You comment makes it sound like the worst part of Lyme disease is the anxiety over having to check for ticks. This is inaccurate - preventing 3/4 of Lyme infections is a massive net win.
Lyme disease can be horrible. The value is in vaccine is to prevent most cases, not to eliminate the annoying tick checks.
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?