  $SU(2)_L$ triplet scalars appear in models motivated for the left-right
symmetry, neutrino masses and dark matter (DM), etc.. If the triplets are the
main decay products of the DM particle, and carry nonzero lepton numbers, they
may decay dominantly into lepton pairs, which can naturally explain the current
experimental results reported by PAMELA and Fermi-LAT or ATIC. We discuss this
possibility in an extended left-right symmetric model in which the decay of DM
particle is induced by tiny soft charge-conjugation ($C$) violating
interactions, and calculate the spectra for cosmic-ray positrons, neutrinos and
gamma-rays. We show that the DM signals in the flux of high energy neutrinos
can be significantly enhanced, as the triplets couple to both charged leptons
and neutrinos with the same strength. In this scenario, the predicted
neutrino-induced muon flux can be several times larger than the case in which
DM particle only directly decays into charged leptons. In addition, the charged
components of the triplet may give an extra contribution to the high energy
gamma-rays through internal bremsstrahlung process, which depends on the mass
hierarchy between the DM particle and the triplet scalars.
