Nematodes in fish of genus Cottocomephorus (Cottidae)

The data on the morphology and relative abundance of nematodes in bottom-pelagic cottids Cottocomephorus grewingki and C. inermis met in Lake Baikal are presented. Three species of nematodes (Comephoronema werestschagini, Ichtiobronema hamulatum, Contracaecum osculatum baicalensis) were found. The differences in cottids invasion with nematodes are shown.

Evidence of IgE-Mediated Cross-Reactions between Anisakis simplex and Contracaecum osculatum Proteins

Fish consumers may develop allergic reactions following the ingestion of fish products containing nematode larvae within the genus Anisakis. Sensitized patients may cross-react with proteins from insects, mites and mollusks, leading to allergic reactions even in the absence of the offending food. Potential cross-reactivity in Anisakis-allergic patients with larval proteins from other zoonotic parasites present in freshwater and sea fish should be investigated due to an increasing occurrence in certain fish stocks, particularly Contracaecum osculatum. In this work, we evaluated IgE-cross reactions by in vivo (skin prick tests with parasites extracts) and in vitro methods (IgE-ELISA and IgE-immunoblot). In vivo skin prick tests (SPT) proved the reactivity of Anisakis-sensitized patients when exposed to C. osculatum antigens. Sera from Anisakis-sensitized patients confirmed the reaction with somatic antigens (SA) and excretory/secretory proteins (ES) from C. osculatum. Only anecdotal responses were obtained from other freshwater worm parasites. Consequently, it is suggested that Anisakis-sensitized humans, especially patients with high levels of specific anti-Anisakis antibodies, may react to C. osculatum proteins, possibly due to IgE-mediated cross-reactivity.

HELMINTOS GASTROINTESTINALES DE OTARIA FLAVESCENS SHAW 1800 (MAMMALIA: OTARIIDAE) LEÓN MARINO SUDAMERICANO DE LA COSTA CENTRAL DEL PERÚ

El objetivo de este estudio fue determinar la composición de la fauna helmíntica y la carga parasitaria presente en el lobo marino (Otaria flavescens Shaw, 1800) que fue hallado muerto en la playa Chorrillos del distrito de Barranca, provincia de Barranca, Lima, Perú. Se realizó la necropsia para extraer los órganos internos y los helmintos fueron colectados del tracto gastrointestinal aplicando la técnica de tamizaje Travassos. Los nematodos fueron aclarados con lactofenol de Amann para su identificación. Para el estudio morfológico de los platelmintos y acantocéfalos se coloreó con carmín acético de Semichon. Se recolectaron 982 especímenes y se identificaron los siguientes taxas de helmintos con su respectiva carga parasitaria: Nematoda: Contracaecum osculatum Rudolphi, 1802 con 822 ejemplares, Trematoda: Ogmogaster heptalineatus Carvajal, Durán & George-Nascimento, 1983 con 120 especímenes, Acantocephala: Corynosoma australe Johnston, 1937, 20 especímenes. Con respecto a Cestoda, se encontraron 20 especímenes del género Adenocephalus, con la especie A. pacificus Nybelin 1931. En conclusión, se registra por primera vez los helmintos gastrointestinales de O. flavescens en la costa central peruana. El helminto con mayor carga parasitaria fue C. osculatum.

Anisakis physeteris and Pseudoterranova decipiens in the Mugil curema fish caught in Tumaco, Colombia

Objetivo. Identificar nematodos de la familia Anisakidae en el pez de consumo Mugil curema. Materiales y métodos. Para este estudio, se recolectaron 16 peces Lisa (M. curema) del puerto de Tumaco, una ciudad en la costa colombiana del Pacífico. La identificación morfológica de las larvas se realizó mediante taxonomía clásica y se calculó el porcentaje de infestación de larvas. Para la identificación molecular, se realizó una PCR múltiple con cebadores para las especies Anisakis physeteris, Pseudoterranova decipiens, Anisakis simplex sensu stricto, Contracaecum osculatum, Hysterothylacium aduncum y Anisakis pegreffii. Resultados. La revisión taxonómica permitió la identificación de larvas de tipo II del género Anisakis y larvas del género Pseudoterranova. Las larvas se aislaron principalmente del intestino, donde se encontró que el 94% de los peces estaban parasitados por nematodos anisakidos. La PCR multiplex permitió la identificación de la especie A. physeteris (Larva tipo II) y P. decipiens. Conclusiones. Este estudio en el primer reporte del nematodo Anisakidae en Tumaco, Colombia. Estos resultados proporcionan una justificación convincente para un estudio adicional sobre la familia Anisakidae en Colombia, como un problema de salud pública.

Local immune depression in Baltic cod (Gadus morhua) liver infected with Contracaecum osculatum

Third-stage larvae of the anisakid nematode Contracaecum osculatum infecting cod (Gadus morhua) liver elicit a host immune response involving both innate and adaptive factors, but the reactions differ between liver and spleen. Inflammatory reactions occur in both liver and spleen, but a series of immune effector genes are downregulated in liver infected with nematodes whereas these genes in spleen from the same fish are upregulated. A series of novel primer and probe sets targeting cod immune responses were developed and applied in a real-time quantitative polymerase chain reaction set-up to measure the expression of immune-relevant genes in liver and spleen of infected and uninfected cod. In infected liver, 12 of 23 genes were regulated. Genes encoding cytokines associated with inflammatory reactions (IL-1β, IL-6, IL-8) were significantly upregulated, whereas genes encoding effector molecules, assisting the elimination of pathogens, C-reactive protein (CRP)-PII, hepcidin, lysozyme G1, lysozyme G2, C3 and IgDm, were significantly downregulated. The number of downregulated genes increased with the parasite burden. In spleen, 14 of 23 immune genes showed significant regulation and nine of these were upregulated, including genes encoding CRPI, CRPII, C3, hepcidin and transferrin. The general gene expression level was higher in spleen compared to liver, and although inflammation was induced in nematode-infected liver, the effector molecule genes were depressed, which suggests a worm-induced immune suppression locally in the liver.

Physiological condition of Eastern Baltic cod, Gadus morhua, infected with the parasitic nematode Contracaecum osculatum

Establishing relationships between parasite infection and physiological condition of the host can be difficult and therefore are often neglected when describing factors causing population declines. Using the parasite–host system between the parasitic nematode Contracaecum osculatum and the Eastern Baltic cod Gadus morhua, we here shed new light on how parasite load may relate to the physiological condition of a transport host. The Eastern Baltic cod is in distress, with declining nutritional conditions, disappearance of the larger fish, high natural mortality and no signs of recovery of the population. During the latest decade, high infection levels with C. osculatum have been observed in fish in the central and southern parts of the Baltic Sea. We investigated the aerobic performance, nutritional condition, organ masses, and plasma and proximate body composition of wild naturally infected G. morhua in relation to infection density with C. osculatum. Fish with high infection densities of C. osculatum had (i) decreased nutritional condition, (ii) depressed energy turnover as evidenced by reduced standard metabolic rate, (iii) reduction in the digestive organ masses, and alongside (iv) changes in the plasma, body and liver composition, and fish energy source. The significantly reduced albumin to globulin ratio in highly infected G. morhua suggests that the fish suffer from a chronic liver disease. Furthermore, fish with high infection loads had the lowest Fulton’s condition factor. Yet, it remains unknown whether our results steam from a direct effect of C. osculatum, or because G. morhua in an already compromised nutritional state are more susceptible towards the parasite. Nevertheless, impairment of the physiological condition can lead to reduced swimming performance, compromising foraging success while augmenting the risk of predation, potentially leading to an increase in the natural mortality of the host. We hence argue that fish–parasite interactions must not be neglected when implementing and refining strategies to rebuild deteriorating populations.

Baltic cod endohelminths reflect recent ecological changes

We suggest helminthological investigations of cod as a supplement to traditional biological and hydrographical methods for elucidation of ecological changes in the Baltic Sea. It is under discussion if oxygen deficit or seal abundance should explain the present critical situation of Baltic cod. A comparative investigation of endoparasitic helminths in Baltic cod (Gadus morhua), captured in the same marine habitat with an interval of 35 years (1983/2018) recorded 11 species of helminths comprising trematodes (Hemiurus luehei, Podocotyle atomon, Lepidapedon elongatum), nematodes (Contracaecum osculatum, Hysterothylacium aduncum, Capillaria gracilis, Cucullanus cirratus), cestodes (Bothriocephalus sp.) and acanthocephalans (Echinorhynchus gadi, Pomphorhynchus laevis, Corynosoma semerme). Significant prevalence and intensity increases were recorded for third-stage larvae of the nematode C. osculatum (liver location) and larvae of C. semerme (encapsulated in viscera). Both parasite species use grey seal as their final host, indicating the recent expansion of the Baltic seal population. A lower E. gadi intensity and an increased prevalence of L. elongatum of small cod (31–40 cm body length) suggest a lowered intake of amphipods (intermediate host) and elevated ingestion of polychaetes, respectively, but no significant changes were seen for other helminths.