Written By
Hannah Gray
College
College of Public Health, Medical and Veterinary Sciences
Publish Date
28 June 2024
Related Study Areas
Researching neglected tropical diseases
With tropical diseases occurring primarily in the world’s tropical and sub-tropical regions, addressing their impact is particularly important for the wellbeing of communities in northern Australia. As we near the International Day of the Tropics, Associate Professor Richard Bradbury shines a light on the important research happening in this space by answering key questions about the current state of neglected tropical diseases (NTDs) in Australia.
Q) What are neglected tropical diseases?
A) Tropical diseases are those which occur exclusively or primarily in the world’s tropical or sub-tropical regions. Most are infectious in origin. The most famous are diseases like malaria, dengue fever, and leishmaniasis. There is a lot of funding for research, intervention and public health control of these diseases globally.
However, there are other tropical diseases that are not so well known and don’t get the same attention or funding. The World Health Organisation (WHO) recognises 25 of these as neglected tropical diseases. These diseases are not a major focus of research and public health funding globally but do have significant impacts on the health of those affected. NTDs disproportionately affect low income and socially marginalised communities in tropical areas, with sometimes devastating and fatal outcomes.
Most NTDs are infectious, vector-borne diseases, meaning they are spread by worms or biting insects such as mosquitoes. A few have non-infectious origins, such as the injected venom of a snakebite.
Q) Why are these diseases still present in Australia and the Tropics?
A) The epidemiology of NTDs is complex, and often related to environmental conditions. Their complex life cycles which sometimes include domestic, feral, or wild animals makes their public health control challenging. Another great challenge for Australia is the remoteness of many communities affected by NTDs, making the delivery of many practical public health interventions much more complicated, expensive, and difficult.
Q) Which are the most prevalent?
A) The WHO estimates that NTDs affect more than 1 billion people worldwide, and there are seven NTDs found in Australia. Only two of these – snakebite envenoming and some rare fungal ulcers transmitted through cuts or contact with vegetation – are diseases which we cannot eliminate.
The others include Buruli ulcer, scabies, trachoma, and intestinal worm diseases such as strongyloidiasis, hookworm and whipworm. Believe it or not, we still occasionally find cases of leprosy in very remote parts of Australia.
Q) What is your current research focus within neglected tropical diseases?
A) I am currently researching effective control methods and diagnostic tests for a disease called strongyloidiasis, a soil transmitted helminth (worm) disease of humans. It is caused by a microscopic worm called Strongyloides stercoralis that enters the body through the skin, most commonly via the foot. Some of the highest rates in the world are found in some remote parts of Northern Australia, where Aboriginal and Torres Strait Islander communities are disproportionately affected.
Apart from this, I work on a range of other intestinal and blood parasitic infections. I also do consultations for pathology labs in Australia and overseas to help identify really weird or unusual parasites infecting humans on the rare occasions they crop up.
Q) What work is currently being done to combat these NTDs within Australia and overseas?
A) There is important work happening right here at JCU. I am currently working as part of a group from several universities on a National Health and Medical Research Council (NHMRC) funded project to determine how to control strongyloidiasis in northern Australia. The hope is to find an example of how to best control this disease in the unique context of Australia, and what we find may be used by State Public Health Departments to initiate their own control programs.
JCU is the national leader in the field of tropical diseases. Our courses, such as the Master of Public Health and Tropical Medicine, prepare doctors, nurses and allied health professionals in Australia and overseas to address the issues unique to the Tropics.
Led by the Australian Institute for Tropical Health and Medicine, we also punch well above our weight in tropical diseases research. For example, Professor Alex Loukas and his colleagues in Cairns are doing fantastic work on the immunology of hookworm infections and working towards a vaccine. Associate Professor Stephan Karl is working closely with the Papua New Guinea Institute of Medical Research on malaria control. Associate Professor Tanya Russell is leading the PacMOSSI Project, which trains people in Pacific Island countries on methods of controlling and mitigating mosquito-borne diseases. In Townsville, Dr Mary Castellanos Reynosa is doing work on mosquito-borne virus surveillance and control in the Pacific.
Q) What strategies inform your work both with strongyloidiasis and other NTDs?
A) A ‘One Health’ approach is essential to the control and elimination of strongyloidiasis and other intestinal worm diseases. This aligns with the five core strategic interventions recommended by the WHO for addressing neglected tropical diseases:
- Intensive and innovative disease management
- Preventative chemotherapy (giving people in at-risk populations the treatment for the disease on a regular basis)
- Veterinary public health
- Provision of safe water, sanitation and hygiene
- Improved diagnostic tests for humans and affected animals.
This approach ensures that researchers and health professionals consider the health of a person, their animals and their environment relevant to the control of the disease.
Q) The WHO has a road map for 2021 – 2030 to reduce the presence of NTDs. What progress do you think has been made to achieve this goal?
A) Globally, we have made massive strides in the control of tropical diseases. For example, dengue fever appears to have been eliminated from Queensland by releasing Wolbachia-infected mosquitoes. The rates of malaria worldwide are a fraction of what they were twenty years ago. We are making great progress in specific NTDs such as lymphatic filariasis, river blindness and many common intestinal helminths. We have also nearly eliminated Guinea worm disease through the combined efforts of the WHO and the Carter Center.
Unfortunately, the need to shift public health resources towards the COVID-19 pandemic did slow us down in our elimination goals, and some diseases are much harder to control than others. This may be due to many factors, such as how they spread, who has been infected, remoteness and ease of access for control programs.
Our major roadblocks are funding and the political will to make these changes. Some countries are doing a tremendous amount while others are not as focused on NTDs, which can be seen in their control and elimination data.
Q) Finally, why is it worth spotlighting this issue when focusing on the Tropics?
A) Australia is a high-income nation, yet we still have NTDs. Strongyloidiasis in particular is a potentially fatal intestinal worm that is fast becoming a focus for WHO control efforts. Yet we still have some of the highest rates in the world, with up to 60 per cent of people infected in many remote Aboriginal and Torres Strait Islander communities.
I was invited to meet with Parliamentary Joint Select Committee on Northern Australia in April this year and discuss this urgent matter. My team and I submitted a proposed elimination program to the Committee that outlined what we need to begin controlling strongyloidiasis in northern Australia. This reflects that NTDs are not just something to spotlight, but something to actively address.
A/Prof Richard Bradbury is an internationally recognised parasitologist, with his work taking him across Australia, West Africa, Eastern Europe, and the United States of America. He is the former head of the parasitology diagnostic reference laboratory at the CDC in the United States of America and a member of the World Health Organisation (WHO) Diagnostic Technical Advisory Group for Neglected Tropical Diseases as well as a lead researcher at the JCU School of Public Health and Tropical Medicine, which includes the WHO Collaborating Centre Vector-borne and Neglected Tropical Diseases.