Vertical transmission of Ovipleistophora ovariae (microspora) within the eggs of the golden shiner.

Abstract

Fertilized eggs collected from broodfish infected by Ovipleistophora ovariae were tested by quantitative polymerase chain reaction (PCR) and found to be positive for the O. ovariae genome at 7.77 X 10(2) to 3.26 x 10(7) copies per microgram of host DNA. Fry hatched from these eggs contained from 1.37 X 10(2) to 9.89 X 10(6) copies of the O. ovariae genome per microgram of host DNA. Surface treatments of fertilized eggs with 150 mg formalin/L (used by farms as a fungicide) or a 1.5% solution of sodium sulfite (which removes the adhesive egg matrix) did not reduce vertical transmission to fry. Treatment of eggs with a 10% solution of bleach or a proprietary commercial DNA denaturant did not reduce the number of egg-associated copies of the O. ovariae genome. Histology of ovaries of infected fish demonstrated spores within the oocytes. However, no spores were observed by histology in positive fry hatched from infected eggs. The PCR and histological demonstration of the presence of O. ovariae spores in oocytes and fry, and the failure of strong DNA denaturants to reduce egg-associated copies, give evidence that O. ovariae is vertically transmitted within eggs.