Acute Salmonella infection in swine

The objectives of this dissertation are focused on defining acute Salmonella infection in swine, and contains six chapters and two appendices. Acute Salmonella infection is defined as the ability of swine to infect alimentary and non-alimentary tissues within 3 hours following inoculation.;Chapter 1 provides a general overview of Salmonella. It includes a description of swine salmonellosis, the pig\u27s response to Salmonella infection, methods of Salmonella detection, an overview of intervention used for the reduction of Salmonella infections, and describes acute Salmonella infection in swine.;Chapter 2 indicates that the most common swine associated Salmonella serotypes are capable of acutely infecting pigs. Pigs were inoculated with varying Salmonella serotypes, necropsied, and alimentary and non-alimentary tissues were cultured for the presence of Salmonella . In conclusion, Salmonella wildtype isolates were capable of acutely infecting pigs more so than vaccine strains.;Chapter 3 helps elucidate the mechanisms utilized by Salmonella to acutely infect swine. Varying Salmonella wildtype isolates, mutant strains, and vaccine strains were inoculated and evaluated in there abilities to acutely infect pigs. Reduction in acute Salmonella infection was seen in avirulent deletion mutants in which the cya/crp genes had been inactivated or in those strains attenuated by neutrophil passage. This study also indicated that acute infection virulence may be enhanced after continual passage of Salmonella through pigs.;Chapter 4 indicates the minimal number of Salmonella that are required to induce acute Salmonella infection. Pigs were exposed to various levels of Salmonella by either intranasal inoculation, or subjecting them to a contaminated environment. Greater than 1 X 103 Salmonellae were required to induce acute Salmonella infection.;Chapter 5 analyzes acute Salmonella infection in germfree pigs. Germfree pigs were inoculated with probiotic bacteria and subsequently challenged with Salmonella. This study established a germfree probiotic model for the reduction of acute Salmonella infection, and indicates that germfree pigs are susceptible to acute Salmonella infection.;Chapter 6 is a general conclusions chapter. Additionally, it provides suggestions for further work to advance science in the field of acute Salmonella infection in swine

Beneficial Microorganisms in Low-Input Agriculture

The overall involvement of microorganisms in crop production still remains much of a mystery. Because of their distribution and size, most studies have been done in the laboratory and the implications of these studies referred back to the field. With this approach, unfortunately, much remains unknown, not only about the growth of individual organisms, but certainly the interactions of organisms in nature. Several nontraditional soil amendments have been marketed over the years that capitalize on our lack of understanding of soil microbial processes. Terms such as soil activators, soil enhancers, and enzyme stimulators have been used, claiming to improve soil structure, the life of the soil, reduce soil erosion, release pent up nutrients (one of my favorites), and others claims. Often the product is based on revolutionary new research that has yet to be tested by the local land-grand university. From my perception, more often than not, an idea is being sold rather than a viable product. Those of us in science, nevertheless, know there are happenings occurring in nature that we don\u27t adequately understand, and some chance discovery of one of these products may have scientific merit. But until it is thoroughly tested by independent researchers not tied to the product, one should be very cautious of product claims

Nitrogen conservation in swine manure composting land-application systems

The use of bedding in the popular hooped houses for swine production generates large volumes of manure that composts easily. However, composting results in nutrient losses, especially for nitrogen, which then diminish its value as a fertilizer. This study looks at carbon and nitrogen dynamics in the composting process and subsequent soil mineralization

Artificial soils to assess temperature sensitivity of the decomposition of model organic compounds: effects of chemical recalcitrance and clay-mineral composition

Understanding the temperature sensitivity of soil organic matter (SOM) decomposition is important to predict the response of soil carbon (C) dynamics to projected global warming. There is no consensus, however, as to whether or not the decomposition of recalcitrant soil C is as sensitive to temperature as is that of labile soil C. Soil C is stabilized by three mechanisms: chemical recalcitrance, mineral interaction and physical accessibility. We used artificial soils with controlled compositions to assess the effects of chemical recalcitrance (cellulose compared with lignin) and clay-mineral composition with montmorillonite (M) or kaolinite (K) on the decomposition of model organic compounds at 2, 12, 22 and 32°C. When only substrate composition was varied, the presence of cellulose enhanced the decomposition rate of lignin. Treatments with relatively large amounts of cellulose were very sensitive to temperature only at low temperatures (2–12°C), whereas treatments with relatively large amounts of lignin had similar temperature sensitivities at all temperatures. When only clay-mineral composition was varied, CO2 production rates were greatest in soils containing kaolinite-montmorillonite mixtures (10% K:20% M) and least in soils containing kaolinite only at temperatures ≥12°C. Clay mixtures and pure montmorillonite treatments had their greatest temperature sensitivities at 2–12°C, whereas pure kaolinite treatments had the greatest temperature sensitivities at 12–22°C. Temperature sensitivities at the highest temperatures (22–32°C) were all small (Q10 \u3c 1.1 on days 30 and 140). Artificial soils with controlled but flexible compositions may serve as simple and useful models for evaluating SOM dynamics with a minimum of confounding factors

Optimizing microbial associations to enhance N and P soil nutrient availability

Sustainable farming systems rely in part on recycling nutrients through materials such as crop residues, manure, or biological inputs. Three nutrients commonly added as fertilizers in agricultural production systems are nitrogen (N), phosphorus (P), and potassium (K). Past research has shown that fungal and bacterial microbial systems may be an important way to add nutrients to the soil or to enhance availability of those nutrients already present. But the interaction of beneficial fungi and bacteria in a synergistic relationship with higher plants is still poorly understood. Moreover, very little is known about the ecology of these beneficial soil fungi

Integrated soil and weed management production systems for perennial food crops

Several alternative weed management tactics for strawberry and grape production were tested for their effects on weed control, crop yield and soil quality enhancement

Reducing pesticide use in Iowa vineyards: Alternatives to herbicides for vineyard weed management

Mulches can play a role in vineyard management. This project explored the optimum uses and practices for applying various mulches to grape agroecosystems

Nitrous oxide emissions from riparian forest buffers, warm-season and cool-season grass filters, and crop fields

Denitrification within riparian buffers may trade reduced nonpoint source pollution of surface waters for increased greenhouse gas emissions resulting from denitrification-produced nitrous oxide (N2O). However, little is known about the N2O emission within conservation buffers established for water quality improvement or of the importance of short-term N2O peak emission following rewetting dry soils and thawing frozen soils. Such estimates are important in reducing uncertainties in current Intergovernmental Panel on Climate Change (IPCC) methodologies estimating soil N2O emission which are based on N inputs. This study contrasts N2O emission from riparian buffer systems of three perennial vegetation types and an adjacent crop field, and compares measured N2O emission with estimates based on the IPCC methodology. We measured soil properties, N inputs, weather conditions and N2O fluxes from soils in forested riparian buffers, warm-season and cool-season grass filters, and a crop field located in the Bear Creek watershed in central Iowa, USA. Cumulative N2O emissions from soils in all riparian buffers (5.8 kg N2O-N ha−1 in 2006–2007) were significantly less than those from crop field soils (24.0 kg N2O-N ha−1 in 2006–2007), with no difference among the buffer vegetation types. While N2O peak emissions (up to 70-fold increase) following the rewetting of dry soils and thawing of frozen soils comprised 46–70% of the annual N2O emissions from soils in the crop field, soils in the riparian buffers were less sensitive to such events (3 to 10-fold increase). The ratio of N2O emission to N inputs within riparian buffers (0.02) was smaller than those of crop field (0.07). These results indicate that N2O emission from soils within the riparian buffers established for water quality improvement should not be considered a major source of N2O emission compared to crop field emission. The observed large difference between measured N2O emissions and those estimated using the IPCC\u27s recommended methodology (i.e., 87% underestimation) in the crop field suggests that the IPCC methodology may underestimate N2O emission in the regions where soil rewetting and thawing are common, and that conditions predicted by future climate-change scenarios may increase N2O emissions

Evaluation of the impact of tillage/cropping systems on soil microflora and week seedbank predation

Soil erosion and pesticide use are critical issues in sustainable agriculture. With a view to decreasing the amount of pesticides used for weed control, researchers assessed the impact of tillage, cropping systems and weed management regimes on seasonal and long-term weed and weed seedbank population dynamics, especially in Conservation Reserve Program land being returned to production

Equine Arteritis Virus Has Specific Tropism for Stromal Cells and CD8\u3csup\u3e+\u3c/sup\u3e T and CD21\u3csup\u3e+\u3c/sup\u3e B Lymphocytes but Not for Glandular Epithelium at the Primary Site of Persistent Infection in the Stallion Reproductive Tract

Equine arteritis virus (EAV) has a global impact on the equine industry as the causative agent of equine viral arteritis (EVA), a respiratory, systemic, and reproductive disease of equids. A distinctive feature of EAV infection is that it establishes long-term persistent infection in 10 to 70% of infected stallions (carriers). In these stallions, EAV is detectable only in the reproductive tract, and viral persistence occurs despite the presence of high serum neutralizing antibody titers. Carrier stallions constitute the natural reservoir of the virus as they continuously shed EAV in their semen. Although the accessory sex glands have been implicated as the primary sites of EAV persistence, the viral host cell tropism and whether viral replication in carrier stallions occurs in the presence or absence of host inflammatory responses remain unknown. In this study, dual immunohistochemical and immunofluorescence techniques were employed to unequivocally demonstrate that the ampulla is the main EAV tissue reservoir rather than immunologically privileged tissues (i.e., testes). Furthermore, we demonstrate that EAV has specific tropism for stromal cells (fibrocytes and possibly tissue macrophages) and CD8+ T and CD21+ B lymphocytes but not glandular epithelium. Persistent EAV infection is associated with moderate, multifocal lymphoplasmacytic ampullitis comprising clusters of B (CD21+) lymphocytes and significant infiltration of T (CD3+, CD4+, CD8+, and CD25+) lymphocytes, tissue macrophages, and dendritic cells (Iba-1+ and CD83+), with a small number of tissue macrophages expressing CD163 and CD204 scavenger receptors. This study suggests that EAV employs complex immune evasion mechanisms that warrant further investigation