Four strains of non-encysting amoebae were isolated from organs of freshwater fishes and characterized using light and electron microscope. Morphology of three clonal strains was consistent with amoebae which had already been described from water habitats. Two strains, one isolated from kidney tissue of common goldfish, Carassius auratus (Linnaeus, 1758), and the second one from brain of chub, Leuciscus cephalus Linnaeus, 1758, were identified with Vannella platypodia (Gläser, 1912) Page, 1976. Both strains were identical, except for the length of glycostyles. The strain isolated from the liver of perch, Perea fluviatilis (Linnaeus, 1758), was assigned to the genus Vexillifera Schaeffer, 1926 as Vexillifera expectata sp. n. The taxonomic position of the fourth non-encysting strain could not be safely established, although it shares some trophic cell structures with protostelids (Protostelia, Eumycetozoea). We present its detailed description here also to demonstrate that amoeba stages of this type of organisms are capable to infect fishes.
Water-borne transmission of the coccidium Cryptosporidium parvum Tyzzer, 1912 is frequently responsible for outbreaks of human cryptosporidiosis. One of the most important was reported in 1993 in Milwaukee in the United States, where 403,000 cases were recorded. The determination of the percentage of oocysts excystated is the first step in evaluating their viability, but it alone is not sufficient. This percentage depended on the conditions of storage and also the presence of oxidant or disinfectent agents in water. The percentage of excystation is not always related to viability. Therefore, determination of the viability of excysted sporozoites by determining their infectivity for enterocytic Caco2 cell lines in culture provides information essential for evaluating the risk of contaminated drinking water.
This is a followup report on the viability of pathogenic Acanthamoeba castellami, Naegleria australiensis, and N. fowleri during 5 years of cryopreservation and the virulence of N. fowleri during 30 months of cryostorage, all at -70’C. The greatest decrease in viability occurred during the first year of freezing and was 10-fold greater than the average yearly decrease during years 2-5. At 5 years of cryostorage, viability was 33 % for A. castellana, 38 % for N. fowleri and 51% for N. australiensis. Virulence of N. fowleri did not decrease during 30 months of freezing and what appeared to be an increase in virulence during cryopreservation may be the result of reduced viability of the less virulent amebae in a culture.