Quantitative investigation of Enteromyxum leei (Myxozoa: Myxosporea) infection and relative condition factor in cultured olive flounder Paralichthys olivaceus (Temminck and Schlegel)

Abstract

Enteromyxum leei has been reported to cause emaciation disease in various fish species. To determine the effect of parasite intensity on cultured olive flounder Paralichthys olivaceus, we investigated the relationship between the relative condition factor (rCF = CF/standard CF × 100) and parasite load with quantitative polymerase chain reaction (qPCR) and the challenge test. A total of 57 cultured olive flounders were obtained from 11 fish farms and divided into five groups based on their rCF. We investigated the parasite intensity in the posterior intestine of the fish. The parasite load was closely matched to severe loss of body weight. In addition, olive flounders were inoculated either orally or anally with intestinal scrapings of infected fish or phosphate‐buffered saline. The fish were reared at natural water temperature and transferred to different tanks, and the water temperature was adjusted to 20°C after 6 weeks of inoculation. When the water temperature was increased to 20°C, the rCF decreased in the experimentally infected group. The results demonstrated that qPCR can be utilized to determine the relative abundance of E. leei in olive flounders and water temperature is an important factor to track the progress of the emaciation disease.

Disruption of gut integrity and permeability contributes to enteritis in a fish-parasite model: a story told from serum metabolomics

“…Altered permeability may lead to impaired digestive functions and reduced fish growth [75], and arrested growth is one of the disease signs of this enteritis [76, 77]. In the present study, this was also evidenced by the differences in weight between R and C fish at the end of all trials.…”

Infection dynamics of Enteromyxum leei (Myxozoa, Myxosporea) in culture water and its effects on cultured olive flounder, Paralichthys olivaceus (Temminck & Schlegel)

“…Both Farms A and B had a decrease in rCF from September to November. In our previous study, olive flounder infected by E. leei showed that rCF decreased by approximately 10% over 9 w (Shin et al., 2018b). An experimental infection of E. leei in tiger puffer, Takifugu rubripes (Temminck & Schlegel), showed high mortality, with emaciation occurring 42 to 63 days after infection (Yanagida et al., 2006).…”

“…The pellets were used in the genomic DNA extraction, using the QIAamp DNA Mini Kit (Qiagen), as per the manufacturer's protocol. The E. leei 28S ribosomal DNA (rDNA) copy number in each sample was determined using the method described previously (Shin et al., 2018b). Briefly, partial 28S rDNA of E. leei was amplified by PCR and purified.…”