Epizootics in farm‐raised channel catfish, Ictalurus punctatus (Rafinesque), caused by the enteric redmouth bacterium Yersinia ruckeri

Abstract

In the winters of 1995 and 1996, unusual disease outbreaks occurred on two separate channel catfish farms in Arkansas, USA. Affected fish exhibited extraordinary haemorrhaged rings around the eyes and raised haemorrhaged areas overlying the frontal foramens. Other signs included abnormal swimming, lethargy, loss of equilibrium, and exophthalmia. Bacterial isolates from the moribund fish were identified as Yersinia ruckeri by biochemical tests, no lysis by the Hafnia‐specific bacteriophage 1672, and Y. ruckeri‐specific growth patterns on Shotts‐Waltman media. Fingerling catfish injected intraperitoneally with the bacterial isolate at 7.8 × 106 bacteria fish−1 developed lesions characteristic of the epizootics at 13, 18, and 22 °C and a biochemically identical isolate was recovered. Fingerling rainbow trout injected with the channel catfish isolate at 1 × 105 bacteria fish−1 and held at 20 °C developed signs typical of enteric redmouth by 4 days post‐inoculation and were moribund by 5 days post‐inoculation. Some differences of clinical signs occurred between experimentally infected rainbow trout and channel catfish. Clinical and biochemical similarities between infections of Y. ruckeri and many warmwater pathogens in affected catfish may lead to incorrect diagnosis of ERM infections.

Route of entry and tissue distribution of Yersinia ruckeri in experimentally infected rainbow trout Oncorhynchus mykiss

“…Yersinia ruckeri was found to cause significant losses in the field at water temperatures of 15 to 18°C (Roberts 1983). Danley et al (1999) observed a higher incidence of infection at 18°C than at 22°C in channel catfish Ictalurus punctatus (Rafinesque) intraperitoneally injected with Y. ruckeri. Increased severity of infection may be due to upregulation of different Y. ruckeri virulence factors at lower temperatures, as has been demonstrated by Fernández et al (2007).…”

Biochemical and molecular heterogeneity among isolates of Yersinia ruckeri from rainbow trout (Oncorhynchus mykiss, Walbaum) in north west Germany

“…The bacterium was isolated from different host species [2,23,24], including several salmonid species, channel catfish, goldfish, common carp, European eel, coalfish, and perch. Typing of Y. ruckeri isolates from various geographic locations or different fish species has been performed for taxonomic or epidemiological purposes and initially it was based on phenotypical characteristics including the results of biochemical and serological tests [10,25,26].…”

Foodborne Agents Associated with the Consumption of Aquaculture Catfish

“…Yersinia ruckeri is the known causative agent of enteric redmouth disease in channel catfish (33); however, no links to human illness have been reported. Yersinia enterocolitica is the species most often associated with foodborne illness, but this microorganism has rarely been studied in catfish.…”