Virulence factors and antimicrobial susceptibility profile of extraintestinal Escherichia coli isolated from an avian colisepticemia outbreak.

In this study an avian colisepticemia outbreak was investigated. Two isolates from a chicken with colisepticemia were characterized for antimicrobial susceptibility and virulence factors profile. For this purpose 7 antimicrobial and 29 genes (fimH, hrlA/hek, iha, papC, sfa/focCD, tsh, mat, tia, gimB, ibeA, chuA, fyuA, ireA, iroN, irp2, iucD, sitD. chr., sitD. ep., iss, neuC, ompA, traT, astA, hlyA, sat, vat, pic, malX, cvi/cva) were tested. The outbreak happened in a hick chicken breeding located in the northwestern region of Rio Grande do Sul state in South of Brazil and caused 28.3% (102 deads of a total of 360 chickens) of mortality rate. Escherichia coli isolates obtained from the avian spleen and liver belong to the same phylogenetic group A and present resistance to all antimicrobials tested (ampicillin, tetracycline, gentamicin, neomycin, sulfa + trimethoprim, enrofloxacin, and norfloxacin). Both isolates harbor virulence factors related to adhesion (fimH, papC, mat), invasion (tia), iron acquisition system (iroN) and serum resistance (iss, ompA, traT), showing that these groups are important for Avian Pathogenic E. coli (APEC). However, they present different virulence profiles for some genes, whereas liver-isolate carries more hrlA/hek (adhesin), gimB (invasin), sitD ep. (iron acquisition system), sat (toxin) and hylA (toxin) genes, the spleen-isolate harbors fyuA (iron acquisition system) gene. Here, we highlight a coinfection by different strains of APEC in the same animal with colisepticemia, the great antimicrobial resistance of these bacterial isolates and the genetic traits that modulate the virulence for high mortality rate of chickens for human consumption.

Time series evaluation of traumatic lesions and airsacculitis at one poultry abattoir in the state of São Paulo, Brazil (1996-2005).

Ten year official condemnation records of one officially inspected poultry abattoir in state of São Paulo, Brazil, were analyzed. Seasonal and cyclical trends were analyzed in relation to traumatic lesions and airsacculitis, which were the most relevant official condemnation causes. Time series analysis of the records, seasonal indexes and moving averages was used to describe the adherence to the mathematical model and to offer preventive management strategies for the slaughterhouse industry. Although cause-effect relationships were not defined, some insight was given into the causal mechanisms that generated the series.

Protection conferred by a live Salmonella Enteritidis vaccine against fowl typhoid in laying hens.

Fowl typhoid is under control in poultry farms of developed countries, but it still endemically subsists in commercial laying hen farms of some countries. It has been demonstrated that Salmonella live vaccines can elicit cross-immunity against members of the same Kauffmann-White scheme serogroup. In this work, we explored the protection conferred by TAD Salmonella vac E, a live Salmonella enterica serovar Enteritidis vaccine, against fowl typhoid. Three groups of laying hens were vaccinated with different vaccination schedules starting on the first day of life, and afterwards were infected with 2 x 10(5) CFU of a virulent Salmonella Gallinarum strain, either at wk 28 or wk 52. Mortality, fecal shedding, and organ invasion of Salmonella Gallinarum were assessed. In this work we demonstrated that this Salmonella Enteritidis vaccine is able to cross-immunize against Salmonella Gallinarum. At wk 28, hens vaccinated with three oral doses or with two oral doses combined with one subcutaneous dose were protected by the vaccine. At wk 52, when hens were infected 36 wk after the final immunization, the vaccine was not able to confer protection. Thus, revaccination every 3 mo would be highly recommended. In countries where Salmonella Gallinarum subsists together with Salmonella Enteritidis, control programs should include vaccination of laying hens using safe attenuated Salmonella strains.

Intoxication of Crotalaria pallida seeds to growing broiler chicks.

The adverse effects of feeding Crotalaria pallida (CP) seeds to chicks was investigated in a 21-day randomized trial of 4 dietary treatments (control, 1,2 and 3% ground CP seeds). Mortality rates in birds fed 0, 1, 2, and 3% dietary CP were 0, 2.1, 6.2, and 16.7%, respectively. Body weight gain and feed efficiency were adversely affected by all levels of inclusion of CP seeds, but feed intake was decreased only by dietary levels of 2 and 3%. Dietary CP of 2 and 3% increased the relative weight of lung, heart and spleen. Relative liver weight was increased by 2% dietary CP, but decreased by 3% CP. At day 14, serum GGT was increased by 2 and 3% dietary CP; serum ALT was significantly increased by 3% CP. No differences in ALT, AST or GGT were observed at day 21. Dietary levels equal to or greater than 1% CP are toxic for growing broiler chicks.

Virulence analysis of a Salmonella gallinarum strain by oral inoculation of 20-day-old chickens.

In order to know the effect of in vitro passages on the pathogenicity of the Salmonella gallinarum strain INTA 91, a lyophilized culture was compared with the same strain recently isolated from a sick bird. The mean lethal dose (LD50) of the orally administered lyophilized culture was determined as 2.04 x 10(8) colony-forming units (CFU)/chicken. There was no correlation between the LD50 dose and the degree of disease produced; doses 10 or 100 times higher than the calculated LD50 did not produce a more severe disease. In trial 1, chickens were challenged with 1.02 x 10(9) CFU per chicken (5LD50) of the lyophilized strain and reached 52.2% mortality at the end of the assay. In trial 2, three different groups of chickens were infected with a recent isolate of the same strain: 2.04 x 10(8) CFU/chicken, 4.1 x 10(8) CFU/chicken, and 2.1 x 10(9) CFU/chicken (i.e., 1LD50, 2LD50, and 10LD50 of the dose calculated for the lyophilized strain, respectively). These chicken groups presented higher mortality rates (90%, 100%, and 95%, respectively) than previous trials, showing that the S. gallinarum strain used here increased its virulence by in vivo infected chicken passage. In all assays, the disease started after an incubation period of around 5-6 days. To obtain reliable and reproducible results in future challenge experiments, a fixed limited number of in vitro passages of the S. gallinarum strain must be determined.

Metabolic disturbances in male broilers of different strains. 1. Performance, mortality, and right ventricular hypertrophy.

Two trials were carried out to test the susceptibility for metabolic disturbances of different strains of male broilers. In Trial 1, 1,890 male chickens were allotted in a randomized block design with seven treatments (Arbor Acres, Avian Farms, Cobb-500, Hubbard-Peterson, ISA, Naked Neck, and Ross) and six blocks of 45 chickens. Trial 2 involved 2,184 male chickens of six strains (Arbor Acres, Avian Farms, Cobb 500, Hubbard-Peterson, ISA Naked Neck, and Ross) allotted in seven complete blocks of 52 birds. The same management system was adopted for all birds, reared up to 42 d in an open house during late winter (Trial 1) or late autumn (Trial 2). The most marked differences observed among the strains tested was the lower BW and higher feed conversion of Naked Neck broilers. Total percentage mortalities were high among the most productive broilers, being more than 50% due to sudden death (SDS) and ascites syndrome (AS). No Naked Neck birds died as a consequence of these disturbances and the total mortalities were significantly lower (P < or = 0.05) than the other strains. The ratio of right ventricle weight to total ventricle weight of the dead birds was over 0.25, except for Naked Neck birds, which presented a nonhypertrophic ratio. The two trials confirmed the relationship between high productivity and high incidence of SDS and AS and indicated that Naked Neck male broilers are resistant to these metabolic disturbances.

Factors affecting mortality of crossbred and exotic chickens kept under backyard systems in Yucatan, Mexico.

Chicken mortality was studied in 24 randomly selected smallholder flocks in one village in Yucatan, Mexico between July and December 1993. Each family received a package of 10 to 12 chicks of 3 weeks of age. Approximately half of the chicks were purebred and the remainder were crosses produced by mating exotic with local breeds. All smallholders were visited twice a week. Feeding and management (except vaccination and medication) were left to smallholders. Data were processed by Chi-square, Mantel-Haenzel test and survival analysis. Before reaching 140 days of age 43.2% of the birds died. The highest mortality was observed during the 113 to 140 days of age period and the lowest was in the period between 22 and 56 days of age. Of all birds, 10.5% died from coccidiosis and 7.6% from Marek's disease. Of the risk factors investigated only medication and genotype showed significant effects on mortality. The effect of genotype was significant up to 112 days of age (P < 0.05). Crossbred birds lived longer than purebred; independently, medicated birds lived longer than non-medicated birds.

Effect of pelleted feed on the incidence of ascites in broilers reared at low altitudes.

A study was conducted to investigate whether the use of pelleted feeds might influence the incidence of ascites in broilers reared at low altitudes (730 meters above sea level). In two trials carried out under commercial conditions, broilers were fed practical-type rations from 1 day to 7 weeks of age, in either mash or pellet form. In both trials, low incidences of ascites (less than 5%) were recorded for broilers receiving feed as pellets. No cases of the syndrome were observed in birds fed mash, either in the field or at the processing plant. These data suggest that the positive relationship between pelleted feeds and incidence of ascites observed at high altitudes also exists at lower elevations.