Diseases of aquatic organisms最新文献

Parasitic sea lice (Copepoda: Caligidae) colonising marine salmonid (Salmoniformes: Salmonidae) aquaculture production facilities have been implicated as a possible pressure on wild salmon and sea trout populations. This investigation uses monitoring data from the mainland west coast and Western Isles of Scotland to estimate the association of the abundance of adult female Lepeophtheirus salmonis (Krøyer) colonising farmed Atlantic salmon Salmo salar L. with the occurrence of juvenile and mobile L. salmonis on wild sea trout, anadromous S. trutta L. The associations were evaluated using generalised linear mixed models incorporating farmed adult female salmon louse abundances which are temporally lagged relative to dependent wild trout values. The pattern of lags, which is consistent with time for L. salmonis development between egg and infective stage, was evaluated using model deviances. A significant positive association is identified between adult female L. salmonis abundance on farms and juvenile L. salmonis on wild trout. This association is consistent with a causal relationship in which increases in the number of L. salmonis copepodids originating from lice colonising farmed Atlantic salmon cause an increase of L. salmonis abundance on wild sea trout.

In the 1980s, a mass die-off of the long-spined sea urchin Diadema antillarum occurred on Florida and Caribbean coral reefs. D. antillarum populations largely did not recover, and in 2022, remaining populations experienced another mass mortality event. A ciliate most similar to Philaster apodigitiformis was identified as the causative agent of the 2022 event, which was named D. antillarum scuticociliatosis (DaSc). Here, we investigated possible treatments for this pathogen. We tested the efficacy of 10 compounds at final concentrations of 100, 50, 25, 12.5, 6.25, and 3.13 µM, or a 10-fold serial dilution series, against ciliates cultured from an infected D. antillarum specimen. Of the tested compounds, 8 induced 100% ciliate mortality at some dose after 24 h. The most effective (defined as those requiring the lowest dose to induce 100% ciliate mortality) were quinacrine and tomatine (both effective at 12.5 µM), followed by furaltadone and plumbagin (25 µM), bithionol sulfoxide and 2'4' dihydroxychalcone (50 µM), and oxyclozanide and carnidazole (100 µM). Toltrazuril and a commercially available anticiliate product containing naphthoquinones were not effective at any dose tested. Shortened (15 min) time trials were performed using ciliate cultures reared in natural seawater to better reflect natural environmental conditions, and revealed that 2 of the compounds (quinacrine and tomatine) induced 100% ciliate mortality at 100 µM, with tomatine also effective at 50 µM. This study identified several treatments effective against the causative agent of DaSc in vitro, but their toxicity and utility in vivo remain unknown.

Before 2019, adults of the sea louse Caligus undulatus were reported exclusively in plankton from ocean samples worldwide and were not known to parasitize fish hosts. In 2019, the first instance of this caligid parasitizing a fish host, Japanese sardinella Sardinella zunasi, was reported in the Seto Inland Sea, Japan. The presently reported study aimed to investigate the biology and ecology of adult C. undulatus in plankton communities in the Seto Inland Sea and surrounding waters from March 2020 to November 2021. The occurrence of sea lice in plankton communities was restricted to the period of August-January, mainly between October and December with maximum plankton abundance (10.5 ind. per 1000 m3) recorded on 30 November 2020. All post-naupliar stages of C. undulatus were found on the host fish, and they represented a typical life cycle pattern known for Caligus species. The sex ratios in both planktonic and parasitic adults were not significantly different. The frequency of occurrence of planktonic and parasitic adult females with egg strings was 68 and 46%, respectively. The number of eggs per string was significantly higher in parasitic adult females (mean ± SD: 16.9 ± 8.6) than in planktonic females (10.4 ± 10.8). These data suggest that adult females were detached from their hosts and continued to produce eggs without feeding. Seasonal migration of S. zunasi to brackish water for spawning may result in the detachment of mature caligids from the host and may be effective in protecting the offspring, which are less tolerant of less brackish water.

Mass mortality of farmed 1 yr old common carp Cyprinus carpio occurred at a carp farm in April 2022. In addition to high mortality, diseased fish exhibited papillomatous growths on the skin and fins, characteristic of carp pox. To investigate a possible viral cause, tissue samples were collected and nucleic acid was extracted using standard procedures. In a pooled sample from the gills and kidneys, carp edema virus (CEV) was detected by real-time PCR. In a skin tissue sample with papillomatous growths, cyprinid herpesvirus 1 (CyHV1) was detected by a conventional PCR targeting a conserved region of the DNA polymerase of cyprinid herpesviruses. PCR products were visualized through agarose gel electrophoresis, and the presence of CyHV1 DNA was confirmed by Sanger sequencing. This represents the first molecular confirmation of CyHV1 in common carp in Serbia.