Veterinary Pathology - Integral to both Research and Surveillance
Pathology – learning from tissues
Pathology is the study of animal tissues under the microscope in order to recognize how a particular organ or tissue is affected by disease. Pathology helps scientists to identify different types of destruction of cells, as well as the different types of inflammation produced by the animal’s own white blood cells, in an effort to attack and hopefully resolve a particular infection.
As Moredun’s research focuses on infectious diseases of livestock, information provided by pathological studies is crucial to almost all of its studies. Moredun’s own specialist Pathology Unit employs four full time veterinary pathologists and a team of scientific support staff who can apply their specialist skills to a range of research projects.
Cutting edge techniques being developed by Moredun not only allow the accurate identification of the different inflammatory cells involved in infections but also the potent chemicals (cytokines) that they release. These methods have already been used to analyse the diseased placenta from sheep with enzootic abortion (infection with Chlamydophila abortus) and are helping to explain how pregnancy is disrupted, killing the developing foetus. In turn this is informing Moredun’s research into novel chlamydial vaccines. These new techniques are also now being gradually introduced to other research areas such as bovine abortion caused by Neospora caninum, calf septicaemia caused by Pasteurella multocida and certain aspects of Moredun’s research into the transmissible spongiform encephalopathies (TSEs).
The Pathology Unit plays an integral role in Moredun TSE research as well as the projects studying the skin conditions, orf and scab. Current research into respiratory diseases encompassing ovine pulmonary adenocarcinoma (OPA or jaagsiekte) and infections with the caseous lymphadenitis organism, Pasteurella, Mannheimia and Mycoplasma as well as intestinal conditions including nematode and mycobacterial problems also benefit from expertise of the Pathology Unit. In addition, the Pathology Unit provides general support for all of Moredun’s research by supplying digital image capture and analysis of cell preparations and tissues.
Monitoring Disease through Surveillance
Moredun’s Pathology Unit, in partnership with the Scottish Agricultural College’s Veterinary Services (SAC VS), undertakes specialist histopathological surveillance of neuropathological and reproductive conditions of farm animals (and sea mammals such as whales, dolphins, porpoises and seals) for the whole of Scotland.
Perhaps as a reflection of an upturn in farming in Scotland, over 1,100 cases were examined by the Pathology Unit in 2003 - a 33% increase in ovine submissions and a 44% increase in cattle cases compared to 2002. Listeriosis, toxoplasma abortion, cerebrocortical necrosis, swayback, copper poisoning and other bacterial and toxic conditions were all encountered.
Reproductive conditions such as bovine neosporosis, ovine toxoplasmosis, chlamydial abortion, Border disease and infections with Campylobacter and fungi were all recognized from samples submitted to the unit during 2003.
The diagnosis of disease by histopathology is a complex and arduous job, requiring highly trained and experienced individuals. It is mystery solving at its most extreme and the staff within the Pathology unit frequently encounter unusual cases – some of which are highlighted here.
Louping Ill in Llamas
Louping-ill encephalitis continues to be a problem in Scotland. This disease is transmitted by the tick and is generally seen in sheep as they are particularly susceptible to the virus. However, all warm blooded animals are capable of becoming infected, a fact that was highlighted in 2002 when louping-ill was confirmed as the cause of death in a llama introduced to a croft on Harris as part of a diversification scheme. Clinically it was presented as a case of “sudden death” and did not display the neurological signs normally associated with the disease. It is tempting to suggest that this apparent extra susceptibility may be because, as a ruminant from South America, the species has not encountered louping-ill virus, or a related virus, during its evolution and therefore not evolved any innate resistance to this type of attack.
Tick Borne Fever Outbreak
In a severe outbreak of late abortion in Perthshire, 150 ewes in a flock of 250 lost their lambs. Neuropathology consistently revealed damage to the white matter in the foetal brains of those submitted to Moredun’s Pathology Unit which suggested starvation of oxygen in late pregnancy and pointed to a placental problem. While the latter appeared normal under the microscope concurrent examination of blood smears revealed organisms characteristic of Anaplasma phagocytophila, the cause of tick borne fever (TBF). While the fever induced by TBF has been incriminated in abortion in sheep before, this is the first time brain pathology has been linked directly with the disease.
For further information please contact Dr David Buxton
This research is funded by SEERAD via SAC.