Kumas Kaan, Al-Jubury Azmi, Kania Per W, Abusharkh Taghrid, Buchmann Kurt
Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.
Int J Parasitol Parasites Wildl. 2024 Apr 17;24:100937. doi: 10.1016/j.ijppaw.2024.100937. eCollection 2024 Aug.
We here describe the location of anisakid third stage larvae in Atlantic herring L. caught in the North Sea in August 2023. We further demonstrate how industrial processing (mechanical gutting, removal of entrails, head, tail, hypaxial anterior musculature and vertebral column) reduces the overall infection and worm load in the musculature. The isolated anisakid larvae were identified as sensu stricto by a combination of morphometrics and molecular methods (PCR of rDNA and mtDNA, sequencing, BLAST analysis). As a baseline we examined a total of 75 specimens of freshly caught and ungutted herring and showed a positive correlation between host size (fish length and weight) and infection level. The overall prevalence of infection was 84 %, the mean intensity 11.3 (range 1-38 parasites per fish) and the abundance 9.52. The main part of the overall worm population was associated with stomach and pyloric caeca in the body cavity (77 %) and only 5 % was found in the musculature. Larvae occurred in the hypaxial part of the musculature (21), the epaxial part (7 worms) and the caudal part (5 worms). The prevalence of muscle infection was 28 % and the mean intensity 1.6 (range 1-5) parasites per fish and abundance 0.44 parasites per fish. In order to assess the effect of industrial processing on worm occurrence in the fish we examined a total of 67 specimens of herring, from exactly the same batch, but following processing. This included removal of organs in the body cavity, cutting the lower part of the hypaxial segment but leaving the right and left musculature connected by dorsal connective tissue. Five out of these fish carried one larva (prevalence 7.5%, mean intensity 1, abundance 0.07 larvae per fish), and these worms were located in the ventral part of the anterior musculature (2), in the central part of the anterior musculature (2) and one larva in the central part of the caudal musculature. The industrial processing reduced the overall occurrence (abundance) of worms in the fish from 9.52 to 0.07 (136 times reduction) and the occurrence in the musculature from 0.44 to 0.07 (6.28 times reduction). The overall prevalence was reduced from 84 % to 7.5 % (11.2 times reduction). Muscle infection prevalence fell from 28 % to 7.5 % (3.7 times reduction). We then followed another batch of herring following a marinating process (11% NaCl for 24 h and subsequent incubation in acetic acid and vinegar) by artificially digesting the flaps during week 1-8. Although a total of 31 larvae were recovered from 144 fish examined no live nematode larvae were isolated. The importance of fish handling, processing and marination for consumer safety is discussed.
我们在此描述2023年8月在北海捕获的大西洋鲱鱼中异尖线虫第三期幼虫的位置。我们还进一步展示了工业加工（机械去内脏、去除内脏、头部、尾部、体轴前侧肌肉组织和脊柱）如何降低肌肉组织中的总体感染率和蠕虫负荷。通过形态测量学和分子方法（rDNA和mtDNA的PCR、测序、BLAST分析）相结合，将分离出的异尖线虫幼虫鉴定为狭义种。作为基线，我们总共检查了75条刚捕获且未去内脏的鲱鱼样本，结果显示宿主大小（鱼的长度和重量）与感染水平之间存在正相关。总体感染率为84%，平均感染强度为11.3（每条鱼的寄生虫数量范围为1 - 38），感染丰度为9.52。总体蠕虫种群的主要部分与体腔中的胃和幽门盲囊相关（77%），只有5%在肌肉组织中。幼虫出现在肌肉组织的体轴下部（21条）、轴上部分（7条蠕虫）和尾部（5条蠕虫）。肌肉感染率为28%，每条鱼的平均感染强度为1.6（范围为1 - 5），感染丰度为每条鱼0.44个寄生虫。为了评估工业加工对鱼体内蠕虫出现情况的影响，我们总共检查了来自同一批次但经过加工的67条鲱鱼样本。这包括去除体腔中的器官，切割体轴段的下部，但保留左右肌肉组织通过背侧结缔组织相连。这些鱼中有5条携带1条幼虫（感染率7.5%，平均感染强度1，每条鱼的感染丰度0.07条幼虫），这些蠕虫位于前侧肌肉组织的腹侧部分（2条）、前侧肌肉组织的中央部分（2条）以及尾侧肌肉组织的中央部分（1条）。工业加工使鱼体内蠕虫的总体出现情况（感染丰度）从9.52降至0.07（降低了136倍），肌肉组织中的出现情况从0.44降至0.07（降低了6.28倍）。总体感染率从84%降至7.5%（降低了11.2倍）。肌肉感染率从28%降至至7.5%（降低了3.7倍）。然后，我们在第1 - 8周通过人工消化鱼块，跟踪了另一批经过腌制处理（11%氯化钠处理24小时，随后在醋酸和醋中孵育）的鲱鱼。尽管在检查的144条鱼中总共回收了31条幼虫，但未分离出活的线虫幼虫。本文讨论了鱼类处理、加工和腌制对消费者安全的重要性。
