Koalas are thought to be a source of the original spillover of chlamydia pneumonia to humans; and are known to be heavily infected with immortal intracellular pathogens, including chlamydia pneumonia and chlamydia pecorum. The infectious burden in koalas is damaging fertility, limiting lifespan, and threatening koalas with extinction. Tasmanian devils are similarly heavily infected with immortal intracellular pathogens, and similarly threatened with extinction. When Tasmanian devils bite each other, during courting or battle, the animals can transmit an aggressive form of cancer, suggesting infectious pathogens can initiate development of cancer.
Chlamydia pathogens attack any cell with a nucleus, and cause many of the same chronic diseases in animals and humans. A high infectious burden with immortal intracellular pathogens can cause a variety of chronic diseases over time, accelerated aging, and premature death, in animals and humans; and can even cause the extinction of a species.
Veterinary science provides a wealth of knowledge about immortal intracellular pathogens, the transmission of these pathogens, and the effect of intracellular pathogens. Collaboration between veterinary science and medical science, and the integration of veterinary and medical knowledge, could provide significant insight into the origins of chronic disease—in animals and humans.