With growing pressure from medical groups to increase access to medicinal marijuana in Australia, research from North America, where recreational use has been legalised in some states for a decade, shows an unexpected fallout – incidents of cannabis induced toxicosis in pets are on the rise.
Over the past six years there was a 448% increase in accounts of cannabis poisoning amongst pets in the US and Canada, with the Animal Poison Control Centre reporting a 765% increase in calls regarding pets ingesting cannabis in 2019 compared to the previous year.
Lead author Richard Amissah, from the Department of Biomedical Sciences at Canada’s University of Guelph, examined the frequency, diagnostic criteria, clinical signs, and prognoses of cannabis toxicoses in pets in North America.
The clinical signs that veterinarians reported to have observed most were urinary incontinence, disorientation, ataxia, lethargy, hyperesthesia, bradycardia, stupor/obtundation, and twitching, with a small number of veterinarians reporting head bobbing and hyperthermia.
The products that often led to cannabis toxicosis in pets were edibles and dried cannabis, but also included other sources such as discarded joint butts, human faeces, cannabis-infused butter/oil, and compost.
Usually, the pet owner did not know the source of cannabis exposure, however, among those who did know the source, most reported that they were obtained from government regulated producers, followed by home cultivated plants, and the black market.
Diagnosis was frequently based on the presence of supportive clinical signs, and the most common treatment was outpatient monitoring, which lasted for less than 48 hours.
Except for 16 patients that were reported to have died in association with cannabis exposure, all patients recovered completely after treatment.
The researchers state that the presence of other toxins (e.g., chocolate) in the edible product may have contributed to clinical illness and may explain some of the deaths reported.
The findings also suggest that ‘dog people’ may use marijuana more than ‘cat people,’ with a higher prevalence of cannabis toxicoses reported in dogs.
In dogs, the onset of clinical signs ranges from within minutes post-inhalation to several hours post-ingestion and when compared to humans, dogs seem to have similar oral absorption, but a much longer duration and wider range of clinical signs.
Dogs produce the additional THC metabolites 8-OH-Δ9-THC and 11-OH-THC, which may contribute to the additional clinical signs observed only in dogs.
Consistent with previous work, participants also reported cannabis toxicoses in other companion animal species such as horses, ferrets, and iguanas – and in previously unreported species such as pet cockatoos.
The most common reason for pet exposure to cannabis was eating it while unattended, followed by intentional administration for recreation – people wanting to get their pets high.
In 1996, California became the first state to legalize medical cannabis, sparking a trend that spread to most states by 2016, and in 2012, Washington and Colorado became the first states to legalize cannabis for recreational use.
Recreational cannabis use is now legal for adults in 19 states, with medical use authorised in 36, and last year the legal industry generated $25 billion in sales, a 43% increase over 2020, and is expected to hit $65 billion in 2030.
Early last month, the U.S. House of Representatives narrowly passed the Marijuana Opportunity Reinvestment and Expungement (MORE) Act, a bill that would end the federal prohibition on cannabis, removing it from the list of banned controlled substances.
Canada became the second country to legalize recreational use of the drug (for adults in all provinces and territories) when it passed The Cannabis Act on Oct. 17, 2018, and although the total number of cannabis toxicoses reported in pets are fewer than in the US, they are also on the rise.