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Brucella is a genus of zoonotic, intracellular alphaproteobacteria known to cause disease in marine mammals as well as livestock and companion animals. Specifically, Brucella ceti may be associated with severe neurological, respiratory, and reproductive disease in small cetaceans. Nematodes, particularly members of the Pseudaliidae, are common in small cetaceans and may harbor Brucella ceti, although the nature of this relationship remains unclear. This study investigated the prevalence of Brucella spp. in nematodes collected at necropsy from 64 small cetaceans that stranded on the central California coast between 2017 and 2023, to better document this host-parasite-pathogen relationship and its potential implications for cetacean population health. A total of 2703 nematodes were analyzed using real-time PCR to identify Brucella at both the genus and marine mammal specific species level. Five individual nematodes of three separate species collected from five individual animals were found to have marine brucellae and from one of these, sequencing confirmed the identity as B. ceti . The pooled prevalence of marine mammal Brucella spp. in all parasites was estimated at 0.18%. No significant associations were found between marine mammal Brucella -positive parasites and host demographics, Brucella- clinical hosts, parasite species, or tissue location. While no associations existed between the presence of Brucella within host parasites and host Brucella infection status, demographic features, or parasite characteristics, this is the first time marine Brucella has been detected within parasites from cetaceans in this geographic region. This, along with the novel finding of a Brucella -positive parasite within cetacean mammary tissue, suggests that marine mammal brucellosis and parasitism may coexist within hosts and brucellosis may be more prevalent than anticipated, highlighting the need for additional research to clarify the dynamics between Brucella , parasites, and vulnerable small cetaceans.
Natural infections of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been documented in over 60 animal species, some distantly related. Several marine mammals have been predicted as highly susceptible to SARS-CoV-2 infection based on the homology of their ACE2 receptors to those of humans. To assess potential exposure of marine mammals to SARS-CoV-2, we conducted an opportunistic survey from 2020 to 2025 and tested 1,808 swabs and 378 serum samples from 21 marine mammal species in the United States. All the swabs tested by RT-qPCR were negative, indicating the absence of active infection. A low level of SARS-CoV-2 neutralizing antibodies was detected in three pinniped species, including Phoca vitulina (harbor seal, 13.6%, 95% CI: 5.2-27.4%), Zalophus californianus (California sea lion, 7%, 95% CI: 1.9-17.0%), and Halichoerus grypus (grey seal, 3.7%, 95% CI: 0.5-12.7%). These findings represent the first serological evidence of SARS-CoV-2 exposure in marine mammals in the United States, highlighting the need for continued monitoring of these populations and further research on SARS-CoV-2 transmission dynamics in wildlife.
In order to reveal the acute toxicity and physiological changes of the spotted babylon (Babylonia areolata) in response to environmental manipulation, the spotted babylon was exposed to three pH levels (7.0, 8.0 and 9.0) of seawater and four concentrations of nitrite nitrogen (0.02, 2.7, 13.5 and 27 mg/L). The activities of six immunoenzymes, superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), catalase (CAT), acid phosphatase (ACP), alkaline phosphatase (AKP) and peroxidase (POD), were measured. The levels of pH and nitrite nitrogen concentrations significantly impacted immunoenzyme activity over time. After the acute stress of pH and nitrite nitrogen, the spotted babylon appeared to be unresponsive to external stimuli, exhibited decreased vigor, slowly climbed the wall, sank to the tank and could not stand upright. As time elapsed, with the extension of time, the spotted babylon showed a trend of increasing and then decreasing ACP, AKP, CAT and SOD activities in order to adapt to the mutated environment and improve its immunity. In contrast, POD and GSH-PX activities showed a decrease followed by an increase with time. This study explored the tolerance range of the spotted babylon to pH, nitrite nitrogen, and time, proving that external stimuli activate the body's immune response. The body's immune function has a specific range of adaptation to the environment over time. Once the body's immune system was insufficient to adapt to this range, the immune system collapsed and the snail gradually died off. This study has discovered the suitable pH and nitrite nitrogen ranges for the culture of the spotted babylon, and provides useful information on the response of the snail's immune system.
The aim of this study was to investigate the circadian rhythm of muscle-related gene expression in mackerel tuna under different weather conditions. The experiment was carried out under two weather conditions at four sampling times (6:00, 12:00, 18:00, and 24:00) to determine the expression of growth, function, and rhythm genes: white muscle rhythm genes were rhythmic on sunny and cloudy days, except for PER3 and RORA; all functional genes had daily rhythmicity. Red muscle had daily rhythmicity on both sunny and cloudy days; functional genes had daily rhythmicity except for MBNL. The expression levels of the rhythm gene PER1 were determined to be significantly different by independent t-test samples in white muscle at 6:00, 12:00, 18:00, and 24:00 under different weather conditions; the expression levels of the functional genes MBNL and MSTN were both significantly different. In the red muscle, the expression of the rhythm genes PER3, REVERBA, and BMAL1 was determined by independent t-test samples at 6:00, 12:00, 18:00, and 24:00 on cloudy and sunny days; the functional gene MBNL was significantly different. The present study showed that mackerel tuna muscle rhythm genes and functional genes varied significantly in expression levels depending on weather, time of day, and light intensity and that the expression levels of myogenic genes were closely related to clock gene expression. The fish were also able to adapt to changes in light intensity in different weather conditions through positive physiological regulation.
