Pit viper envenomation in a military working dog

Military working dogs are often trained and/or work in locations where the potential for snake bites is increased. Knowledge of the local venomous snakes, the effects of their venom, and appropriate initial stabilization is essential for the US Army Veterinary Corps officer (VCO). As military practitioners, VCOs are uniquely situated to benefit from collaboration with other military assets for air evacuation and treatment of their patients. A recent clinical case of envenomation is presented, along with a review of the most current literature regarding treatment of envenomation in veterinary patients.

[Practical guidelines for the treatment of cases of adder envenomation in dogs]

Every year, dogs are presented to veterinary clinics in the Netherlands after having been bitten by a viper. The viper is the only venomous snake native to the Netherlands. Clinical signs after an acquired viper bite can range from none (after a 'dry' bite) to very mild up to life threatening following a 'wet' bite. To prevent mortality it is important to monitor the animals for a period of time and provide adequate treatment. Clotting disorders and multiple organ failure can occur several days to a week after the viper bite, appropriate follow up is therefore important. In the Netherlands, a specific antiserum is available for veterinarians. The use of this antiserum is strongly recommended in severe cases of viper envenomation.

Clinical and biochemical changes in 53 Swedish dogs bitten by the European adder--Vipera berus

BACKGROUND

Every year many dogs in Sweden are bitten by Vipera berus, the only venomous viper in Sweden. This prospective study investigated clinical signs, some biochemical parameters, treatment, and progress of disease after snakebite in 53 dogs. Effects of treatment with and without glucocorticoids were evaluated.

METHODS

All fifty-three dogs bitten by Vipera berus were examined the same day the dog was bitten and the next day. Two more examinations during 23 days post snake bite were included. Creatinine, creatine kinase (CK), alanine aminotransferase (ALT), glutamate dehydrogenase (GLDH), alkaline phosphatase (ALP) and bile acid results were followed through 3 to 4 samplings from 34 of the dogs.

RESULTS

All dogs had variable severity of local swelling in the bite area and 73 per cent had affected mental status. Initial cardiac auscultation examination was normal in all dogs, but six dogs had cardiac abnormalities at their second examination, including cardiac arrhythmias and cardiac murmurs. All dogs received fluid therapy, 36 dogs were given analgesics, 22 dogs were treated with glucocorticoids, and ten dogs were treated with antibiotics. Evidence of transient muscle damage (increased CK) was seen one day after the snake bite in 15 (54%) of 28 sampled dogs. Moderate changes in hepatic test results occurred in 1 dog and several dogs (22 of 34) had transient, minor increases in one or more hepatic test result. No dog died during the observation period as a consequence of the snake bite.

CONCLUSIONS

Snake bite caused local swelling in all dogs and mental depression of short duration in most dogs. Some dogs had transient clinical signs that could be indicative of cardiac injury and some other had transient biochemical signs of liver injury. Treatment with glucocorticoids did not have any clear positive or negative effect on clinical signs and mortality.

Haemostatic abnormalities and clinical findings in Vipera palaestinae-envenomed dogs

The venomous viper Vipera palaestinae (Vp) is responsible for most envenomations in humans and animals in Israel. Its venom contains proteases, haemorrhagins, L-amino acid oxidase and phospholipase A2 but its effects on haemostasis have yet to be characterised. This prospective study aimed to characterise haemostatic abnormalities in Vp-envenomed dogs from presentation to discharge or death, and their association with mortality. Samples from 39 Vp-envenomed dogs were collected periodically and examined for haematology, prothrombin time (PT), activated partial thromboplastin time (aPTT), antithrombin activity (ATA), fibrinogen level and D-dimer concentration. All dogs presented with severe local signs and most (79%) had systemic signs. Six dogs (15%) died. Haemostatic abnormalities were present in 37/39 dogs. Increased D-dimer concentrations were detected in 28/31 dogs. Disseminated intravascular coagulation was diagnosed in 10 dogs and in all non-survivors. Platelet and leucocyte counts at presentation, maximum PT and aPTT, and minimum ATA during hospitalisation were significantly different between survivors and non-survivors and were good predictors of the outcome. The results show that hypercoagulability, consumption and derangement of haemostasis are common in Vp-envenomed dogs and are associated with mortality. Haemostasis should be closely monitored in such dogs.

Toxicologic information resources for reptile envenomations

The United States is the largest importer of reptiles in the world, with an estimated 1.5 to 2.0 million households keeping one or more reptiles. Snakes account for about 11% of these imports and it has been estimated that as many as 9% of these reptiles are venomous. Envenomations by nonindigenous venomous species are a rare but often serious medical emergency. Bites may occur during the care and handling of legitimate collections found in universities, zoos, or museums. The other predominant source of exotic envenomation is from amateur collectors participating in importation, propagation, and trade of non-native species. This article provides toxicologic information resources for snake envenomations.

Boomslang envenomation in 2 dogs in KwaZulu-Natal, South Africa : clinical communication

Although snakebites are frequently seen in small animal practice in South Africa, boomslang (Dispholidus typus) bites are infrequent due to their shy habits. Boomslang venom is a potent procoagulent, causing a consumption coagulopathy and profuse haemorrhage. Boomslang monovalent antivenom is the most effective treatment. This case report describes and discusses 2 small dogs that were presented to a private practice after being bitten by the same boomslang. Boomslang monovalent antivenom administration to both resulted in cessation of bleeding within 45 minutes. One of the dogs developed severe adverse reactions to the antivenom, including vomiting, dyspnoea and nystagmus, which responded well to intravenous cortisone and symptomatic treatment.

Rattlesnake envenomation

Snake envenomation has been widely reported throughout the human and veterinary literature. The effects of venom include coagulation disorders, neurotoxicity, and tissue effects, such as local swelling and necrosis. Significant progress has been made in understanding the pathophysiology of envenomation, leading to changes in treatment protocols. Recent developments include the production of a new antivenin and a canine rattlesnake vaccine.

Snake bite: coral snakes

North American coral snakes are distinctively colored beginning with a black snout and an alternating pattern of black, yellow, and red. They have fixed front fangs and a poorly developed system for venom delivery, requiring a chewing action to inject the venom. The severity of a coral snake bite is related to the volume of venom injected and the size of the victim. The length of the snake correlates positively with the snakes venom yield. Coral snake venom is primarily neurotoxic with little local tissue reaction or pain at the bite site. The net effect of the neurotoxins is a curare like syndrome. In canine victims there have been reports of marked hemolysis with severe anemia and hemoglobinuria. The onset of clinical signs may be delayed for as much as 10 to 18 hours. The victim begins to have alterations in mental status and develops generalized weakness and muscle fasciculations. Progression to paralysis of the limbs and respiratory muscles then follows. The best flied response to coral snake envenomation is rapid transport to a veterinary medical facility capable of 24 hour critical care and assisted ventilation. First aid treatment advocated in Australia for Elapid bites is the immediate use of a compression bandage. The victim should be hospitalized for a minimum of 48 hours for continuous monitoring. The only definitive treatment for coral snake envenomation is the administration of antivenin (M. fulvius). Once clinical signs of coral snake envenomation become manifest they progress with alarming rapidity and are difficult to reverse. If antivenin is not available or if its administration is delayed, supportive care includes respiratory support. Assisted mechanical ventilation can be used but may have to be employed for up to 48 to 72 hours.

Snake Bite: Pit Vipers

Pit vipers are the largest group of venomous snakes in the United States and are involved in an estimated 150,000 bites annually of dogs and cats. The severity of any pit viper bite is related to the volume and toxicity of the venom injected as well as the location of the bite, which may influence the rate of venom uptake. The toxicity of rattlesnake venom varies widely. It is possible for pit vipers' venom to be strictly neurotoxic with virtually no local signs of envenomation. Venom consists of 90% water and has a minimum of 10 enzymes and 3 to 12 nonenzymatic proteins and peptides in any individual snake. The onset of clinical signs after envenomation may be delayed for several hours. The presence of fang marks does not indicate that envenomation has occurred, only that a bite has taken place. Systemic clinical manifestations encompass a wide variety of problems including pain, weakness, dizziness, nausea, severe hypotension, and thrombocytopenia. The victim's clotting abnormalities largely depend upon the species of snake involved. Venom induced thrombocytopenia occurs in approximately 30% of envenomations. Many first aid measures have been advocated for pit viper bite victims, none has been shown to prevent morbidity or mortality. Current recommendations for first aid in the field are to keep the victim calm, keep the bite site below heart level if possible, and transport the victim to a veterinary medical facility for primary medical intervention. The patient should be hospitalized and monitored closely for a minimum of 8 hours for the onset of signs of envenomation. The only proven specific therapy against pit viper envenomation is the administration of antivenin. The dosage of antivenin needed is calculated relative to the amount of venom injected, the body mass of the victim, and the bite site. The average dosage in dogs and cats is 1 to 2 vials of antivenin.

Four cases of snake envenomation responsive to death adder antivenom

Death adder envenomation is rare in humans and there is only one brief report previously in dogs. This paper details three cases of canine common death adder (Acanthophis antarcticus) envenomation and one case of bardick (Echiopsis curta) envenomation which were responsive to death adder antivenom. The available literature on death adder envenomations is also reviewed. The main clinical sign in the four dogs was severe lower motor neuron paralysis. There was no clinical evidence of coagulopathy or myopathy. Use of a snake venom detection kit was essential for selection of appropriate antivenom. Death adder and bardick envenomation in dogs potentially has a good prognosis if sufficient antivenom is administered and intensive supportive care is available.

Anuric renal failure in a dog after Red-bellied Black snake (Pseudechis porphyriacus) envenomation

A case of Red-bellied Black snake envenomation resulting in intravascular haemolytic anaemia, rhabdomyolysis and anuric renal failure is described in the dog. A 12-year-old female desexed Golden Retriever was presented with a 15 hour history of profuse salivation, progressive lethargy, obtundence, inappetence and collapse. Significant findings on clinical examination were pallor, icterus, tachypnoea and dyspnoea with increased respiratory sounds and crackles in all lung fields. Generalised abdominal and muscular pain was apparent and dark red-brown urine was present around the perineal region. A diagnosis of Red-bellied Black snake (Pseudechis porphyriacus) envenomation was made and the dog was treated with intravenous fluid therapy, Tiger/Brown snake antivenom, packed red cell transfusions and Intermittent Positive Pressure Ventilation. Continued clinical deterioration occurred and a diagnosis of acute renal failure secondary to myohaemoglobinuric pigmenturia was made 12 hours after admission. Intensive treatment was attempted with diuresis and volume expansion. Oliguria and subsequent anuria ensued and the dog was euthanased due to a grave prognosis and lack of clinical response to treatment. Necropsy examination revealed muscular necrosis, accumulation of fluid in the thoracic and peritoneal cavities, and marked renal tubular necrosis with intraluminal occlusion secondary to pigmentary casts.

Snake envenomation in dogs in New South Wales

OBJECTIVE

To obtain baseline data on the prevalence of elapid snake envenomation in dogs presented to veterinary practices in New South Wales and to assess attitudes of veterinarians to this clinical entity.

PROCEDURE

A mailed questionnaire, sent to all veterinary clinics within New South Wales, was utilised to collect epidemiological information regarding elapid snake envenomation in dogs.

RESULTS

A response rate of 68% was obtained and a yearly prevalence of snake envenomation in dogs across New South Wales veterinary clinics was estimated as 0.31%. The most common species reported to be responsible for envenomation within NSW was the Red Bellied Black snake (Pseudechis porphyriacus) followed by the Brown snake (Pseudonaja textilis) and then Tiger snake (Notechis scutatus). The reported envenomation syndromes caused by these common snake species were perceived to be similar for Brown and Tiger snakes but differed for Red Bellied Black snakes. Diagnosis of snake envenomation was based predominantly on the recognition of clinical signs. Specific diagnostic tests, such as venom detection kits, were used infrequently. The most common treatment was reported to be a combination of intravenous fluid therapy and antivenom, and monitoring of response to this treatment was usually through assessment of clinical signs. Survival after antivenom administration was reported to be highest for Red Bellied Black snake species. Survival was perceived to be associated with time between envenomation and presentation to the veterinary clinic and with antivenom administration.

CONCLUSIONS

Current attitudes and perceptions of veterinarians have been defined. Diagnosis of species-specific snake envenomation is shown to be made on the basis of clinical signs which are, however, reported as similar for each species. Clearer definition of these envenomation syndromes and identification of accessible diagnostic testing procedures are needed.

Fatal Vipera xanthina palestinae envenomation in 16 dogs

Sixteen fatal dog envenomations by the snake Vipera palaestinae over a 14-y period are described. Most envenomations occurred during the late night hours in the warm months, and 8/16 dogs were bitten on the limbs. The most frequent clinical signs upon admission were soft tissue swelling and edema, local pain, depression, bleeding, lameness, dyspnea, and 6 dogs were in shock. Thrombocytopenia was present in 14/16 cases and increased hematocrit (13/16) and hemoglobin (9/16) concentration were the most common hematological abnormalities upon admission. Biochemical abnormalities included increased activities of muscle enzymes and alkaline phosphatase, hypocalcemia, and hypocholesterolemia. Creatine kinase activity was markedly increased in 2 dogs. During hospitalization serious complications in many dogs were disseminated intravascular coagulation, acute renal failure, seizures, cardiac arrhythmias, acute necrotizing pancreatitis and severe laryngeal edema; these required intensive and expensive therapies. Specific antivenin (10 ml) administered to 8/16 dogs did not prevent death. Glucocorticosteroids were given in 8 cases; however, their use was associated with complications. Four dogs suffered sudden death, 2 of which died 1-2 d after discharge. Necropsy performed on 3/16 dogs found soft tissue swelling and local bleeding at the envenomation sites as well as bleeding in several distal body organs and tissues.

The diagnosis and management of snakebite in dogs--a southern African perspective

Cases of snakebite envenomation are frequently presented to veterinary practitioners in southern Africa. Despite this, no published guidelines exist on how this medical emergency should be managed. Southern African snake venoms can be classified into 3 main types based on the main mechanism of venom action and clinical presentation. A polyvalent antivenom is manufactured in South Africa and contains antibodies against the most important southern African snake venoms. The cytotoxic venoms are represented mainly by the puff-adder (Bitis arietans), Mozambique spitting cobra (Naja mossabica), black-necked spitting cobra (Naja nigricollis) (in the Western Cape and Namibia) and the stiletto snake (Atractaspis bibronii). These venoms may cause dramatic local swelling, high morbidity and low mortality and infrequently require the use of antivenom for survival (the only cytotoxic venoms used to prepare the antivenom are the puff-adder and Mozambique spitting cobra). The neurotoxic venoms (represented chiefly by the non-spitting cobras and mambas) cause high mortality due to rapid onset of paresis and require antivenom and mechanical ventilatory support which is life-saving. The boomslang (Dispholidus typus) and the vine snake (coagulopathic venom) rarely bite humans but dogs may be bitten more frequently. These venoms cause a consumption coagulopathy and successful treatment of boomslang bites requires the use of snake species-specific monovalent antivenom. There is no antivenom available for treating vine snake (Thelotornis capensis), berg adder (Bitis atropos), night adder (Causus spp.), stiletto snake and other lesser adder bites. There are some important differences between the way snakebites are managed in humans and dogs.

Vipera palaestinae envenomation in 327 dogs: a retrospective cohort study and analysis of risk factors for mortality

Vipera palaestinae (Vp), formerly a subspecies of the near east viper Vipera xanthina, is the most common poisonous snake in Israel and neighbouring countries (Jordan, Lebanon and Syria), and is responsible for most envenomations in humans and domestic animals. Hospital records were retrospectively reviewed for confirmed cases of Vp envenomations in dogs over a 13-year period and 327 cases were included in the study. Most envenomations occurred between May and October, and between 02:00 and 10:00 PM. The most frequent clinical signs included: local swelling and oedema (99.6%), viper teeth penetration marks (51%), tachypnoea (50%), panting (44%), increased body temperature (19.2%), tachycardia (>160/min, 19%), salivation (18%) and lameness (15.6%). Common haematological findings included: increased haematocrit (47%), increased haemoglobin concentration (45%), leucocytosis (39%), and thrombocytopenia (30%). The prothrombin time and activated partial thromboplastin time were prolonged in 68 and 21% of the dogs, respectively. Blood biochemistry abnormalities included increased activities of muscle enzymes, hyperglycaemia, hyperbilirubinaemia, hyperglobulinaemia and hypocholesterolaemia. The mortality rate was 4% (13 dogs). The following variables were significantly (p < 0.05) associated with mortality: body weight below 15 kg (p = 0.01), limb envenomation (0.008), envenomation at night (p = 0.025), severe lethargy (P < 0.001), hypothermia (p = 0.04), systemic bleeding (p = 0.001), shock (p = 0.007), dyspnoea (p = 0.002), tachycardia (p = 0.002), thrombocytopenia (p = 0.02), and glucocorticosteroid therapy (p = 0.002). Dogs younger than 4 years had a lower death risk (p = 0.01). The association of steroid therapy with increased mortality suggests that the use of steroids in Vp envenomations may be harmful. Specific antivenom therapy (10 ml/dog) was not associated with a higher survival rate, thus its use, dose and timing of administration should be further investigated.

Retrospective study of snake envenomation in 155 dogs from the Onderstepoort area of South Africa

A retrospective study was undertaken to evaluate the incidence, signalment, haematological and biochemical changes, therapy, and outcome of dogs presented to the Outpatients section of the Onderstepoort Veterinary Academic Hospital for confirmed snake envenomation. Three hundred and seventy-six records of dogs presented for snake envenomation from 1998 to 2002 were reviewed and 155 were selected on the basis of there being a positively identified snake. The 2 most commonly encountered snake envenomations in dogs were puff-adders (Bitis arietans) and snouted cobras (Naja annulifera annulifera). The majority of cases (56 %) occurred in the autumn (March to May), with most being bitten by puff-adders. Dogs were 3 to 168 months old with a median of 36 months.No sex predilection was identified. Ten per cent of cases died because of the snake envenomation. Fifty-seven per cent and 43 % of snakebites were puff-adders and cobras, respectively. There was no difference in mortality between the 2 groups of snakes. Of the cobras 60%were the snouted cobra, 14 % Mozambique spitting cobra, and 24 % rhinkals. Swelling in the area of the bite, usually the face and forequarters, was the primary clinical abnormality. Significant haematological findings were leukocytosis (median 17.3 × 109/ℓ ; range 0.4-44), neutrophilia (median 13.6×109/ℓ ; range 0.3-39.9), band neutrophilia (median 0.4×109/ℓ ; range 0-5.32), and thrombocytopaenia (median 124 × 109/ℓ ; range 3-555). Dogs envenomated by a puff-adder and Mozambique spitting cobra had a greater degree of thrombocytopaenia: median of 68 and 66, respectively, versus 243 for the cobra group. The most commonly used treatments were intravenous fluids, antibiotics and glucocorticoids. Thirty-eight dogs were treated with polyvalent antiserum: 9 for puff-adder envenomation and 29 for cobra envenomation. Only 2 of the dogs that received antisera died, both of them of cobra envenomation. The study concluded that snake envenomation in dogs is associated with high morbidity but moderate mortality rate and that the most significant haematological abnormality is thrombocytopaenia.

Vine snake (Thelotornis capensis) bite in a dog

A vine snake bite in a dog is reported. There was continued minor bleeding from the assumed nose bite site for 4 days. Currently manufactured snakebite antivenom is not effective against vine snake bites and treatment is supportive.

Clinical findings associated with prairie rattlesnake bites in dogs: 100 cases (1989-1998)

OBJECTIVE

To identify clinically relevant variables and treatments for dogs bitten by prairie rattlesnakes (Crotalus viridis viridis).

DESIGN

Retrospective study.

ANIMALS

100 client-owned dogs.

PROCEDURE

Records of dogs evaluated for rattlesnake envenomation from 1989 to 1998 were reviewed. Analysis was performed to test for significant associations among clinical variables or treatments and cell counts, costs, and duration of hospitalization.

RESULTS

Most prairie rattlesnake bites occurred between May and September. Dogs were 3 months to 12 years old (median, 3.7 years); most were bitten on the head in the late afternoon. There was no sex predilection. Median time to evaluation was 1 hour (range, 15 minutes to 13 hours). Swelling in the area of the bite was the primary physical abnormality. Principal initial laboratory findings were echinocytosis, thrombocytopenia, leukocytosis, and prolonged activated clotting time. Ninety-four dogs were hospitalized; 48 were discharged the following day. Antimicrobials and crystalloid fluids, glucocorticoids, antihistamines, and antivenin administered i.v. were the most commonly used treatments. One dog died, and small dogs were hospitalized longer than large dogs. Antivenin administration was not significantly associated with duration of hospitalization but was associated with higher platelet counts after treatment and higher total hospital costs.

CONCLUSIONS AND CLINICAL RELEVANCE

Prairie rattlesnake envenomation in dogs is associated with high morbidity rate but low mortality rate. The efficacy of administration of antivenin for dogs with bites from this snake species is questionable.

Newer antidotal therapies

Although the availability of an antidote for a toxic agent does not take away the primary responsibility of the clinician to manage the patient's clinical signs, the use of antidotes in appropriate situations can result in a more rapid recovery with potentially fewer long-term complications. Recent advances in pharmacology and molecular biology have resulted in the development of new and safer antidotal therapies for the management of toxicosis. The progress in immunotoxicotherapy over the last two decades continues and may ultimately lead to an era when the clinical toxicologist has a vast array of antibody fragments available for use with specific toxic agents. Development of specific pharmacologic antagonists for other agents should also enable the clinician to more reliably manage toxicoses. In spite of all these potential advances, the management of most toxicoses still relies on the application of sound veterinary medical principles.

Lethality in a ram from the bite of a Palestine viper (Vipera xanthina palestinae)

A lethal bite to a 5-y-o ram from a Palestine viper is described. Severe edematous swelling in the pectoral area developed into skin, subcutaneous and muscle necrosis, accompanied by tachypnea, tachycardia, salivation and depression. Prominent biochemical findings were increased LDH, CK, urea and protein. The ram died because delayed treatment prevented successful antivenin administration.

Megaoesophagus in adult dogs secondary to Australian tiger snake envenomation

Four cases of megaoesophagus secondary to tiger snake envenomation are reported. History in all cases suggested megaoesophagus was not present prior to snake envenomation. Diagnosis of megaoesophagus was confirmed by thoracic radiography in all cases. One dog died of respiratory failure. The remaining three dogs recovered, with gradual resolution of clinical signs associated with megaoesophagus.