Efficacy of passive sand filtration in reducingexposure of salmonids to the actinospore of Myxobolus cerebralis

[摘要] ABSTRACT: The aquatic oligochaete Tubifex tubifex parasitized by Myxobolus cerebralis releases triactinomyxon (TAM) actinospores that can infect some species of salmonids and cause salmonid whirling disease. Silica sand was tested as afiltration medium for removal of TAMs from water containing the parasite. Laboratory tests indicated sand filtration removed >99.99% of TAMs. In 2 different field tests, groups of 1 mo old rainbow trout Oncorhynchus mykiss were exposed for 2 wkto filtered and unfiltered water from a spring-fed pond enzootic for M. cerebralis. In November 2000, the exposure dose was estimated as between 3 and 5 TAMs fish^-1. During a March 2001 exposure, the estimated dose was between 286 and404 TAMs fish^-1. Fish were held for 6 mo post exposure (p.e.) in laboratory aquaria for observation and evidence of clinical signs of whirling disease. We used 4 diagnostic techniques to assess the prevalence and severity of infection by M.cerebralis among fish exposed to filtered and unfiltered water. These included polymerase chain reaction (PCR) for genomic DNA of the parasite, histological evaluation for tissue damage, tissue digestion for quantification of cranial myxospores of theparasite, and total non-sampling mortality that occurred over 6 mo p.e. All diagnostic tests verified that the prevalence and severity of infection was significantly reduced among fish in treatment groups exposed to filtered water compared tothose exposed to unfiltered water in both the low-dose and high-dose exposures.

[学科分类] 生物科学（综合）

[关键词] Salmonid whirling disease;Myxobolus cerebralis;Sand filtration