The Biology and Pathogenicity of a Recent Field Isolate of Eimeria praecox Johnson, 1930

Abstract

A recent isolate of E. praecox, strain G, was obtained from Georgia [USA] and purified. Studies of the life history, pathogenicity and cross-immunity of the isolate were conducted to verify its identity. In inoculated 3-wk-old chickens, the occurrence of merogony and gametogony was limited to the superficial epithelium of the upper intestine. Oocysts, 23 .times. 19.5 .mu.m, with a shape index of 1.17 were first observed 83 h after inoculation. Mortality and morbidity were not observed in any of the experimental birds. There was a positive correlation between oocyst dose, reduced weight gain, and the incidence of exudative diathesis. E. praecox depresses weight gains in chickens and may be of economic importance. Although complete immunity to avian coccidiosis is believed to be species specific, chickens immune to E. praecox (G) or E. acervulina had a degree of cross-immunity to a heterologous challenge. Electrophoretic analysis of glucose phosphate isomerase and lactate dehydrogenase prepared from the European strain of E. praecox and E. praecox (G) showed no differences, confirming the identity of the isolate as E. praecox.