Protection against velvet disease in goldfish recovered from ichthyophthiriasis

Abstract Goldfish when exposed to Oodinium pillularis for 21 days showed an 88% mortality rate. On the contrary, only an 8% mortality rate was found in fish which were previously exposed to and recovered from the infection of Ichthyophthirius multifiliis . The protection against O. pillularis in the latter could be attributed to the presence of higher antibody levels against O. pillularis in their blood. The results therefore suggest that I. multifiliis and O. pillularis might share some common cell-surface antigens.