If a kitten latched onto my skin to just hang out and engorge itself, that'd be gross too. Being gross isn't a matter of intent or etymology, it's an action.
You're making judgments about animals that are wholly inappropriate for their "actions". Seems to be trendy on HN to call things gross lately...maybe its the new generation?
This part is true no matter how effective the vaccine is. Ticks are gross, diseased or not.