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EXPERT REACTION: Thai boys being freed from cave - Possible infections

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As the good news that all the boys and their coach are likely to be freed from the cave tonight breaks, Australian experts comment on the possible risks of infection associated with being stuck in a cave for more than two weeks.

Organisation/s: The Australian National University, Monash University

Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Distinguished Professor Andy Ball is Director of the Centre for Environmental Sustainability and Remediation at RMIT University

Histoplasmosis (Cave disease) is a disease caused by the fungus  Histoplasma capsulatum  .

The Symptoms of this infection vary greatly, but the disease affects primarily the lungs .

Histoplasma capsulatum is found in soil, often associated with decaying bat guano or bird droppings.

In a cave environment the longer the time spend exposed to the environment the more likely that the spores from the fungus of soil Histoplasma capsulatum will be inhaled. Once inhaled the spores will settle into the lung.  Symptoms will begin 12–14 days. Most affected individuals  show no apparent ill effects.

Acute  histoplasmosis is characterized by non-specific respiratory symptoms, often cough or flu-like. Antifungal drugs are used to treat severe cases of acute histoplasmosis and all cases of chronic and disseminated disease.

However  Histoplasmosis is not contagious; it cannot be transmitted from an infected person or animal to someone else.

Last updated: 11 Jul 2018 10:20am
Declared conflicts of interest:
None declared.
Associate Professor Hosam Zowawi is a Research Fellow & Group Leader & Honorary Fellow at the UQ Centre for Clinical Research. He is a microbiologist who has done research in caves.

It is not a surprise that there is concern about the children developing pneumonic histoplasmosis (which is caused by a fungus named Histoplasma capsulatum). This disease has been known for a long time as "caver's disease". It occurs around the world, but very common in humid conditions, hence caves. Victims can get exposed by inhaling the fungus spores, which can exist in the soil or droplets of infected birds or bats. However, caves can also be a fertile ground for many already known infectious diseases such as rabies (exposure to infected bats), leptospirosis (exposure to infected rodents urine), tick-borne relapsing fever and many others. Caves make excellent environments for bats and bats make excellent reservoir for many viruses. That is why virologists are studying bats from caves for their potential carriage for lethal viruses, such as Ebola and Nipah viruses. 

Yet, it is also very important to consider that a very small portion of the caves on planet earth have been discovered and the microbial ecology of the discovered caves are heavily understudied! 

Thus, the risk of encountering other undiscovered pathogens is very likely. After our expedition for the recently discovered Imawari Yeuta cave in Venezuela we studied the cave microbial ecology and the results were astonishing! Less than one third of the samples we have collected had bacterial species that are known to science. However many of the samples had unclassified types of bacteria (unrevealed to science before) - but it is too soon for us to know if these are useful or harmful microbes. I really hope that the cave kids story in Thailand will stimulate the public and funding agents to support scientists to carry out more research to study innovative ways to tackle infectious diseases, particularly those occurring from exposure to the environment. 

Last updated: 10 Jul 2018 6:12pm
Declared conflicts of interest:
None declared.
Associate Professor Sanjaya Senanayake is a specialist in Infectious Diseases and Associate Professor Of Medicine at The Australian National University

These most unfortunate children trapped in watery caves would be at increased risk of infections specific to this incident. From bats, which live in caves, comes a fungal infection called histoplasmosis. This can cause a wide spectrum of disease from pneumonia, heart infections, joint problems or meningitis. It can take around 2.5 weeks to manifest itself. Although rabies or rabies-like viruses from bats is not a common issue in Thailand, it has to be considered too.

The water in the caves can be a source of a number of pathogens that can cause serious skin or gastrointestinal infections. This includes Aeromonas,Vibrio and mycobacterium marinum. Leptospirosis is a waterborne infection that can cause a serious illness with fevers, lung, kidney and liver manifestations.
Overall, being malnourished through their stay in the caves might increase their susceptibility to contracting certain infections, including reactivation of latent diseases, such as tuberculosis.
But hopefully, none of these will be an issue for these brave children.

Last updated: 10 Jul 2018 6:10pm
Declared conflicts of interest:
None declared.
Professor Dee Carter is from the School of Life and Environmental Sciences, Faculty of Science, University of Sydney

Histoplasmosis is a very serious fungal disease caused by Histoplasma capsulatum, a fungus that lives in soil enriched with bat and bird guano, and it can reach high concentrations in bat caves. However, it’s not a communicable disease; it isn’t passed from person to person or animal to person. Infection occurs when a large amount of the fungus is inhaled from the environment. To the best of my knowledge, there is no recorded case of infection being transmitted by coughing or touching.
If contracted, there are various degrees of infection. Generally, in a healthy child or adult the immune system will deal with the disease and they will only show flu-like symptoms if any symptoms at all. The boys in Thailand should have healthy immune systems but may perhaps be compromised by malnourishment, and their quarantine may be to deal with any potential contamination of hair, clothing or other belongings.
If histoplasmosis does progress – which can sometimes happen even in otherwise healthy people and it’s not known why this happens in some cases and not in others - the initial flu-like symptoms can turn into a pneumonia-like condition. In a very small number of cases, there is dissemination to other organs and this is a very grave condition. There is a small number of drugs that can be used in treatment but at the latter stages these aren’t terribly effective and can have serious side-effects. Recent data suggests even with treatment, the mortality level in people with disseminated disease can be up to 50%

Last updated: 10 Jul 2018 6:08pm
Declared conflicts of interest:
None declared.
Professor Allen Cheng is Professor of Infectious Diseases Epidemiology at Monash University

Histoplasmosis is an infection caused by the fungus Histoplasma capsulatum. It is common in some areas, such as mid-western United States, and is also found in those who enter caves in many other countries. The fungus is found in chicken and bat droppings, and thus activities associated with exposure to droppings (excavation, renovation of chicken coops/farms, exploration of enclosed caves with bat guano) are associated with infection.
It most often presents as an infection of the chest, most commonly the lungs, but also can affect other organs in the chest cavity including lymph nodes or the lining of the heart. Most patients don't have any symptoms, and infection may show up as an shadow on chest x-ray some time later. Mild cases may not require any treatment, but with exposure to high fungal loads, severe infection can occur. In some people, progressive, chronic disease may also require treatment with antifungals. People who had compromised immune systems, such as those with HIV/AIDS, are also at risk of severe or chronic histoplasmosis.

Last updated: 10 Jul 2018 6:05pm
Declared conflicts of interest:
None declared.
Professor Peter Collignon is Director of Infectious Diseases and Microbiology, The Australian National University

Caves can present a danger for a relatively rare fungal infection called Histoplasmosis (histo). It mainly infects the lungs but it can spread throughout the body. It is much more common in some areas of the world especially in parts of the USA (Ohio Valley), but also in parts of Canada and India many people seem to be exposed. Histoplasmosis is found around the world e.g. in Australia but here it is very rare.

Caves with large numbers of bats or birds and their droppings seem to be a higher risk for histo. Presumably the droppings allow the fungus to grow better in the dirt/soil and then people inhale the fungal spores.

How much the risk is in Thailand, I don’t know. I would need information from local health authorities on how often they see histo cases to better evaluate the risk for caves in Thailand.

Water is a risk for many infections. If there is a wound or skin cut, then water loving bacteria such as vibrio, Klebsiella, Enterobacter can be common bacteria that infect wounds. Bacteria such as legionella can be inhaled or ingested if in water and if water is contaminated by animals then it is bacterial diseases like leptospirosis or salmonella that could be a problem. 

Meliodiosis is also common bacterial infection in Thailand with water a common source for infection.

If water is contaminated with human waste, then that can be a risk for viral and bacterial infections for example typhoid, if people are carrying this bacteria.

Last updated: 10 Jul 2018 6:03pm
Declared conflicts of interest:
None declared.

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