Effect of Dipping Eggs in Antibiotic Solutions on PPLO Transmission in Chickens

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Abstract
Commercial eggs naturally infected with PPLO and warmed to 37[degree]C were dipped 30 minutes in erythromycin solution (400 ppm) at 5[degree]C with no adverse effect on hatchability, no respiratory tract lesions in pipped embryos, and yielded no PPLO on culture. Untreated eggs yielded lesions and PPLO cultures in 7 trials. S6-type PPLO injected into the posterior thoracic air sacs caused birds in production to become "false layers." Pipped embryos from S6-infected hens yielded more than 5 times the number of cultures yielded by embryos from eggs previously dipped 15 minutes in 400 ppm erythromycin solution at 5[degree]C. Chicks from treated eggs in 3 hatches were negative to the PPLO agglutination test. Stress with E. coli and infectious bronchitis affected the control group more strongly than the treated group. In 7 trials, broiler chicks hatched from eggs dipped 5 minutes in erythromycin solution (900 ppm) at 5[degree]C yielded no lesions or PPLO cultures from pipped embryos. The treated chicks grown in the same building as the controls had fewer condemnations and gave fewer agglutination reactions with PPLO antigen. In one trial, a spontaneous outbreak of CRD occurred in 3 untreated pens while a 4th treated pen remained free from disease. An 8th trial with heavily infected eggs from a commercial flock did not yield favorable results. Experimentally produced S6-infected eggs at 21 or 37[degree]C were dipped 5 and 15 minutes in erythromycin and Tylosin solutions, 1200-1500 ppm, at 5[degree]C. No isolations were obtained from pipped embryos of the Tylosin group, and the efficiency of the erythromycin reached 88%. It is concluded that the efficiency of erythromycin in dip solutions is reduced when the eggs treated are heavily infected with PPLO. The egg-dipping technique for PPLO control has promise not only as a means of controlling CRD in broilers but also as an adjunct with other methods to produce PPLO-free breeding stock.

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