You can also tell him that only about 1 in every 3 or 4 rattlesnake bites are envenomed, according to my EM doc daughter. Rattlesnake venom is not fatal like a mamba or cobra venom. You can survive a rattlesnake bite, even an envenomed one, without treatment**, although the experience is likely to be plenty painful.
Besides UNM Hospital and all other regional hospitals stock antivenom.
** Assuming you aren’t doing stupid party tricks with live snakes like that guy in Arizona who wrapped a rattlesnake snake around his neck to show off and got bit repeatedly on his neck & face.