dsRNA associated with virus-like particles in Eimeria spp. of the domestic fowl.

RNA segments, identified as double-stranded, were found in sporozoites of the Guelph strains of Eimeria acervulina, E. brunetti, E. maxima and E. necatrix and in 8 of 11 strains of E. acervulina obtained from poultry houses across the United States. These RNAs were resistant to RNase A digestion in the presence of high salt concentrations (0.3 M NaCl). On agarose-gel electrophoresis, E. acervulina had one obvious band at 1.7 kb and a faint band at 3.5 kb; E. brunetti had two bands at 2.1 and 3.3 kb, respectively; E. maxima had one band at 4.5 kb; and E. necatrix had two major bands at 4.5 and 5.6 kb, respectively. No dsRNA band was seen in the three strains of E. tenella examined. Virus-like particles were purified by cesium chloride density centrifugation of homogenates of E. necatrix sporulated oocysts. The fraction at peak virus concentration had a buoyant density of 1.39 g ml-1. These virus-like particles were icosahedral, had no envelope and measured 42-44 nm in diameter. Only one RNA band at 5.6 kb was observed when nucleic acids from gradient fractions containing virus were subjected to electrophoresis. The 4.5-kb dsRNA segment of E. necatrix was not associated with a virus-like particle.