| Paramoebiasis caused by the amphizoic amoeba Neoparamoeba pemaquidensis is a significant disease in various commercially important finfish and invertebrates worldwide. Outbreaks of paramoebiasis have recently become more severe and are not longer restricted to the warmer months of the year. The lack of understanding of the biology of this parasite is reflected by the unavailability of effective drugs in invertebrates while an increased resistance to treatment in finfish is observed. Its loss of virulence on artificial media and the inability to obtain axenically large numbers of pathogenic parasites are major limitations to many areas of paramoebiasis research. Recently, it was shown that N. pemaquidensis grows rapidly on a rainbow trout gill cell line and is cytopathogenic to the monolayer. This thesis further investigated this newly established method of culture. First, its advantages and limitations were compared to conventional maintenance methods of N. pemaquidensis; so far, this is the only method that yields a pure and dense culture of amoebae at a reasonable cost. Secondly, the potential recovery of the initial pathogenicity of N. pemaquidensis towards two susceptible salmonid hosts was explored via transmission studies. Using immersion with a high concentration of amoebae, Amoebic Gill Disease could not be induced in Atlantic salmon or rainbow trout. Finally, the suitability of this source of amoebae for in vitro experiments was tested by developing a reproducible and fast method of screening various treatments (freshwater, lasalocid, oxytetracycline, VirkonRTM) using flow cytometry (FCM). Although the results indicate that N. pemaquidensis grown on rainbow trout gill cells are not good organisms for chemotherapeutant screening, FCM remains a useful method for evaluation of antiparasitic agents. |
