Porcine circovirus type 2 (PCV2) is the primary causative agent for porcine circovirus-associated disease (PCVAD). PCVAD has been the cause of considerable economic losses to the pork industry worldwide. The disease is primarily characterized by wasting, enlarged lymph nodes, jaundice and weight loss in affected weanling pigs. Several other complex syndromes involving reproductive failure, enteritis, pneumonia and necrotizing dermatitis have also been associated with PCV2 infection. Lymphoid depletion, which is the hallmark lesion of PCVAD, predisposes the host to immunosuppression. Disease progression is further complicated by co-infections with other bacterial and viral pathogens. Despite the availability of effective vaccines for the last 2 years, newly emerging strains of the virus have been reported to cause more severe outbreaks in parts of the USA and Canada. While knowledge of the biology and pathogenesis of PCV2 has progressed considerably over the last 12 years since the disease was recognized, many questions still remain to be answered.

The North American beef cattle industry has endured many changes throughout the years but is encountering some of the most dramatic challenges in history during the first decade of the 21st century. The US beef cattle inventory increased from 1990 to a high of 103.5 million in 1996 and since has declined to a low of 94.5 million on 1 January 2009. Even though economic signals have encouraged the cow herd to increase over the last 5 years, a significant decrease occurred during 2008. It is difficult to determine the precise cost of bovine respiratory disease (BRD) to the industry but it is reported to be greater than US$500 million per year. Data from our practice indicate that losses from BRD over the last 18 years have been characterized by 5-year cycles of decreases and increases. Perhaps it is time for the industry to look for ways to reduce death loss by methods that focus on the animal's response to the pathogens instead of continuing to focus on the pathogens.

Mastitis is not only a major cause of economic losses to the dairy industry but also a major problem in ensuring the quality and safety of the milk, associated with high somatic cell counts and residues of antibiotics used for treatment. One innovative approach to protection against mastitis is to stimulate the animal's natural defense mechanisms. Technological advances in immunological research have increased our ability to exploit the immunity of the bovine mammary gland during periods of high susceptibility to disease. The trace element selenium affects the innate and the adaptive immune responses of the mammary gland through cellular and humoral activities. Substantial research has been carried out on the effect of selenium (Se) on the immune function of the mammary gland and subsequent improvement in bovine udder health and mastitis control. Levels higher than current recommendations and Se-yeast can potentially be used to enhance our capacity to modulate the physiological mechanisms of the bovine mammary gland to respond to infection. This article provides an overview of the most recent research in this field.

The risk of bovine respiratory disease (BRD) has a significant effect on the value of cattle in the marketplace. Calves sold in larger groups have $6.37/45.45 kg more value than those sold as singles or in small groups. Morbidity is higher in unweaned commingled calves than those marketed in groups more than 45 days following weaning. Calves with an aggressive disposition have significantly less value than docile calves, due largely to depressed performance and less carcass value. The value of cattle in the marketplace can be improved by offering larger, uniform lots of cattle that have been weaned at least 45 days. Cattle that suffer BRD in the feedlot have from $23.23 to $151.18 less value than those remaining healthy.

The postnatal period is a ‘critical window’, a time when innate and passive immunity protect the newborn mammal while its own adaptive immune system is developing. Neonatal piglets, especially those reared in isolators, provide valuable tools for studying immunological development during this period, since environmental factors that cause ambiguity in studies with conventional animals are controlled by the experimenter. However, these models have limited value unless the swine immune system is first characterized and the necessary immunological reagents developed. Characterization has revealed numerous features of the swine immune system that did not fit mouse paradigms but may be more generally true for most mammals. These include fetal class switch recombination that is uncoupled from somatic hypermutation, the relative importance of the molecular mechanisms used to develop the antibody repertoire, the role of gut lymphoid tissue in that process, and the limited heavy chain repertoire but diverse IgG subclass repertoire. Knowledge gained from studies of adaptive immunity in isolator-reared neonatal pigs suggests that isolator piglets can be valuable in identification of virulence factors that are often masked in studies using conventional animals.

Dairy cattle are susceptible to increased incidence and severity of disease during the periparturient period. Increased health disorders have been associated with alterations in bovine immune mechanisms. Many different aspects of the bovine immune system change during the periparturient period, but uncontrolled inflammation is a dominant factor in several economically important disorders such as metritis and mastitis. In human medicine, the metabolic syndrome is known to trigger several key events that can initiate and promote uncontrolled systemic inflammation. Altered lipid metabolism, increased circulating concentrations of non-esterified fatty acids and oxidative stress are significant contributing factors to systemic inflammation and the development of inflammatory-based diseases in humans. Dairy cows undergo similar metabolic adaptations during the onset of lactation, and it was postulated that some of these physiological events may negatively impact the magnitude and duration of inflammation. This review will discuss how certain types of fatty acids may promote uncontrolled inflammation either directly or through metabolism into potent lipid mediators. The relationship of increased lipid metabolism and oxidative stress to inflammatory dysfunction will be reviewed as well. Understanding more about the underlying cause of periparturient health disorders may facilitate the design of nutritional regimens that will meet the energy requirements of cows during early lactation and reduce the susceptibility to disease as a function of compromised inflammatory responses.

The costs of bovine respiratory disease (BRD) to the beef producer can be estimated by identifying and summing the direct and indirect costs associated with the disease. The major direct costs are attributable to the cost of the feeder, production costs and carcass disposal. The indirect costs are mainly associated with infrastructure and labour.

Respiratory disease is a significant economic burden for United States dairies. Although there has been quality research, there is a need to translate the academic findings to the dairy barn. In particular, there is a need to implement solutions in the context of the economic ramifications of disease management. Plans to combat respiratory disease need to be simple, implemented incrementally and require low ‘management energy’. If respiratory disease is prevented at an early age, this will ensure the greatest chance that the animals will reach their full genetic potential to produce.

Streptococcus suis is an invasive porcine pathogen associated with meningitis, arthritis, bronchopneumonia and other diseases. The pathogen constitutes a major health problem in the swine industry worldwide. Furthermore, S. suis is an important zoonotic agent causing meningitis and other diseases in humans exposed to pigs or pork. Current knowledge on pathogenesis is limited, despite the enormous amount of data generated by ‘omics’ research. Accordingly, immunprophylaxis (in pigs) is hampered by lack of a cross-protective vaccine against virulent strains of this diverse species. This review focuses on bacterial factors, both surface-associated and secreted ones, which are considered to contribute to S. suis interaction(s) with host factors and cells. Factors are presented with respect to (i) their identification and features, (ii) their distribution among S. suis and (iii) their significance for virulence, immune response and vaccination. This review also shows the enormous progress made in research on S. suis over the last few years, and it emphasizes the numerous challenging questions remaining to be answered in the future.

Bovine respiratory disease (BRD) is important for the Ontario dairy industry due to the large economic and welfare costs of this disease. Practical science-based management techniques are needed to control and reduce the risk of this disease. Currently, the emphasis on BRD is focused on early detection of disease and prevention. These areas are important but it is not practical to assume this disease will be eliminated in the near future. It is necessary to determine the best practices for caring for sick animals, monitoring their recovery and making changes to their management to facilitate health and recovery. If management changes can be made for animals that are failing to thrive in a current situation, a more complete recovery may be possible and the welfare and economic costs of BRD may be minimized.

Bovine herpes virus 1 (BHV-1) is primarily associated with clinical syndromes such as rhinotracheitis, pustular vulvovaginitis and balanoposthitis, abortion, infertility, conjunctivitis and encephalitis in bovine species. The main sources of infection are the nasal exudates and the respiratory droplets, genital secretions, semen, fetal fluids and tissues. The BHV-1 virus can become latent following a primary infection with a field isolate or vaccination with an attenuated strain. The viral genomic DNA has been demonstrated in the sensory ganglia of the trigeminal nerve in infectious bovine rhinotracheitis (IBR) and in sacral spinal ganglia in pustular vulvovaginitis and balanoposthitis cases. BHV-1 infections can be diagnosed by detection of virus or virus components and antibody by serological tests or by detection of genomic DNA by polymerase chain reaction (PCR), nucleic acid hybridization and sequencing. Inactivated vaccines and modified live virus vaccines are used for prevention of BHV-1 infections in cattle; subunit vaccines and marker vaccines are under investigation.

The heritability estimates for resistance and/or susceptibility to bovine respiratory disease (BRD) are small, suggesting response to direct selection will be slow. The number of mammalian genetic markers associated with resistance to specific pathogens or improved immunity is increasing and will provide additional information for developing selection criteria for producing animals with an innate resistance to BRD. Environmental and management factors play significant roles in the prevalence of BRD and must be considered in a holistic approach to reducing BRD. Although no single solution for preventing BRD is likely to be discovered in the immediate future, the long-term outlook appears very promising.

The number of cattle operations which manage their livestock as certified organic or as natural is constantly increasing. Common conditions that practitioners often see have bacterial, viral or parasite etiologies. With restrictions on treatments allowed, either by the United States Department of Agriculture (USDA) Certified Organic program or by other niche programs, it would help practitioners to know what is allowable to use and how to approach cases in these settings. This presentation aims to provide veterinarians with an awareness of animal health care when working with organic/natural producers and alternative therapies that are understandable to medically trained professionals.

An animal's welfare should be governed by five freedoms, namely, freedom from hunger and thirst, freedom from discomfort, freedom from pain, injury or disease, freedom to express normal behavior and freedom from fear and distress. If the essence of veterinary medicine is to act like a physician for animals then the profession must be vocal in opposition to production diseases, which can be prevented by changing the system of production.

Bovine respiratory disease (BRD) research has provided significant understanding of the disease over the past 26 years. Modern research tools that have been used include monoclonal antibodies, genomics, polymerase chain reaction, immunohistochemistry (IHC), DNA vaccines and viral vectors coding for immunogens. Emerging/reemerging viruses and new antigenic strains of viruses and bacteria have been identified. Methods of detection and the role for cattle persistently infected bovine viral diarrhea virus (BVDV) were identified; viral subunits, cellular components and bacterial products have been characterized. Product advances have included vaccines for bovine respiratory syncytial virus, Mannheimia haemolytica and Pasteurella multocida; the addition of BVDV2 to the existing vaccines and new antibiotics. The role of Mycoplasma spp., particularly Mycoplasma bovis in BRD, has been more extensively studied. Bovine immunology research has provided more specific information on immune responses, T cell subsets and cytokines. The molecular and genetic basis for viral–bacterial synergy in BRD has been described. Attempts have been made to document how prevention of BRD by proper vaccination and management prior to exposure to infectious agents can minimize disease and serve as economic incentives for certified health programs.

Bovine respiratory disease (BRD) involves complex interactions amongst viral and bacterial pathogens that can lead to intense pulmonary inflammation (fibrinous pleuropneumonia). Viral infection greatly increases the susceptibility of cattle to secondary infection of the lung with bacterial pathogens like Mannheimia haemolytica and Histophilus somni. The underlying reason for this viral/bacterial synergism, and the manner in which cattle respond to the virulence strategies of the bacterial pathogens, is incompletely understood. Bovine herpesvirus type 1 (BHV-1) infection of bronchial epithelial cells in vitro enhances the binding of M. haemolytica and triggers release of inflammatory mediators that attract and enhance binding of neutrophils. An exotoxin (leukotoxin) released from M. haemolytica further stimulates release of inflammatory mediators and causes leukocyte death. Cattle infected with H. somni frequently display vasculitis. Exposure of bovine endothelial cells to H. somnii or its lipooligosaccharide (LOS) increases endothelium permeability, and makes the surface of the endothelial cells pro-coagulant. These processes are amplified in the presence of platelets. The above findings demonstrate that bovine respiratory pathogens (BHV-1, M. haemolytica and H. somni) interact with leukocytes and other cells (epithelial and endothelial cells) leading to the inflammation that characterizes BRD.

Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Mycoplasma bovis and Arcanobacterium pyogenes are all frequently implicated in bovine respiratory disease (BRD). M. haemolytica is considered the most important of the group. These bacteria are commensals in the nasopharynx and establish infection in the lungs of cattle that are subjected to a variety of stresses. Factors that permit adherence to and proliferation in the lungs and factors that cause tissue destruction and inflammation have been identified as having major roles in pathogenesis. These virulence factors include protein adhesins, capsular polysaccharide, outer membrane proteins, iron-binding proteins, lipopolysacharide or lipooligosaccharide, enzymes and toxins. These bacterial products function to evade the immune system, damage the immune system and induce a severe inflammatory response.