Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C., Denmark.
Folia Parasitol (Praha). 2023 May 2;70:2023.011. doi: 10.14411/fp.2023.011.
Evolutionary and ecological processes affecting the interactions between hosts and parasites in the aquatic environment are at display in the Baltic Sea, a young and ecologically unstable marine ecosystem, where fluctuating abiotic and biotic factors affect the parasitofauna in fish. The dynamic infections of Baltic cod, a subpopulation of the Atlantic cod (Gadus morhua Linnaeus), with third stage anisakid nematode larvae of Pseudoterranova decipiens (Krabbe, 1878) and Contracaecum osculatum (Rudolphi, 1802) have increased following a significant increase of the Baltic grey seal Halichoerus grypus (Fabricius) population in the region. Cod serves as a paratenic host and marine mammals, pinnipeds, are definitive hosts releasing parasite eggs, with faeces, to the marine environment, where embryonation and hatching of the third stage larva take place. The parasite has no obligate intermediate hosts, but various invertebrates, smaller fish and cod act as paratenic hosts transmitting the infection to the seal. Contracaecum osculatum has an impact on the physiological performance of the cod, which optimises transmission of the larva from fish to seal. Thus, a muscle mass decrease of nearly 50% may result from heavy C. osculatum infections, probably amplified by a restricted food availability. The muscle atrophy is likely to reduce the escape reactions of the fish when meeting a foraging seal. In certain regions, where fish and seals are restricted in their migration patterns, such as the semi-enclosed Baltic Sea, the predation may contribute to a severe cod stock depletion. The parasites are zoonotic and represent a human health risk, when consumers ingest insufficiently heat- or freeze-treated infected products. Marked infections of the cod were previously reported during periods with elevated seal populations (late 19th and middle 20th century) and various scenarios for management of risk factors are evaluated in an evolutionary context.
在波罗的海，进化和生态过程影响着宿主和寄生虫之间的相互作用，该海域是一个年轻且生态不稳定的海洋生态系统，其中不断变化的非生物和生物因素影响着鱼类寄生虫群。波罗的海鳕鱼（大西洋鳕鱼的一个亚种群，Gadus morhua Linnaeus）的动态感染，第三期拟异尖线虫幼虫 Pseudoterranova decipiens（Krabbe，1878）和 Contracaecum osculatum（Rudolphi，1802），随着该地区波罗的海灰海豹（Halichoerus grypus）数量的显著增加而增加。鳕鱼是副宿主，海洋哺乳动物鳍足类动物是终末宿主，通过粪便将寄生虫卵释放到海洋环境中，在那里第三期幼虫孵化。寄生虫没有必需的中间宿主，但各种无脊椎动物、小鱼和鳕鱼充当副宿主，将感染传播给海豹。Contracaecum osculatum 对鳕鱼的生理性能有影响，这优化了幼虫从鱼向海豹的传播。因此，严重的 C. osculatum 感染可能导致肌肉质量减少近 50%，可能因食物供应受限而加剧。肌肉萎缩可能会降低鱼在遇到觅食海豹时的逃避反应。在某些区域，鱼类和海豹的迁徙模式受到限制，例如半封闭的波罗的海，捕食可能导致鳕鱼种群严重枯竭。这些寄生虫是人畜共患的，当消费者摄入未充分加热或冷冻处理的受感染产品时，会对人类健康构成威胁。在海豹数量增加的时期（19 世纪末和 20 世纪中叶），曾报道过鳕鱼的明显感染，并且在进化背景下评估了各种风险因素管理方案。
