  The presence of non-zero helicity in intergalactic magnetic fields (IGMF) has
been suggested as a clear signature for their primordial origin. We extend a
previous analysis of diffuse Fermi-LAT gamma-ray data from 2.5 to more than 11
years and show that a hint for helical magnetic fields in the 2.5 year data was
a statistical fluctuation. Then we examine the detection prospects of helical
magnetic fields using individual sources as, e.g., TeV gamma-ray blazars. We
find that a detection is challenging employing realistic models for the cascade
evolution, the IGMF and the detector resolution in our simulations.
