Observation of ciliate activity within the shells of living juvenile oysters (characterized by mantle movement, motility of the digestive tract and active ciliary movement in the gills and digestive tract organs) indicates a presumptive diagnosis that should be confirmed histologically However, caution is required when using this method for diagnosis because bacteriophagous and saprophagous ciliates are usually common in juvenile oyster cultures. Whole Mounts: Highly motile ciliates observed in affected oysters. However, subclinical infections occur for several days before the dramatic culture failure ensues. Apparently normal cultures of oyster seed can degenerate to heavily infected terminal cultures in 1 to 2 days. Cumulative mortalities in affected cultures of oyster seed usually exceed 50%, and the infection was considered as serious although sporadic for nursery production of the early seed stage in Washington state, USA. On entering the coelomic cavity, the ciliates replicate rapidly and usually invade the vascular spaces and connective tissue between fibers of the adductor muscle. Significant damage leading to mortality occurs when the ciliate penetrates the thin mantle tissue that separates the coelomic cavity from the extrapallial space. Once within the extrapallial space, minimal to moderate mantle tissue damage as well as effects on shell deposition may occur. The ciliates breaches the barrier formed between the outer lobe of the mantle and the inner surface of the shell. They were invasive causing morbidity and mortality in juvenile (seed) oysters less than about 3 mm in shell height with the disease most common in oysters with shell heights of 0.5 to 1.5 mm. Impact on the hostĬiliate infections were considered primary but opportunistic. Host speciesĬrassostrea gigas and Crassostrea sikamea. In Australia, mixed ciliate infections were common but the primary and most severe invasion appeared to involve a species of Uronema based on light microscopic observations and a positive immunofluorescent antibody test reaction using antibodies for a species of Uronema pathogenic to sea-caged southern bluefin tuna ( Thunnus maccoyii) (Elston 1999). In the United States, morphological features observed in histology suggested that the ciliate may belong to genera of either Anophryoides or Paranophrys. However, they are believed to belong in the family Orchitophryidae of the order Scuticociliatida which includes species that are facultative or obligate parasites and histophages such as that isolated from sea stars. Invasive ciliates have not yet been identified to species. Invasive ciliate infections, Invasive orchitophryid ciliate infection. Invasive Ciliates of Juvenile Oysters CategoryĬategory 1 (Not Reported in Canada) Common, generally accepted names of the organism or disease agent
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