We developed a simple PCR-based method using feces to detect “Candidatus Xenohaliotis californiensis” (Rickettsia-like organism, RLO), which is responsible for withering syndrome (WS). Four abalone groups (Haliotis discus discus and H. gigantea) naturally or artificially infected with WS-RLO were prepared. After daily collection of the feces from individual animals over a seven-day period, the posterior esophagus (PE) was excised, and subjected to PCR for WS-RLO. WS-RLO-positive results were obtained from the feces of 30-67% animals, and from the PE of 17-97% animals. For the fecal PCR, more than one animal was positive from each group every day, although the WS-RLO-positive rate daily varied. When the sensitivity of the PCR was compared between DNA extracted from feces by boiling and that by QIAamp® DNA Stool Kit, there was no difference between the two methods. Fecal PCR combined with boiling DNA extraction is rapid and simple for screening abalone groups infected with WS-RLO.
Mortalities of three-lips Opsariichthys uncirostris occurred in a river in Shiga Prefecture, Japan, during the summer of 2013. The gills of diseased fish were heavily infected with the parasitic ciliate Chilodonella hexasticha. The intensity of parasite was 0.73-1.15 millions in dead fish, and 0.45-0.52 millions in apparently healthy fish. The cause of fish death may be a respiratory dysfunction by congestion due to the heavy infection with C. hexasticha on the gills. This is the first report of C. hexasticha infection of wild fish in Japan.
In this study, we report outbreak of viral nervous necrosis (VNN) in wild Epinephelus species, which are of an endangered fish group, in different Tunisian coastal areas in 2012. Seven fish of E. marginatus and E. costae caught at dead or moribund condition were investigated. Betanodavirus was detected in the brain and retinal tissues of all fish by RT-PCR and at high infective titers (106.0-8.8 TCID50/g) in five of seven fish. Sequence and phylogenic analyses of the viral genes revealed that the viruses belonged to RGNNV genotype and were closely related to some previously reported Mediterranean betanodavirus strains, suggesting virus exchanges among different fish populations in the Mediterranean Sea.
Damselfish Chromis chromis collected from the Black Sea coasts of Sinop, Turkey, were examined for myxosporeans in June and July 2013. One of 25 healthy fish and 2 dead fish had infections with Enteromyxum leei. Developing plasmodia and fully developed spores were numerously observed in the intestine and gall bladder of infected fish. This finding suggests that E. leei can develop normally in this fish species. Absence of fish farms close to the sampling site suggests that the parasite was not originated from farmed fish. This is the first report of E. leei in the Black Sea.
Experimental infection of ayu Plecoglossus altivelis with Edwardsiella ictaluri PH-0744 was performed under two different water temperatures, 20°C and 28°C. The strain exhibited higher virulence at 28°C than at 20°C in intraperitoneal injection challenge, with the LD50 values being < 6.0 × 10 CFU/fish at 28°C and 7.4 × 103 CFU/fish at 20°C. In immersion challenge at a dose of 2.5 × 107 CFU/mL for 30 min, mortality of fish was 95% at 28°C and 0% at 20°C. This high virulence of E. ictaluri at 28°C may explain frequent occurrence of E. ictaluri infection of ayu at high water temperature in rivers.