Nocardiosis and other common diseases of cultured golden pompano (Trachinotus blochii) in Taiwan.

Golden pompano (Trachinotus blochii) is a carnivorous teleost cultured in the Asia-Pacific region. Fish culture in high densities and numbers results in disease outbreaks, causing huge economic losses. Here, we collected cultured golden pompanos from 2021 to 2022 and identified the pathogens isolated from the diseased fish. Out of a total of 64 clinical cases observed in both sea cages and fish ponds, it was found that Nocardia seriolae was the predominant pathogen (26%), followed by Lactococcus garvieae (13%). Trichodina spp. was the most prevalent parasite in sea cages and earthen ponds (21%), while Neobenedenia spp. was the primary parasitic pathogen (16%) in sea cages. Given these findings, further investigations were conducted, including antibiotic susceptibility and pathogenicity tests specific to N. seriolae in golden pompanos. Antibiotic susceptibility tests of N. seriolae revealed that all strains were susceptible to doxycycline, oxytetracycline, florfenicol and erythromycin but resistant to amoxicillin and ampicillin. Additionally, a pathogenicity assessment was carried out by administering an intraperitoneal injection of 0.1 mL containing 107 CFU of N. seriolae per fish. The mortality rates observed varied between 40% and 90%, with the P2 strain exhibiting the highest level of virulence, resulting in a cumulative mortality of 90%. Therefore, disease outbreaks in fish can be minimized by developing effective treatments and prevention methods.

First report of a Kudoa lutjanus outbreak in farmed Chicken Grunts Parapristipoma trilineatum.

OBJECTIVE: As part of the National Disease Surveillance Program for Taiwanese Aquaculture, we investigated the causative agent of disease outbreaks in farmed Chicken Grunts Parapristipoma trilineatum. METHODS: In this study, outbreak cases on two separate farms were noticed in coastal Pingtung County, Taiwan. In total, 50 juvenile fish showing clinical signs (such as emaciation and erratic swimming behavior) and broodstock (two females and two males) from both farms were collected to perform gross lesion assessment, histopathological examination, and molecular identification of the pathogen. RESULT: Clinical symptoms were infected fish exhibited erratic swimming behavior, such as whirling and floating on the surface of the water. In the following months, cumulative mortality had reached 19% and 24%, respectively. The gross lesions in the infected fish included white oval cysts in the muscle, serosa of the internal organs, sclera of the eyes, and cerebral meninges. After conducting a wet mount examination of cysts using a light microscope, we observed a significant quantity of spores with morphological characteristics, suggesting their affiliation with the Myxosporea group. The spores were semiquadrate, with four tiny suture notches at the periphery; the mean spore length was 7.3 µm (SD = 0.5), and the mean spore width was 8.2 µm (SD = 0.6). The mean length and width of the pyriform polar capsules (nematocysts) were 3.6 µm (SD = 0.5) and 2.2 µm (SD = 0.5), respectively. The 18S and 28S ribosomal RNA sequences of these specimens were identical to those of Kudoa lutjanus. CONCLUSION: As this was the first time an outbreak of K. lutjanus in Chicken Grunts was confirmed, its reappearance with substantial mortality should serve as a warning to the aquaculture industry.

First identification, molecular characterization, and pathogenicity assessment of Lactococcus garvieae isolated from cultured pompano in Taiwan.

Lactococcosis, caused by Lactococcus garvieae, is an acute hemorrhagic septicemia in fish recorded in marine and freshwater aquaculture during the summer months. In 2020-2021, several sea cage Pompano farms recorded sudden fish mortality events. Based on the results of phenotypic and biochemical tests, L. garvieae was predicted to be the cause. PCR with L. garvieae specific primers (pLG1 and pLG2) targeting the 16S rRNA region further confirmed the etiological agent as L. garvieae after amplifying an 1100 base pairs (bp) product. Furthermore, the 16S rRNA sequences of the two representative strains (AOD109-196-2B and AOD110-215-2B) shared 99.81% identity with L. garvieae (GenBank accession number: MT597707.1). The genetic profiles of the strains were classified using pulsed-field gel electrophoresis after digestion with SmaI and ApaI, which clustered our strains under the same pulsotype. Multiplex PCR targeting the capsule gene cluster and serotype-specific PCR collectively showed that the strains were non-capsulated; thus, they belonged to serotype I. An experimental infection was designed to fulfil Koch's postulates by infecting healthy Pompano with case-driven L. garvieae strains (AOD109-196-2B and AOD110-215-2B) with a cumulative mortality of 70%. Overall, L. garvieae infection in Pompano emphasizes the need for better monitoring and control procedures in aquaculture settings.

[Efficacy and safety of sildenafil in the treatment of high altitude heart disease associated with severe pulmonary arterial hypertension in children: a preliminary evaluation].

OBJECTIVE: To observe the clinical efficacy and safety of sildenafil in the treatment of high altitude heart disease associated with severe pulmonary arterial hypertension (PAH) in children. METHODS: Fifty children (aged 2 months to 2 years) with high altitude heart disease associated with severe PAH, who were continuously transferred to the Intensive Care Unit between January 2011 and October 2013, were randomly assigned to observation and control groups. The control group was given conventional treatment, while the observation group received oral sildenafil [1 mg/(kg . d)] three times daily for 7-10 days in addition to the conventional treatment. Before and after treatment, hemodynamics, blood gas, routine blood parameters, and blood biochemical parameters were recorded. RESULTS: After treatment, the observation group had a significantly higher decrease in mean pulmonary artery pressure and significantly higher increases in arterial partial pressure of oxygen, cardiac output, cardiac index, and oxygenation index compared with the control group (P<0.05). In the observation group, there were no significant changes in mean arterial pressure, routine blood parameters and blood biochemical parameters (P>0.05), and no obvious adverse reactions were found. CONCLUSIONS: For children with high altitude heart disease associated with severe PAH, sildenafil can effectively reduce pulmonary artery pressure and improve cardiac function and does not cause adverse reactions. This therapy has good safety according to the preliminary evaluation.