The evaluation and development of diagnostic tools for the detection of ichthyophonus hoferi in fish host tissue samples

Abstract

Ichthyophonus hoferi is a highly pathogenic histozoic parasite that has low host specificity capable of producing mass mortalities of epizootic proportions in marine commercial fish populations. Currently in Southern Africa, I. hoferi has been reported from flathead mullet (Mugil cephalus) from the Kowie lagoon and from multiple species on exhibit at the Two Oceans Aquarium. Since epizootiologists rely on accurate assessments of prevalence to establish patterns of morbidity and mortality within populations, using the most accurate diagnostic techniques for accurate assessments of infection is imperative. Currently, several diagnostic techniques have been employed to detect I. hoferi in infected fish hosts. These include macroscopic examination of tissues, microscopic examinations of wet-mount squash preparations of tissue, histological examination of tissue sections, in vitro culture of tissue explants, the polymerase chain reaction (PCR) using I. hoferi-specific primers and real-time quantitative PCR (qPCR) using I. hoferi-specific primers and a hydrolysis probe.