Thirteen highly inbred lines of chickens of Leghorn, Spanish, and Egyptian Fayoumi origin, four partly inbred Leghorn lines selected for MHC alleles and immune response to GAT (Ir-GAT), and two replicated, noninbred Leghorn lines divergently selected for multiple immune response traits were subjected to molecular genotyping for endogenous viral (ev) gene sequences. In all highly inbred lines of Leghorn origin, ev1 alone or both ev1 and ev2 were observed. The Spanish and Fayoumi lines had three and five ev genes, respectively, most of which were not readily identifiable with standard Leghorn ev gene loci. The Leghorn lines selected for MHC and Ir-GAT had ev1 fixed in the population. Differences in ev3 and ev5 gene frequency were associated with Ir-GAT in the B1 haplotype, but not in the B19 haplotype. In the noninbred lines, which were divergently selected for multiple traits of immune responsiveness, ev6 and ev9 differed in frequency between lines, and both were in lower frequency in the lines selected for high immunoresponsiveness. These two ev genes are the only ones known in White Leghorns that have the gs-chf+ phenotype [expressing chicken helper factor (chf) but not expressing group-specific antigen (gs)].

Organic poultry production in the Netherlands is developing. Although consumers assume organic products to be safer and healthier, there are aspects of organic animal husbandry, like access to an outdoor run, that can result in increased risks of food safety problems. The aim of this study was to compare housing and management of organic and conventional broiler farms in the Netherlands and to study the occurrence of Salmonella and Campylobacter infections on the former. Large differences were found between the two farming systems with respect to mixed or single farming, manure storage, drinking-water system, ventilation, access to an outdoor run, and pest control. From the 31 organic flocks sampled for Salmonella and Campylobacter in 2003, 13% were positive for Salmonella and 35% for Campylobacter. Results for the summer period are missing due to an outbreak of avian influenza, so the actual number of flocks infected with Campylobacter can be expected to be even higher. Campylobacter appears to be the main risk on organic broiler farms, so that it would be interesting to study specific risk factors of infection with this pathogen on these farms.

The endogenous viral (ev) gene patterns of White Leghorn (WL; 6 lines), medium heavy (MH; 4 lines), White Plymouth Rock (WPR; 8 lines), and Cornish types (2 lines) of commercial chickens were compared. Southern blot analysis of SstI-digested genomic DNA of 151 chickens revealed that the number of ev gene-containing fragments in a chicken from the MH, WPR, or Cornish type is about twice twice the number of that in WL chickens. Also, the number of hybridizing fragments of different size found within one line was twice as high in the broiler (on average 16.0 bands per line) and MH lines (20.5 bands per line) than in the WL lines (10.0 bands per line). In studies with subregion-specific probes, all ev fragments detected contained the env (3') part of the viral genome. Only eight ev fragments, found in 7 animals of 2 lines, lacked the gag (5') part of the viral genome. Studies with the ev-1-specific flanking probe, pGd111, revealed that ev-1 is commonly present in the DNA of the WL chickens, but not within the DNA of the WPR chickens. The results suggest that use of the standard nomenclature for the ev genes based on restriction fragment length is not feasible within the WPR, MH, and Cornish lines because of the complexity of the ev gene patterns found within these lines.

Endogenous viral (ev) loci were studied in three broiler lines. In 5 birds of each of line cw1 and line cw2 (White Plymouth Rock lines) 19 and 14, respectively, different SstI ev-junction fragments were found, while in 8 R line birds (Cornish type) 15 different Sst I junction fragments were found. Further characterization of the line R loci with a second restriction enzyme, BamHI, revealed that these junction fragments represent 25 different loci, of which at least 21 have not been reported previously. SstI RFLP analysis of progeny from crosses between chickens of the three broiler lines and White Leghorns demonstrated that within line R and cw1 approximately 90% of the ev loci were hemizygous. In line cw2 at least 50% of the ev loci were hemizygous. There was no evidence for polymorphic loci, and only two ev loci were found to be linked genetically. Intertype crosses revealed that overall differences in the RFLP patterns observed between Cornish, White Plymouth Rock and White Leghorn chicken lines were due to the presence of different ev loci in each of the lines rather than to polymorphism. The few shared ev loci always contained similar allelic fragments.

Resistance of Campylobacter jejuni to environmental stress is regarded as a risk factor for the transmission of C. jejuni from poultry or poultry products to humans. So far, the mechanisms underlying the capacity of C. jejuni to survive environmental stress conditions are not fully understood. In this study, we searched for polymorphisms in C. jejuni genes, potentially involved in resistance to chill stress. To this end, we assessed 3 groups of C. jejuni isolates (clinical, retail chicken meat, and feces) for survival of experimentally induced chill stress. For each isolate we sequenced 3 genes encoding the C. jejuni sigma factors FliA, RpoD, and RpoN as well as the genes for the transcriptional regulator SpoT and the periplasmic protein HtrA. Data suggest a higher prevalence of a specific polymorphism in spoT in clinical isolates compared with poultry meat or farm isolates. Moreover, this genotype correlated with enhanced survival of chill stress. The observation that the prevalence of this SNP is relatively high in clinical isolates, which most likely have been exposed to multiple forms of stress, suggest that this SNP may be a biomarker for enhanced survival of stress.