Anisakis Detection in Fish Fillets by Multiple-wavelength Analysis of Photoacoustic Images

Anisakis larvae parasitizes several species of fishes. Ingesting raw seafood containing the parasite Anisakis can cause a serious disease called anisakiasis. Therefore, it is necessary to remove the parasites from fish before consumption. Conventional screening methods, such as the candling method, are easy to use for detecting surface parasites but lack the accuracy an d sensitivity to detect parasites embedded deep within fish muscle. To resolve these shortcomings, we devised a method using photoacoustic imaging. This imaging modality combines high tissue specificity with better penetration depth.We measured the photoacoustic spectra of Anisakis and fillets of fish such as mackerel. To investigate the ability to distinguish Anisakis from fish tissue using differences in the photoacoustic spectra, we calculated the intensity ratio of the photoacoustic signal. Our results showed that two specific wavelengths can be used to distinguish Anisakis from fish tissue, although the optimal wavelength combination may vary depending on the fish species. Furthermore, we constructed a photoacoustic imaging device based on this principle and demonstrated the ability to visualize Anisakis hidden in fillets.