The Gran Acuario Mazatlán (GAM), Mexico’s largest aquarium, is located at the entrance of the Gulf of California. In April 2023, fish in the Ocean Tank (OT) began exhibiting disease symptoms, followed by significant mortality, primarily affecting Caranx caninus, Chaetodipterus zonatus, and Lutjanus colorado. Parasitological examinations identified heavy infestations of Neobenedenia sp. (Monogenea: Capsalidae), with parasites extensively covering body surfaces and gills of some individuals. To control the outbreak, an environmental management strategy was implemented, involving a gradual reduction in water temperature (from 26 °C to 22 °C) and salinity (from 35 ppt to 26 ppt), increased cleaning frequency, and parasite egg abundance monitoring. Over time, egg abundance declined, and by July, fish behavior and feeding rates had returned to normal, with parasite-associated mortality dropping below 2%. Preventive measures, including strict quarantine protocols for new fish, have been implemented to maintain optimal conditions in the OT. This case highlights the challenges of managing parasite outbreaks in large, multi-species aquaria and underscores the importance of environmental control strategies in marine animal care.

Objective. To analyze histological and immunological changes in the Pacific white snook (PWS) Centropomus viridis during primary infection and re-infection with the monogenean Rhabdosynochus viridisi. Materials and methods. Samplings were performed at three timepoints (0,1, and 2). Histological alterations in gills were evaluated by the severity degree and the degree of tissue change. RT-qPCR assays were developed to investigate the expression of il1B, il8, il10, il12, il17, igM, igT, ifnγ, tnfα, tbet, hsp70, foxp3a, stat4, and cmip in gills and head kidney. Results. The prevalence of infection was 100% in challenged fish. During the primary infection, the mean intensity was 152 parasites per fish at Time 1 and 94 at Time 2, while in the reinfection, it was 367 parasites at Time 1 and 129 at Time 2. Histological analysis of gills showed fusion of the secondary lamellae, hyperplasia, infiltration of mononuclear inflammatory cells, and increase of chloride cells in both primary infections and reinfections. Only the expression of cmip in gills at Time 1 was significantly higher in reinfections than in primary infections, and the expression of il12β showed a fold-change value >100 in head kidney at Time 2 in primary infections. Conclusions. The monogenean R. viridisi may cause histological alteration in its fish host. As showed by the decrease of the intensity of infection from Time 1 to Time 2, it seems that the PWS is able to combat R. viridisi; however, our immunological analysis did not reveal strong evidence of a possible mechanism.

The Pacific thread herring, Opisthonema libertate, is a fishery resource in the eastern tropical Pacific, yet its population dynamics are poorly understood. The aims of this work were to document the metazoan parasite species in O. libertate from the Gulf of California in Mexico, determine latitudinal changes in their infection levels, and assess their potential as biological tags. Six parasitic species were identified: Myosaccium ecaude and Parahemiurus merus digeneans, Cribromazocraes cf. travassosi and Mazocraeoides georgei monogeneans, Pseudoterranova sp. nematodes, and Lepeophtheirus sp. copepods. The monogenean and copepod species are reported for the first time in O. libertate. Many fish were infected with digeneans, and there was a rare occurrence of other parasites. While the prevalence and median intensity of M. ecaude and P. merus significantly varied among sampling localities, a multivariate analysis revealed a distinct separation between some localities; these results suggest that individual fish form several discrete populations. However, the utility of these parasites as biological tags will be further probed because they cannot satisfy all requirements for good biological tags. The present results might be helpful in complementing other techniques to determine the movement and stock structure of O. libertate, albeit with certain limitations.

El consumo de pescado y mariscos crudos o semicrudos representa un riesgo para la salud pública debido a posibles infecciones parasitarias. Entre los parásitos transmitidos por productos marinos destacan los nematodos de la familia Anisakidae, causantes de anisakidosis, una zoonosis emergente con potencial impacto en la salud humana. Una de las anisakidosis más conocidas es la anisakiasis, causada por nematodos del género Anisakis. El objetivo de este estudio fue evaluar el nivel de conocimiento sobre la anisakiasis entre consumidores en Sinaloa, México. Se aplicó una encuesta a 501 participantes. La mayoría de los participantes reportó consumir ceviche o sushi al menos una vez al mes. Aunque la mayoría de los encuestados reconoce el riesgo general de adquirir parásitos a través del consumo de pescado crudo o semicrudo, existe un desconocimiento marcado sobre Anisakis como agente etiológico específico. Adicionalmente, mediante el análisis de tendencias de búsqueda de Google Trends, se observó un aumento sostenido en el interés por preparaciones como ceviche y sushi durante los últimos 20 años. Estos hallazgos resaltan la necesidad de implementar campañas educativas enfocadas en la prevención de anisakiasis y la promoción de prácticas seguras de consumo.

Some parasitic nematodes from the Anisakidae family can cause stomach illnesses in humans. These parasites naturally inhabit fish and mollusks and can infect us if we consume raw or undercooked seafood. This condition, known as anisakidosis, is increasing globally. Despite its rise, awareness of anisakidosis remains low in many regions, both among the general public and medical professionals. This is partly because identifying these nematodes is a challenging task, and effective diagnostic tools are not widely accessible. To address this issue, it is essential for consumers, healthcare providers, policymakers, and seafood industry professionals to work together. By improving knowledge and implementing preventive measures, we can reduce the risk of anisakidosis and protect public health.

Thread herrings (Opisthonema spp.) are economically important fish species in the Tropical Eastern Pacific. Knowledge of the parasitofauna of commercially exploited species is useful as it can increase our understanding of fish biology and ecology. However, our knowledge of the parasites of Opisthonema spp. is limited. During a fisheries exploration survey in April 2022, samples of Opisthonema bulleri and O. libertate were collected from three oceanographic stations in the Gulf of Tehuantepec in the Mexican Pacific. Parasitological analysis of these materials uncovered four parasite species: Myosaccium ecaude (Trematoda), Cribromazocraes sp. (Monogenea), Pseudoterranova sp. (Nematoda), and an unidentified crustacean of the family Pennellidae (Copepoda). All these species appeared rarely, except for M. ecaude, which reached a prevalence of 100%. The median intensity of M. ecaude infection was significantly higher in O. bulleri than in O. libertate. We analyzed the relationship between parasitic infection intensity and three host traits (fork length, body weight, and age). Only body weight showed a significant positive association with intensity. Future studies are required to analyze the possible effects of seasonality, locality, and host ontogeny on the occurrence of M. ecaude in thread herrings in the Tropical Eastern Pacific.