And the second half of the 19th century, a devastating animal plague spread across northern Europe. It wasn't a new disease, in fact, it had been seen many times before, but it was a particularly nasty outbreak and it actually threatened the economies of several countries. In English language, the disease was known by one of three names steppe murrain, cattle plague, or rinderpest. It was a disease of cattle and some other even toward animals such as buffaloes, and had been recognized as I said for hundreds of years. But what's what was happening in the 19th century was its appearance began to be intensified by changing patterns of livestock husbandry. Developments and farming meant that large numbers of animals were being kept closer together, and moved around in close proximity between farms and markets. When the plague struck these large groups, it literally wiped out thousands of animals at a time. Most of those that became infected died within a week from a high fever, loss of appetite, and dehydration brought on by severe diarrhea. It must have been a terrible sight to witness. The loss of these vast numbers of cattle, in turn produced food shortages, threatened livelihoods, and even jeopardize the entire economies of several countries. No one really knew what caused this plague and little could be done once it struck. In churches across Europe, prayers were said to try to halt its progress. As I mentioned in section one, rinderpest was vitally important in the development of veterinary schools in Europe. What was needed was a coordinated effort to look at this disease, to share knowledge about it, and then to try to work out ways in which it could either be treated or prevented. That only became possible once a small group of people where with a similar background and similar training, were able to apply themselves to this problem. By the time of the massive European pandemic of rinderpest in the middle of the 19th century, some progress had been made. But the veterinary and medical professions became split by two competing theories about how this disease was actually caused. One theory was based on the idea that disease arose spontaneously in the environment. That might occur for a variety of reasons including things such as sudden changes in the weather, or local factors such as poor drainage and boggy ground. This was thought to produce dangerous vapors which could spread out and cause illness. Today we still recognize elements of this type of theory and well-known phrases such as catching a chill, and the belief that muggy weather and humid, and poorly ventilated areas may be unhealthy. The theory that disease was produced in this sort of way was known as spontaneous generation, and was applied to many different diseases not just rinderpest. Spontaneous generation was a major sophisticated scientific theory of its day, and to understand it fully, it requires considerable study. The second disease theory became known as germ theory. This explanation suggested that disease was always present, or be it at a low level, but that certain events could occur which caused periodic outbreaks. And in the case of cattle plague, that these were worsened by collecting large numbers of animals together which allowed the disease to spread easily. And in many ways, the twp disease theories weren't quite as separate as they sound. Some people believed for example, that a disease could arise spontaneously through poor drainage or whatever, and then once it had arisen, it could then spread between animals in a contagious way. And so that was a kind of mixture of the two theories of any infectious disease. And it took a long time before the spontaneous generation theory was finally rejected as a possible disease mechanism. But it was really measures that were put in place to control cattle plague, that helped to eliminate spontaneous generation as a working theory. And those measures which were put in place were pretty drastic. It basically involved mass slaughter of infected animals or potentially infected animals in order to contain the disease and stop it spreading. And when that was put into place, and rigorously carried out, then outbreaks of this disease could be brought under control and it stopped them spreading amongst countries. So rinderpest is important for that reason. It evolved the veterinary profession, and it also evolved thinking about contagious diseases because it proved if you like that diseases could be controlled, they could be spread only by contagion and they could be controlled by restricting that spread, all be it in a pretty dramatic way. Today we understand rinderpest as being caused by a virus, which is closely related to the virus that causes measles and people, and distemper in dogs. We can see the causal organism directly through an electron microscope. It's strange to think that such a tiny object can have such a devastating effect. Electron Microscopy was not developed until well into the 20th century. It was first used in the late 1930's. So ideas about the contagious spread of disease had to be inferred by careful observation, experiment, and reasoning, well before the agent that causes the disease could be physically seen. So it's easy to forget how challenging this must have been at the time, and how difficult to prove. Bacteria, another major cause of animal and human disease are larger than viruses, but they're still invisible to the naked eye. They're visible through the simpler light microscope. The first bacteria were seen in 1676, but their role in disease was not made clear until Louis Pasteur and Robert Koch conclusively proved the germ theory of disease around 1860. Pasteur worked on a veterinary disease called fowl cholera caused by the bacterium pasteurella multocida, which can also infect humans. And Robert Koch who sometimes called the father of modern bacteriology, worked on another important veterinary disease called anthrax. The famous Koch's postulates are a set of rules and principles, which must be applied before any microorganism can be said to be the cause of a disease. And these developments changed the way that infectious disease was understood, whatever the patient species. So germ theory which was to completely transform thinking about spreading diseases was initially worked out on a veterinary disease, and thereafter the principles of dealing with spreading disease were completely changed. But it's still a very sobering thought to remember the only two diseases have been completely eradicated from the world. Smallpox which is a human infectious disease, and rinderpest which was pronounced eradicated in June, 2011. Other periodic animal plagues such as foot and mouth disease, and avian influenza, still have to be controlled by drastic and distressing measures such as the slaughter of all potentially infected or in-contact animals in order to stop the spread of the disease. It seems a brutal policy, but it's one that is deemed necessary by many countries for economic reasons. I've mentioned that human measles was related to the virus that cause rinderpest. They are both members of the genus Morbillivirus and the virus family known as paramyxoviridae. These strange sounding names are part of the discipline of taxonomy of classifying things, which as you may remember was an important feature of 18th century science. The other closely related virus in this family causes a well-known dog disease called canine distemper. Measles, distemper, and rinderpest in some ways a bit like first cousins. Canine distemper regularly caused widespread illness and death in domestic dogs until a vaccine was developed in the early 1930's. This work was undertaken by the British Medical Research Council as part of a program that was looking for a cure for the common human cold and flu. A vaccine was initially developed in ferrets which are also susceptible to distemper. And it was then made available to the dog population where it proved extremely popular and effective. The paper cited in the further reading section for this week, provide accounts of canine distemper and its vaccine written from the perspective of a social history of medicine. You might like to have a go at reading these papers. Thanks to vaccination, dog distemper is a rare sight in wealthy countries today. But another viral dog plague known as parvovirus, is unfortunately alive and well and still occasionally causes outbreaks in dogs, they have not received any protective vaccination. Like distemper, parvovirus is an unpleasant and frequently fatal disease, and causes high mortality in young dogs through severe hemorrhagic diarrhea, vomiting, dehydration, and secondary infections, when bacteria move in to infect the body that's already been weakened by parvovirus. The virus also attacks the heart, and it can cause sudden heart failure. A very important part of the everyday work of a vet in practice is providing vaccinations against these important killer diseases of dogs and cats. So what can these brief examples of animal plagues tell us about the history of veterinary medicine? One interesting issue, is that it's easy to view history from the present day and wonder why some strange and incorrect disease theories such as spontaneous generation persisted for so long. It's easy to ridicule them, and ask why people couldn't have realized where the truth seemed to lie sooner. This is a common problem within the history of science and medicine, and requires us to understand the nature of the debates in historical context. In this case of spontaneous generation versus germ theory, these debates took place at a time before viruses and bacteria were identified, or when they were only just beginning to be identified. It's not that people were less knowledgeable or slower to see where the truth lay, more than they were living in a different world where truth and reality had slightly different meanings because the context was not the same. And the second point is one we've made before, the close connection between human and veterinary medicine. Some people like Rudolph Virchow, argued that this is an artificial split and that there's really only one medicine which crosses between this species. Certainly, most medical breakthroughs, whether the discovery of microorganisms, or the causes of other diseases such as diabetes, seem to prove this point. Separating humans from animals too much doesn't really make sense in biological or other terms. So in the next session, we're going to look at how veterinary medicine was studied and learned. And once again, we're going to take a historical perspective on this, and look at student learning materials from the 18th, 19th, 20th and in fact, 21st centuries. One of the interesting things about this is that some things change, but other things stay almost exactly the same.
