Intratracheal infection as an efficient route for testing vaccines against Chlamydia abortus in sheep

After the experimental infection, isolation of the microorganism in several organs, with pathological and immunohistochemical analyses, antibody production assessment and investigation by PCR of the presence of chlamydia in the vagina or rectum were carried out. Experimental IT inoculation of C. abortus induced pneumonia in sheep during the first few days post-infection, confirming the suitability of the IT route for testing vaccines in the natural host. The course of infection and the resulting pathological signs were less severe in vaccinated sheep compared with non-vaccinated animals, demonstrating the success of vaccination. IN infection did not produce evident lesions or demonstrate the presence of chlamydial antigen in the lungs and cannot be considered an appropriate model for testing vaccines.