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Broiler production is highly dependent on good health in the parent flocks. The so-called normal mortality in these flocks remains to be addressed to further reduce mortality of the breeders and to improve the quality of broilers. The aim of the present study, therefore, was to investigate the etiology of this breeder mortality to map out possible critical periods during production in relation to possible risks of importance to the offspring. Dead birds from four flocks were subjected to postmortem and bacteriologic examination from onset of lay until slaughter (20-60 weeks). Causes of mortality were divided into noninfectious and infectious etiology. The infectious group could be subdivided into suppurative salpingitis/peritonitis caused by Escherichia coli and other infections (e.g., sepsis, endocarditis, and arthritis) mainly caused by Gram-positive cocci. Data analysis showed that 41% of the birds died from noninfectious causes, while 55% died from infectious causes, and 4% had no known cause of death. The prevalence of noninfectious mortality was highest in the youngest birds and lowest in the oldest birds. In contrast, the infectious mortality was lowest in the young birds and highest at the end of production. Within each age group, the prevalence of salpingitis/ peritonitis was 26% in young birds (20-29 weeks) and progressed throughout production to 41% in the oldest birds (≥50 weeks of age). Mortality due to other infections was low at onset of production (12%), peaking at 40-49 weeks of age (25%). Consequently, 40-49 weeks of age is identified as a critical period with regard to causes of mortality, possible vertical transmission of E. coli to the offspring, and increased risk of Gram-positive coccal infections.

Outbreaks of salpingitis and peritonitis cause major economic losses due to high mortality, reduced egg-production, and culling. The aim of the present study was to characterize, in detail, lesions associated with increased mortality in layers due to avianpathogenic Escherichia coli (APEC) and to investigate the population structure of the E. coli involved, which is important for selection of optimal treatment and prophylactic strategies. Among 322 layers received from eight farms with increased mortality due to E. coli, three lesion types were observed; sepsis-like lesions, chronic salpingitis and peritonitis, and chronic salpingitis and peritonitis associated with sepsis-like lesions. One hundred isolates of E. coli obtained in pure culture from the different lesion types were selected for genetic characterization. Six out of 10 submissions (two farms with two submissions) were considered clonal as defined by more than 85% of the typed isolates of E. coli belonging to the same sequence-type (ST). B2 was the most-prevalent phylogroup, including the clonal complex of ST95. The most-important virulence genes of E. coli were demonstrated from both clonal and nonclonal outbreaks, and major differences as to phylogeny and virulence genes were not observed between the lesion types. Cannibalism was more-often observed during polyclonal outbreaks. A new pathotype of APEC is suggested based upon lesions and route of infection, high similarity of virulence genes including plasmid-associated genes, and high frequency of ST95 and other isolates belonging to phylogroup B2. Compared to the best-known pathotypes of E. coli, this needs further investigations, including infection experiments to show if single virulence factors can be pointed out that are specific for the salpingitis-peritonitis pathotype and possibly not found in other pathotypes of E. coli.

A genital and potentially fatal form of Pasteurella multocida infection was reported on two turkey-breeding farms on which birds were vaccinated against Pasteurella multocida. Both outbreaks were linked to the use of semen from young vaccinated toms with a history of respiratory pasteurellosis followed by treatment during rearing. Typing by agar gel immunodiffusion and rapid slide agglutination of P. multocida isolated from cloacal swabs was completed by multilocus sequence typing. Restriction enzyme analysis showed that that the isolates were clonal. They belonged to sequence type (ST) 30, described in chickens, cats, and ducks. This strain differed in sequence type from the ones used in the vaccine (ST8, ST60, ST53, and ST235), which might have limited its effectiveness. No contamination of the semen (n = 30) was found, suggesting fecal contamination during semen collection.

The aim of this investigation was to determine the presence of the opportunistic pathogen Clostridium perfringens by PCR and DNA sequencing, without previous cultivation. This methodology was then used to investigate how C. perfringens was affected by different preventive measures, such as ionophores and feed additives, for necrotic enteritis in broilers chickens. DNA was extracted from the intestinal content or intestinal tissue by DNA extraction kits. Detection limits for 16S rRNA, alpha-toxin, and cpb2 PCR gene targets were approximately 1 x 10(3), 5 x 10(4), and 1 x 10(6) cells per g of intestinal content or tissue, respectively, as determined with samples spiked with C. perfringens. The method was evaluated with samples from single conventional broilers or from pools of six birds of experimentally reared broilers. Conventional chickens, raised with salinomycin in their feed, showed reduced numbers of C. perfringens-positive samples (P < 0.05) for all three PCR tests. With respect to cpb2, a tendency to detect more samples as positive for C. perfringens was observed with increasing age. The addition of sodium butyrate and lactic acid in the feed for experimental birds had a minor effect (P < 0.10) on positive samples, as detected with the 16S rRNA PCR. For experimental birds fed whole wheat, only three out of six pools of six birds allowed detection of C. perfringens by the 16S rRNA PCR, compared to five for the untreated controls or the Avilamycin- or prebiotic-treated birds. All 16S rRNA partial gene sequences obtained were identical and were 99.5% similar to the rrnB gene of the type strain of C. perfringens. Two types of the partial cpb2 gene sequence were detected with a similarity of 93%. One type was translated into protein, whereas a stop codon was found in the other type. Both types were located in the "atypical" phylogenetic group of the cpb2 gene sequences. The PCR test, based on extraction of DNA from intestinal content, provided rapid screening of poultry for C. perfringens without the need to have access to facilities in order to immediately cultivate and identify bacteria at the location of sampling. Further work is suggested to determine the relationship between the degree of necrotic enteritis, the actual level of C. perfringens in the animal, and the detection achieved by PCR.

Infectious bursal disease (IBD) is a worldwide distributed immunosuppressive viral disease in young chickens, controlled by vaccination. Emergence of several strains of IBD virus (IBDV) has created a demand for strain-specific diagnostic tools. In the present experiment, five different reverse transcription polymerase chain reaction (RT-PCR) assays, including two recently developed strain-specific assays, were employed for detection of ribonucleic acid (RNA) from three different IBDV strains in bursa tissue samples from experimentally infected specific pathogen free chickens. The virus strains included vaccine strain D78, classical strain Faragher 52/70, and the very virulent Danish strain DK01. The presence of the virus infection was confirmed by histopathologic evaluation of bursa lesions. The largest number of positive samples was obtained with a strain-specific two-step multiplex (MPX) RT-PCR assay based on iScript enzyme, and the commercially available Qiagen one-step RT-PCR. Between these methods, agreement was obtained for 57 of 59 samples. Because the Qiagen one-step RT-PCR assay was suggested as the more sensitive of these two assays, it was used for detection of IBDV in bone marrow, spleen, thymus, and cecal tonsils from experimentally infected chickens. The identity of the virus strains involved was confirmed by MPX RT-PCR. In conclusion, the MPX RT-PCR represented a reliable assay for detection and differentiation of IBDV strains in selected lymphoid tissues of chickens. All three of the IBDV strains used were detected in bursa tissues, whereas only the two virulent strains were detected in bone marrow, spleen, and thymus.

The present study was aimed at elucidating the role of heterophil granulocytes during the initial infection with Pasteurella multocida subsp. multocida in chickens. Chickens (17 and 19 wk old) were depleted of their heterophil granulocytes by 5-fluorouracil treatment. When the heterophil blood counts were significantly reduced, the birds were inoculated intratracheally with 1.8-4.3 x 10(4) colony-forming units of P. multocida. Twelve, 24, or 48 hr postinoculation, the birds were euthanatized and examined for macroscopic and histologic lesions in the lungs. Bacterial invasion was determined by culture of P. multocida from the spleen. Recruitment of heterophils into the respiratory tract during infection was found to contribute considerably to the lung lesions in chickens and was found to mediate tissue damage, possibly allowing a more rapid systemic spread of P. multocida. However, during progression of the infection, the heterophil-mediated necrosis in chickens seemed to stimulate giant cell demarcation of infected lung tissue, which coincided with the clearance of P. multocida from the spleen, thus hampering further invasion. Consequently, heterophil activation plays a dual role for the outcome of a P. multocida infection in chickens, where it initially seems to promote invasion and systemic spread but subsequently helps limit the infection by giant cell formation and bacterial clearance.