Monitoring Ceratomyxa shasta infection during a hatchery rearing
cycle: comparison of molecular, serological and histological
Department of Microbiology, Oregon State
University, Corvallis, Oregon 97331-3804, USA.
The prevalence of Ceratomyxa shasta infection in
production stocks of steelhead Oncorhynchus mykiss and cutthroat trout
O. clarki was monitored using a parasite-specific polymerase chain
reaction (PCR) assay. For all 4 stocks of fish followed through their 1
yr rearing cycle, C. shasta infection was detected despite their genetic
resistance to the disease and the treatment of the incoming water with
ozone. Infection was confirmed using serological methods and standard
histological procedures, except when prevalence was low (<10%). This
suggests that at the lowest infection levels PCR is more sensitive than
other methodologies, and can be used as an early indicator of infection.
Results of the PCR assay continued to correlate with histological and
serological detection as the numbers of parasites and the lesion
severity increased over the rearing cycle. For both steelhead and
cutthroat trout, early infections were characterized by large numbers of
parasites on the epithelial surface, but with little associated
inflammation. At release as yearlings, the infection prevalence in all
stocks was greater than 90 % and the inflammatory response in many fish
was extensive, with tissue necrosis and mucosal damage. Although C.
shasta infections no longer result in high mortality at this facility,
results of this study indicate that the parasite remains a contributor
to low condition indices in these fish, despite their genetic resistance
and ozone disinfection of the water supply.
PMID: 15648834 [PubMed - indexed for MEDLINE]