Carp pox (CP)
Carp pox is a relatively benign proliferative disease of cyprinids, known for more than 400 years in common carp in Europe. It is caused by a virus similar to a herpes virus. The disease is characterized by skin proliferation, which appears histologically as a plaque-warty hyper-plasia of the epidermis. In the advanced stages of the disease, mineral metabolism may be impaired and this can result in softness of the bones. Carp pox seldom causes mortality, but the cutaneous growth reduces marketability of the fish. Certain strains and inbred lines have a genetic predisposition to this disease. The carp louse (Argulus) can act as virus-carrier and transmit the virus within a pond population. The occurrence of carp pox can be reduced or eliminated by avoiding inbreeding or by genetic selection methods. No chemotherapy exists for the disease, but recovery can be speeded up by liming the ponds. It has been reported that infected carp recover if they are transferred to ponds supplied with large volumes of clear, oxygenated water (Ghittino, 1972).