Try to hold one of his paws while petting him, this will prevent the static buildup.
Also a humidifier inside the RV can help. I had 19 in my RV in the NY snow over christmas, and they were all happy and non-sparky b/c the humidity was sufficient inside.
02 40' Monaco Diplomat: 1020 watts solar, Victron inverter. FASS, TRW steering, 23 cuft Frigidaire, D/W, W/D, Magneshade, Wood Floor, New cabinets, diesel heater