  Recent studies of merging black holes suggest that the cosmological mass
fraction of primordial black holes (PBHs) is not completely negligible. The
mass of a PBH can be as massive as an intermediate mass black hole (IMBH). In
this article, we assume that dark matter particles are thermal relic particles
and they can self-annihilate. The dark matter around an IMBH may have formed a
density spike so that the rate of dark matter annihilation would be greatly
enhanced. Using the gamma-ray data of the Fornax cluster and assuming merging
events in the cluster are not important, we show that the amount of IMBHs
(including PBHs) is very sub-dominant compared with the amount of baryons and
dark matter. The upper limit on the IMBH-to-baryon ratio is $\sim 7\times
10^{-4}$ for $m_{\rm DM} \le 10$ TeV.
