Sudden cardiac death due to caffeine toxicosis in a dog
Felipe Reggeti, Nick Schrier, Glenna McGregor, Riley Wilkinson, Andrew Moore
Animal Health Laboratory, University of Guelph, Guelph, ON (Reggeti, Schrier); Animal Health Centre, BC Ministry of Agriculture, Abbotsford, BC (McGregor); Agriculture and Food Laboratory, University of Guelph, Guelph, ON (Wilkinson, Moore).
AHL Newsletter 2024;28(4):26.
A 4-year-old Shetland sheepdog died suddenly 2 hours after an acute onset of vomiting. The family found some “mystery ground meat” surrounded by dead slugs in the backyard. Malicious poisoning was suspected, and the carcass was submitted to the Animal Health Centre in Abbotsford, BC, for postmortem examination. The dog weighed 14.2 kg and had abundant subcutaneous and visceral adipose tissue, with an estimated body condition scoring of 6/9. Gross examination revealed severe diffuse congestion of the liver and kidneys, acute pulmonary edema and congestion, and cyanosis of mucous membranes (Fig. 1), suggesting possible acute heart failure as the cause of death. Histologic findings were consistent with those of the gross examination. In addition, skeletal muscle myocytes occasionally had flocculated cytoplasm and contraction bands.
Figure 1. Postmortem examination. Severe congestion of the lungs and liver suggestive of acute heart failure.
Liver samples and the suspect meat were submitted to the AHL toxicology section for analysis. Upon examination, the mystery meat was noted to contain multiple small (1-2 mm) white particles/crystals (Fig. 2A). During the extraction for chromatography, an unusual pure white precipitate was noted at the bottom of the tube. These samples were forwarded to the AFL Microscopy laboratory, and the crystals in the meat and white precipitate were identified as pure caffeine by Fourier Transform Infrared Spectroscopy (FTIR) (Fig. 2B). The liver and meat samples were negative for hundreds of targeted pesticides and drugs by GC-MS/MS and LC-MS/MS, however, caffeine was found in both samples with the open GC screen. A sub-sample of the meat was forwarded to an external laboratory for caffeine quantification and the concentration was 49,100 ug/g (approximately 5%).
The LD50 for caffeine in dogs is 140 mg/kg; therefore, a small 40 g piece of the meat patty would have been enough to deliver a lethal dose to a 14 kg dog, and even smaller doses have been reported to be toxic to dogs in other cases. These findings, along with identification of caffeine in the liver (confirming exposure), rapid clinical course and postmortem findings supported a diagnosis of caffeine toxicosis. The source was suspected to be crushed caffeine pills that are easily accessible and may contain up to 200 mg of caffeine per tablet.
Excessive caffeine can lead to severe cardiovascular problems, including tachycardia and arrhythmias, potentially causing sudden cardiac death. Gastrointestinal (vomiting and diarrhea) and nervous system (hyper-reactivity, ataxia, seizures) signs are also common. Caffeine has been used as an ecological alternative to control slugs, but it is typically applied in the form of coffee grounds to the soil, or caffeine tablets dissolved in water. In this case, addition of presumptive crushed caffeine tablets to ground meat was unusual and concerning for malicious poisoning.
Figure 2. Mystery meat found in backyard. 2A. Small white crystals in the meat were removed for analysis. 2B. Fourier Transform Infrared Spectroscopy (FTIR) spectrum showed an almost perfect match with the caffeine reference.
References
1. Hoffberg JE. Chocolate and caffeine. In: Blackwell's Five-Minute Veterinary Consult Clinical Companion: Small Animal Toxicology. 2nd ed. Osweiler DO, et al, eds. Wiley-Blackwell, 2016:480.
2. https://www.merckvetmanual.com/toxicology/food-hazards/chocolate-toxicosis-in-animals.