Diagnostic dilemma: Growing weed with bat poop left 2 men with deadly infections

The patients: A 59-year-old man (patient one) and a 64-year-old man (patient two) in Rochester, New York

The symptoms: Patient one was initially admitted to the hospital for respiratory failure after experiencing various symptoms, including a sore throat, difficulty swallowing and extensive weight loss for about six weeks. At the hospital, doctors ordered a computed tomography (CT) scan of the patient's neck, which revealed that he had mucus clogging his upper voice box and right-side vocal cord.

Patient two, meanwhile, was initially hospitalized for having low salt levels in his blood, which caused tissue swelling. His teeth were also in poor condition, which made it harder for him to eat or drink, leading to weight loss, and he had a chronic cough.

What happened next: When he was admitted to hospital, patient one seemed to be wasting away and had signs of bacterial blood poisoning. An additional CT scan, this time of his chest, showed that he had a buildup of fluid in his lungs. Doctors treated him with antibiotics and briefly put him on ventilation to support his breathing. The medical team later identified traces of fungi in the patient's urine and in coughed-up mucus from his respiratory tract.

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In the hospital, patient two had a fever of 100 degrees Fahrenheit (38 degrees Celsius). A CT scan revealed multiple lesions in his chest and abdomen. In addition, traces of fungi were detected in his urine.

The diagnosis: Both patients — who were not affiliated in any way but were from the same area — were diagnosed with a rare fungal lung infection called histoplasmosis.

This condition occurs when people inhale spores of a harmful fungus named Histoplasma capsulatum, which usually grows in soil and the poop of birds and bats. Approximately 1 to 2 people per 100,000 in the United States are infected with histoplasmosis each year. However, most people exposed to the fungus don't develop any symptoms. Symptoms are more likely to emerge in people with lung conditions or weakened immune systems, compared to the general population.

In these two cases, the patients' symptoms may have been exacerbated by other diseases that they had before they developed histoplasmosis. For example, patient one had emphysema, a common type of chronic obstructive pulmonary disease (COPD) in which air sacs in the lungs are damaged, which constrains breathing.

The pair also smoked tobacco and cannabis.

The treatment: Following their diagnoses, the patients were prescribed antifungal drugs to combat their infections. However, despite this treatment, both died. Between 5% and 7% of patients who are hospitalized with histoplasmosis die of their infection.

What makes the case unique: Both patients in these cases were already using or planning to use bat poop as fertilizer to grow cannabis for personal use. Patient one had ordered bat poop — or guano — online, while patient two intended to use guano he'd found in his attic following a bat infestation.

In a report describing the cases, doctors noted that various online sources claim that bat guano is a "natural superfood" for cannabis plants because it contains lots of nutrients, such as nitrogen, phosphorus and potassium. Meanwhile, numerous U.S. states have recently legalized the recreational use of cannabis — including Arizona in 2020, New York in 2022 and Ohio in 2023 — which may be encouraging more people to grow their own cannabis, the report authors noted.

The dangers of using bat guano as fertilizer aren't unique to cannabis — the product would be risky for any gardening, the authors emphasized. But given guano is being marketed for cannabis specifically, there is a need to raise public awareness around the potential risks associated with using the poop in this way, they warned.