The impact of coccidiosis outbreaks on the productivity of broiler chicken farms can be substantial, depending on the severity of disease caused by particular species and strains of Eimeria. We examined the genetic diversity of Eimeria species present in commercial broiler farms in relation to their performance level. Four groups of broiler chicken farms in Arkansas (AR) and North Carolina (NC), having either high or low performance levels, were sampled for Eimeria spp. oocysts. We amplified gDNA from oocysts by using genus-specific primers targeting 18S ribosomal RNA, the first and second internal transcribed spacer regions, and cytochrome c oxidase subunit I as the established species-specific primers. Eimeria spp. diversity was not homogenous among the 4 farm groups, with less-pathogenic species (E. mitis and E. mivati-like) associated with AR and NC high-performance farms, respectively, and a pathogenic species (E. brunetti) associated with AR low-performance farms. Sequence analyses identified multiple E. maxima and E. mitis genetic variants, from which 2 E. maxima variants were unique to low-performance farms. Distinct populations of sequences at the NC high-performance farms were identified as E. mivati-like, based on homology searches. Our study demonstrated the utility of analyzing multiple genomic loci to assess composition and polymorphisms of Eimeria spp. populations.

The effect that breeder-flock immune status regarding the infectious bursal agent (IBA) and two avian adenoviruses (DPI-1 and DPI-2) has on the susceptibility of their commercially reared Delmarva broiler progeny to the hemorrhagic-aplastic-anemia syndrome and concurrent gangrenous dermatitis was determined. Lack of immunity to the IBA in breeder flocks was related to an increased susceptibility of progeny to anemia and dermatitis. Breeder-flock immunity to the two adenoviruses tested could not be related to the resistance or susceptibility of their progeny to the hemorrhagic-aplastic-anemia syndrome and gangrenous dermatitis.

Four isolants of Newcastle disease virus (NDV) obtained from free-flying Canada geese in the Atlantic flyway were characterized and compared with the B1, LaSota, Roakin, and Texas-GB strains of NDV. The 4 isolants were identified as lentogenic strains on the basis of embryo mean death times of greater than 100 hours and relative lack of pathogenicity for 1-day-old and 3-week-old chickens. The hemagglutinin of 2 of the isolants was stable at 56 C for 15 minutes, 1 for 30 minutes, and the other for at least 2 hours. When held at 4 C for 24 hours, none of the 4 isolants could be eluted from chicken erythrocytes. All 4 of the isolants produced plaques in chicken embryo fibroblast cell cultures without additives, whereas the B1 and LaSota strains did not. The 4 lentogenic NDV isolants from Canada geese differed in many respects from currently used commerical vaccine strains (B1 and LaSota).

The purpose of the present study was to evaluate the species composition and salinomycin sensitivity of Eimeria oocysts isolated from commercial broiler farms that differed by means of coccidiosis control (anticoccidial drugs [ACD] vs. live oocyst vaccines [VAC]). A comparison of Eimeria species composition and salinomycin sensitivity was also made before and after a producer switched from salinomycin to live oocyst vaccines. In general, no significant difference was observed in the concentration of Eimeria spp. oocysts in litter from VAC-utilizing farms compared to litter from ACD-utilizing farms. Application of PCR-based methods to detect coccidia found that Eimeria species distribution in litter from VAC operations more closely resembled the species composition in the live oocyst vaccines. Drug sensitivity testing found that Eimeria oocysts from VAC operations displayed greater salinomycin sensitivity as measured by weight gain and feed conversion efficiency compared to oocysts from ACD farms. These findings provide additional evidence for the usefulness of live oocyst vaccines to restore ionophore sensitivity in poultry operations that contain an ionophore-resistant population of Eimeria spp. oocysts.

No abstract