Definition of the term "pathogen"

This whole discussion has been superceded by my third article in the Scandinavan Journal of Immunology. So please follow the link.

However, here is a taster.

Should you address multiple dictionaries you will find various definitions of a "pathogen". At one extreme will be something like "a disease causing micro-organism" and at the other "any agent that causes disease" with shades in between.

If a pathogen is - without question - an organism, then the term "pathogenic organism" becomes problematic. It translates into a "pathogenic pathogen" which is akin to a "cardiac heart", a "renal kidney" or a "pulmonary lung". Whoops! Something is wrong.

I suggest the problem has come from the sloppy tendency to abbreviate "pathogenic organism" to "pathogen" and slowly escalate this into a correct and legitimate synonym for the former. Without question, a pathogenic organism is a pathogen (provided it HAS damaged its host) but the corollary, a pathogen is, without question, a pathogenic organism is clearly corrupt. There are a multitude of abiotic pathogens. My favourite example is asbestos. This generic nature of a "pathogen" is in keeping and logically consistent with the way we talk of the pathogenesis of disease, pathology in general and the pathogenic mechanisms of disease.

The moment we restrict, by the mass action of common usage, the meaning of a pathogen to just living biotic organisms we drive ourselves into incongruity.

I have a published paper on this theme in the Scandinavian Journal of Immunology (Aug 2008 - see link above)); but this seems to have been largely ignored.

We can infer that a disease causing organism is a pathogen (ie, it has behaved in a pathogenic manner) but we can't infer that a pathogen is a disease causing organism. A pathogen could be all sorts of other agents. It would be like saying an animal is a dog. Animal is generic, dog is specific. An organism, as it relates to pathogen, is specific and a pathogen, as it related to organism, is generic.

"A dog IS an animal" makes sense; "an animal IS a dog" is nonsensical. And the same applies to pathogen. When we talk of a pathogen we should only be talking about the agent's (generic) disease causing behaviour, not its specific classification (ie, a specific reproducing agent or a specific inanimate agent).