There's also the anaphylactic shock issue - how many people would this kill outright? From the sound of it, some meat allergies' onset are unexplained, so if the tick explains them, there may be an unknown number of deaths also explainable by the tick.
However, a mad vegetarian utilitarian might still want to fund research on how to weaponize the tick's saliva and measure the effect: can it be broadened to react to other forms of protein? Can the intensity of the reaction be toned down? What if the reaction is weakened to the point that it merely causes a vague sort of unease or feeling of unwellbeing - over a population, how many would that convert to vegetarianism and is the lower yield more than offset by the few deaths and lowered risk of detection?
(This post is completely jocose. If you can't take it, don't read it. I'm making fun of Rationalists, of Me, of homo economicus, of Vegans and of things I really praise, like Consequentialism and Outsourcing. It is not serious. The Sheldon Sarcasm sign has been lifted, your asperger side has been warned)
One of the features of rationality is that it allows you to mix different units.
By rationally behaving economically, you learn, for you, how many apples costs an orange.
Vegetarians and Vegans sell diminishing suffering. They claim to have the best price in the market, only Singularitarians and Existential Risk avoiding competes with their numbers. Utilitarians are a good target market.
Then a Lesswronger came and noticed that, and said: Well, why not buy someone to be a vegetarian for you, here.
Awesome price actually. You shock a few humans (notice that humans are animals, who clearly would rather be shocked than eaten), one of them enough to make him vegan.
So why not take this to the next level?
Figure out the reproductive cycle and eating habits of this beetle that makes people vegetarian. Make sure the evidence is solid.
Get a basement lab full of them.
Ship them alive to cities where more people consume meat. Wait for population growth.
Save a lot of animals!
Seems straightforward, but is it?
Also, are there similar strategies for other groups? Are there easy, but strange, shortcuts for selfish hedonists, immortalists, rational altruists? Utilitarian hedonists? The ancient school of negative utilitarianists? Cryonicists?