Emergence of Epizootic Ulcerative Syndrome in Native Fish of the Murray-Darling River System, Australia: Hosts, Distribution and Possible Vectors

Abstract

Epizootic ulcerative syndrome (EUS) is a fish disease of international significance and reportable to the Office International des Epizootics. In June 2010, bony herring Nematalosa erebi, golden perch Macquaria ambigua, Murray cod Maccullochella peelii and spangled perch Leiopotherapon unicolor with severe ulcers were sampled from the Murray-Darling River System (MDRS) between Bourke and Brewarrina, New South Wales Australia. Histopathology and polymerase chain reaction identified the fungus-like oomycete Aphanomyces invadans, the causative agent of EUS. Apart from one previous record in N. erebi, EUS has been recorded in the wild only from coastal drainages in Australia. This study is the first published account of A. invadans in the wild fish populations of the MDRS, and is the first confirmed record of EUS in M. ambigua, M. peelii and L. unicolor. Ulcerated carp Cyprinus carpio collected at the time of the same epizootic were not found to be infected by EUS, supporting previous accounts of resistance against the disease by this species. The lack of previous clinical evidence, the large number of new hosts (n = 3), the geographic extent (200 km) of this epizootic, the severity of ulceration and apparent high pathogenicity suggest a relatively recent invasion by A. invadans. The epizootic and associated environmental factors are documented and discussed within the context of possible vectors for its entry into the MDRS and recommendations regarding continued surveillance, research and biosecurity are made.

First record of epizootic ulcerative syndrome from the Upper Congo catchment: An outbreak in the Bangweulu swamps, Zambia

“…Initial outbreaks of disease in Africa (Andrew et al., ; Anon ; Huchzermeyer & Van der Waal, ; McHugh et al., ; Songe et al., ) have been particularly severe in floodplain ecosystems as observed during this study in the Bangweulu swamps where the initial severe outbreak of 2014 was followed by annual reappearance of the disease during the same months in 2015, 2016 and 2017 (personal observations C. F. Huchzermeyer, Bangweulu Wetlands, Chikuni, Zambia 2017). Following the initially severe epidemic, the seasonal resurgence of the disease observed in this study was similar to that reported during outbreaks of EUS in the upper Zambezi (Huchzermeyer & Van der Waal, ; Nsonga, Mfitilodze, Samui & Sikawa, ) and in other parts of the world (Boys et al., ; Pradhan et al., ). As with the initial outbreaks of EUS in the Zambezi floodplains, reported by Huchzermeyer and Van der Waal (), fishermen in the Bangweulu swamps soon accepted the presence of the disease.…”

“…Freshwater and estuarine ecosystems in tropical and subtropical climates are particularly vulnerable to outbreaks of EUS (Boys et al., ). Initial outbreaks of disease in Africa (Andrew et al., ; Anon ; Huchzermeyer & Van der Waal, ; McHugh et al., ; Songe et al., ) have been particularly severe in floodplain ecosystems as observed during this study in the Bangweulu swamps where the initial severe outbreak of 2014 was followed by annual reappearance of the disease during the same months in 2015, 2016 and 2017 (personal observations C. F. Huchzermeyer, Bangweulu Wetlands, Chikuni, Zambia 2017).…”

Mitochondrial genomes and comparative genomics of Aphanomyces astaci and Aphanomyces invadans

“…The disease was first detected in Japan19, but has been subsequently reported from continental Asia, Australia, North America and Africa, with different names being given20. Based on several molecular studies, a single clone of A. invadans has been broadly distributed worldwide2122. A. astaci and A. invadans seem to be closely related on the genetic level5, and they also share several common life style characteristics; i.e.…”

Emergence of the Epizootic Ulcerative Syndrome in Pond Reared Carp Fish (Cyprinids) and It's Control Measure in Chitwan, Central Nepal

“…EUS has been reported in more than 94 fish species spread across 26 countries (Lilley et al, 1998;Andrew et al 2008;Saylor et al 2010;Boys et al 2012;Huchzermeyer et al 2012;Oidtmann, 2012). EUS was spread across Asia from Japan and Australia to Pakistan in 1996 and to southern Africa in 2006 (Baldock et al, 2005).…”