Charles Cameron: a zoonotic pioneer in a Dublin full of animals and disease

In 1920, after nearly six decades of service to the public health of Dublin, Dr Charles Cameron declared his intention to "die in harness". This he did, one year later, at the age of 91.

Cameron was well known in medical and scientific circles during his long life, although his contribution is less known today. His life and career as an analyst involved in food inspection and as medical officer of health in the city have been ably documented by historian Lydia Carroll (In the Fever King's Preserves: Sir Charles Cameron and the Dublin Slums, 2011).

He was a striking and familiar character on the Dublin streets in the late 19th and early 20th centuries. A cartoon from the Leprechaun depicted him peering intently at an apparently perfect egg while Dublin's food traders cowered in the background.

Food inspection was Cameron’s principal focus, even as he became the dominant figure in the public health administration of Dublin Corporation (now City Council), assuming all three of the most senior posts – city analyst, superintendent medical officer of health, and executive sanitary officer – in 1879. As city analyst he was charged with the detection of fraud, such as watered-down milk or flour bulked out with alum.

Cameron pursued fraudulent traders doggedly, but through his attempts to curb the selling of unsound meat he developed another interest that was perhaps his greatest contribution to public health and to medical science. Cameron’s examination of hundreds of thousands of pounds of allegedly diseased meat encouraged him to investigate the transmission of disease between animals and humans.

Dublin in the late 1800s was a city full of animals. Sheep, pigs and cattle all passed through the Dublin Cattle Market and were exported to Britain to feed the increased demand from industrialisation. But pigs and cattle were also kept in surprising numbers in backyards and even living spaces. One public health worker estimated the city had a cattle population of 7,000 animals, although 2,000 seems more likely. By the 1870s most of these cattle were infected with contagious bovine pleuropneumonia (CBPP).

As he saw more and more diseased cattle sold for food, Cameron focused on the possibility of cattle diseases passing to humans through meat. Before Robert Koch had established "the germ theory" and while ideas about contagion were still much debated, Cameron examined the materials before him for signs diseases were contagious, and for identifiable particles that might be agents of transmission. He examined sick cattle and dissected them after death.

Diseased animals

Diseased meat had long been of interest in urban public health, but for different reasons. Doctors believed diseased meat decayed more rapidly than meat from healthy animals. Most doctors did not believe, until Koch's work on tuberculosis, that meat from diseased animals could pass diseases to humans.

After the cattle plague (rinderpest) outbreak of 1865, Cameron began to look for evidence that meat from diseased animals was harmful to humans even before it decayed. Under the microscope he tried to locate poisons or germs or viruses (the words were still used interchangeably) in flesh from diseased animals. In the case of CBPP he did not find any such particles, but he remained convinced certain human conditions such as carbuncles were caused by eating meat from animals with the disease. He also investigated the passage of human and animal diseases by the medium of milk, one of the first doctors to do so in Ireland. He may also have been the first person to highlight the role of shellfish in the transmission of typhoid.

Later research proved Cameron was right to be concerned about zoonotic disease. CBPP was not contagious to humans and thus the disease with which Cameron had most experience was a dead end. However, his work contributed significantly to the debate on germs and disease during the late 19th century.

Today the link between animal disease and human disease is apparent. The epidemics that caused the most alarm in recent decades all have animal links: Ebola is thought to circulate in African bats, HIV is believed to have an origin in nonhuman primates, and flus come to us from birds and pigs. Zoonotic disease is now a major public health concern, as seen in the establishment of the international One Health Initiative, which seeks to unite human and veterinary medicine. Charles Cameron would approve.

• Juliana Adelman lectures in history at St Patrick's College, Drumcondra