Adder Bite (Vipera Berus)
The adder (Vipera berus) is the only venomous snake widespread in Germany and belongs to the viper family. As a protected species under the Federal Nature Conservation Act, it is strictly protected. The adder reaches a body length of 60 to 80 cm and is recognizable by its characteristic zigzag pattern on its back. In Germany, in addition to the adder, the rarer asp viper (in the far southwest) and the Aesculapian snake (non-venomous) also occur regionally with varying frequency.
Adders are naturally shy animals that avoid contact with humans and pets. Bites usually only occur when the snake feels threatened and has no escape route. Curious dogs that sniff or touch the snake with their paw are particularly often bitten. Cats can also become victims of adder bites due to their hunting behavior.
The geographical distribution of the adder in Germany extends primarily to moist forest areas, heaths, moors, and mountainous regions. It is particularly common in Bavaria, Baden-Württemberg, parts of Lower Saxony, Brandenburg, and Mecklenburg-Vorpommern. The adder shows the highest activity in the warm months between April and October, with the risk of bites being highest in the summer months.
The most important facts at a glance
Poisoning from an adder bite is a medical emergency in dogs and cats that requires immediate veterinary treatment. The adder (Vipera berus) is the most common venomous snake in Germany and is a protected species. Bites usually occur when the snake feels threatened and has no escape route.
Adder venom contains various toxic components, including proteases and phospholipases, which can lead to local tissue damage, coagulation disorders, and neurological symptoms. Small animals under 10 kg body weight are particularly at risk, as the injected amount of venom is higher in relation to body weight.
Clinical symptoms include local swelling, pain, and bleeding at the bite site, as well as systemic manifestations such as weakness, vomiting, coagulation disorders, and in severe cases, circulatory and respiratory problems. Diagnosis is based on anamnesis, clinical picture, and laboratory diagnostic tests.
Treatment consists of first aid measures, the possible administration of an antiserum, and symptomatic treatment, which includes fluid therapy, pain medication, antihistamines, and, if necessary, surgical interventions. With timely and adequate treatment, the prognosis for most animals is good, although smaller animals and those with bites in the head and neck area have a higher risk of serious complications.
Aftercare includes continued medication, wound care, restricted movement, and regular check-ups. Preventive measures such as leashing dogs in known adder areas and avoiding dense undergrowth can reduce the risk of a bite.
Causes, development and progression
When an adder bites, the snake’s venom glands inject 20–100 mg of venom into the bitten animal’s tissue. The amount of venom varies depending on the snake’s age and size, as well as the time since its last prey capture. The lethal dose (LD50) for a subcutaneous injection is approximately 6.45 mg/kg body weight. For an intravenous injection, the LD50 is reduced to just 0.55 mg/kg body weight.
These values clearly show that small pets under 10 kg body weight are particularly at risk. For a medium-sized dog weighing 20 kg, the average venom quantity of 50 mg transferred during a bite would correspond to approximately 2.5 mg/kg body weight – a value below the LD50, but still capable of causing severe poisoning symptoms. Accordingly, dogs under 10 kg body weight, i.e., young dogs, small dog breeds, and cats, are particularly at risk.
Adder venom is a complex mixture of various biologically active substances, mainly proteins and enzymes. The composition can vary regionally, which may explain different courses of poisoning. Furthermore, the location of the bite plays a crucial role: bites to the head and neck area are particularly dangerous due to their proximity to vital organs and faster venom distribution.
Mechanism of action
- Various proteases that inhibit blood clotting and increase the permeability of blood vessels,
- Phospholipases that can damage nerve and muscle cells and cause the dissolution of red blood cells.
- Together, they lead to local tissue destruction.
- A special neurotoxin inhibits transmission in the nerve pathways and can lead to paralysis.
Depending on the bite site, venom quantity, and general condition, the venom can trigger local to systemic reactions in dogs and cats.
Composition of Adder Venom
Adder venom is a complex mixture of biologically active proteins and enzymes, including:
- Proteases (e.g., metalloproteinases, serine proteases)
- Phospholipases A₂
- Hyaluronidase
- Collagenase
- Hemorrhagic components
- Slightly neurotoxic peptides (rarely relevant)
The effect is mainly local and systemic-inflammatory, not paralytic.
Main Mechanisms of Action in the Organism of Dogs and Cats
Local Tissue Destruction (Cytotoxic Effect)
- Phospholipase A₂ and other enzymes damage cell membranes, leading to cell lysis, muscle necrosis, and edema formation.
- Result: severe local swelling, pain, hemorrhages, possibly tissue necrosis.
- Most commonly affected areas (80–90% of animal bites), especially paws or snout.
Increased Vascular Permeability and Hemorrhage
- Metalloproteinases and other enzymes destroy capillary walls → leakage of plasma and blood components into the tissue.
- This promotes edema, hematomas, and potentially hypovolemia and shock in severe cases.
Inflammatory Reaction
- Release of cytokines, histamine, prostaglandins → strong local and systemic inflammation.
- Can lead to fever, circulatory dysregulation, leukocytosis.
- Risk of systemic inflammatory response syndrome (SIRS).
Coagulation Disorders (Coagulopathy)
- Enzymatic activation or inhibition of coagulation factors → consumptive coagulopathy possible.
- In rare cases: disseminated intravascular coagulation (DIC).
Slightly Neurotoxic Effects
- In Central Europe, the neurotoxic component of adder venom is minimal.
- In very rare cases: ataxia, muscle tremors, pupil dilation – mostly in young or weakened animals after a strong venom injection.
Species-specific Characteristics
Dog:
- Most commonly affected (80–90% of animal bites), especially on paws or snout.
- Dogs often show pronounced local reactions, occasionally also systemic symptoms: apathy, fever, circulatory problems, arrhythmias.
- In small dogs or with a large amount of venom → risk of hypovolemia or anaphylactoid reaction.
Cat:
- Less commonly affected, as cats are more cautious.
- Clinical reactions often milder, but possible with bites to the face or in young animals: shortness of breath, lethargy, fever, mucous membrane swelling.
- Stronger reaction in cases of pre-existing immune system damage or reduced constitution.
Summary of Toxic Mechanisms of Action
| Level of Action | Toxic Effects of Adder Venom |
| Local Tissue | Cytolysis, Necrosis, Pain, Swelling |
| Vessels | Increased Permeability, Edema, Hemorrhages, Hypotension |
| Immune System/Inflammation | Release of Mediators → Fever, SIRS, Circulatory Stress |
| Coagulation System | Consumptive Coagulopathy, Thrombocytopenia, rarely DIC |
| Central Nervous System (rare) | Seizures, Ataxia, Altered Consciousness (only in severe poisoning) |
An adder bite is a veterinary emergency for dogs and cats. The venom primarily causes local cell and vascular damage and promotes inflammation, with the potential for systemic circulatory and coagulation disorders. Rapid, symptom-oriented therapy is crucial for the prognosis. Small dogs, puppies, and animals with pre-existing conditions are particularly at risk. An antivenom is available but is only used in severe cases.
Symptoms of intoxication
The clinical symptoms of adder poisoning in dogs and cats typically develop within minutes to hours after the bite and can vary depending on the severity of the poisoning. The symptoms can be divided into local and systemic manifestations.
Local symptoms include:
- Painful, rapidly increasing swelling at the bite site
- Redness and warmth of the affected tissue
- Visible bite marks (two pinpoint punctures approximately 0.5-1 cm apart)
- Bleeding at the bite site
- Progressive, very painful edema that can spread to adjacent tissue areas.
Systemic symptoms include:
- General weakness and lethargy
- Staggering and coordination disorders
- Vomiting and diarrhea
- Increased respiratory and heart rate
- Pale or cyanotic mucous membranes
- Coagulation disorders with spontaneous bleeding
- Hemolysis (destruction of red blood cells)
- Neurological symptoms such as tremors, seizures, or paralysis
- In severe cases: circulatory collapse, shock, and respiratory paralysis
Bites to the head and neck area can lead to life-threatening airway constriction due to severe swelling. Symptoms can vary greatly depending on the animal’s individual sensitivity, the amount of venom, and the location of the bite. Especially in small dogs and cats, a life-threatening condition can develop within a few hours.
Diagnosis
The diagnosis of adder poisoning is primarily based on the anamnesis and clinical presentation. In many cases, the actual bite is not observed by the pet owner, which can make diagnosis difficult. The following diagnostic steps are indicated if an adder bite is suspected:
The clinical examination includes careful inspection of the suspected bite site. Characteristic features are two pinpoint puncture marks about 0.5-1 cm apart, originating from the snake’s fangs. However, these are not always clearly visible, especially in animals with dense fur or if some time has passed since the bite.
Laboratory diagnostic tests are necessary to assess the severity of the poisoning and to detect complications early:
- Blood count: Indications of hemolysis, thrombocytopenia, and leukocytosis
- Coagulation parameters: Prolonged clotting times (PT, aPTT), reduced fibrinogen levels
- Clinical chemistry: Increased creatine kinase (CK) as an indicator of muscle damage, kidney and liver values for assessing organ damage
- Urine examination: Hemoglobinuria as an indication of hemolysis, proteinuria in case of kidney involvement
Imaging procedures such as ultrasound can be helpful to assess the extent of tissue damage and to detect complications such as compartment syndrome. In unclear cases, a differential diagnosis for other causes of acute swelling and systemic symptoms may be necessary, such as insect bites, bite injuries from other animals, or allergic reactions.
Timely diagnosis is crucial for treatment success, as therapy should be initiated as early as possible to avoid serious complications.
Therapeutic principles
Treating an adder bite in dogs and cats requires a rapid and systematic approach. Therapeutic measures depend on the severity of the poisoning and include both first aid and veterinary care. Decontamination in the classical sense is not possible.
First Aid Measures:
If an adder bite is suspected, the most important immediate measure is to keep the affected animal calm to slow down the rapid distribution of the venom in the body. The animal should be carried if possible and transported to the vet immediately.
Do not do the following:
- Tie off the limb
- Suck or cut the wound
- Cool the bite site with ice
- Administer medication without veterinary instruction
Veterinary Treatment:
The use of an antidote (anti-snake venom serum, antivenom) is possible, but it carries significant risks, so the benefits and risks must be weighed.
Even if early use of a snake venom antiserum has better chances of success than later use, symptomatic treatment is often preferred first due to the risks.
If the use of a snake venom antiserum is advisable, e.g., for very small animals or bites to the head, the risk can be better assessed by a preliminary allergy test.
The veterinarian can clarify the possible procurement of an anti-snake venom serum through poison control centers.
The snake venom immune serum “Europa” (adder, mountain viper, sand viper, asp viper, Levantine viper), originally produced by Sanofi for the European region, is no longer offered by this company.
Symptomatic therapy is based on the expected and/or already present symptoms due to the known toxins.
This includes shock prevention, the use of antihistamines, antibiotics, and possibly glucocorticosteroids for allergic reactions.
A possible complication due to very severe swelling is compartment syndrome. Due to the severe swelling, structures (muscles, blood vessels, and nerves) within tight and inflexible sheaths (fascia) become increasingly compressed and receive less and less blood flow. This can lead to tissue death.
If therapy with anti-inflammatory drugs (antiphlogistics) is not sufficient to reduce swelling in the region, surgical decompression (fasciotomy) may be necessary.
Summary of clinical therapy includes several components:
- Antiserum therapy: Procurement can be coordinated through poison control centers.
- Symptomatic therapy:
- Intravenous fluid therapy for circulatory stabilization and promotion of venom excretion
- Analgesics for pain relief (mostly opioids)
- Antihistamines to reduce the allergic component
- Glucocorticoids for pronounced swelling and allergic reactions
- Antibiotics for prophylaxis of secondary infections
- Oxygen administration for respiratory distress
- Surgical intervention: In cases of severe compartment syndrome, surgical decompression by fasciotomy may become necessary. This measure prevents tissue death due to compression of blood vessels and nerves within swollen tissue fascia.
- Intensive medical monitoring: Close monitoring of vital parameters, coagulation status, and organ functions over several days.
Therapy must be individually adapted to the patient’s condition. With timely and adequate treatment, the prognosis is good in most cases, especially for larger animals.
Prognosis & follow-up care
Snake venoms, including that of the adder, are extremely toxic.
The fact that a fatal outcome usually does not occur is due to the small dose transferred during a bite.
For animals over 10 kg body weight, the prognosis is very good. For small animals, the prognosis must be made with appropriate caution.
The prognosis after an adder bite depends on various factors, including the animal’s body weight, the location of the bite, the amount of venom injected, and the time until veterinary treatment. Generally, the smaller the animal and the later the treatment, the worse the prognosis.
For animals weighing over 10 kg, the prognosis with adequate treatment is generally very good. For smaller animals under 10 kg body weight or for bites to the head and neck area, the prognosis must be made with more caution, as the risk of severe complications is significantly increased here. The mortality rate in dogs and cats after adder bites is less than 5% with timely treatment.
Aftercare following an adder bite involves several aspects:
- Continued medication: Depending on the severity of the poisoning, continuation of antibiotic therapy, pain management, and anti-inflammatory therapy may be necessary for several days.
- Wound care: For open wounds or after surgical interventions, regular wound inspection and care are required.
- Restricted movement: In the first few days to weeks after the bite, the animal should be physically rested to promote healing and minimize stress on the affected tissue.
- Follow-up examinations: Regular veterinary check-ups are important to monitor the healing process and detect possible complications early. These include clinical examinations and, if necessary, laboratory controls.
- Long-term consequences: In rare cases, long-term consequences such as chronic tissue damage, scarring, or functional limitations of the affected limb can occur after adder bites. In individual cases, neurological deficits may remain after head bites.
Full recovery after an adder bite can take several days to several weeks, depending on the severity of the poisoning. Careful aftercare is crucial for optimal healing and the prevention of long-term complications.
Research outlook
Research in the field of snakebite poisoning in pets has made significant progress in recent years. Current studies focus on several key areas that could improve the understanding and treatment of adder bites in dogs and cats.
An important research focus is on the development of improved antiserum preparations. Modern biotechnological methods enable the production of highly purified, species-specific antibody fragments (Fab fragments) that have less allergenic potential than conventional antisera. These could significantly reduce the risk of anaphylactic reactions during antiserum therapy and thus increase the safety of the treatment.
Molecular biological investigations of adder venom have led to the identification of specific toxin components responsible for the various poisoning symptoms. This knowledge could lead to the development of targeted antidotes that specifically act against the most toxic components of the venom.
In the field of diagnostics, rapid tests are currently being researched that are intended to enable quick confirmation of a snakebite and an assessment of the severity of the poisoning. Such tests could be particularly helpful in situations where the bite was not observed and the clinical symptoms are not yet clear.
Research into regional differences in the composition of adder venom could lead to a better understanding of the variable clinical courses. Studies have shown that the venom composition can vary considerably within different adder populations, which could explain different poisoning patterns.
Last but not least, research is concerned with innovative treatment approaches such as the use of matrix metalloproteinase inhibitors, which could inhibit the tissue-destroying effects of snake venom, or with nanoparticle-based drug delivery systems for more efficient antidote administration.
These research approaches promise improved diagnostics and therapy for adder bite poisonings in pets in the future, which could ultimately lead to a reduction in morbidity and mortality rates.
Frequently asked questions (FAQs)
- How do I recognize an adder and how can I distinguish it from non-venomous snakes?
The adder is recognizable by its characteristic zigzag pattern on its back, has a triangular head, and vertical pupils. Non-venomous native snakes like the grass snake have round pupils and a more slender head. The adder reaches a length of 60–80 cm and can be found in various color variants from gray to brown, reddish, or black.
- Is an adder bite always life-threatening for my dog or cat?
Not every adder bite is life-threatening. The danger depends heavily on the animal’s body weight, the amount of venom injected, and the location of the bite. Small animals under 10 kg, as well as bites to the head and neck area, are particularly at risk. With timely veterinary treatment, the prognosis is good in most cases.
- What are the first signs of an adder bite in my pet?
The first signs are primarily a painful swelling at the bite site that spreads rapidly, as well as restlessness and signs of pain from the animal. Later, lethargy, vomiting, breathing difficulties, and circulatory problems may occur. Symptoms typically develop within minutes to a few hours after the bite.
- What should I do if I suspect my pet has been bitten by an adder?
Stay calm and transport your animal to the vet as quickly as possible. Try to keep the animal calm and move the affected body part as little as possible. Avoid first aid measures such as sucking, cutting, or tying off the bite site, as these can do more harm than good.
- How is an adder bite treated at the vet?
Treatment, depending on severity, includes fluid therapy, pain medication, antihistamines, and antibiotics. In severe cases, administration of an antiserum may be considered. For severe swelling, surgical measures for decompression may be necessary. Intensive medical monitoring is important in the first 24–48 hours.
- Is there an antidote for viper bites and is it available at every veterinary hospital?
There are specific antivenoms for viper venom; however, these are not stocked at every veterinary hospital. Availability is limited in Germany, and procurement often occurs through specialized poison control centers. Not every viper bite requires the administration of an antivenom, as the risks of its use must be weighed against the benefits.
- How long does recovery take after an adder bite?
Recovery time varies depending on the severity of the poisoning and can range from a few days to several weeks. Acute symptoms usually subside within 3–5 days, but local swelling and tissue damage may persist longer. Full recovery with healing of all tissue damage can take 2–4 weeks.
- Can I protect my dog or cat from adder bites?
Complete protection is not possible, but you can reduce the risk by keeping your dog on a leash in known adder areas and avoiding dense undergrowth, rock piles, and tall grass. Keep your cat indoors or supervised in such areas if possible. There are also special snake aversion trainings for dogs.
- Can an adder bite through a terrarium?
No, an adder cannot bite through glass or other solid materials of a terrarium. However, extreme caution is required when handling adders in terrariums and should only be done by experts with appropriate permits, as these animals are protected by nature conservation laws.
- Are certain dog breeds more susceptible to severe courses after adder bites?
There is no scientific evidence that certain dog breeds are generally more susceptible to severe poisoning courses. Factors such as body weight, age, and general health are more decisive. However, dogs with existing clotting disorders, immunodeficiency, or organ diseases may have an increased risk of complications.
Literature
- Brandeker, E., Hillström, A., Hanås, S., Hagman, R. and Ström Holst, B., 2015. The effect of a single dose of prednisolone in dogs envenomated by Vipera berus – a randomized, double-blind, placebo-controlled clinical trial. BMC Veterinary Research, 11, Article 44. Available at: https://doi.org/10.1186/s12917-015-0352-6
- Lervik, J. B., Lilliehöök, I. and Frendin, J. H., 2010. Clinical and biochemical changes in 53 Swedish dogs bitten by the European adder – Vipera berus. Acta Veterinaria Scandinavica, 52(1), Article 26. Available at: https://doi.org/10.1186/1751-0147-52-26 [Accessed July 6, 2025].
- Löwe, G. and Löwe, O., 2021. Poisoning in Dogs and Cats – A Veterinary Guide. 2nd edition. Kreuztal: Kynos-Verlag. 208 pages.
- Marti Scharner, E., Langenegger, J., Nentwig, A. et al., 2020. The European adder (Vipera berus) bite in a cat: a case report. Journal of Veterinary Emergency and Critical Care, 30(3), pp. 348–355. Available at: https://doi.org/10.1111/vec.12945
- Turkovic, V., Teichmann, S. and Dörfelt, R., 2019. European Adder bites in dogs in southern Germany: A retrospective study over a 6.5-year period. Journal of Veterinary Emergency and Critical Care, 29(4), pp. 418–425. Available at: https://doi.org/10.1111/vec.12853 [Accessed July 6, 2025].
- Vetpharm – Toxicological Database of the University of Zurich. Plant data sheet on Vipera berus (European adder). Available online at: https://www.vetpharm.uzh.ch/clinitox/toxdb/KLT_080.htm [Accessed July 6, 2025].