Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2024

The Koala cough: New insights into bacterial and viral coinfections in koalas with respiratory symptoms (#77)

Samuel Phillips 1 , Vasilli Kasimov 1 2 , Harry Ling 2 , Bernadette Rushton 2 , Lilly Russo 2 , Amber Gillet 3 , Ludovica Valenza 3 , Nina Pollak 1 2 , Martina Jelocnik 1 2
  1. Centre for Bioinnovation, University of the Sunshine coast, Sippy Downs, QLD, Australia
  2. School of Science, Technology and Engineering, , University of the Sunshine Coast, Sippy Downs, Queensland, Australia
  3. Australia Zoo Wildlife Hospital, Beerwah, Queensland, Australia

Chlamydial ocular and urogenital tract disease is highly prevalent among koala populations [1]. Despite reports of various pathogens such as Bordetella bronchiseptica [2] and Chlamydia pecorum [3], respiratory infections and disease in koalas remain poorly understood. Furthermore, there is also limited understanding of the roles each pathogen plays in coinfections. To bridge these knowledge gaps, we assessed the prevalence of known koala pathogens in koalas admitted to Queensland wildlife hospitals with signs of respiratory disease.

 

Using species-specific qPCR assays, we screened 102 upper and lower respiratory tract samples collected from 49 unique koalas with signs of respiratory disease. Our findings revealed an overall detection rate of 42.86% (21/49; CI 0.3002–0.5673) for Chlamydia (C. pecorum, C. pneumoniae or C. psittaci), 40.82% (20/49; CI 0.2822–0.5475) for KHV-1, and 12.24% (6/49; CI 0.0573–0.2424) for B. bronchiseptica, with 38.8% (19/49; CI 0.2640–0.5280) testing negative for all targeted organisms. We also identified coinfections, with Chlamydia and KHV-1 being the most common, detected in 20.41% koalas (10/49; CI 0.1148–0.3364). Additionally, coinfections involving B. bronchiseptica and KHV-1 were observed in two koalas, Chlamydia and B. bronchiseptica in one koala, and all three pathogens were found in 6.12% of koalas (3/49; CI 0.021–0.1652). Among the chlamydial species investigated, C. pecorum exhibited the highest detection rate, accounting 40.82% (20/49; CI 0.2822–0.5475), while C. pneumoniae was identified in one koala and C. psittaci was not detected.

 

This study provides additional evidence that Chlamydia, often present in high loads, is prevalent among koalas with respiratory infections and may indeed contribute to respiratory disease. Coinfections with Chlamydia and KHV-1 [4] were observed, as well as coinfections with Chlamydia and B. bronchiseptica. However, it is essential to acknowledge that other pathogens may also be implicated in respiratory disease [5] and should be considered in future studies.

  1. Quigley B, Timms P. (2020) Helping koalas battle disease – Recent advances in Chlamydia and koala retrovirus (KoRV) disease understanding and treatment in koalas. FEMS Microbiol. Rev. 44 (5):583–605.
  2. Letcher J, Weisenberg E, Jonas A. (1993) Bordetella bronchiseptica pneumonia in a koala. J Am Vet Med Assoc. 202(6):985-987.
  3. Mackie, J. T., Gillett, A. K., Palmieri, C., Feng, T., & Higgins, D. P. (2016). Pneumonia due to Chlamydia pecorum in a Koala (Phascolarctos cinereus). Journal of Comparative Pathology, 155(4):356–360.
  4. Wright BR, Casteriano A, Muir YSS, Hulse L, Simpson SJ, Legione AR, Vaz PK, Devlin JM, Krockenberger MB, Higgins DP. (2024) Expanding the known distribution of Phascolartid gammaherpesvirus 1 in koalas to populations across Queensland and New South Wales. Sci Rep. 14(1):1223.
  5. Stephenson T, Lee K, Griffith JE, McLelland DJ, Wilkes A, Bird PS, Trott DJ, Speight NK, Hemmatzadeh F, Woolford L. (2021) Pulmonary Actinomycosis in South Australian Koalas (Phascolarctos cinereus). Veterinary Pathology, 58(2):416-422.