An Unusual Case of Relay Pentobarbital Toxicosis in a Dog

Abstract

Sodium pentobarbital and phenytoin are common constituents of veterinary euthanasia solutions in the United States. Relay, or secondary, barbiturate toxicosis has been reported in carnivorous animals that have fed from the carcasses of euthanized livestock. This case report presents barbiturate toxicosis in a dog. A 2-year-old female spayed Australian shepherd presented comatose 2 h after ingesting an unknown substance on the beach. The material was retrieved from the stomach by gastric lavage and visually identified as fish or other animal tissue. The dog recovered with symptomatic and supportive therapy and was released on the third day of hospitalization. Tissue found on the beach near where the dog walked and a urine sample from the dog were analyzed by gas chromatography/mass spectrometry. Both samples were positive for pentobarbital and phenytoin. The tissue was consistent with mammalian blubber based on gross and histological examination. Three weeks previously, a juvenile humpback whale had stranded on the beach where the dog had ingested the unknown substance. The whale had been euthanized with a barbiturate solution, necropsied, and removed from the beach. It was not definitively determined that the pentobarbital-containing blubber ingested by the dog was from the euthanized whale, but that was the most likely source. Although attempts were made to remove the whale's remains from the beach, practical considerations made complete removal challenging, if not impossible.

Low-Residue Euthanasia of Stranded Mysticetes

“…Prolonged (36 hr) sedation occurred in a dog that consumed tissue possibly from a humpback whale euthanized with pentobarbital (and other drugs) 23 days previously in the same vicinity (Bischoff et al 2011). Even when deep burial of euthanized animals is possible, detection of pentobarbital in surface waters and decades-long persistence in ground waters is a potential concern (Eckel et al 1993;Peschka et al 2006).…”

Deathly Silent: Exploring the Global Lack of Data Relating to Stranded Cetacean Euthanasia

“…Despite the longer TTD during chemical euthanasia, in some cases it will cause less suffering than if inappropriate physical methods are applied or are applied incorrectly. Finally, possible eco-toxicological hazards may occur due to residues bioaccumulating in the environment and there is the possibility of secondary toxicosis [16,[47][48][49]-this is one of the primary reasons that such chemical methods are not employed in NZ stranding events (L. Boren DOC, pers. comm.).…”

A review of secondary pentobarbital poisoning in scavenging wildlife, companion animals and captive carnivores

“…Notwithstanding that to date only a single case has been uncovered, this discovery should be sufficiently compelling to instigate routine monitoring, notably where deliberate poisoning of animals is a known practice, as in many parts of Europe (Guitart et al 2010). Bischoff et al (2011) reported on a dog that evidently fed on tainted whale blubber encountered on a beach where, three weeks prior, a stranded juvenile humpback whale was euthanized and necropsied. Complete removal of the whale carcass was attempted but proved challenging.…”

“…Samples of the dog's urine and from tissue recovered at the beach both tested positive for pentobarbital and the anticonvulsant phenytoin. The authors noted that while the dog was not determined with certainty to have ingested the pentobarbital-tainted blubber, it appeared to have been the likeliest source of exposure (Bischoff et al 2011). A workshop summary report on humane euthanasia protocols for stranded cetaceans highlight that "when considering chemical euthanasia, it must be remembered that the size of the animal also necessitates large quantities of euthanasia agents" (IWC 2015).…”