Adriana Vivas

Prevalence of Cryptosporidium spp. and Giardia spp., spatial clustering and patterns of shedding in dairy calves from Córdoba, Argentina.

The objectives of this study were to estimate calf and herd prevalence of Cryptosporidium spp. and Giardia spp., the herd prevalence clustering, spatial distribution according to soil type and shedding patterns in dairy calves from Cordoba, Argentina. Six hundred twenty calves younger than 7 weeks of age from 43 dairy herds were sampled. Samples were processed with the formol-ether and modified Ziehl-Neelsen techniques. Univariate analysis and Kruskall-Wallis tests were used. Factors associated were subjected to multivariate analysis with calf shedding intensity as the response variable. Clustering of herd prevalence was assessed by a scan method, and spatial analysis was applied to explore the overlapping of high prevalence herds and soil type. Overall calf prevalence for Cryptosporidium spp. oocysts and Giardia spp. cysts were 19.35% (95% CI: 16.14; 22.54) and 34.50% (95% CI: 30.69; 38.34), respectively. Calves younger than two weeks of age were almost four times more likely to be infected with Cryptosporidium, in comparison to older ones (RR: 3.78, 95% CI: 2.27; 6.26). Giardia spp. shedding showed a similar age pattern (RR: 1.33, 95% CI: 1.02; 1.75). A primary cluster of high Cryptosporidium prevalence was found, and high prevalence herds were located in areas with poor drained soil.

IgY against enterotoxigenic Escherichia coli administered by hydrogel-carbon nanotubes composites to prevent neonatal diarrhoea in experimentally challenged piglets

In previous studies, the applicability of polymeric hydrogels for the protection of egg yolk immunoglobulin (IgY) against simulated gastric conditions was established. Thereafter, the performance of the hydrogels was improved with the addition of chitosan wrapped carbon nanotubes and the in vitro toxicity for porcine intestinal cells of these nanocomposites was assessed. The objective of the present study was to evaluate in vivo the protective efficacy of the nanocomoposite matrix for IgY when the immunoglobulin is used against enterotoxigenic Escherichia coli (ETEC) in challenged piglets. Groups of piglets orally challenged with 10(11)CFU/mL of ETEC were treated with non-protected and protected IgY. The clinical response of each group was monitored and evaluated in terms of dehydration, rectal temperature, faecal consistency score and body weight gain. Blood parameters and histological aspects were also studied. The results showed that treatment of infected piglets with protected IgY reduced significantly the severity of diarrhea. Non-protected IgY group show a lower recovery rate. Blood parameters and histological aspects were normal in both groups. Collectively, these results support previous in vitro studies showing that the nanocomposites can be an effective method of IgY protection against gastric inactivation.

Molecular screening of pathogenic Escherichia coli strains isolated from dairy neonatal calves in Cordoba province, Argentina

Abstract The aim of this study was to perform a current molecular characterization of bovine pathogenic Escherichia coli strains isolated from random samplings in Argentinean dairy farms. Rectal swabs were obtained from 395 (63.7%) healthy and 225 (36.3%) diarrheic calves, belonging to 45 dairy farms in Cordoba Province, Argentina. E. coli isolates were examined for virulence genes (f5, f41, f17, sta, stb, lt, eae, vt) using PCR and the prevalence of E. coli virulence profiles was spatially described in terms of spatial distribution. A total of 30.1% isolates were found to be positive for at least one of the virulence genes. Depending on the different gene combinations present, 11 virulence profiles were found. Most of the isolates analyzed had a single gene, and no combination of fimbrial and enterotoxin gene was predominant. There was no association between the frequency and distribution of E. coli virulence genes and calf health status. Most of the virulence profiles were compatible with ETEC strains and showed a homogeneous distribution over the sampled area. A clustering pattern for E. coli virulence profiles could not be recognized. This work provides updated information on the molecular characterization of pathogenic E. coli strains from dairy herds in Cordoba, Argentina. These findings would be important to formulate prevention programs and effective therapies for diarrhea in calves caused by E. coli.

Characterization of egg yolk immunoglobulin (IgY) against enterotoxigenic Escherichia coli and evaluation of its effects on bovine intestinal cells

Enterotoxigenic Escherichia coli (ETEC) infection is common in calves. Egg yolk antibodies (IgY) have been used to treat gastrointestinal infectious diseases. This study aimed to characterize IgY against bovine ETEC and to evaluate its effects on bovine intestinal cell culture challenged with a bovine ETEC strain. IgY was isolated from the egg yolks of hens immunized with ETEC. The characteristics of IgY were determined by Bradford, ELISA, gel electrophoresis and immunoblotting. Significant differences in anti-ETEC activity between anti-ETEC IgY and non-specific IgY were found in lyophilized fractions. In the bacterial growth assay, anti-ETEC IgY (40 mg/mL) showed growth inhibition of ETEC after 2 h of incubation (p<0.05). The difference in bacterial growth between anti-ETEC IgY and non-specific IgY groups was 0.51 log CFU/ml after an 8 h incubation (p<0.05). The bacterial adhesion assay indicated that anti-ETEC IgY (40 mg/ml) significantly decreased the adhesion of ETEC to bovine intestinal epithelial cells within 4 h (about 1.36 log units compared with the control group; p<0.05). This study demonstrates that anti-ETEC IgY inhibits the growth and adherence of ETEC to bovine intestinal cells and is a potential alternative to traditional treatments of E. coli infections.

Adrenal response of male rats exposed to prenatal stress and early postnatal stimulation

Abstract Stress in pregnant rats caused by chronic immobilization alters the pattern of secretion of corticosterone and modifies the hypothalamic-pituitary-adrenal axis (HPA) of the fetus. Early postnatal handling, however, may reverse the effects of increased secretion of corticosterone. We investigated the effects of prenatal stress and postnatal handling on the activity of the HPA axis of male offspring of stressed female rats. Male 90-day-old rats from four groups were investigated: prenatally stressed animals without postnatal handling, prenatally stressed animals with postnatal handling, unstressed control animals with postnatal handling, and unstressed control animals without postnatal handling. After sacrifice, the adrenal glands were weighed to determine the adrenal-somatic index. Apoptosis was evaluated by TUNEL assay and active caspase-3 expression. We found that the adrenal gland cortex:medulla ratio increased in animals with prenatal stress and that eventually the stress caused apoptosis. Handling newborns to simulate maternal activity ameliorated some of the negative effects of prenatal stress.

Immunohistochemical distribution of early pregnancy factor in ovary, oviduct and placenta of pregnant gilts

Abstract Early pregnancy factor (EPF) is an immunosuppressant that promotes maternal immune system tolerance of the allogenic fetus. Little is known about localization of this factor in different tissues and nothing has been reported about localization in swine reproductive and placental tissues. We determined the concentration of EPF in serum of gilts and porcine placenta conditioned medium (PPCM). We also analyzed the expression of EPF in different reproductive tissues of pregnant gilts at 10, 30, 60 and 90 days of pregnancy. EPF concentration in serum and PPCM was determined by western blot and densitometry. EPF expression in reproductive tissue was assessed by immunohistochemistry. The highest concentration of EPF was observed at 30 days in serum and PPCM; the concentration was higher in PPCM than in serum at the stages we evaluated. All reproductive tissues from the gestational stages analyzed showed specific labeling of EPF, but this labeling did not appear in non-pregnant gilts. At 30 days pregnancy, the EPF expression in the ovary was predominantly in follicular lutein cells, probably owing to its function as a luteotrophic factor. In the oviduct, EPF was expressed in unciliated secretory epithelial cells and in the cilia of ciliated cells. In the placenta, EPF was expressed in the fetal portion (mesoderm chorioallantois and epithelium of endoderm). EPF acts as an autocrine and paracrine growth factor for the trophoblast during the peri-implantation period.

Nanocomposites based on pH-sensitive hydrogels and chitosan decorated carbon nanotubes with antibacterial properties

The present work aimed to study the properties of a novel nanocomposite with promising biomedical applications. Nanocomposites were prepared by the addition of different concentrations of chitosan decorated carbon nanotubes to acrylamide-co-acrylic acid hydrogels. The nanocomposites chemical structure was characterized by Fourier Transform Infrared Spectroscopy (FT-IR). The FT-IR shows the typical bands due to the hydrogel and additionally the peaks at 1750 cm-1 and 1450 cm-1 that correspond to the carbon nanotubes incorporated into the polymer matrix. Mechanical properties and swelling measurements in different buffer solutions were also performed. The nanocomposites showed improved mechanical properties and a stronger pH-response. In order to evaluate antimicrobial activity, the growth and adhesion of Staphylococcus aureus to nanocomposites were studied. Cytocompatibility was also evaluated by MTT assay on MDCK and 3T3 cell lines. The nanocomposites were found to be cytocompatible and showed a reduced bacterial colonization.

Attenuation effects of prenatal stress by early postnatal stimulation in different research models

The prenatal and early postnatal life stages are both dynamic and vulnerable phases during mammalian development. Exposure to adverse factors that interfere with this critical sequence of events places the exposed individual to a higher risk of developing various disorders in adult life.1–3 For instance, high blood glucocorticoids concentration in pregnant stressed females crossing the placenta and the fetal blood-brain barriers,4 can affect brain development, birth weight and HPA axis function in offspring.5

Egg Yolk Antibodies and Nanotechnology Applied to Animal Health and Production

Nanotechnology is a rapidly developing area of science and technology, which deals with the application, production and processing of materials with sizes less than 100nm (a nanometer being one billionth of a meter). In addition, it is an interdisciplinary science comprising of various disciplines such as physics, chemistry, electronics, material science, health science, biology, and veterinary science, and it has impact on many industries [1].

Gut-Associated Lymphoid Tissue: A Key Tissue Inside the Mucosal Immune System of Hens Immunized with Escherichia coli F4

Immunoglobulin Y (IgY) is the predominant antibody found in hen’s (Gallus domesticus) egg yolk. This antibody, developed against several microorganisms in hen egg yolk, has been successfully used as an alternative to immunoglobulins from mammals for use in immunodiagnostics and immunotherapy. Enteropathogenic Escherichia coli (E.coli) F4 is the main etiological agent associated with swine neonatal diarrhea, and it causes notable economic losses in swine production. The aim of the present study was to evaluate the relationship between humoral immune response and the activation of gut-associated lymphoid tissue (GALT) in laying hens intramuscularly immunized with E. coli F4. Adult laying Shaver hens were immunized with a bacterin based on an inactivated lysate E. coli F4 strain that was originally isolated from neonatal piglet diarrhea, following a recommended schedule. The percentage of B lymphocytes in blood and spleen homogenates was determined by flow cytometry. Villi histomorphometry and the size of germinal centers (GC) activated in GALT and the spleen were measured in histological samples either stained with hematoxylin/eosin or through immunofluorescence. Antibody and isotype-specific antibodies in serum and egg yolk were measured using indirect enzyme-linked immunosorbent assay (ELISA). Secretory and serum immunoglobulin A (IgA) were measured by ELISA tests. Laying hen with intramuscular immunization with E. coli F4 lysate, activated both mucosal and systemic protection. Mucosal protection was provided through B lymphocytes, and most of them were activated on Peyer’s patches and esophageal tonsils, in GALT. Furthermore, increased B lymphocyte number in the lamina propria of the gut, and increased intraepithelial plasmatic cell number, produced high levels of mucosal IgA. Activated B lymphocytes interacted with absorptive cells, immune cells, and microbiota in the gut, producing signals that were translated into a powerful physical defense by producing a greater volume of mucin from an increased number of goblet cells. Systemic protection was provided through B lymphocyte activation of spleen GC, which produced hugely specific IgY serum levels. One week later, this specific IgY was deposited in the yolk. This suggests that GALT is a key immunologic tissue inside the mucosal immune system, acting as the “command center” for humoral reaction.