Strongyloidiasis in remote communities
Strongyloidiasis is a soil transmitted parasitic infection. It is one of the world’s most neglected tropical diseases and it exists in Australia. With reports that the disease is common in remote communities in Australia, we spoke with Associate Professor Rob Baird, Director of Pathology and Infectious Diseases Physician at Territory Pathology, to find out why researchers are calling for a ramped-up health response to this deadly parasitic disease.
“Strongyloidiasis is a human infection which is caused by worms, the common species being Strongyloides stercoralis. Largely, it is associated with inadequate sanitation and spreads when there is human faeces in the open environment. The worms are shed in faeces and the infected larvae live in the soil for a short period of time. Consequently, if a person comes into contact with the contaminated soil then the worm can enter the body through the skin” said A/Prof Baird.
An estimated 30–100 million people are infected with strongyloidiasis worldwide; precise data on prevalence are unknown in endemic countries. In Australia, strongyloidiasis is most commonly seen in those living in or travelling to Aboriginal communities, World War II veterans, refugees from Southeast Asia, and African and South American tropical and subtropical regions. Some remote Aboriginal and Torres Strait Islander communities in Australia have previously had prevalence of the disease reported in up to 60% of participants. The parasite is endemic in tropical Australia, defined as above the tropic of Capricorn.
“The presence of the parasite is directly associated with poverty. Unfortunately, the highest rates of strongyloidiasis tend to be in remote aboriginal communities which have numerous health hardware issues, from poor housing, unemployment, poor education, drug and alcohol problems, overcrowding, and other disease burdens, all of these are inter-related issues.
“This particular worm is special as infections can be lifelong, and in particular patient groups. It is important to diagnose and treat strongyloidiasis quickly to prevent cases of fatal hyperinfection. Unless strongyloidiasis is deliberately considered, the diagnosis is not always made. Many infected people have no symptoms, and the worm can live inside a human for 30-40 years. One of the current issues with strongyloides infection is re-activation of the worm in later life when a person becomes immune suppressed; for example, if they have been on steroids or receiving chemotherapy. This can cause an overwhelming hyper-infection, which blocks up the lungs and brain and can be fatal.
“Interestingly, in the Northern Territory, we test and treat everyone who is undergoing chemotherapy as the infection is common and it is devastating if the worm reactivates. We assume that indigenous patients from remote communities have probably been exposed, as current diagnostics are not 100% reliable to determine inactive infection,” said A/Prof Baird.
Exposure to strongyloidiasis can be determined with a blood test. The infection may also be diagnosed by detecting larvae in a stool sample when examined under the microscope. Nucleic acid based diagnostic methods have also recently come to the fore as an alternative technique for diagnosing the disease, and may prove more sensitive. Once diagnosed the parasite can be treated with specific anti-worm medication, depending on the age of the person with the infection. For a community response, improvements in health hardware are required.
“In addition to use of individual anti-worming medication, there have been some really interesting developments in the past five years in regard to treatment. A drug commonly used for scabies, called ivermectin, has a secondary action as an anti-worming drug. There is developing evidence that in areas of high ivermectin use decreases in worm infections have occurred. It is suspected that this association is related because, unfortunately, the people who get scabies are the individuals most at risk for strongyloidiasis. This has been recognised in Queensland and the Northern Territory, so there may be a very beneficial secondary effect of treating scabies with newer agents. However, it is important to note that improvements in sanitation is the best way to prevent strongyloidiasis. Improving aboriginal socio-economic circumstances would be just as beneficial as concentrating on individual diseases such as this,” said A/Prof Baird.
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This article appeared in the August 2019 Edition of ePathWay which is an online magazine produced by the Royal College of Pathologists of Australasia (http://www.rcpa.edu.au/Library/Publications/ePathway).
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