Cannabis as vector for a dangerous fungal infection? A case study

A gloved hand holding a petri dish

In California, cannabis grown outdoors was for the first time identified as the trigger for a dangerous illness. A study that has attracted little attention so far shows that a woman became seriously ill from smoking contaminated cannabis. What really happened and how can consumers protect themselves?

As the Daily Mail reported back in January, a case study has proven that cannabis infected with a fungus was the cause of a fungal infection in a woman from California. The symptoms and the course of the illness of so-called valley fever are similar to those of meningitis.

However, this illness is not normally fatal to healthy people. It comes from the fungus coccidioides immitis, which enters the body from the dust of contaminated mouse droppings or contaminated food.

The British Medical Journal published an article, which so far has mainly been ignored, that reports on a 48-year old woman and cannabis patient who reportedly smoked up to six blunts per day (i.e. pure cannabis wrapped in a tobacco leaf).

A human skeleton with a close up view of an infection in the brain

After the appearance of initial flu-like symptoms, such as dizziness and exhaustion, the patient became aggressive and as the illness progressed, could no longer remember her own name. After a few weeks, doctors diagnosed a coccidioidomycosis infection as the cause, although initially it was not known how the patient had become infected. In the meantime the patient has recovered.

Plants as carriers of spores

The coccidioides immitis fungus is present in the soil, especially in the many dry areas of California. It is a trigger for coccidioidomycosis, more commonly known as cocci, valley fever, Californian fever or desert rheumatism. Plants growing in fungus-infected soil will inevitably become carriers for coccidioides immitis spores.

Once the doctors made the initial diagnosis, they tested the patient’s samples from the cannabis dispensary in Bakersfield, California. In all the strains, the presence of coccidioides immitis and the equally dangerous cryptococcus neoformans spores were detected.

Incidentally, 20 varieties in the dispensary included a high level of mould spores and the laboratory that carried out the testing also found high levels of trace pesticides in more than 90% of the plants.

After analysing the case very carefully, the doctors now agree that the fungus spores survive the high temperatures of a burning joint and were therefore able to infect the woman. This is not the first time that cannabis grown outdoors in California has been suspected of transmitting this dangerous fungus.

However, until the publication of this case study, it had been assumed that only people with a damaged immune system were at risk of becoming infected by cannabis contaminated with fungi. This means that this case of the 48-year old woman is the first case in which it has been shown that a person with an intact immune system can catch desert fever by inhaling cannabis infected with the fungus.

How to know if cannabis in contaminated?

The doctor who headed up the study, Dr. Bryan Shapiro, recommends patients to only use controlled products grown indoors:

“Make sure that you know where your cannabis comes from. I recommend buying indoor varieties. For people with a weak immune system, like HIV patients or with other infections, I would recommend avoiding inhaling cannabis products altogether. Edible products, on the other hand, are probably safer.”

Want to know more about how to dertermine if your cannabis is contaminated?

Clean cannabis – where can you find it?

In Europe, only the indoor varieties that are grown in Canada and the Netherlands for medical purposes are currently being tested for mould and pesticides. In addition, only a very few coffeeshops in the Netherlands and Cannabis Social Clubs in Spain will provide test results for their products.

As cannabis is only tolerated in both these countries, there are no government guidelines in place, unlike as is the case in Colorado, California, or British Columbia. At best, there are just some very committed campaigners on the cannabis scene who are pushing for transparency.

Canada and most of the states in the US require producers to provide lab analyses before they can sell their products. In those places where the sale of cannabis products to adults is legal and regulated, the same sort of analysis is required for its recreational use as is for medicinal cannabis.

Green and purple mould covering cannabis

“Patients who are already struggling with serious illnesses really do not need any additional problems from their medication,” comments the US cannabinoid specialist Bonni Goldstein on the problems with cut or otherwise contaminated buds.

“They should not have to worry about whether the products they are using are polluted or poisonous. Medical dispensaries help patients to find the right medication. It is also their responsibility to identify dangerous products and only supply tested goods.”

Unfortunately and with increasing frequency, we are hearing or reading international news about polluted cannabis buds finding their way into shops. But on the plus side, things are now often being reported while in the past, they would have found their way, no questions asked, onto the black market.

In the Netherlands and Spain, the problem is becoming larger and more evident than ever, thanks to the problem of the lack of controls and the legal grey zone, which does not include any checks.

  • Disclaimer:
    This article is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with your doctor or other licensed medical professional. Do not delay seeking medical advice or disregard medical advice due to something you have read on this website.


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  • Michael_Knodt

    Michael Knodt

    Berlin-based Michael Knodt specialises in cannabis and hemp-related journalism. Over the years, he’s written extensively on the topic for various German and English magazines, including Vice Magazine. Michael is the face and moderator of DerMicha, the popular German YouTube channel on cannabis and its prohibition.
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