Anti-ice is found on engines with a static support structure at the compressor inlet where there is a pressure drop and hence temperature drop. Shedding ice is a problem and also changing the shape of the inlet can lead to stall and/or flameout.
Early A109's had RR 250 engines which have a manual anti-ice. i.e. depending on the airframe install bleed air for anti-ice is used when OAT = -5C and moisture is visible. i.e fog, clouds, rain etc. Importantly you do not need to be in the fog, clouds or rain. It needs to be used if you can see any of the phenomena.
Not all engines have a manual anti-ice in smaller helicopters, PW 200 Series / Safran Arrius where the inlet is part of the oil tank and is therefore constantly heated, Safran Arriel where there is no static front support.
Later A109's have the PWC 200 Series engine so no anti-ice required.
As an aside there is a trap for the unwary on the AS350 if left out in the snow with no inlet cover. The snow / ice accumulates in the inlet plenum area but not enough to restrict flow until after starting the engine warms the plenum and a large slug of snow / ice then enters the compressor and "poof". Usually just after you get airborne - it has caught a few over the years. As the inlet is on top of the cowling and not visible it gets neglected.