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Semantics/terminology question here.

Prion diseases such as BSE/vCJD (Mad Cow Disease) and Kuru can be transmitted between individuals, primarily via consumption of diseased neural tissue where the ingested prions themselves are what trigger the runaway protien-misfolding process.

Does that make prions a type of pathogen? Or is there a different more fitting blanket term?

My layman's understanding of the definition of "pathogen" is something as follows: pathogens are living agents (including viruses) causing disease which can be transmitted between individuals.

In that sense, bacteria, viruses, and things like transmissible cancer cells are pathogens, but things like heavy metals (i.e. mercury in fish) are not included even though they cause illness and are transmissible. Prions are in the grey area here: they are certainly more "biological" than heavy metals, but they are less "alive" than viruses (which at least have a genome). What side of the line does a misfolded protein complex fall on?

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Yes, the misfolded prion proteins are a type of pathogen. Considering the literal meaning of "pathogen", any agent causing a disease would qualify; however, only agents of biological origin have historically been referred to as "pathogens" (not to be confused with "alive", which is more difficult to defne), perhaps due to readily available umbrella terms for other agents (e.g. poisons).

The very article that coined the term "prion" implicitly categorizes them as pathogens once in its text, though unfortunately the full-text version doesn't seem to be available for free.

Rigid categorization of the scrapie agent at this time would be premature. Determination of its molecular structure will be required prior to deciding whether prions represent a distinct subgroup of extraordinarily small viruses or a completely different type of pathogen which lacks a nucleic acid genome. [Emphasis mine]

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A bit of historical perspective follow-up to M.A.R.'s excellent answer....

The word has actually been far more generic than the definition you provided for quite some time.

Stedman's Medical Dictionary, 6th edition, published in 1920, defines it as:

Any virus, microorganism, or other substance causing disease.

(Note that your browser may object to downloading the PDF because it's not a secure connection, but the link and the PDF are perfectly safe.)

Stedman's Medical Dictionary, 26th edition, published in 1995, has exactly the same definition, and by then prions were a known entity:

Any virus, microorganism, or other substance causing disease.

Merriam-Webster's current definition is:

a specific causative agent (such as a bacterium or virus) of disease.

So even going back 95 years the term was recognized as not being limited to living (or "near" living) organisms. Some heavy metals, toxins, and prions would all qualify as pathogens even in 1920 (though prions were unknown until 1982).

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