The First Detection ofKudoa hexapunctatain Farmed Pacific Bluefin Tuna in South Korea,Thunnus orientalis(Temminck and Schlegel, 1844)

Abstract

Simple Summary In this study, we detectedKudoa hexapunctatain Pacific bluefin tuna (Thunnus orientalis) individuals that did not show any gross pathology lesions. Giemsa staining was used to identify clearer lesions than haematoxylin and eosin (H&E) staining that is used in general histological analysis.K. hexapunctatawas separated through molecular biological methods, other than haematolocial and histological analysis. Individuals infected withK. hexapunctatashowed relatively low haemoglobin (Hb) and haematocrit (Ht) values, and histological analysis revealed clear pseudocysts in the abdominal and dorsal muscles. The consumption of fish and shellfish worldwide is steadily increasing, and tuna is a particularly valuable fish species. However, infection caused byKudoaspp. is causing problems in many fish including the Pacific bluefin tuna (Thunnus orientalis), and there is much controversy about the association of these infections with foodborne disease. In this study, using haematological and histological analyses of the blood and internal organs (liver, spleen, kidney, heart, stomach, intestine, gill, and muscle) of Pacific bluefin tuna cultured in South Korea, infection with Myxosporea was first identified, and molecular biological analysis was conducted. In this study,Kudoa hexapunctatawas finally identified. The Pacific bluefin tunas analysed in this study did not show any gross pathology lesions, such as visible cysts and/or myoliquefaction, of infection with this species. The histological analytical results can provide guidelines for the identification ofK. hexapunctata. In the case ofK. hexapunctata-induced infection, unlike other countries, such as Japan, there have been no reports in South Korea, and this study is the first to detectK. hexapunctatainfection in Pacific bluefin tuna cultured in South Korea. The correlation betweenK. hexapunctataand food poisoning is not yet clear, however, it is thought that continuous observation of its infection is necessary.