Answer: You should advise him that this is not an Ixodes scapularis tick, which is the agent of Lyme disease, as well as babesiosis and anaplasmosis. Instead, it is a Dermacentor tick, which can transmit Rocky Mountain spotted fever. Unlike I. scapularis, Dermacentor spp. ticks have a "chalise-shaped" anal groove and festoons (not well visible here). The most striking feature of the photographs shown are the markings on the scutum, which also are suggestive of Dermacentor, and not Ixodes spp. ticks.
Routine prophylaxis of tick-borne diseases is not generally recommended; instead, you should tell him to monitor himself for symptoms of a tick borne disease (e.g. headache, myalgia, fever, rash, influenza-like illness) and see a physician immediately should any symptoms appear.