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Authors: Zsuzsanna Varga, Boglárka Sellyei, Petra Paulus, Melitta Papp, Kálmán Molnár and Csaba Székely

The objective of this study was to survey the incidence of Flavobacterium columnare in wild and cultured freshwater fish species in Hungary. This bacterium usually causes disease in waters of more than 25 °C temperature. However, with the introduction of intensive fish farming systems, infected fish exposed to stress develop disease signs also at lower temperatures; in addition, the temperature of natural waters rises to the critical level due to global warming. Twenty-five isolates from wild and cultured freshwater fishes were identified as F. columnare by specific PCR, although both the fragment lengths and the results of PCRRFLP genotyping with BsuRI (HaeIII) and RsaI restriction enzymes raised doubts regarding this species classification. Sequencing of the 16S ribosomal RNA gene revealed that 23 isolates belonged to the species F. johnsoniae and two represented Chryseobacterium spp. The isolates were found to have high-level multidrug resistance: all were resistant to ampicillin and polymyxin B, the 23 F. johnsoniae strains to cotrimoxazole, 88% of them to gentamicin, and 72% to chloramphenicol. The majority of the 25 isolates were sensitive to erythromycin (88%), furazolidone (76%), and florfenicol (68%).

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Authors: Gábor Cech, Diána Sándor, Kálmán Molnár, Petra Paulus, Melitta Papp, Bálint Preiszner, Zoltán Vitál, Ádám Varga and Csaba Székely

Abstract

Two species of the genus Posthodiplostomum (Digenea: Diplostomatidae) (Posthodiplostomum brevicaudatum Nordmann, 1832 and Posthodiplostomum cuticola Nordmann, 1832) are known as parasites of Hungarian native fishes. Metacercariae of P. cuticola are widespread in Europe and cause black spot disease. Several species of Posthodiplostomum were described also from North America but none of them has been isolated in Hungary up to now. Posthodiplostomum centrarchi Hoffman, 1958 has been detected recently in pumpkinseeds (Lepomis gibbosus L., 1758) in several European countries. Posthodiplostomum centrarchi was isolated for the first time in Hungary from pumpkinseeds caught in the Maconka water reservoir in 2015. Thereafter, several natural waters (e.g. the River Danube, Lake Balaton and the Sió channel) were sampled in order to determine its presence and distribution. Only the native species P. cuticola was detected in Lake Balaton on cyprinids but a relatively high infection rate of P. centrarchi was observed in the Sió channel close to the lake. Pathological changes were absent, and metacercariae were mostly attached to the surface of the liver, kidney and heart. The phylogenetic analysis of the ITS and COI sequences of P. centrarchi and P. cuticola clustered into two distinct branches, which was in agreement with the morphological results.

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Authors: Gábor Cech, Diána Sándor, Kálmán Molnár, Petra Paulus, Melitta Papp, Bálint Preiszner, Zoltán Vitál, Ádám Varga and Csaba Székely

Abstract

Two species of the genus Posthodiplostomum (Digenea: Diplostomatidae) (Posthodiplostomum brevicaudatum Nordmann, 1832 and Posthodiplostomum cuticola Nordmann, 1832) are known as parasites of Hungarian native fishes. Metacercariae of P. cuticola are widespread in Europe and cause black spot disease. Several species of Posthodiplostomum were described also from North America but none of them has been isolated in Hungary up to now. Posthodiplostomum centrarchi Hoffman, 1958 has been detected recently in pumpkinseeds (Lepomis gibbosus L., 1758) in several European countries. Posthodiplostomum centrarchi was isolated for the first time in Hungary from pumpkinseeds caught in the Maconka water reservoir in 2015. Thereafter, several natural waters (e.g. the River Danube, Lake Balaton and the Sió channel) were sampled in order to determine its presence and distribution. Only the native species P. cuticola was detected in Lake Balaton on cyprinids but a relatively high infection rate of P. centrarchi was observed in the Sió channel close to the lake. Pathological changes were absent, and metacercariae were mostly attached to the surface of the liver, kidney and heart. The phylogenetic analysis of the ITS and COI sequences of P. centrarchi and P. cuticola clustered into two distinct branches, which was in agreement with the morphological results.

Open access