The cannabis conundrum

Testing cannabis for impurities and fungi is vital for immunocompromised patients. Celtic’s Product Specialist, Kyle Warren looks at the sensitivities and highlight the tests. 

First off, the guidelines for growing medicinal cannabis in South Africa?

It's tightly regulated here. You need a SAHPRA license, notoriously difficult to get (fewer than 100 have been issued) and compliance for growing and manufacturing requires biometric security, detailed auditing, reporting and tracking as well as complicated export and manufacturing protocols. That all means the industry is relatively small, especially when compared to the unregulated domestic cannabis market, which is worth roughly R36 billion, annually. 

Briefly, what is current research on the benefits of medicinal cannabis?

In a nutshell it helps reduce pain and anxiety. The headline development in 2025 has been a pair of phase-3 trials of a standardised low-THC cannabis extract (VER-01) for chronic low-back pain. The THC outperformed both placebo and opioids on pain, sleep and physical function, with fewer constipation and withdrawal issues than opioids. And then in 2024 an evidence-map of 140+ systematic reviews found potentially positive effects most consistently for chronic pain, cancer pain, multiple-sclerosis–related spasticity and certain seizure disorders. 

So the research is generally positive. But there's a caveat.

Yes. The issue is cultivating – cannabis flowers can be colonised by toxigenic and pathogenic fungi if humidity is too high or there's poor airflow, dense inflorescences or slow, uneven drying. Of most concern are four common mould fungi – Aspergillus fumigatus, flavus, niger and terreus. They can cause allergic reactions and lung infections, which, given that much medicinal cannabis is inhaled, can be problematic and potentially lethal. Smoking or vaping can deliver fungal spores directly into the lungs. If you're a cancer patient, HIV-positive or an organ transplant recipient, that's a serious issue. 

So testing is crucial. How?

Yes, and PCR testing is preferred over culture methods (which can miss low levels of spores). Real-time PCR tests, such as Celtic's PrimerDesign tests are commonly used in the USA and other countries because they’re quick and sensitive and can differentiate species, which is important. PrimerDesign for example offers a test that will pick up all the relevant Aspergillus species, as well as individual tests for each of the relevant species.
Other kits, such as our YouSeq offering, can pick up other potential contaminants. It's even possible to custom design a kit for a contaminant we may not actually have a test for yet.

Great intel, thanks Kyle. What's your cannabis background?

Brief but a great learning experience! After studying plant biotechnology at The University of Stellenbosch I was involved in the drying and curing of medicinal cannabis. In essence it's like any other pharmaceutical setting: sterile, free of contamination, with everything monitored under strict conditions to ensure consistent product quality. There's very little wiggle room for any deviation. I think it's important to remember that this is a product that will, in most cases, be sold to sick people. So really you need to make sure that your product is free of potential contaminants that could harm that patient.