Oral Presentation 64th International Conference of the Wildlife Disease Association 2015

Immunization against Chlamydia pecorum in wild-caught koalas (Phascolarctos cinereus) is associated with a reduced chlamydial burden and less progression to pathology  (#19)

Courtney A Waugh , Shahneaz Ali Khan , Scott Carver , Kenneth Beagley , Adam Polkinghorne , Jon Hanger , Jo Loader , Peter Timms

Chlamydia pecorum is a significant cause of decline in koala (Phascolarctos cinereus) populations in Queensland (QLD) and New South Wales (NSW), Australia (1).  Current treatments have limited efficacy, and cannot restore fertility in sterile female koalas (2) .  Newly developed vaccines have been tested in captive animals under controlled conditions with promising results (e.g. 3), so the vaccination of free-ranging koalas was an obvious and important next step.  Here, we recruited 60 free-ranging koalas, with varying levels of chlamydial infections but no clinical signs of disease, in one south-east QLD population in Australia. Thirty koalas were immunized against Chlamydia pecorum with adjuvanted chlamydial major outer membrane protein (MOMP), while 30 acted as the non-immunized control group. All koalas received a comprehensive veterinary check, and whole blood and swabs (urogenital and ocular) were collected before they were radio-collared and re-released.  Koalas were then recaptured at 6 and 12 months post-immunization for veterinary checks and sampling.  Results from the first vaccination study in a wild koala population show that immunization can significantly reduce chlamydial burden up to 12 months post-immunization in animals already infected compared to a non-immunized control group.  Incidence of new infections was low and did not differ greatly between the immunized and non-immunized group, however, progression to disease was higher in non-immunized animals than in immunized animals.   Lastly, the reproductive success and fitness of immunized female koalas and their offspring was greater than that of their non-immunized counterparts.  This study provides the first evidence that a MOMP based vaccine against Chlamydia pecorum can reduce Chlamydia shedding and progression to disease in free-ranging koalas.

  1. Polkinghorne, A., Hanger, J., Timms, P. (2013). Recent advances in understanding the biology, epidemiology and control of chlamydial infections in koalas. Veterinary Microbiology. 165 (3-4): 214-223
  2. Govendir, M., Hanger, J., Loader, J., Kimble, B., Griffith, J., Black, L., Krockenberger, M., Higgins, D. (2012). Plasma concentrations of chloramphenicol after subcutaneous administration to koalas (Phascolarctos cinereus) with chlamydiosis. Journal of Veterinary Pharmacology and Therapeutics. 35 (2): 1365-2885
  3. Waugh, C.A., Timms, P., Andrew, D., Rawlinson, G., Brumm, J., Nilsson, K., Beagley, K.W. (2015) Comparison of subcutaneous versus intranasal immunization of male koalas (Phascolarctos cinereus) for induction of mucosal and systemic immunity against Chlamydia pecorum. Vaccine. 33 (7): 855-860