Landscape Changes Influence the Occurrence of the Melioidosis Bacterium Burkholderia pseudomallei in Soil in Northern Australia

Melioidosis is a severe disease affecting humans and animals in the tropics. It is caused by the bacterium Burkholderia pseudomallei, which lives in tropical soil and especially occurs in southeast Asia and northern Australia. Despite the recognition that melioidosis is an emerging infectious disease, little is known about the habitat of B. pseudomallei in the environment. We performed a survey in the Darwin area in tropical Australia, screening 809 soil samples for the presence of these bacteria using molecular methods. We found that environmental factors describing the habitat of these bacteria differed between environmentally undisturbed and disturbed sites. At undisturbed sites, B. pseudomallei was primarily found in close proximity to streams and in grass- and roots-rich areas. In disturbed soil, B. pseudomallei was associated with the presence of animals, farming or irrigation. Highest B. pseudomallei counts were retrieved from paddocks, pens and kennels holding livestock and dogs. This study contributes to the elucidation of the habitat of B. pseudomallei in northern Australia. It also raises concerns that B. pseudomallei may spread due to changes in land management

Long term impacts of phytophthora cinnamomi infestation on heathy woodland in the great otway national park in south-eastern Australia

The significant impacts of the introduced plant pathogen Phytophthora cinnamomi on native Australian vegetation have been well documented, but there is less knowledge of long-term effects. We assessed long-term (26 years) disease progression and impacts on vegetation floristics and structure at a heathy woodland site in the Great Otway National Park, eastern section. Disease progressed dramatically between 1989 and 2005 and by 2015 only 0.08% of the site was non-diseased. There were significant declines in plant species richness and numbers of susceptible species; and increases in percentage cover of resistant sedges and grasses overall, and in cover of Leptospermum continentale (prickly tea-tree) in post-disease areas. There were significant declines of Xanthorrhoea australis (Austral grass-tree), a keystone species that contributes greatly to vegetation structure and fauna habitat. There is an urgent need to map the distribution of P. cinnamomi affected vegetation and identify floristically important non-diseased vegetation in the national park. It is imperative that quarantine of non-infested areas, phosphite application, track closures and vehicle wash-downs be implemented to reduce disease extension and protect the significant biodiversity of the region including species rich heathlands and nationally listed threatened plant and fauna species and their habitats.</jats:p