Aspergillus

Why is Aspergillus dangerous to cannabis users?

Aspergillus is especially dangerous to immunocompromised individuals, in whom the airborne spores can lead to a debilitating invasive infection, called aspergillosis, that oftentimes proves to be fatal. A 1992 study found the incidence of cases of aspergillosis per year to be 1 – 2 patients per 100,000 people; however, this number is likely much higher today due to the increased use of immunosuppressants and stem cell therapy. A 1983 study isolated Aspergillus fumigatus spores from cannabis smoke, indicating the spores do in fact survive combustion. There are a variety of factors that can increase an individual’s likelihood of developing aspergillosis including, but not limited to:

• The ingestion of immunosuppressive drugs (after undergoing bone or organ transplants)
• Low white blood cell count (resulting from chemotherapy)
• Asthma or cystic fibrosis
• Long-term corticosteroid therapy

While immunocompromised individuals are at greater risk of Aspergillus infection, there has been at least one confirmed case of aspergillosis developing in an immunocompetent cannabis user.

There are several hundred different species of Aspergillus, and not all are dangerous to humans. A. fumigatus is the species that most commonly causes infection, and it has been linked to the death of at least one immunocompromised cannabis user. A. flavus, A. niger, and A. terreus have also been shown to cause infection.

Who requires Aspergillus testing on cannabis?

A. fumigatus, A. flavus, A. niger, A. terreus                              A. fumigatus, A. flavus, A. niger

• Arizona                                                                                        – Alaska
• California                                                                                     – Hawaii
• Florida                                                                                         – Vermont
• Iowa
• Michigan
• Missouri
• Nevada*

*Only required for select matrices, view the page for the State you’re interested in for more information

Why Use qPCR for Aspergillus testing on Cannabis?

Aspergillus grows poorly on various culture-based microbial tests. As a result, there are no Aspergillus-specific culture tests on the market. This is likely due to Aspergillus forming heterogeneous macro-colonies in solution and thus single CFUs are actually derived from a clump of hundreds to thousands of viable cells.

Only DNA-based testing can accurately differentiate between Aspergillus species. This is important because only specific species  cause Aspergillosis, the potentially deadly lung infection. On the other hand, labs that rely on visual inspection to differentiate Aspergillus species have incorrectly identified A. brasiliensis as A. niger, leading to false failures.