TABLE 6.
Effects of turkey line on the ID50 of parental and selected mutant B. avium strainsa
| B. avium strainb | Avg (SD) ID50 in linec:
|
||||
|---|---|---|---|---|---|
| Hybrid | Orlopp | BUT-A | BUT-B | Nicholas | |
| Parent | 7.9 × 106 (7.4 × 106) | 5.2 × 106 (3.4 × 106) | 6.1 × 106 (5.7 × 106) | 4.7 × 106 (4.1 × 106) | 2.1 × 106 (2.0 × 106) |
| Mot− | 9.5 × 106 (7.7 × 106) | 1.2 × 106 (ND) | 4.1 × 106 (4.7 × 106) | 1.1 × 106 (5.8 × 106) | 7.9 × 106 (6.2 × 106) |
| Dnt− | 1.8 × 1010 (ND) | 1.6 × 109 (ND) | 1.5 × 1013 (ND) | 2.2 × 1013 (ND) | 6.0 × 1010 (ND) |
| Hag− | >108 (ND) | >108 (ND) | >108 (ND) | >108 (ND) | >108 (ND) |
Birds of the listed lines were inoculated at 1 week old by the standard procedure described in the text. ID50 was assessed after 2 weeks by tracheal culturing and phenotypic characterization of the isolated B. avium organisms, again as described in the text. A bird was termed colonized when B. avium of the inoculated phenotype was recovered from a tracheal swab.
DNT-negative (Dnt−), nonmotile (Mot−), and hemagglutination-negative (Hag−) mutants were tested. Hag− mutants were not recovered from any bird in any experiment, although Kanr Hag+ pseudorevertants were readily isolated (see text for additional details).
BUT-A, British United Turkeys of America; BUT-B, British United Turkeys of Britain. ANOVA for groups in which an SD was calculated revealed no differences between lines for infectivity of the parental strain (P > 0.05) and the nonmotile (Mot−) mutant (P > 0.05). ID50 values for the Dnt− mutant were estimated by extrapolation from a very few birds infected at very high doses in a single experiment. Consequently, the significance of the ID50 value differences (e.g., between lines) could not be calculated. ND, not determined.