Black spot disease (diplopstomiasis), an external melanized host inflammatory response caused by a number of digenetic trematode parasites, results in slow growth, deformities and increased mortality among many freshwater fish species globally. We investigated the severity of infection, and genetic parameters for black spot disease among 150 families of Nile tilapia (Oreochromis niloticus) of the Abbassa strain in ponds in Egypt.