A. pegreffii main first intermediate host also live in deeper waters, compared with A. simplex (s.s.) main first intermediate host. The higher infection levels of A. simplex (s.s.) (most infectious to humans) in S. scombrus suggest that its consumption when slightly cooked, as in grilled fish (so popular in Portugal), could be more problematic for the development of anisakiasis in humans than the consumption of S. colias and thus be of potential public health concern.
Highlights
Portugal has a long tradition of fishing and is the leading country in fish consumption in the European Union (EUMOFA 2016), with 55.3 kg of sea food per capita per year in 2014
The occurrence of anisakids is evaluated in S. colias and Scomber scombrus, and the potential zoonotic risk associated with consumption of these two fishes is evaluated according to the recorded infection levels
No correlation was detected between anisakid intensity and host total length, total weight, condition factor, and hepatosomatic and gonadosomatic indices for both fish species, but significantly higher intensity values were detected for more mature S. scombrus, i.e. fish recording a higher gonadosomatic index
Summary
Portugal has a long tradition of fishing and is the leading country in fish consumption in the European Union (EUMOFA 2016), with 55.3 kg of sea food per capita per year in 2014 For this reason, zoonotic infections such as anisakiasis are a potential risk and a case of major public health concern in this country. Anisakid nematodes are the most abundant parasites of marine fishes worldwide (Mattiucci and Nascetti 2008) They are parasites of zoonotic potential, having the ability to infect humans through the consumption of raw or lightly cooked fish, causing the emerging infection anisakiasis, and being a food safety concern (MacCarthy and Moore 2000). In Spain, France, Italy, Germany, the Netherlands and Japan, severe episodes of anisakiasis have already been recorded (Arizono et al 2012, Mattiucci et al 2013, Ubeira et al 2000)
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