title: Differences in virulence between two serotypes of Ichthyophthirius multifiliis.
abstract: Naive channel catfish Ictalurus punctatus were infected by 2 isolates of the parasitic ciliate Ichthyophthirius multifiliis that differed in virulence. The isolates, NY1 and G5, Serotypes A and D, respectively, express different surface immobilization-antigens. The virulence of the 2 isolates was compared using tail-fin infections to quantitate parasite numbers and by analysis of the survival of infected fish. Although NY1 infected fish at a lower level than G5, all NY1-infected fish died, but 51% of G5-infected fish survived. The greater virulence of NY1 is apparently a consequence of its shorter life cycle, which results in overwhelming reinfection of fish before they can develop a protective immune response. This report represents the first experimental evidence for differences in virulence between serotypes of I. multifiliis.
authors.affiliation: Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens 30602, USA.
authors.forename: Alton G
authors.initials: AG
authors.lastname: Swennes
authors.forename: Jane G
authors.initials: JG
authors.lastname: Noe
authors.forename: R Craig
authors.initials: RC
authors.lastname: Findly
authors.forename: Harry W
authors.initials: HW
authors.lastname: Dickerson
mesh_terms: D000818:Animals; D016770:Ciliophora Infections / Q000145:classification / Q000401:mortality / Q000469:parasitology / Q000662:veterinary*; D005393:Fish Diseases / Q000453:epidemiology / Q000401:mortality / Q000469:parasitology*; D016803:Hymenostomatida / Q000145:classification* / Q000276:immunology / Q000472:pathogenicity*; D007059:Ictaluridae / Q000469:parasitology*; D007249:Inflammation / Q000469:parasitology / Q000662:veterinary; D012703:Serotyping / Q000662:veterinary; D013997:Time Factors; D014774:Virulence