Abstract
Anisakidae, marine nematodes, are underrecognized fish-borne zoonotic parasites. Studies on factors that could trigger parasites to actively migrate out of the fish are very limited. The objective of this study was to assess the impact of different environmental conditions (temperature, CO2 and O2) on larval motility (in situ movement) and mobility (migration) in vitro. Larvae were collected by candling or enzymatic digestion from infected fish, identified morphologically and confirmed molecularly. Individual larvae were transferred to a semi-solid Phosphate Buffered Saline agar, and subjected to different temperatures (6 ℃, 12 ℃, 22 ℃, 37 ℃) at air conditions. Moreover, different combinations of CO2 and O2 with N2 as filler were tested, at both 6 °C and 12 °C. Video recordings of larvae were translated into scores for larval motility and mobility. Results showed that temperature had significant influence on larval movements, with the highest motility and mobility observed at 22 ℃ for Anisakis spp. larvae and 37 ℃ for Pseudoterranova spp. larvae. During the first 10 min, the median migration of Anisakis spp. larvae was 10 cm at 22 ℃, and the median migration of Pseudoterranova spp. larvae was 3 cm at 37 ℃. Larval mobility was not significantly different under the different CO2 or O2 conditions at 6 °C and 12 ℃. It was concluded that temperature significantly facilitated larval movement with the optimum temperature being different for Anisakis spp. and Pseudoterranova spp., while CO2 and O2 did not on the short term. This should be further validated in parasite-infected/spiked fish fillets.
Highlights
Anisakidae, marine nematodes, are underrecognized fish-borne zoonotic parasites
They lead to human a nisakidosis[1,2,3], which is mainly caused by Anisakis simplex sensu stricto, Anisakis pegreffii and Pseudoterranova decipiens[4,5,6], while other members of the Anisakidae and Raphidascaridae family are less commonly responsible for human infections[7,8]
There is an association between temperature and gene expression levels of some antigenic and functional proteins released by zoonotic species of Anisakis, which may be involved in the host tissue migration of the parasite in the hostile target tissues of the fish h ost[28]
Summary
Anisakidae, marine nematodes, are underrecognized fish-borne zoonotic parasites. Studies on factors that could trigger parasites to actively migrate out of the fish are very limited. It was concluded that temperature significantly facilitated larval movement with the optimum temperature being different for Anisakis spp. and Pseudoterranova spp., while CO2 and O2 did not on the short term. This should be further validated in parasite-infected/spiked fish fillets. Because of the public health risk, the European Union Regulation No 853/2004 stipulates that all fish destined for raw consumption, cold-smoking processing with internal temperature below 60 °C, marinated or salted process should be frozen at a temperature of no higher than -20 °C for at least 24 h19 This leads to an important cost for the industry and has consequences on the quality of the fish. The study will provide information about the potential of the above-mentioned factors to trigger larvae to actively move, which could potentially be applied to quickly remove larvae from fish in an industrial setting
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