Paramyxoviruses are responsible for a wide variety of diseases both in humans and in animals. Common to many paramyxoviruses is the fact that they can cause neurological symptoms in their final host. Newly discovered paramyxoviruses, such as the Hendra and Nipah viruses, show the same pattern of pathogenesis as that of the paramyxoviruses already known. Canine distemper virus (CDV) is a well-studied member of the genus Morbillivirus. Study of the neuropathogenesis of CDV might give insight into disease mechanisms and suggest approaches for the prevention of other recently discovered paramyxovirus infections.

Thermophilic Campylobacter species, including Campylobacter jejuni and Campylobacter coli, are responsible for foodborne campylobacteriosis in humans and are increasingly resistant to fluoroquinolone (FQ) antimicrobials. The therapeutic use of FQ antimicrobial agents in food animal production, particularly in poultry, has become a concern for public health, because the practice may promote the emergence of FQ-resistant Campylobacter that can be transmitted to humans through the food chain. Recent studies have indicated that Campylobacter displays a hypermutable phenotype in response to in vivo treatment with FQ antimicrobials, resulting in the rapid emergence of resistant mutants. Distinct from other Gram-negative bacteria, the acquisition of FQ resistance in Campylobacter does not require stepwise accumulation of gyrA mutations and overexpression of efflux pumps, and is mainly mediated by single-step point mutations in gyrA in the presence of a constitutively expressed multidrug efflux pump, CmeABC. The simplicity of the resistance mechanisms may facilitate the rapid adaptation of Campylobacter to FQ treatment. The FQ-resistant Campylobacter mutants derived from chickens do not show a fitness cost in vivo and are ecologically competitive in the colonization of chickens even in the absence of antimicrobial selection pressure. These findings suggest that FQ-resistant Campylobacter may continue to persist regardless of antimicrobial usage, and highlight the need for extra effort to prevent the occurrence and spread of FQ-resistant Campylobacter in animal reservoirs.

In the last 5 years, numerous molecular methods have been published for the detection and characterization of bacteria in the field of veterinary medicine. PCR has been the most commonly used technology. Although not currently used for clinical veterinary diagnosis, new technologies such as liquid-phase hybridization, real-time PCR, pathogen load determination and DNA/protein microarray have been described and have many possible applications in the clinical bacteriology laboratory because of their sensitivity and efficiency. This review describes the basic principles and application of recently published DNA-based molecular techniques for the purpose of veterinary clinical bacteriological diagnosis. It covers advances in probe hybridization technology, DNA/RNA amplification techniques and other molecular detection methods, including 16S rRNA analysis for bacterial characterization and DNA microarrays for bacterial detection. The review briefly summarizes the application of molecular methods for the diagnosis of specific important bacterial infections of animals, and for other animal pathogens that are slow or difficult to isolate in the clinical bacteriology laboratory. In addition, the molecular detection of antimicrobial resistance genes and of bovine mastitis pathogens is briefly described and current commercially available tests are listed.

Based on current commercial aquaculture production practices, the production cycle for Atlantic salmon (Salmo salar) extends over a 36-month period during which time the fish are first exposed to intensive freshwater rearing conditions followed by transportation to marine netpen sites for ongrowing. It is predictable that, because of the duration of the production cycle and the variety of water conditions, deleterious environmental conditions have many opportunities to affect salmon health directly and indirectly. Furthermore, diseases which are iatrogenic arise from current methods used to prevent or treat infectious diseases. Specific, more frequently encountered examples are explored, with reference to the possible roles which these diseases may have in favouring the onset of infectious diseases.

Cryptosporidium species are intestinal protozoan parasites and are excreted in animal feces as stable oocysts. Cryptosporidium has now been detected in the feces of a wide range of ruminant and non-ruminant farmed animals, wild animals, domestic pets and birds and the parasite appears to be well adapted to survive and persist in feces for extended periods, ranging from several weeks to many months. Because of this persistence, these materials are important as potential vehicles of transmission within herds, farms, the water chain, the fresh food chain, and the wider environment. Appropriate handling of animal waste is necessary to control spread of this pathogen and to limit the significant risks of human infection. While water is a well-recognized vector of Cryptosporidium, it has only recently emerged that food may play a more significant role than previously realized in the transmission of the Cryptosporidium to humans. In the last 3–5 years, research efforts have been directed both at the development of suitable methods for isolation and detection of the parasite in foods and at the application of these methods to assess the prevalence and persistence of the parasite in a range of foods. Additionally, molecular subtyping methods have been used to establish the transmission routes of the parasite. This paper summarizes the general biology of Cryptosporidium and overviews the current research on C. parvum in the food chain. The risks posed by certain foods, such as salad/vegetable crops and beef, are discussed and control measures which may be useful in the farm-to-fork chain for these products are described.

American canine hepatozoonosis is an emerging, tick-transmitted infection of domestic dogs caused by a recently recognized species of apicomplexan parasite, Hepatozoon americanum. The known definitive host of the protozoan is the Gulf Coast tick, Amblyomma maculatum. Presently recognized intermediate hosts include the domestic dog and the coyote, Canis latrans. Laboratory-reared larval or nymphal A. maculatum can be infected readily by feeding to repletion on a parasitemic intermediate host; sporogony requires 35–40 days. Transmission of infection to the dog has been produced experimentally by oral administration of mature oocysts or oocyst-containing ticks. Canine disease follows experimental exposure in 4–6 weeks and is characterized by systemic illness, extreme neutrophilic leukocytosis, muscle and bone pain, and proliferation of periosteal bone. Histopathological findings include multifocal skeletal and cardiac myositis associated with escape of mature merozoites from within the host-cell environment. There is also rapid onset of periosteal activation and osteogenesis and, less frequently, glomerulopathy and amyloidosis. Sequential stages of development of H. americanum in both the dog and the tick have been elucidated. Gamonts potentially infectious to ticks have been observed in peripheral blood leukocytes of the dog in as few as 28 days after exposure to oocysts. Young coyotes experimentally exposed to a canine strain of H. americanum acquired disease indistinguishable from that of similarly exposed young dogs.

The few data collections that evaluate the involvement of organ systems in horse diseases are in agreement that the locomotor, gastrointestinal and nervous systems are the sites of primary disease in the vast majority of sick horses. When compared with diseases of these organ systems, equine cardiovascular diseases occur infrequently. The most detailed and comprehensive survey of equine cardiac pathology was reported in 1972 by Else and Holmes, who summarized the gross and microscopic cardiac findings from 1500 abattoir horses. This paper reviews the pathology of the cardiovascular diseases typically encountered in horses. Most of the pathological examples are from the files of the Veterinary Medical Teaching Hospital at the University of Florida, encompassing 24 years (1978–2002) and some 6000 equine necropsy cases. Preceding the specific topics are principles of the anatomy and function of the normal equine heart. Pathological entities include equine congenital cardiovascular diseases, acquired diseases of the pericardium, myocardium, endocardium and valves, cardiac neoplasms, and common equine vascular diseases and vascular neoplasms. Extensive use is made of photographs to illustrate the features of individual case examples.

Effective, sustainable control of nematode parasites of grazing livestock is becoming evermore challenging and difficult. This is largely due to two contrasting issues. One is the rapid escalation of resistance to anthelmintic drugs, which is arguably the greatest problem now facing the small ruminant industries worldwide. Secondly, there is the increasing trend towards organic farming, in which there is prohibition of the prophylactic use of all chemical compounds. Livestock producers urgently need non-chemotherapeutic alternatives in parasite control. Researchers have responded to this challenge and a variety of quite different approaches have been the subject of intense investigation in many countries for several decades now. These vary in relation to their stage of development for on-farm use, their utility, and their applicability across the spectrum of grazing livestock enterprises throughout the world. One relatively recent innovation is the biological control approach to nematode parasites. This has now reached the stage of commercialization. This review focuses on these issues and provides an overview of the possible ways in which the biological control of nematode parasites could be employed in grazing ruminant livestock systems worldwide.

Dendritic cells have been shown to be the main antigen-presenting cells in vitro and in vivo, playing a pivotal role in the induction of both tolerance and immunity. Dendritic cells from humans and mice have been extensively studied and dendritic cell-based vaccines have been shown to be effective in the prevention and treatment of infectious, allergic and neoplastic diseases. Studies of dendritic cells of domestic animal origin are becoming available and confirm a role for these cells in the pathogenesis of a variety of animal diseases, suggesting that dendritic cells could be used as adjuvants for prophylactic and therapeutic strategies in veterinary medicine.

Infection of sheep with the abomasal nematode Teladorsagia circumcincta can cause a relative protein deficiency and reduce growth rate in growing lambs. A key event appears to be the destruction of junctions between epithelial cells. If the infection is heavy or prolonged, this leads to increased mucus production, hyperplasia, decreased acid production, gastrinemia, inappetance and pepsinogenemia. The severity of the infection depends upon the extent of concurrent infection, the nutritional status of the host and genetically controlled variation in the ability to mount protective immune responses.

Cryptosporidium parvum is recognized as a major cause of diarrheal disease in neonatal bovine calves. In addition, this protozoan parasite has emerged as an important cause of disease in both immunocompromised and immunocompetent humans. Despite years of research, no consistently effective means of prevention or treatment are readily available for cryptosporidiosis in any species. Infection through ingestion of contaminated water has been widely documented; C. parvum was reported to be responsible for the largest waterborne outbreak of infectious disease in US history. In addition to its role as a primary disease agent, C. parvum has potential to initiate or exacerbate other gastrointestinal disorders, such as inflammatory bowel disease. Thus, control of C. parvum infection in both animals and humans remains an important objective. Research in our laboratory has focused on understanding mechanisms of resistance to C. parvum. We have demonstrated that acquisition of intestinal flora increases resistance to C. parvum. Substances present in the intestinal mucosa of adult animals can transfer resistance when fed to susceptible infants. Both expression of intestinal enzymes and rate of proliferation of epithelial cells may be altered following C. parvum infection. These and other changes may have profound effects on host resistance to C. parvum.

The porcine tonsils are a group of lymphoepithelial tissues located at the common openings of the gastrointestinal and respiratory tracts. The tonsils participate in a variety of functions involving innate, cellular and humoral immunity at the local and systemic levels. Among these immunological functions is the continuous surveillance for the presence of foreign antigens at the openings of the gastrointestinal and respiratory tracts. Within the pig, the movement of lymphocytes, cytokines and chemotactic molecules from the tonsils to other lymphoid organs confers immunity to other portals of pathogen entry and facilitates an efficient and rapid systemic immune response. In spite of the immunological nature of the tonsils, some microorganisms have acquired adaptations that allow them to circumvent the tonsillar immune defenses and utilize the tonsils as a site of entry, replication and colonization. Several bacterial and viral pathogens persist asymptomatically within the tonsils, making identification of asymptomatic carrier animals difficult in disease control and/or pathogen elimination. This paper reviews the current information on the anatomy, immunology and pathobiology of porcine tonsils and discusses the tonsils as a site of pathogen entry, replication and colonization using Salmonella spp., classical swine fever virus and porcine reproductive and respiratory syndrome virus as examples.

Although there are over 250 zoonotic diseases, only 30–40 of them involve dogs and cats. Transmission of zoonotic infections occurs via bites, scratches or touch; exposure to saliva, urine or feces; inhalation of particles or infectious aerosols; contact with a transport or intermediate host (e.g. ticks, fleas); or exposure to contaminated water, soil or vegetation. This paper summarizes the most important common zoonotic dermatological diseases of dogs and cats. The most common dermatological zoonoses are flea and tick infestations and the diseases they transmit; dermatophytosis; and mite infestations (Sarcoptes and Cheyletiella). Prevention of zoonotic infestations or infections can be accomplished easily by the use of routine flea and tick control, screening of new pets for dermatophytosis, and routine hand-washing.