title: Parental genetic diversity of brown trout (Salmo trutta m. fario) brood stock affects offspring susceptibility to whirling disease.
abstract: BACKGROUND
  Whirling disease, caused by the myxozoan parasite Myxobolus cerebralis, has high economical and ecological importance worldwide. Susceptibility to the disease varies considerably among salmonid species. In brown trout (Salmo trutta) the infection is usually subclinical with low mortality, which increases the risk of parasite dissemination, especially when farm fish are used for stocking natural habitats. The influence of intraspecific genetic differences (especially the level of homozygosity) on susceptibility is unknown. Therefore, we examined the possible correlations between parental genetic diversity and offspring susceptibility of brown trout stocks to whirling disease.
  
  
  METHODS
  Two brown trout brood stocks from a German and a Hungarian fish farm were genetically characterized using microsatellite and lineage-specific genetic markers. The individual inbreeding coefficient f and pairwise relatedness factor r were estimated based on eight microsatellite markers. Brood stock populations were divided into groups according to low and high f and r value estimates and subjected to selective fertilization. The offspring from these separate groups were exposed to M. cerebralis actinospores, and the infection prevalence and intensity was measured and statistically analysed.
  
  
  RESULTS
  The analysis of phylogeographic lineage heritage revealed high heterogeneity in the Hungarian brood stock since > 50% of individuals were Atlantic-Danubian hybrids, while only pure Atlantic-descending specimens were detected in the German population. Based on f msat and r msat estimations, classified non-inbred (NIB), inbred (IB) and a group of closely related fish (REL) were created. The susceptibility of their offspring varied considerably. Although there was no significant difference in the prevalence of M. cerebralis infection, the mean intensity of infection differed significantly between NIB and IB groups. In REL and IB groups, a high variability was observed in infection intensity. No external clinical signs were observed in the exposed brown trout groups.
  
  
  CONCLUSIONS
  Our findings indicate that the allelic diversity of brown trout brood stock may constitute a significant factor in disease susceptibility, i.e. the intensity of parasite infection in the subsequent generation.
authors.affiliation: Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, 21 Hungária krt, H-1143, Budapest, Hungary. eszterbauer.edit@agrar.mta.hu.
authors.forename: Edit
authors.initials: E
authors.lastname: Eszterbauer
authors.affiliation: Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, 21 Hungária krt, H-1143, Budapest, Hungary. forro.barbara@agrar.mta.hu.
authors.forename: Barbara
authors.initials: B
authors.lastname: Forró
authors.affiliation: Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, 21 Hungária krt, H-1143, Budapest, Hungary. zjtolnai@gmail.com.|Present address: Semmelweis University, Faculty of Medicine, 26 Üllői út, H-1085, Budapest, Hungary. zjtolnai@gmail.com.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Tolnai
authors.affiliation: Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, 21 Hungária krt, H-1143, Budapest, Hungary. guti.csaba@agrar.mta.hu.
authors.forename: Csaba Ferenc
authors.initials: CF
authors.lastname: Guti
authors.affiliation: Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, 21 Hungária krt, H-1143, Budapest, Hungary. zsigmond.gergely@gmail.com.|Szent István University, Faculty of Veterinary Medicine, 2 István utca, H-1078, Budapest, Hungary. zsigmond.gergely@gmail.com.
authors.forename: Gergely
authors.initials: G
authors.lastname: Zsigmond
authors.affiliation: Lillafüred Trout Farm, 55 Erzsébet sétány, H-3517, Miskolc-Lillafüred, Hungary. hoitsy@t-online.hu.
authors.forename: György
authors.initials: G
authors.lastname: Hoitsy
authors.affiliation: Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, 21 Hungária krt, H-1143, Budapest, Hungary. d.kallert@gmx.de.|Present address: Kallert & Loy GbR, 11 Birkenweg, 91325, Adelsdorf, Germany. d.kallert@gmx.de.
authors.forename: Dennis Marc
authors.initials: DM
authors.lastname: Kallert
mesh_terms: D000818:Animals; D004198:Disease Susceptibility; D005260:Female; D005393:Fish Diseases / Q000469:parasitology*; D014644:Genetic Variation; D007178:Inbreeding; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D055766:Myxobolus / Q000502:physiology*; D010273:Parasitic Diseases, Animal / Q000469:parasitology*; D058974:Phylogeography; D014337:Trout / Q000235:genetics* / Q000469:parasitology