Prevalence of Bordetella bronchiseptica Infection in Swine of Southeastern Alabama

SUMMARY Prevalence of Bordetella bronchiseptica infection in swine herds of southeastern Alabama was determined by cultural and serologic methods. Nasal swabs and blood sera were obtained from small and commercial herds selected from a 15-county area during a 2-year continuous study. Nasal secretions were collected from adult and growing swine by swabbing both nasal cavities with sterile cotton swabs. The cotton swabs were placed in transport medium (trypticase soy broth) and streaked on MacConkey agar containing 1% dextrose and nystatin (50 mg/ml) within 6 hours after collection. After 48 hours' growth at 37 C, characteristic colonies were transferred to tryptose phosphate broth and incubated for 24 hours. Biochemical characterization of the isolates was determined by inoculation of urea, citrate, sucrose, lactose, and dextrose agars with tryptose phosphate broth cultures. Serologic evidence of Bordetella infection was determined by a whole cell-tube-agglutination test with the use of formalin-killed antigen. Sensitivity patterns of drugs presently used to control the organism were carried out, using commercial disks. Of a total of 4,524 swine tested from 185 commercial and small herds, 503 (11%) were positive by culture method, compared with 2,316 (52%) by serologic testing. A relatively high frequency of B bronchiseptica infection occurred in every age group of swine, with definite seasonal correlation by both test procedures. The prevalence was greatest during the testing periods from October to March and was comparable in both small and commercial herds of all age groups of hogs tested by the culture method. In comparison, the prevalence of Bordetella infection in all hogs, as determined by serologic test, was greatest during the testing periods from July to December for commercial herds and January to June for small herds. The greatest prevalence of Bordetella infection was found in pigs ranging in age from 8 to 12 weeks old. Bordetella isolates were sensitive to most of the antibiotics often used to treat respiratory tract infections.