Relationship between Southern Bluefin Tuna, Thunnus maccoyii, melanomacrophage centres and Cardicola spp. (Trematoda: Aporocotylidae) infection

Widdicombe, Maree; Power, Cecilia; Gelderen, Rebecca van; Nowak, Barbara F.; Bott, Nathan J.

doi:10.1016/j.fsi.2020.09.004

Cited by 10 publications

(9 citation statements)

References 39 publications

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“…Splenic MMC surface area was positively correlated to copy numbers of ITS2 rDNA C. forsteri in the gills. This is consistent with observations of positive correlation between splenic and renal MMC surface area and blood fluke egg count in the gills observed in ranched SBT at harvest in another season [8].…”

Section: Discussionsupporting

confidence: 92%

“…Splenic MMC size (measured as percentage surface area) was within the range previously reported for ranched SBT [7,8]. MMCs size increased significantly over ranching time from transfer to pre-treatment and harvest for both cohorts.…”

Section: Discussionsupporting

confidence: 79%

“…This may be both (or either) due to an increase in blood fluke infection between those time points and to the increase in the fish size during ranching. A positive relationship between splenic, renal and hepatic MMC and SBT size was shown for harvest size SBT sampled in a different ranching season [8] and between splenic and renal MMC size and blood fluke infection measured as blood fluke eggs count in the gills [8] or splenic MMC size and copy number of C. forsteri ITS2 rDNA in the gills (present study).…”

Section: Discussionsupporting

confidence: 60%

“…Splenic MMCs significantly increased in size during ranching possibly due to increasing blood fluke infection, however, the infection presence or severity was not determined in that study [8]. A recent study showed a significant positive correlation between MMC size (determined as percentage surface area) and Cardicola spp.…”

Section: Introductionmentioning

confidence: 58%

“…Blood fluke eggs were mainly present in gills and heart of SBT with a few eggs in renal MMCs. Blood fluke eggs were reported in hepatic MMCs in ranched SBT [8]. Eggs of another blood fluke Cruricola lates were trapped in hepatic and renal MMCs in barramundi, Lates calcarifer [10].…”

Section: Discussionmentioning

confidence: 99%

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Changes in the Splenic Melanomacrophage Centre Surface Area in Southern Bluefin Tuna (Thunnus maccoyii) Are Associated with Blood Fluke Infections

Nowak

Dang

Webber³

et al. 2021

Pathogens

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Melanomacrophage centres (MMCs) are aggregates of macrophages accumulating various pigments. They have been proposed as an indicator of fish immune response. Blood flukes are common parasites in farmed fish. Two cohorts of wild Southern Bluefin Tuna (Thunnus maccoyi) were examined at transfer, before treatment against blood flukes (pre-treatment) and at harvest. MMCs were assessed in histological sections using image analysis, while Cardicola forsteri and Cardicola orientalis infection severity was determined using qPCR, count of adult flukes in heart flushes and count of eggs in gill filaments. Fish from both cohorts showed the same pattern in the changes in the surface area of MMCs. The surface area of splenic MMCs increased over the ranching duration and was positively correlated to the PCR determined copy numbers of Cardicola forsteri ITS2 rDNA in the gills of those fish. However, the infection with blood fluke was more variable, both between cohorts and individuals within the same cohort. Eggs of blood fluke were detected in renal MMCs using histology. Cardicola forsteri had a higher prevalence than Cardicola orientalis. This study contributes to our understanding of blood fluke infections in Southern Bluefin Tuna and their interactions with MMCs.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 79%