Chlamydia pecorum: successful pathogen of koalas or Australian livestock?

Abstract

In Australia, the obligate intracellular bacterium Chlamydia pecorum is best known as the notorious koala pathogen that causes debilitating ocular and urogenital tract disease. While globally published data suggests that this species is essentially ubiquitous in livestock, little is known about the epidemiology of livestock C. pecorum infections here in Australia. My research is focused on investigating the genetic diversity and transmission patterns of C. pecorum, and why it causes disease. Using our newly developed C. pecorum-specific molecular epidemiology typing scheme we provided the first epidemiological data on infections in sheep and cattle in Australia, identifying strains associated with a range of diseases in livestock, and uncovering an unexpected level of diversity for this pathogen. Most importantly, we observed that the same strain can infect koala and sheep, indicating on ongoing cross-host transmission and ‘spill-over' risks to wildlife. Further, by dissecting koala, sheep, cattle and pig C. pecorum strains genomes, we have also identified novel virulence-associated factors that could be explored as vaccine candidates for both livestock and koala infections.