Ancient records show that infectious diseases have been a constant threat and a problem to be overcome, controlled and prevented throughout the centuries. As such, these transmissible diseases have seemingly always been present in animals (and humans).
The concept that sickness was related to genies, devils and demons that had to be vanquished evolved in antiquity. All plagues and other destructive phenomena, such as earthquakes, floods, thunder and lightning, were also believed to be supernatural in origin and caused by the gods showing their displeasure with human sinfulness. This belief allowed priests to gain influence by offering spells, incantations and sacrifices to please and placate the gods.
A documented example of this practice and belief is found in the Old Testament, which describes the ten Egyptian plagues inflicted on the Pharaoh by God. Based on the description, the fifth plague, or “the pestilence of livestock” (Exodus 9:1-7), was probably carbuncular anthrax.
Graeco-Roman period
As experience with diseases grew in the Greek, Roman and Byzantine periods, there was a progressive increase in knowledge: contagious diseases (spread by contact) were recognised but not understood. The Romans were well aware of contagion, and their farmers and veterinary advisors knew that having large herds or flocks was potentially dangerous. They would divide them into smaller groups so that when a plague arrived, they would hopefully not lose all their stock.
The Romans were well aware of contagion, and their farmers and veterinary advisors knew that having large herds or flocks was potentially dangerous
This observation was not made by the medical profession, which resulted in significant human mortality following plague attacks. The best early descriptions of disease are found in the writings of Aristotle (384-322 BC), who described several animal ailments. These included: “podagra”, which was probably foot-and-mouth disease (FMD); “craurus”, which was likely contagious bovine pleuropneumonia; and in pigs, “bronchos” and “craurus”, with the former possibly anthrax and the latter swine fever. He also described rabies and glanders. Yet Aristotle was not a clinician; he was an early pathologist.
While contagion was obviously recognised, the actual role of infectious disease was still unclear – in fact, they had no knowledge of the causes of disease
Later, other “veterinarians”, such as Apsyrtus, Hierocles, Pelagonius and Vegetius, wrote significant treatises and books on animal disease. And while contagion was obviously recognised, the actual role of infectious disease was still unclear – in fact, they had no knowledge of the causes of disease. This meant that while some treatments helped, spells and amulets still played a role in medicine for years. For centuries, plagues of varying types and morbidity swept across Europe. Records of these years enumerate the losses but not the causes.
Girolami Fracastoro
Slowly, an understanding of disease and its transmission was being made. The word “contagion”, from the Latin “contagio” or “a touching contact”, was introduced between 1350 and 1400, with “infection”, from the late Latin “infectio” or “to put in, stain” appearing later, around 1535 to 1545.
The first significant investigations into infectious diseases were made by Italian physician Girolami Fracastoro (1480-1553), who wrote a reliable description of the disease and symptoms of FMD. Following his study of an epizootic in cattle in 1514, he published a three-volume treatise in 1546 titled De Contagione et Contagiosis Morbis et Eorum Curatione (on contagion and contagious diseases). In this treatise, he discussed diseases in animals, humans and plants, providing a perceptive analysis of various modes of contagion.
FMD is one of the most contagious diseases and while Fracastoro did not give an opinion on the cause, he did speculate that “the essence of these diseases was infective matter spread by contagion”. It is now recognised that FMD can occur in cattle, sheep, goats and pigs and is one of the most serious infectious diseases.
The influence of medieval European plagues
Although European plagues had created a seriously bad situation in the 17th century, they were a terrible disaster in the 18th century. In the plague in France between 1710 and 1714, it is estimated nearly half of all cattle died (incidentally, this was a major factor in the French government supporting Claude Bourgelat in opening the first veterinary college in 1761).
However, when the plague reached Italy, Giovanni Lancisi (1656-1720) studied the disease (now known as rinderpest) and produced the first system for its control. Lancisi’s 1715 publication confirmed and supported fellow researcher Bernado Ramazzini’s (1633-1714). These two men famously demonstrated methods for the practical control of rinderpest. They were followed by Thomas Bates (died 1760) in England, who independently devised a similar programme.
It gradually became clearer that there were different types of plague: some affected only cattle, sheep or horses, some affected several species while others also affected humans. However, there was much confusion as other disease problems in these periods were coincidentally attributed to “the plague”.
It gradually became clearer that there were different types of plague […] however, there was much confusion as other disease problems in these periods were coincidentally attributed to ‘the plague’
Eventually, similar symptoms began to be recognised, and it became apparent that rinderpest/cattle plague, contagious bovine pleuropneumonia and anthrax were the most serious diseases. Frequently (and confusingly), FMD was sometimes also involved. Sheep pox became a major issue in continental Europe, in particular France, but was very rare in Britain. Glanders was the most obvious and serious in equines, but was often confused with strangles. Then, swine erysipelas and other infectious diseases, including canine distemper, swine fever and those in poultry, were identified.
Rabies
Rabies was well known but recognised as a human rather than animal disease. More has likely been written about rabies since ancient times than any other disease, starting with a possible suggestion in the 18th century BC by Eshunna Laws in Mesopotamia. Hydrophobia, a symptom only seen in humans, was first described by Paul of Aegina in the 7th century.
In 1613, English physician Thomas Spackman wrote A Declaration of Such Grievous Accidents as Commonly Follow the Biting of Mad Dogges. He described rabies in dogs well, but action to undertake legal restrictions on rabid dogs in Britain only occurred after William Youatt (1776-1847), who had set up his own veterinary practice, addressed the House of Commons on the role of the dog in rabies and methods of control. It was only when the infectious aspect of rabies was studied that we realised control measures had to be used.
The dawn of immunology
Later, the first vaccines (after Jenner’s smallpox method) were developed. The defining moment was when Louis Pasteur (1822-1895) developed a rabies vaccine, initially as a curative procedure. He also produced a fowl cholera vaccine, followed by a demonstration of the effectiveness of an anthrax vaccine and, later, a vaccine for swine erysipelas.
The discipline of immunology was established and today, with hygiene and other measures, provides the highly sophisticated viral, bacterial and other vaccines used to control most infectious diseases.
One of the more notable events in international animal infectious disease control took place in Hamburg, Germany, in 1863. John Gamgee, MRCVS, (1831-1894) had been campaigning, with little success, to get the British government to take action to prevent the introduction of rinderpest. He called a well-attended meeting of the leading European researchers into infectious diseases to discuss an international control system. This was agreed, and following the conference there was intensive lobbying in all major European countries, which finally resulted in agreed international control measures. Gradually, rinderpest was eliminated in Europe. That initial conference gave rise to the World Veterinary Association.
Final thoughts
Infectious diseases continue to be a major animal health problem. Isolation and control of movement orders, together with vaccination programmes, have enabled the global eradication of rinderpest (2011), a notable achievement of veterinary medicine. Control measures in tandem with vaccine use allow a good measure of control against contagious bovine pleuropneumonia and FMD disease in ruminants, swine fever in pigs, certain poultry diseases, glanders in horses and distemper in dogs, but not yet eradication. Intensive farming methods with continual virus mutations provide an effective incubator for prolonging disease outbreaks, in particular with influenza virus in poultry, swine and horses.
As vaccines were developed and diseases controlled, a belief arose in the early 1900s that there would soon be no need for veterinarians… how wrong they were!
As vaccines were developed and diseases controlled, a belief arose in the early 1900s that there would soon be no need for veterinarians… how wrong they were! Infectious diseases of new types and forms continue to evolve; fortunately, so do vaccine developments and introductions.
It is estimated that over 60 percent of known infectious diseases and 75 percent of new and emerging infectious diseases occurring in humans are derived from animals. The plagues that made life difficult in antiquity are still present, but fortunately we now have the legacy of Edward Jenner, Louis Pasteur and many more, which has obviously helped to placate the gods.
