A bacterial infection spread through contaminated water, soil, and animal urine is emerging as a growing health threat in Australia, with cases increasingly detected in regions previously unaffected. Leptospirosis, a zoonotic disease historically confined to tropical areas, is now spreading southward, driven by climate change and increasingly frequent extreme weather events.
The disease, which can cause a range of symptoms mimicking influenza or even COVID-19, often goes undiagnosed or misdiagnosed. This lack of recognition, coupled with a scarcity of surveillance, particularly in southern regions, is contributing to its spread. Symptoms can progress to more severe illness, including pneumonia, organ failure, and meningitis.
Sylvia Morris, a veterinary science student in Townsville, experienced firsthand the rapid progression of leptospirosis. Initially presenting as a common cold, her illness quickly escalated to pneumonia, ultimately requiring a two-week course of antibiotics and six months of recovery. “But it can be just a muddy puddle or having a cut that becomes an issue,” she explained, highlighting the often-unclear routes of infection. She noted the difficulty in pinpointing the source of her infection due to her work and pet ownership.
Leptospirosis is caused by Leptospira bacteria, shed in the urine of infected animals – rodents, livestock, and wildlife are common carriers. Humans become infected through contact with this contaminated urine, or with water or soil that has been in contact with it. Exposure can occur through seemingly minor incidents, such as wading through floodwater, gardening, or even a small cut coming into contact with contaminated soil.
Globally, the World Health Organization estimates approximately 1 million cases of leptospirosis occur annually, resulting in nearly 60,000 deaths. The Australian Centre for Disease Control monitors and reports on case numbers and trends within the country, recognizing it as a notifiable disease.
New research, led by the University of New England, underscores the increasing prevalence of the disease in Australia, particularly within rural and agricultural communities. Associate Professor Jacqueline Epps, a rural GP involved in the research, noted, “We have seen over time more outbreaks heading further south, particularly in New South Wales.” The research points to a direct link between more frequent storms and flooding – events exacerbated by climate change – and the expansion of the disease’s range.
The changing climate isn’t the only factor at play. The role of rodents, particularly rats and mice, in spreading the disease is becoming increasingly significant. A 2018 outbreak on a New South Wales berry farm, affecting up to 84 workers, was traced back to contamination from rat urine on harvested fruit. Recent mouse plagues have also been linked to surges in infection rates. “The most common form of transmission is from mice and rats and that’s new,” Dr. Epps stated.
While dairy farmers routinely vaccinate their cattle against leptospirosis, no human vaccine currently exists. Treatment relies on early diagnosis and the administration of specific antibiotics. However, the non-specific nature of early symptoms – resembling common illnesses like the flu or COVID-19 – often delays diagnosis and treatment.
The disease also poses a significant economic threat to the agricultural sector. In New Zealand, a report estimated the annual cost to the cattle, sheep, and deer industry at US$14 million, including preventative vaccinations. In Australia, the bacteria can cause abortion storms in cattle herds, leading to substantial financial losses for farmers.
Australian College of Rural and Remote Medicine president Rod Martin highlighted the need for increased awareness among healthcare professionals and the public, particularly as the disease spreads into areas where it has not previously been seen. “We may need to educate doctors in emergency departments and patients in rural areas as the weather keeps heading south and the tropics spread beyond Rockhampton,” he said.
Researchers are calling for expanded human testing, improved surveillance systems, and urgent investment in preventative measures. Dr. Epps emphasized the need for renewed investment in testing, noting that Australia has not conducted comprehensive human prevalence studies since 2011. She advises individuals to avoid floodwater, cover any cuts or wounds, minimize exposure to rodents, and take appropriate precautions in high-risk occupations.
The spread of leptospirosis serves as a stark reminder of the interconnectedness of human, animal, and environmental health – a concept known as “One Health.” Addressing this emerging threat requires a collaborative, multi-faceted approach, encompassing public health surveillance, veterinary medicine, and climate change mitigation.
