Bulletin January 2017 Number 177

This article is the first in our series showcasing new developments in our specialties with fewer Fellows: please contact publications@rcpath.org if you would like to see your specialty featured.

The University of Surrey in Guildford recently opened its brand new Veterinary School, which includes an £11 million Veterinary Pathology Centre, providing a focus for pathology research, education, surveillance and commercial activity. The new Centre is one of the largest and most sophisticated of its kind in Europe, offering high-containment post-mortem examination facilities for all animal species. It is staffed by a team of highly skilled, board-certified veterinary pathologists, veterinary investigation officers and technicians, with expertise in farm-animal, equine, exotic, small-animal and forensic pathology.

The Centre is close to many leading-edge scientific research centres including Pirbright, the Animal and Plant Health Agency, Public Health England and the National Physical Laboratory. It has close links with medical colleagues through the NHS Surrey Pathology Service and a comparative pathology clinical academic group.

The Centre and the University of Surrey are working closely with the veterinary and scientific community to address some of the unique challenges associated with farm animal health surveillance. Its state-of-the-art facilities and focus on digital pathology are further enhanced by close links with the 5G centre, business school and the Veterinary Innovation Health Engine (vHive).

The new building centres on a large Containment Level (CL) 2 post-mortem examination room with high ceilings, natural lighting, post-mortem examination tables, biological safety cabinets and integrated cold rooms, all served by a powerful winch system. This means that post-mortem examinations can be performed on a wide range of species. A viewing gallery overlooks the suite and the latest digital technology can be used to record and stream post-mortem examinations for training purposes. The Centre also houses a high containment CL3/SAPO3 post-mortem room. Thus, the Centre offers the opportunity to inspire the next generation of veterinary pathologists and complements the centres of excellence that already exist in other vet schools and research institutes.

We have a growing team of pathologists with varied skills and expertise, who work closely with colleagues specialising in infectious diseases. Veterinary pathology is a rapidly evolving discipline with the emergence of specialists within groups of animals (e.g. livestock or companion animals) or specific organs, and in particular dermatopathologists and neuropathologists who mirror the increasing specialisations of human pathologists.

An important thread running across departments in the new Veterinary School is the concept of ‘One Health’. Many infectious and non-infectious diseases in veterinary species have direct analogues or useful comparative aspects between animals and humans. In this respect, the Department of Pathology and Infectious Diseases is fostering relationships with pathologists and other specialists at the Royal Surrey County Hospital through our involvement with the Comparative Pathology Clinical Academic Group (CAG).

As an example of comparative pathology, we see a number of cases of listeriosis in cattle and sheep through our involvement with livestock surveillance pathology. This is a bacterial disease caused by Listeria monocytogenes. In ruminants, listeriosis mostly presents as neurological disease due to encephalitis and cases of late abortion, but can also lead to septicaemia in newborn calves, mastitis and keratoconjunctivitis. Listeriosis may also be subclinical, with the possibility of transmission by asymptomatic carriers through faecal shedding. Most livestock cases are associated with the feeding of poorly prepared and or stored silage during winter months, but spread via faecal shedding cannot be excluded. Treatment for ruminant listeriosis involves antibiotics, but the mortality rate is high and antimicrobial resistance is increasing. Similar clinical symptoms are observed in humans, with Listeria being an important source of CNS infections, ranking third or fourth as a cause of bacterial meningitis. Initial symptoms include fever, diarrhoea and abdominal pain, and can progress to bacteraemia and subsequent CNS infection.

Listeria monocytogenes is a Gram-positive, facultative intracellular bacterium that does not form spores, and is ubiquitous in the environment. It is equally well equipped to survive outside in the environment and in many mammalian hosts, and can grow at temperatures ranging from –1.5°C to 45°C, i.e. including refrigeration temperatures. Listeria uses the environmental temperature as a signal to orchestrate its potential as microbial pathogen, with many of its genetic repertoire involved in virulence only switched on at temperatures of 37≤C or higher. Once it has reached the gastrointestinal tract, it invades the intestinal epithelium, followed by dissemination to the bloodstream and systemic infection. It is able to cross the blood-brain barrier. Listeria monocytogenes is able to invade and replicate within a multitude of host cell types, including professional phagocytes, and infected monocytes assist in the rapid spread of the systemic infection.

Human cases of listeriosis occur mostly in vulnerable groups, such as pregnant women, new-born infants and elderly and immunosuppressed patients, and there are clear parallels with the same disease in ruminants. Pathogenesis and microscopic lesions are strikingly similar between veterinary species and humans, and the limited number of studies investigating Listeria monocytogenes from cattle and small ruminant farms do show the presence of strain types known to cause human disease. This suggests that measures taken to reduce Listeria infections in humans may also be useful for prevention of veterinary infections. In the Western world, Listeria infections are commonly food-borne, especially through contaminated or unpasteurised dairy and other chilled ready-to-eat products; however occasional cases may be a consequence of direct zoonotic infection. While the overall incidence of listeriosis is low in humans (approximately 180 cases annually in the UK), it carries a high rate of hospitalisation and death compared to other food-borne infections, emphasising its importance as a pathogen, and making this a problem in human and animal health for consumers, farmers, regulators, industry and healthcare. This is also recognised by the UK Food Standards Agency, which has made reducing the incidence of food-borne Listeria infections one of its two main priorities. This is just one example where we have much to learn from one another under the ‘One Health’ umbrella and comparative pathology collaborations.