I think the use of "holocaust" has two parameters: One, a specific group must be responsible for the carnage and, two, a specific group must be targeted. I've never seen the word used as in "bubonic plague inflicted a holocaust on Europe between 1346 and 1350".
Also, for a plausible use of the word, I think that the act of destruction has to be quite deliberate. Here in Zild, a Maori politician given to disengaging her brain before opening her mouth last year accused the Europeans of "inflicting a holocaust" on the Maori during the middle of the 19th century. Her justification for this was arbitrary confiscation of land which drove Maori away from their traditional sources of food (as an unintended consequence); the introduction of measles, chicken pox and tuberculosis (endemic among the European population who arrived from elsehwere) the NZ Wars (which had an extremely low casualty rate) and the very occasional deliberate attempt to spread smallpox through contaminated goods.
Maori extremists and bleeding-heart liberal non-Maori agreed with her, but the majority of NZers saw it as grandstanding. While there was a steep decline in Maori population following the European arrival, there is absolutely no evidence to support the concept of a deliberate official policy on the part of European leaders to destroy the Maori. Ergo, no holocaust.
See also "post-colonial stress disorder" ...
