Patterns of the innate immune response in tambaqui Colossoma macropomum: Modulation of gene expression in haemorrhagic septicaemia caused by Aeromonas hydrophila.

The production of tambaqui Colossoma macropomum has recently reached a milestone, being considered the main native species produced in South American continental waters. Despite the importance of this fish, its immunity is not well understood. In this study we established some patterns of innate immunity for the species via two experiments. Both studies evaluated the fish in the absence (intraperitoneal saline) or presence (intraperitoneal, 3 x 107 CFU/mL of Aeromonas hydrophila at 0.1 mL/10 g of living weight) of infection at 5 points over time-course of 14 days (0 h, 6 h, 24 h, 7 d, 14 d). In the first experiment, the partial gene sequences and gene expression of IL-1ß, IRAK-1, C3, C4, lysozyme, IL-10, HSP70 and ß-actin were determined in the main secondary lymphoid organs of fish: the spleen and head kidney. The second study was performed to analyse the alternative complement pathway ACH50 in serum to support the elucidation of C3 gene expression. Results of the gene expression assays showed a tendency towards up-regulation of immune genes in infected fish in early phases of infection (mostly around 6 h and 24 h) and in the chronic phase (7 d and 14 d), with the exception of HSP70 which showed a down-regulation in infected fish. Our results also suggested that lysozyme was evolved in both pro- and anti-inflammatory activities. For genes of the complement system, it was demonstrated that C4 regulation followed the tendency of pro-inflammatory genes. However, the C3 gene was, surprisingly, not expressed in most fish and this corroborated with the results of the complement system activity in serum that also did not show activity in most fish. The possible reasons for the regulation of gene expression and association with fish disease are addressed in this paper.

Acute and chronic stress differently alter the expression of cytokine and neuronal markers genes in zebrafish brain.

We report the effects of acute and chronic stress on the expression of selective immune-related genes and markers of neuronal function in the brain of the zebrafish (Danio rerio). Fish were distributed into three groups: the non-stressed control group; the acute stress (AS) group, submitted to a single stressing episode; and the unpredictable chronic stress (UCS) group, submitted to two daily stressing episodes of alternating times and types of stress. The stressing protocols were applied for a period of 14 days. The UCS protocol triggered the expression of the pro-inflammatory cytokine genes IL-1ß and TNF-α, the anti-inflammatory cytokine IL-10 (negative feedback from the immune system), reduction in cFOS gene expression, and caused neuro-inflammation. The AS protocol had no effect on gene expression. Altered expression of cytokine genes, as observed in our study, correlates with several pathologies associated with neuro-inflammation, and the reduction of cFOS gene expression may indicate the occurrence of reduced neuronal plasticity. Our study further extends our knowledge about the interaction of the immune system and the different forms of stress.

Synthetic gene as target to assess the sensitivity of PCR to detect Trichinella spp. larvae in meat from a non-endemic region.

Trichinellosis is a zoonotic disease exotic in Brazil but commonly found worldwide including South American countries like Argentina. International trading of swine meat needs an official Trichinella-free diagnosis commonly carried out by pepsin-HCl digestion of diaphragm tissue fragments followed by microscopic examination for the presence or absence of Trichinella larvae. The easiness of this diagnostic method allows it to be performed at slaughtering plants but, in contrast, it lacks sensitivity and does not allow species differentiation, which is fundamental for determining geographical and species distribution of different genotypes. In our study, we aimed to evaluate a highly sensitive diagnostic method based on the polymerase chain reaction (PCR) that would allow us to detect and classify different species of Trichinella. Thus, we designed a synthetic gene and selected five sets of primers targeting specific regions of the Trichinella genome. The synthetic gene was cloned into a plasmid and then used to optimize PCR conditions. Using our PCR, we were able to detect 0.001 pg of the synthetic gene, which corresponded to 0.01 larvae. Then, we collected 175 samples of Suidae (domestic and wild boars) diaphragm fragments that were pooled into groups, digested with pepsin-HCl, and had the DNA extracted for analysis by PCR. The clinical samples evaluated were negative by PCR. Our results indicate that the PCR-based method might be a useful diagnostic method complementary to the pepsin-HCl digestion method currently in use, mostly in non-endemic areas.

ß-Glucan improves wound healing in silver catfish (Rhamdia quelen).

The immune modulating activity of ß-glucan on aquatic species has been a matter of intense investigation. Here, we aimed to investigate the effect of ß-glucan on wound healing of silver catfish, a Neotropical South American scale-free fish. Small sections of skin and muscle (3 mm in diameter) were removed and fish were bathed daily with ß-glucan (0.1% and 0.5%) up to 28 days when cicatrization was complete. A group of fish similarly injured and non-exposed to ß-glucan was used as control. Wound closure and healing was monitored visually and by histopathological analysis. In fish bathed with 0.5% ß-glucan we found reduced blood cortisol levels at day one post-wounding and, by day 7 post wounding, the deposition of granulation tissue was higher compared to non-exposed fish. In addition, from day 7 forward, wound size was significantly lower in fish bathed with 0.5% ß-glucan. Histopathological analysis of the wounded site indicated a thin layer of immature epidermal cells at day one post wounding. A discrete inflammation with mixed inflammatory cell infiltrate was observed on wounded muscle and was lower by day 7 post wounding on fish bathed with 0.5% ß-glucan. By day 14 post wounding, the deposition of collagen fibers and the presence of fibroblast and new muscle fibers were higher in fish exposed to 0.5% ß-glucan, and dermis restoration was complete. Thus, our results indicate that in silver catfish wound healing occurs rapidly and improves greatly by daily bathing with ß-glucan.

Reduced expression of selective immune-related genes in silver catfish (Rhamdia quelen) monocytes exposed to atrazine.

The effect of atrazine (ATZ) and its metabolites on aquatic vertebrate species has been a matter of concern to researchers and environmentalist. In this study we exposed head kidney monocytes to sublethal concentrations of atrazine (1 and 10 µg/ml-1), corresponding to 1% and 10% of the LC50-96h, to evaluate the expression of immune-related genes central to immune stimulation. The mRNA levels of TNF-α, Mieloperoxidase and Mx genes were significantly reduced following 24 h exposure to both concentrations of ATZ. The mRNA levels of iRAK4 were reduced only at the higher ATZ concentration and the mRNA levels of IL-1ß were not affected. The results reported here support our previous findings on the immunosuppressive effect of ATZ indicating its potential to interfere with the expression of immune-related genes, and strengthen the need to regulate ATZ usage aiming to preserve animal and human health.

Inactivated Parapoxvirus ovis as inducer of immunity in silver catfish (Rhamdia quelen).

Molecules with immune modulating activity are ubiquitously distributed in nature and their impact on aquaculture has been exploited in order to increase fish resistance to pathogens. Here, we investigated the effect of inactivated Parapoxvirus ovis (iPPVO) on blood cells and innate and acquired immune response of silver catfish (Rhamdia quelen). iPPVO inoculation had no effect on respiratory burst activity; however, following iPPVO inoculation, we observed a significant decrease on circulating monocytes concomitantly with an increased number of heterophilic granulocytes and thrombocytes, which are the main cells involved in innate immunity and provide connection with acquired immunity. Fish inoculated with a combination of bovine serum albumin (BSA) + iPPVO had significantly higher levels of antibodies to BSA compared to fish inoculated with BSA alone, but lower than fish inoculated with BSA + Freund's incomplete adjuvant (FIA). These findings points to the potential usefulness of iPPVO as immunomodulator in fish and instigate further research to identify its component that interact with immune cells and that could be exploited as adjuvants in fish.

Differences in Haemophilus parasuis adherence to and invasion of AOC-45 porcine aorta endothelial cells.

BACKGROUND: The pathogenesis of Haemophilus parasuis depends on the bacterium's ability to interact with endothelial cells and invade adjacent tissues. In this study, we investigated the abilities of eight H. parasuis reference strains belonging to serovars 1, 2, 4, 5, 7, 9, 10 and 13 to adhere to and invade porcine aortic endothelial cells (AOC-45 cell line). RESULTS: The strains belonging to serovars 1, 2 and 5 were able to attach at high rates between 60 and 240 min of incubation, and serovars 4, 7 and 13 had moderate attachment rates; however, the strains belonging to serovars 9 and 10 had low adherence at all time points. Strong adherence was observed by scanning electron microscopy for the strains of serovars 5 and 4, which had high and moderate numbers, respectively, of H. parasuis cells attached to AOC-45 cells after 240 min of incubation. The highest invasiveness was reached at 180 min by the serovar 4 strain, followed by the serovar 5 strain at 240 min. The invasion results differed substantially depending on the strain. CONCLUSION: The reference strains of H. parasuis serovars 1, 2, 4 and 5 exhibited high adhesion and invasion levels to AOC-45 porcine aorta endothelial cells, and these findings could aid to better explain the pathogenesis of the disease caused by these serovars.

TbpBY167A-based vaccine is safe in pregnant sows and induces high titers of maternal derived antibodies that reduce Glaesserella parasuis colonization in piglets.

Glässer's disease is one of the main diseases affecting young piglets, particularly during the nursery phase, that can significantly impact pork production. Vaccination of sows has the potential to prevent Glaesserella parasuis infection during the first weeks of life that is to a substantial degree due to the transfer of maternal derived antibodies (MDA) in colostrum. In this study we compare the antibody response to two vaccines administered to pregnant sows. A subunit vaccine containing the mutant transferrin-binding protein, TbpBY167A, and an autogenous vaccine formulated with the LM96/20 strain of G. parasuis (SV4) administered on days 65 and 86 of the gestational period were safe and induced high titers of antibodies in sows. The IgG peak was reached on day 100 of gestation, and the translocation of IgG to the mammary gland was confirmed in colostrum at the time of delivery. Piglets born from vaccinated sows maintained positive IgG titers against TbpBY167A or G. parasuis SV4 for the duration of the experiment (35 days of life). Piglets born from sows vaccinated with the TbpBY167A-based vaccine had a significantly (p = 0.001) lower load of G. parasuis in the respiratory tract compared to those born from sows vaccinated with the autogenous vaccine. Finally, we demonstrate that the LM96/20 (SV4) strain is highly virulent and a primary agent of Glässer's disease.

Oncogenic viral DNA related to human breast cancer found on cattle milk and meat.

Bovine leukemia virus (BLV) is a major cause of lymphoma in cattle and has been recently correlated to breast cancer in humans. How and whether BLV might reach humans remains unknown but it could be through cattle-derived milk and meat. Here our aim was to investigate whether BLV DNA could be found in fresh milk and raw meat destined to human consumption and whether anti-BLV antibodies could be detected in human blood at the same geographical region. Milk (n = 36) and meat (n = 54) samples were collected from cows knowingly seropositive or negative to BLV and evaluated by nested PCR targeting BLV tax gene. Human serum samples (n = 900) were tested by ELISA to detect anti-BLV antibodies. BLV DNA was detected in 39 % of the milk samples and in 32 % of meat samples from BLV positive cows. Anti-BLV antibodies were found in 4.1 % of the human serum samples. Our data further supports the hypothesis that BLV might cause a zoonotic infection and indicate that milk and meat from BLV-infected cattle might be considered a potential source of infection to humans.

Bovine anaplasmosis as a risk factor for retained placenta, mastitis, and abomasal displacement in dairy cattle.

This study aimed to evaluate the frequency of IgG antibodies against A. marginale, the occurrence of this bacterium by qPCR, and the effect of bovine anaplasmosis as a risk factor for clinical cases of retained placenta, mastitis, and abomasal displacement in dairy cattle. For that 179 Holstein cows out of three dairy herds, in the municipality of Sertão, Rio Grande do Sul, Brazil. These cows were on farms that were vulnerable to risk factors that are crucial to susceptibility among these animals to this intracellular hemoparasite. The mean seropositivity for A. marginale from the periods evaluated was 54% on farm A, 69.4% on farm B, and 27.3% on farm C. Molecular diagnosis was performed with qPCR and the mean positivity for A. marginale among the cows on farms A, B, and C in December 2017 was 34.6% (67/179). Infected animals showed clinical cases of retained placenta (6.1%), mastitis (6.1%), and abomasal displacement (0.5%). The association between positivity for anaplasmosis and these clinical cases was assessed through the odds ratio. Our results show that females with a positive qPCR assay for A. marginale had 52.48 times increased probability (OR) to develop clinical cases of retained placenta and mastitis (P < 0.001). These clinical cases negatively impact the productivity of positive females. Thus, implementing preventive and prophylactic control measures to ensure the sanitary quality of the herds is needed to avoid losses due to morbidity and mortality and diminish the economic losses suffered by farmers.

Development and validation of a flow cytometry antibody test for Lawsonia intracellularis.

Lawsonia intracellularis is the etiologic agent of porcine proliferative enteropathy (PPE), an inflammatory bowel disease with a major economic impact on the pig industry. The serological diagnosis of PPE can be performed using Blocking or Indirect ELISA, Immunoperoxidase Monolayer Assay (IPMA) and Indirect Fluorescence Antibody Test (IFAT). Here, we designed a most sophisticated immunological method for the detection of porcine anti-L. intracellularis IgGs, named Flow Cytometry Antibody Test - FCAT. This assay uses whole, live-attenuated L. intracellularis bacteria derived from a commercial vaccine. For the assay, we set up the optimal antigen concentration (106 bacterium/assay), primary antibody dilution (1:100), time of incubation (20 min), antigen stability (15 days), precision (coefficient of variation - CV < 10%), reproducibility (CV ≤ 13%) and Receiver Operating Characteristic (ROC). When using a cut-off of >15.15% for FCAT, we determined that it showed a sensitivity of 98.8% and specificity of 100%. The rate of agreement with IPMA was 84.09% with a kappa index of 0.66. FCAT was used to screen 1,000 sera from non-vaccinated pigs housed in 22 different farms and we found that 730 pigs (73%) from 16 farms (72.7%) had L. intracellularis IgG. This high prevalence confirms that L. intracellularis is endemic on Brazilian pig farms. Finally, we determined that FCAT is an easy to perform diagnostic assay and we would highly recommend it for: i) seroepidemiological studies; ii) evaluation of infection dynamics; and iii) characterization of the humoral response profile induced by vaccines.

Brazilian Clinical Strains of Actinobacillus pleuropneumoniae and Pasteurella multocida: Capsular Diversity, Antimicrobial Susceptibility (In Vitro) and Proof of Concept for Prevention of Natural Colonization by Multi-Doses Protocol of Tildipirosin.

One hundred Actinobacillus pleuropneumoniae (App) and sixty Pasteurella multocida subsp. multocida serogroup A (PmA) isolates were recovered from porcine pneumonic lungs collected from eight central or southern states of Brazil between 2014 and 2018 (App) or between 2017 and 2021 (PmA). A. pleuropneumoniae clinical isolates were typed by multiplex PCR and the most prevalent serovars were 8, 7 and 5 (43, 25% and 18%, respectively). In addition, three virulence genes were assessed in P. multocida isolates, all being positive to capA (PmA) and kmt1 genes, all negative to capD and toxA, and most of them (85%) negative to pfhA gene. The susceptibility of both pathogens to tildipirosin was investigated using a broth microdilution assay. The percentage of isolates susceptible to tildipirosin was 95% for App and 73.3% for PmA. The MIC50 values were 0.25 and 1 µg/mL and the MIC90 values were 4 and >64 µg/mL for App and PmA, respectively. Finally, a multiple-dose protocol of tildipirosin was tested in suckling piglets on a farm endemic for both pathogens. Tildipirosin was able to prevent the natural colonization of the tonsils by App and PmA and significantly (p < 0.0001) reduced the burden of Glaesserella parasuis in this tissue. In summary, our results demonstrate that: (i) tildipirosin can be included in the list of antibiotics to control outbreaks of lung disease caused by App regardless of the capsular type, and (ii) in the case of clinical strains of App and PmA that are sensitive to tildipirosin based on susceptibility testing, the use of this antibiotic in eradication programs for A. pleuropneumoniae and P. multocida can be strongly recommended.

Innate immune response of silver catfish (Rhamdia quelen) exposed to atrazine.

The impact of agrichemicals on aquatic vertebrate species has been a matter of increasing concern to researchers and environmentalist. In the present study, we evaluated the effects of a sublethal concentration of atrazine (10% of the LC(50-96 h)), a world-wide used herbicide, on the innate immune system of silver catfish (Rhamdia quelen). A significant reduction on phagocytic index, bacteria agglutination and bactericidal activity of the serum, serum lysozyme and total serum peroxidase activity was observed in fish exposed to atrazine for 24 h. After 10 days exposure to atrazine, only bactericidal activity of the serum, bacteria agglutination and total serum peroxidase activity were significantly reduced. Atrazine had no effect on the natural complement hemolytic activity. Our results demonstrate that atrazine decreases the innate immune response of fingerlings, which might increase its susceptibility to opportunistic pathogens.

Modulation of expression of proinflammatory genes and humoral immune response following immunization or infection with Aeromonas hydrophila in silver catfish (Rhamdia quelen).

The early immune-related events arising from the interaction of antigen and innate immune cells are central to modulating the acquired immune response. Ideally, the immunizing antigen should elicit immunological changes similar to that observed after infection with the wild type pathogen. Here, we evaluated early changes on the expression of selected proinflammatory genes (TNF-α, IL-1ß, IRAK4 and myeloperoxidase) and innate immune parameters (serum myeloperoxidase, lysozyme and complement hemolytic activity) in silver catfish vaccinated or infected with Aeromonas hydrophila, the etiological agent of hemorrhagic septicemia. The humoral immune response and resistance to challenge were also evaluated in vaccinated and placebo inoculated fish. We found that the expression of TNF-α and IL-1ß genes was higher (p<0.05) in vaccinated or infected fish at 24 h post inoculation (p.i) compared to the control group but returned to basal levels at 72 h p.i. The expression of IRAK4 gene, however, was not altered by vaccination or infection. In addition, the natural hemolytic activity of complement was higher (p<0.05) at 24 h and 72 h p.i. in the vaccinated and infected groups; serum myeloperoxidase was higher (p<0.05) in these groups but only at 24 h p.i. and lysozyme activity was higher (p<0.05) only in the infected group at 72 h p.i. Furthermore, vaccination induced the production of IgM-like antibodies and protection to challenge with the A. hydrophila. Our results indicate that the vaccine formulation induces an immune response similar to that induced by the infecting pathogen and might be a valuable tool in the prophylaxis of hemorrhagic septicemia in silver catfish.

TbpBY167A-Based Vaccine Can Protect Pigs against Glässer's Disease Triggered by Glaesserella parasuis SV7 Expressing TbpB Cluster I.

Glaesserella parasuis is the etiological agent of Glässer's disease (GD), one of the most important diseases afflicting pigs in the nursery phase. We analyzed the genetic and immunological properties of the TbpB protein naturally expressed by 27 different clinical isolates of G. parasuis that were typed as serovar 7 and isolated from pigs suffering from GD. All the strains were classified as virulent by LS-PCR. The phylogenetic analyses demonstrated high similarity within the amino acid sequence of TbpB from 24 clinical strains all belonging to cluster III of TbpB, as does the protective antigen TbpBY167A. Three G. parasuis isolates expressed cluster I TbpBs, indicating antigenic diversity within the SV7 group of G. parasuis. The antigenic analysis demonstrated the presence of common epitopes on all variants of the TbpB protein, which could be recognized by an in vitro analysis using pig IgG induced by a TbpBY167A-based vaccine. The proof of concept of the complete cross-protection between clusters I and III was performed in SPF pigs immunized with the TbpBY167A-based vaccine (cluster III) and challenged with G. parasuis SV7, strains LM 360.18 (cluster I). Additionally, pigs immunized with a whole-cell inactivated vaccine based on G. parasuis SV5 (Nagasaki strain) did not survive the challenge performed with SV7 (strain 360.18), demonstrating the absence of cross-protection between these two serovars. Based on these results, we propose that a properly formulated TbpBY167A-based vaccine may elicit a protective antibody response against all strains of G. parasuis SV7, despite TbpB antigenic diversity, and this might be extrapolated to other serovars. This result highlights the promising use of the TbpBY167A antigen in a future commercial vaccine for GD prevention.

Altered hematological and immunological parameters in silver catfish (Rhamdia quelen) following short term exposure to sublethal concentration of glyphosate.

Using agrichemicals to control unwanted species has become a necessary and common worldwide practice to improve crop production. Although most currently used agrichemicals are considered relatively safe, continuous usage contributes for soil and water contamination and collateral toxic effects on aquatic species. Few studies correlated the presence of agrichemicals on fish blood cells and natural immune system. Thus, in this study, silver catfish (Rhamdia quelen) were exposed to sublethal concentrations (10% of the LC(50-96 h)) of a glyphosate based herbicide and hematological and natural immune system parameters were evaluated. Silver catfish fingerlings exposed to glyphosate for 96 h had a significant reduction on blood erythrocytes, thrombocytes, lymphocytes and total leukocytes in contrast to a significant increase in the number of immature circulating cells. The effect of glyphosate on natural immune system was evaluated after 24h or 10 days exposure by measuring the phagocytic index of coelomic cells, and lysozyme, total peroxidase, bacteria agglutination, bactericidal activity and natural complement hemolytic activity in the serum of fingerlings. A significant reduction on phagocytic index, serum bacteria agglutination and total peroxidase was observed only after 24h exposure to glyphosate. In contrast, fingerlings exposed to glyphosate for 10 days had a significant lower serum bacteria agglutination and lysozyme activity. Glyphosate had no effect on serum bactericidal and complement natural hemolytic activity after 24h or 10 days exposure. Nonetheless, the information obtained in this study indicates that glyphosate contaminated water contributes to alter blood cells parameters and to reduce the activity of natural immune components important to mediate fish resistance to infecting microorganisms.

Orally administered ß-glucan improves the hemolytic activity of the complement system in horses.

BACKGROUND AND AIM: Immune-modulating molecules mainly act on innate immune cells, which are central to early defense against invading pathogens and contribute to developing adaptive immunity. Yeast-extracted ß-glucan, a model immune-modulating molecule, is widely used in several animal species; however, its effect on horse immune parameters has not been thoroughly investigated yet. This study aimed to evaluate the effects of orally administered ß-glucan on selected innate immune parameters in horses. MATERIALS AND METHODS: Eighteen thoroughbred horses were assigned equally into three groups as follows: One control group (no ß-glucan) and two ß-glucan experimental groups (one received 125 mg and the other 2 g of ß-glucan per day for 28 days). Blood samples were collected before and at the end of the experiment for hematological analysis, whole blood phagocytosis, respiratory burst assays, and to assess the serum lysozyme and complement hemolytic activities. RESULTS: At the end of the experiment, significant decreases (p<0.05) in monocyte numbers were observed in the control horses (258.8±45.9 vs. 115.3±41.5) and in those fed 125 mg/day of ß-glucan (208.8±72.3 vs. 99.2±60.7), whereas a significant increase in numbers was noted in the horses that were fed 2 g/day of ß-glucan (303.5±45.8 vs. 429.8±86.0; p<0.05). The natural hemolytic activity of the complement was higher only in horses fed 2 g/day of ß-glucan (p=0.018) compared to the other groups. The hemolytic activity in the classical pathway was higher in those fed 125 mg/day (p=0.0035) and 2 g/day of ß-glucan (p=0.0001). CONCLUSION: ß-glucan improves important innate immune parameters and might be fed to horses before stressful events.

Unusual high prevalence of antibodies to hepatitis E virus in South Brazil.

Hepatitis E virus (HEV) is worldwide distributed and might cause acute or chronic hepatitis mainly in immunocompromised individuals. In previous studies we found a high prevalence of antibodies to HEV within blood donors in south Brazil and also within backyard-raised pigs. Here, we aimed to investigate the prevalence of anti-HEV antibody and HEV RNA within the general population from three major municipalities (Caxias do Sul, Passo Fundo and Santa Maria) in south Brazil. A total of 3000 blood samples were randomly obtained from clinical laboratories at each of the three municipality (n = 1000 each) to determine the presence of anti-HEV antibodies and HEV RNA. Overall, anti-HEV antibodies were detected in 574/1000 (57,4%) samples in Caxias do Sul, 655/1000 (65.5%) samples in Passo Fundo and 554/1000 (55.4%) samples in Santa Maria. The prevalence of HEV-positive samples increased steadily and significantly (P < 0,001) with age and was unusually higher within individual over 40 years. Despite of this, none of the pooled serum samples had detectable levels of HEV RNA. The high anti-HEV antibody prevalence suggests that the virus might be present on the environment and/or foodstuff and poses a permanent threat to immune-compromised individuals.

Exposure to sublethal concentration of glyphosate or atrazine-based herbicides alters the phagocytic function and increases the susceptibility of silver catfish fingerlings (Rhamdia quelen) to Aeromonas hydrophila challenge.

The resistance of fish to microorganisms challenge depends mainly on the efficacy of the immune response. Most studies on the natural immune response of fish have focused on the effect of diets and immunostimulants. Few studies correlated the presence of commonly used agrichemical and susceptibility to infection by aquatic microorganism. Thus, this study aimed to investigate the effect of glyphosate and atrazine-based herbicides on immune cell phagocytosis and susceptibility of silver catfish to Aeromonas hydrophila infection. Following exposure to sublethal concentrations of glyphosate or atrazine (10% of the LC(50-96 h)), a significant decrease in the number of intracelomatic cells and phagocytic index could be observed. In addition, silver catfish fingerlings exposed to glyphosate or atrazine were more susceptible to intracelomatic challenge with pathogenic A. hydrophila. Thus, the presence of these herbicides on the water alters the natural immune response to bacterial and possibly to other aquatic microorganism.

Tildipirosin: An effective antibiotic against Glaesserella parasuis from an in vitro analysis.

Tildipirosin is a latest generation macrolide that is used to battle infection diseases caused by Gram-negative bacteria. Recent studies have shown the effectiveness of this antimicrobial agent against Actinobacillus pleuropneumoniae; however, little information is available about Glaesserella parasuis, the etiological agent of Glässer's disease. In this study, the Tildipirosin activity to 100 Brazilian clinical isolates of G. parasuis was assessed using a broth microdilution assay. A total of 90% of G. parasuis isolates were sensitive at concentrations ≤ 4 µg/mL Tildipirosin, thus showing to be efficiently controlled by the therapeutic concentration recommended for pigs. On the other hand, a total of ten isolates have shown resistance to this antibiotic, with a minimal inhibitory concentration (MIC) ≥ 8 and ≤ 16 µg/ml. Notably, our findings highly support the use of Tildipirosin for treating Glässer's disease outbreaks, and it also advises the using of MIC approach to monitor the evolution of sensitivity or resistance exhibited by G. parasuis to this molecule, as well as to adjust therapeutic doses when necessary.