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RESUMO.-[Efeito imunomodulador da β-glucana usada como aditivo alimentar em jundiás (Rhamdia quelen).]O uso da β-glucana como suplemento alimentar foi avaliado em jundiás. A β-glucana foi adicionada à ração na proporção de 0.01%, e 0.1% e fornecida aos peixes por 21, para avaliar dados hematológicos e parâmetros do sistema imune natural, ou 42 dias, para avaliar ganho de peso e resistência ao desafio com Aeromonas hydrophila. A adição da β-glucana na dieta não afetou o ganho de peso e não induziu alterações hematológicas nem alterações nos níveis de aglutininas e mieloperoxidase sanguínea. No entanto, a atividade hemolítica natural do sistema do complemento foi significativamente maior nos peixes alimentados com β-glucana. Além disso, nos peixes alimentados com β-glucana e desafiados com A. hydrophila, o número de bactérias isoladas do sangue foi significativamente menor, e a sobrevivência ao desafio foi significativamente maior do que nos peixes que não receberam β-glucana. Consequentemente, concluímos que a β-glucana tem potencial imunomodulador quando adicionada à dieta, nas condições experimentais aqui indicadas, e contribui para aumentar imunidade natural e a resistência dos jundiás ao desafio com patógenos específicos. INTRODUCTIONThe occurrence of infectious diseases is one of the major causes of losses in modern aquaculture (Sitjà-Bobadilla The immunomodulatory effects of dietary β-glucan were evaluated in silver catfish. β-glucan was added to the diet (0.01%, and 0.1%) and fed to the fish for 21 days, to evaluate effects on blood and some innate immune parameter, or fed for 42 days, to evaluate growth rate and resistance to challenge with pathogenic Aeromonas hydrophila. We found that adding β-glucan to the diet had no effect on fish growth and no effect on blood cells, or serum bacterial agglutination and serum myeloperoxidase activity. However, fish that received β-glucan in the diet had the natural hemolytic activity of complement significantly higher compared to control fish. Furthermore, fish fed with β-glucan and challenged with A. hydrophila had fewer bacteria in blood and presented a significantly higher survival rate compared to control fish. Thus, we concluded that β-glucan might be explored as feed additive aiming to improve silver catfish innate immunity and resistance to specific pathogen.INDEX TERMS: Silver catfish, Rhamdia quelen, fish, immunostimulants, β-glucan, Aeromonas hydrophila.

The vampire bat ( Desmodus rotundus ) is a haematophagous animal that feeds exclusively on the blood of domestic mammals. Vampire bat feeding habits enable their contact with mammalian hosts and may enhance zoonotic spillover. Moreover, they may carry several pathogenic organisms, including coronaviruses (CoVs), for which they are important hosts. The human pathogens that cause severe acute respiratory syndrome (SARS‐CoV), Middle East respiratory syndrome (MERS‐CoV) and possibly coronavirus disease 2019 (SARS‐CoV‐2) all originated in bats but required bridge hosts to spread into human populations. To monitor the presence of potential zoonotic viruses in bats, the present work evaluated the presence of CoVs in vampire bats from southern Brazil. A total of 101 vampire bats were captured and euthanized between 2017 and 2019 in Rio Grande do Sul state, southern Brazil. The brain, heart, liver, lungs, kidneys and intestines were collected and macerated individually. The samples were pooled and submitted to high‐throughput sequencing (HTS) using the Illumina MiSeq platform and subsequently individually screened using a pancoronavirus RT‐PCR protocol. We detected CoV‐related sequences in HTS, but only two (2/101; 1.98%) animals had CoV detected in the intestines by RT‐PCR. Partial sequences of RdRp and spike genes were obtained in the same sample and the RdRp region in the other sample. The sequences were classified as belonging to Alphacoronavirus . The sequences were closely related to alphacoronaviruses detected in vampire bats from Peru. The continuous monitoring of bat CoVs may help to map and predict putative future zoonotic agents with great impacts on human health.

Crab-eating (Cerdocyon thous) and Pampas foxes (Lycalopex gymnocercus) are wild canids distributed in South America. Domestic dogs (Canis lupus familiaris) and wild canids may share viral pathogens, including rabies virus (RABV), canine distemper virus (CDV), and canine parvovirus 2 (CPV-2). To characterize the virome of these wild canid species, the present work evaluated the spleen and mesenteric lymph node virome of 17 crab-eating and five Pampas foxes using high-throughput sequencing (HTS). Organ samples were pooled and sequenced using an Illumina MiSeq platform. Additional PCR analyses were performed to identify the frequencies and host origin for each virus detected by HTS. Sequences more closely related to the Paramyxoviridae, Parvoviridae and Anelloviridae families were detected, as well as circular Rep-encoding single-stranded (CRESS) DNA viruses. CDV was found only in crab-eating foxes, whereas CPV-2 was found in both canid species; both viruses were closely related to sequences reported in domestic dogs from southern Brazil. Moreover, the present work reported the detection of canine bocavirus (CBoV) strains that were genetically divergent from CBoV-1 and 2 lineages. Finally, we also characterized CRESS DNA viruses and anelloviruses with marked diversity. The results of this study contribute to the body of knowledge regarding wild canid viruses that can potentially be shared with domestic canids or other species.

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Knowledge on fish immunoglobulin (Ig) characteristics and the availability of monoclonal or polyclonal antibodies to fish Igs are essential to evaluate the humoral immune response and the Ig distribution on leukocyte cells. We demonstrated that silver catfish serum Ig is composed of one immunodominant H chain with approximately 75k Da and one L chain with approximately 28 kDa, similar to human IgM. Rabbit polyclonal antibodies to the catfish IgM-like Ig recognized both the H and L chain and were useful in developing an indirect ELISA to measure the production of antibodies in fish immunized with bovine serum albumin. Dot blot and western blot cross-reactivity studies indicated a wide degree of epitope sharing amongst Ig from several Siluriformes and Characiformes fish indigenous to Brazilian rivers. In these fish species, polyclonal antibodies reacted mostly with the H chain. The results presented here are central to the development of tools and strategies to investigate the antibody production to inoculated antigens and tissue distribution of Ig molecules in native fish species. Furthermore, because of the wide range of cross-reactivity, polyclonal antibodies to silver catfish IgM-like Ig might be used to develop immunoassays to measure the humoral immune response in other fish species.