Persistence of Veronaea botryosa in marine and freshwater microcosms and susceptibility evaluation to three disinfectants

Abstract

Veronaea botryosa is a dematiaceous fungus and the causative agent of systemic mycosis known as “fluid belly’, one of the most important emergent diseases in sturgeon aquaculture. A better understanding of the pathogenesis of the disease requires knowledge of environmental conditions that promote colonization, infection and disease. In this study, both traditional cultured-based methods and qPCR assays were used to evaluate V. botryosa persistence in water microcosms at two different temperatures and salinities, as different environmental factors can predispose poikilotherm animals to infection. Results indicate that V. botryosa persisted significantly greater in fresh than marine water microcosms (p-values < .05). However, fungus persisted similarly at 15 °C and 25 °C at both salinities over 60 days without a host. Furthermore, due to the lack of effective preventive and therapeutic methods to combat fungal infections, proper disinfection of aquaculture equipment and facilities is needed. To this end, the susceptibility of V. botryosa to three frequently used disinfectants in aquatic facilities was investigated to provide efficient biocide concentrations against V. botryosa. The results show that a dose of at least 75 mg/L iodine for 5 min, 390 mg/L household bleach for 5 min, and 3.75% hydrogen peroxide for 30 min are effective against V. botryosa and they are applicable in biosecurity protocols for captive sturgeon.