Susceptibility-related differences in the quantity of developmental stages of Myxobolus spp. (Myxozoa) in fish blood

Abstract

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.

Genetic Diversity of Serine Protease Inhibitors in Myxozoan (Cnidaria, Myxozoa) Fish Parasites

“…The triactinomyxon-type actinospores (TAMs) of M. cerebralis (previously characterized by Sipos et al [ 39 ]) and M. pseudodispar lineage GER (NCBI Acc. No.…”

“…EF466088) were harvested from the life cycles maintained in the Fish Parasitology laboratory of the Institute for Veterinary Medical Research, Centre for Agricultural Research, Budapest, Hungary, as described previously by Eszterbauer et al [ 40 ]. The identities of parasite TAMs were confirmed using species-specific 18S rDNA PCR and DNA sequencing, according to Sipos et al [ 39 ]. S. molnari proliferative, presporogonic blood stages were collected from the laboratory lineage maintained by intraperitoneal infection of parasite blood stages into specific pathogen-free common carp ( Cyprinus carpio ) in the Laboratory of Fish Protistology of the Institute of Parasitology, Biology Centre of CAS, Ceske Budejovice, Czech Republic [ 41 ].…”

Selection of suitable reference genes for gene expression studies in myxosporean (Myxozoa, Cnidaria) parasites

“…SPF rainbow trout, Onchorhynchus mykiss (Kamloops strain) was obtained from the Lillafüred Trout Hatchery, Hungary (yolk sac stage) and reared at the IVMR. Fish were infected individually with 5000 freshly filtered actinospores according to 37 . From infected fish, pieces of skulls containing myxospores and sporogonic plasmodia (spore-forming stages) were collected 90 days’ post exposure (n = 4).…”

Serine protease inhibitors of the whirling disease parasite Myxobolus cerebralis (Cnidaria, Myxozoa): Expression profiling and functional predictions

“…A widespread pathogenic species is Myxobolus cerebralis which is responsible for whirling disease and causes declines among susceptible salmonid fry [7][8][9]. Both its intrapiscine and intraoligochaete development has been studied in detail [10,11], and special attention has been paid to host susceptibility [12][13][14][15][16][17]. Although our knowledge on the genetic background of host-parasite interaction of M. cerebralis is scarce, some crucial moments of its development have been studied in this context.…”