Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 24, 2008
Publication Date: July 11, 2008
Citation: Jenkins, M.C., Allen, P., Wilkins, G., Klopp, S., Miska, K.B. 2008. Eimeria praecox infection ameliorates effects of e. maxima infection in chickens. 155:10-14.
Interpretive Summary: Avian coccidiosis is an intestinal disease primarily of poultry that causes U.S. broiler producers an annual loss of over $ 350 million, with losses worldwide exceeding $ 1 billion. The disease has been controlled for decades by medication of feed with anti-coccidial drugs, but the appearance of drug-resistant strains of Eimeria and increased consumer pressure to reduce use of medicated feeds has prompted alternative control measures. One approach that has met with success is vaccination of day-old chicks with a mixture of low doses of virulent or attenuated Eimeria oocysts. Our studies have shown that one species, namely E. praecox, is prevalent in poultry farms using either drugs or vaccines. The purpose of the present study was to determine the effect of E. praecox on other species of Eimeria. This was done for two reasons- (1) to determine if including E. praecox in a vaccine formulation would affect clinical signs associated with vaccination, and (2) to understand the lower pathogenicity of E. praecox. Our research found that E. praecox can ameliorate the clinical effects of E. maxima infection. These findings may have implications for new vaccines, and provide clues on the pathogenicity of and immunity to Eimeria.
The effect of Eimeria praecox on concurrent E. maxima infection was studied in susceptible chickens. Cinical signs of coccidiosis were assessed in single infections with E. praecox or E. maxima and dual infection with both Eimeria species. Compared to uninfected controls, groups infected with 104 E. maxima oocysts displayed a 60% weight gain depression, which was four-fold greater than weight gain depression in chickens infected only with 104 E. praecox oocysts. Average weight gain in chickens infected with both E. maxima and E. praecox was nearly identical to that in E. praecox-infected chickens. Feed utilization (feed conversion ratio, FCR) in mixed-species infection was identical to FCR in non-infected controls or chickens infected with E. praecox alone; all showing a significant difference from solitary E. maxima infection. Although E. praecox did not appear to have a negative effect on weight gain and FCR, it did cause a significant decrease in serum carotenoids. Analysis of oocysts excreted by chickens during dual infection showed little effect of E. praecox on E. maxima oocyst production.