Ants hate spearmint and peppermint, get some essential oil of either and apply a thin barrier stripe of it to the casing of the trailcam, make sure to treat around any opening. You can also water them down with vodka and dispense with a spray bottle. You'll find these oils in the baking supplies aisle of most grocery stores, they're normally sold in very small square bottle as extracts. If you have a stand of wild spearmint available you can just smear the casing with the leaves.