Here, we investigated the early development of two closely related myxozoan parasites, the highly pathogenic Myxobolus cerebralis, the causative agent of the whirling disease in salmonids, and Myxobolus pseudodispar, a common, non-pathogenic parasite of cyprinids. The aim of our study was to examine under in vivo laboratory conditions whether fish blood is involved in the intrapiscine development of the two parasite species and investigate if there is dissimilarity between the parasite infection intensity in blood and if it varies in terms of host susceptibility and parasite pathogenicity. Highly susceptible, less susceptible and non-susceptible hosts were involved. Blood samples were taken 1 day, 1 week and 1 month post exposure to M. cerebralis and M. pseudodispar, respectively. The prevalence and infection intensity was estimated by parasite-specific quantitative real-time PCR. Although previous findings assumed that M. cerebralis might escape from host immune system by migrating via peripheral nerves, our experimental results demonstrated that M. cerebralis is present in blood during the early stage of intrapiscine development. For the non-pathogenic M. pseudodispar, the highest infection prevalence was found in the original host, common roach Rutilus rutilus, whereas the highest infection intensity was detected in rudd Scardinius erythrophthalmus, a “dead-end” host of the parasite. The presence of M. pseudodispar developmental stages in the blood of both susceptible and non-susceptible cyprinids suggests that the susceptibility differences remain hidden during the early stage of infection. Our findings supply further evidence that host specificity is not determined during the early, intrapiscine development involving the vascular system. Furthermore, we found remarkable differences in the infection dynamics of the two parasite species examined, possibly due to their distinct pathogenicity or variations in adaptive capabilities to immune components in host blood.

在这里，我们调查了两个密切相关的粘虫寄生虫的早期发育，即高致病性脑粘液鼠（鲑鱼中旋转疾病的病原体）和拟粘粘鼠（Mypobolus pseudodispar），这是一种常见的非致病性鲤鱼寄生虫。我们研究的目的是在体内实验室条件下检查鱼血是否参与了这两种寄生虫物种的鱼内发育，并研究了血液中寄生虫感染强度之间是否存在差异，以及宿主感染性和敏感性之间是否存在差异。寄生虫的致病性。涉及高度易感，不太易感和不易感的宿主。暴露于M后1天，1周和1个月采集血样。cerebralis和中号。分别为pseudodispar。感染率和感染强度通过寄生虫特异性定量实时PCR估算。虽然以前的研究结果认为中号。脑炎可能通过周围神经的迁移而逃脱宿主免疫系统，我们的实验结果表明，M。cerebralis是在intrapiscine发展初期存在于血液中。对于非致病性的中号。pseudodispar，在原始寄主，普通蟑螂Rutilus rut​​ilus中发现了最高的感染率，而在寄生虫的“死胡同”寄主斯卡迪尼乌斯·红眼球菌中检测到最高的感染强度。M的存在。易感和非易感的鲤鱼的血液中的假性疾病发展阶段表明，在感染的早期，敏感性差异仍然隐藏。我们的发现提供了进一步的证据，即在涉及血管系统的早期鱼内发育过程中，宿主特异性尚未确定。此外，我们发现所检查的两个寄生虫物种在感染动力学上有显着差异，这可能是由于它们的独特致病性或对宿主血液中免疫成分的适应能力的变化。