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

Abstract

A recent isolate of Eimeria praecox, strain G, was obtained from Georgia and purified. Studies of the life history, pathogenicity, and cross-immunity of the isolate were conducted to verify its identity. In inoculated three-week-old chickens, the occurrence of merogony and gametogony was limited to the superficial epithelium of the upper intestine. Oocysts, 23 x 19.5 microns, 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. However, there was a positive correlation between dose of oocysts, reduced weight gain, and the incidence of exudative diathesis. These studies showed that 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.

Eimeriaof American chickens: Characteristics of six attenuated strains produced by selection for precocious development

“…Eimeria praecox has been considered to be of low pathogenicity but these studies do not support that view. Depression of body weight as a result of a single dose of 1 x 10 6 oocysts was similar to that reported by Gore and Long (1982) for the same strain of E. praecox. Depression of body weight by the GA strain was similar to that of the Houghton strain (Long, 1968) although recent work on the latter parasite did not show the same pathogenic effects judged by body weight gain.…”

Investigating a persistent coccidiosis problem on a commercial broiler–breeder farm utilising PCR-coupled capillary electrophoresis

“…The CE method is applicable to any biological sample that may be expected to contain Eimeria, including gut samples from necropsied chickens. Because this technique does not rely on clinical signs for diagnosis, even non-pathogenic species can be detected; this is important under intensive farming conditions because all species may have a negative effect on growth rate and feed conversion efficiency (Gore and Long 1982;Fitz-Coy and Edgar 1992;Williams 1998), particularly in mixed-species infections. While the development and application of anticoccidial drugs to control coccidiosis has facilitated modern intensive farming of poultry (Chapman 1997;Williams et al 1999), there are significant problems with drug resistance and a growing reluctance from the public to use drugs in food-producing animals (e.g.…”

“…Eimeria acervulina, Eimeria brunetti and Eimeria maxima are also widely recognised to cause clinical diseases. The other two species, Eimeria praecox and Eimeria mitis, although considered to be relatively non-pathogenic, do cause a reduced feed conversion efficiency and growth rate (Gore and Long 1982;Fitz-Coy and Edgar 1992); these latter factors can cause massive financial losses in the low profit-margin business of intensive poultry farming. Therefore, all species are important economically.…”

Identification of Eimeria mitis and Eimeria praecox in broiler feces using polymerase chain reaction

“…Despite the current belief that these species have low pathogenicity, they can be responsible for decreased weight gain, poorer feed efficiency and shank pigmentation in broiler chickens (Gore & Long, 1982;Ruff & Edgar, 1982;Fitz-Coy & Edgar, 1992;Jorgensen et al, 1997).…”