| Autor: |
Foott, J.Scott, Stone, R., Wiseman, E., True, K., Nichols, K. |
| Zdroj: |
Journal of Aquatic Animal Health; June 2007, Vol. 19 Issue: 2 p77-83, 7p |
| Abstrakt: |
AbstractInfectious Ceratomyxa shastaand Parvicapsula minibicornisactinospores were present in Klamath River samples collected in April, May, and June 2005. Juvenile Chinook salmon Oncorhynchus tshawytschaexposed to river water maintained at the ambient Klamath River temperature for 0, 4, 24, 72, and 168 h (7 d) developed asymptomatic infections from both parasites. Elevated water temperature (18°C) in June may have reduced actinospore viability, as both C. shastaand P. minibicornisinfection markedly declined in fish exposed for over 72 h. As judged by the prevalence of infection for both parasites, the number of infectious actinospores tended to increase or remain steady through the spring. Ceratomyxa shastainfections were characterized by the presence of a few trophozoites within granulomatous foci in mesentery adipose tissue and were consistently observed outside of the intestine. Similarly, low numbers of P. minibicorniswere observed in kidney glomeruli and tubules but were not associated with inflammation. Parvicapsula minibicornisDNA was consistently detected by quantitative real-time polymerase chain reaction in filtered water samples collected each month and from each time posttransfer. These data and the high prevalence of infection observed in the exposed fish indicate that P. minibicornisactinospores were at a relatively high concentration in the river during the spring. In contrast, C. shastaDNA was only detected in half of the water sample sets and its detection did not correspond well to C. shastainfectivity. An approximately threefold increase in river flow from the April to the May water collection was not associated with a decline in either the detection of actinospores (particularly for P. minibicornis) or the prevalence of infection for both parasites. Actinospores of these myxosporean parasites have the potential to infect salmonids for at least 7 d after release from the alternate polychaete host. |
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