Adder envenoming in dogs and cats: morbidity, fatal outcomes and management challenges
This retrospective study of over 1,300 veterinary enquiries reveals that adder envenoming in UK dogs and cats causes significant morbidity and a 4.9% fatality rate, while highlighting critical management challenges including diagnostic uncertainty and barriers to antivenom access that necessitate improved clinical guidance.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the woodlands, heathlands, and rocky hillsides of the United Kingdom, a small, shy snake called the adder makes its home. It is the only venomous snake native to the country, marked by a distinctive zig-zag pattern along its back and red eyes with vertical pupils. While these snakes are generally timid and avoid conflict, they will bite if they feel threatened or are accidentally stepped on. For humans, such encounters are rare and usually result in only local swelling, though severe reactions can occur. However, for dogs, the risk is far greater. Because dogs are curious and often roam off-leash, they are much more likely to investigate the snake and get bitten. When a dog is envenomated, the venom can cause painful swelling, tissue damage, and serious problems with blood clotting or the heart. While most dogs recover, the situation can be life-threatening, and veterinarians have long relied on a specific medicine called antivenom to neutralize the poison. Yet, until recently, there was a lack of up-to-date information on how often these bites happen, what treatments work best, and what obstacles vets face when trying to save these animals.
A team of researchers set out to fill this gap by looking back at over a decade of records from the Veterinary Poisons Information Service, a 24-hour advice line that veterinarians call when they encounter suspected poisonings. They reviewed more than 1,300 enquiries about adder bites between 2011 and 2024, focusing primarily on dogs and cats. The data revealed that dogs make up the vast majority of these cases, with spaniels and Labrador retrievers being the most frequently affected breeds. The bites happen mostly between April and September, coinciding with the warmer months when the snakes are active. In terms of where the bite occurs, the head and face are the most common targets, followed by the legs and paws, likely because dogs investigate with their noses and paws first.
The clinical picture of an adder bite is often dramatic. The most common sign is significant swelling or oedema at the bite site, which was reported in nearly 80 percent of the dogs. Alongside the swelling, animals often show pain, lethargy, and a rapid heart rate. While many dogs recover with supportive care like pain relief and fluids, the study highlighted that serious complications do occur. A small but significant number of dogs developed issues with blood clotting, tissue death, or heart problems. In the cases where the final outcome was known, about 5 percent of the dogs died or had to be put to sleep due to the severity of the bite. This fatality rate has remained consistent with older studies, suggesting that despite advances in veterinary medicine, the danger remains real.
One of the most significant changes observed over the study period was the shift in the antivenom products used. For many years, a specific antivenom produced in Croatia was the standard treatment. However, supply issues led to a transition toward a different product made in Poland, which became the primary choice in recent years. The researchers found that when veterinarians administered antivenom, they were doing so much sooner after the bite than in previous decades, with a median time of four hours compared to nearly a day in older records. This faster response appeared to correlate with shorter recovery times, with many dogs recovering within three days. However, the study also noted that for the newer Polish product, the evidence of its effectiveness comes from observing real-world cases rather than controlled experiments, so while the results are promising, they are not yet a formal proof of superiority.
Beyond the biology of the bite, the study uncovered substantial challenges in the practical management of these cases. Veterinarians frequently reported difficulties in diagnosing the bite when the snake was not seen, as swelling and pain can also be caused by other injuries or infections. There were also significant hurdles in accessing the antivenom itself. Many vets struggled to find stock, faced high costs, or found the instructions for the newer products difficult to understand because they were written in a foreign language. The researchers also looked at whether giving steroids, a common anti-inflammatory drug, helped. The data suggested that steroids did not improve the response to antivenom and might even be associated with a slightly higher chance of the treatment appearing ineffective, though the study could not definitively prove harm. Similarly, the routine use of antibiotics was found to be much lower than in the past, aligning better with modern guidelines that recommend using them only when there is clear evidence of infection rather than as a precaution.
The study also included a small number of cat cases, which are much rarer than dog bites. The symptoms in cats were similar to those in dogs, dominated by swelling and pain, and most of the cats that had a known outcome recovered. However, the small number of cases meant that firm conclusions about treatment for cats could not be drawn. Ultimately, this research paints a clear picture of a recurring seasonal problem that causes significant suffering and occasional death for pets. It highlights that while veterinary care has improved in terms of speed and resourcefulness, there is still a need for better diagnostic tools to confirm bites without seeing the snake, clearer guidance on how to use the available medicines, and more reliable access to antivenom. The findings serve as a call to action for the veterinary community to refine their approach, ensuring that when a curious dog or cat encounters an adder, the path to recovery is as smooth and certain as possible.
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