Experimental infection of Aphanomyces invadans and susceptibility in seven species of tropical fish

Abstract

Aim:Epizootic ulcerative syndrome (EUS) causes by aquatic oomycete fungus, Aphanomyces invadans is a dangerous fish disease of a wide range of fresh and brackish water, wild and farmed fish throughout the world. The objective of the present study was to determine the susceptibility of a number of tropical fish species to the EUS and compare the severity of infection between experimental groups.Materials and Methods:Snakehead, Channa striata (Bloch, 1793); snakeskin gourami, Trichopodus pectoralis (Regan, 1910); koi carp, Cyprinus carpio (Linnaeus, 1758); broadhead catfish, Clarias macrocephalus (Günther, 1864); goldfish, Carassius auratus (Linnaeus, 1758); climbing perch, Anabas testudineus (Bloch, 1792); and Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) were challenged by intramuscular injection using zoospores of Aphanomyces invadans (NJM9701). The infected fish skins and muscles were examined for EUS histopathological characteristics, and the results on the severity of lesions and mortality were analyzed using SPSS program.Results:All zoospore-injected fish were shown to be susceptible to the EUS infection except Nile tilapia. Although, the general histopathological pattern was similar in the zoospore-injected group, but there were some variation in granulomatous reaction, that is the presence or absence of giant cells, and time of mortality were detected. The result of statistical analysis showed that there was a significant difference between species, (c2=145.11 and p<0.01).Conclusion:Gourami, koi carp, and catfish were demonstrated to be highly susceptible while goldfish and climbing perch were found to be moderately susceptible to the EUS infection. These findings suggested that the cellular response of fish to mycotic infection and granulomatous reaction varied in different fish species, which could not be an indicator of susceptibility or resistant to the EUS itself, although it was shown that the granulation rate and the level of maturity or solidification (consolidation of granulomas) were higher in resistant fish.

The acute toxicity of the metaldehyde on the climbing perch

“…A study shows that Climbing perch was found to be moderately susceptible to the Epizootic ulcerative syndrome (EUS) infection causes by aquatic oomycete fungus (Aphanomyces invadans), compared to EUS susceptible such as Snakehead (Channa striata), tropical snakeskin gourami (Trichopodus pectoralis), koi carb (Cyprinus carpio), and broadhead catfish (Clarias macrocaphalus) [28]. Behavioural changes could be the first response of an organism to environmental change.…”

Molecular characterisation of oomycetes from fish farm located in Mymensingh sadar during summer

“…In their work, live zoospores of EUS were injected to show the histopathological responses of tilapia, however, no visible inflammatory response was found. Afzali et al (2015) stated that in Nile tilapia, fully mature granulomata of varying sizes fused with multinucleated giant cells and formed large granuloma, surrounded with dense fibrous layers and melanin pigments that filled the whole affected area in very early stages of infection. Thompson et al (1999) suggested that giant cell formation did not seem to be an indicator of resistance to EUS while the actual impact of this type of response in respect to fungal infection is still unclear.…”

“…Thompson et al (1999) suggested that giant cell formation did not seem to be an indicator of resistance to EUS while the actual impact of this type of response in respect to fungal infection is still unclear. According to Afzali et al (2015), mycotic granulomatous reaction could prevent and halt A. invadans growth only in resistant fish such as Nile tilapia, however in susceptible fish, for example snakehead, gouramies, koi carp, catfish, goldfish, and climbing perch, the rate of hyphal growth was more rapid than granulomatous reaction. Granulomatous reaction could not be an indicator of susceptibility or resistance to the EUS as it varied to the cellular responses of different fish species.…”

Infectious diseases in aquarium ornamental pet fish

“…Infection with Aphanomyces invadans, also known as epizootic ulcerative syndrome (EUS), is an OIE-listed disease. It has historically caused mass mortality in cultured and wild fish in Asia and Oceania and recently in North America and Africa (Afzali et al, 2015;Majeed et al, 2017;Iberahim et al, 2018; The World Organisation for Animal Health, 2017).…”