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 x 10(9)/l; range 0.4-44), neutrophilia (median 13.6 x 10(9)/l; range 0.3-39.9), band neutrophilia (median 0.4 x 10(9)/l; range 0-5.32), and thrombocytopaenia (median 124 x 10(9)/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.     

Boomslang envenomation in 2 dogs in Kwazulu-Natal, South Africa

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.     

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.     

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.     

An investigation, in vitro, of the actions of three Western Australian snakes on the blood coagulation of the dog, cat, horse and wallaby

Venoms of the tiger snake and brown snake were procoagulant, in vitro, when tested with cat, dog, horse and wallaby plasma. In the absence of calcium and phospholipid the coagulant activity of tiger snake venom was minimal. In contrast, brown snake venom alone had marked procoagulant activity. This activity, however, was enhanced by the presence of calcium and phospholipid. Death adder venom exerted an anticoagulant effect. Apparent species' differences in susceptibility to the coagulant venoms were noted. However, the probable explanation of these differences was attributed to variation in the control values of the special studies rather than to a difference in the postulated actions of the venoms on prothrombin. A possible role for clotting studies in suspected snake bite in veterinary practice is suggested.     

A check-list of the nematode parasites of South African Serpentes (snakes) and Sauria (lizards)

Published records, in combination with own data have been brought together to provide data on parasite/host relationships of reptiles that occur in the Republic of South Africa. A total of 62 nematode species belonging to 23 genera and 11 families are recorded from 20 snake and 21 lizard species. The genera Kalicephalus, Spauligodon, Ophidascaris and Abbreviata are especially well represented with between five and eight species per genus. The most nematode species were recorded from the flap-neck chameleon, Chamaeleo dilepis (eight), the puff-adder, Bitis arietans (eight) and the water monitor, Varanus niloticus (seven). All synonyms of parasites and hosts are given.     

Histology of the venom gland of the puff-adder (Bitis arietans)

The histology of the venom gland of the puff-adder (Bitis arietans) has been investigated in the resting and stimulated state. No accessory venom gland was found to be associated with the main venom gland or duct in the same position as has been reported for other snakes. In the resting state the parenchyma of the venom gland was found to consist of tubules lined by a single layer of tall columnar secretory cells. After being stimulated to secrete by repeated milkings, the histological appearance of the gland changed and the epithelium was found to be more foliaceous and the component cells to be taller and more slender. A pronounced increase of pigment was also observed in the connective tissue septae. Micro-organisms were observed in the secretion pools of resting glands and by culturing the venom it could be shown that these were Staphylococcus aureus, Staphylococcus epidermidis and Klebsiella ozaenae. The presence of these organisms would suggest that the venom is not cytotoxic to all cells at this level of production.     

Elapid snake envenomation in dogs in New South Wales: a review

Elapid snake envenomation in dogs is a commonly occurring yet poorly described clinical entity. Twelve species of dangerously venomous elapid snakes are found in New South Wales that are capable of causing disease in dogs. Geographical distribution of these species varies, as does their venom composition and systemic envenomation syndromes produced in target species. Elapid venom may be divided into the components of prothrombin activating enzymes, lipases and peptidic neurotoxins. Each species of elapid snake may possess venom components that fit any or all of these classifications. The action of these venom components may result in neurotoxic (pre-synaptic and post-synaptic), haemotoxic (red-cell destruction and coagulation disturbance), cardiovascular, myotoxic and secondary nephrotoxic effects. Marked variability may occur in venom composition between and within snake species, resulting in varying toxicity between species and also potentially unreliable clinical syndromes following envenomation. The existence of certain components consistently within the venom of each snake species allows the broad definition of basic pathological processes and clinicopathological changes resulting from snake species-specific envenomation and these are discussed. Diagnosis of snake envenomation is unreliable if based on clinical signs alone and the use of these signs in conjunction with history, physical examination and laboratory investigation, including snake venom detection kits, is recommended. Treatment of systemic envenomation should be undertaken with initial effective first aid and subsequent administration of snake species-specific antivenom.     

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.     

Snake bites recorded by veterinary practices in Australia

Objective To determine the extent of the snake bite problem in domestic animals, its regional significance and the effects of antivenom treatment.
Design A questionnaire was designed seeking information on the number and type of domestic animals referred, whether treated or untreated, type of snakes and management of the bite.
Procedure The survey form was sent to 10% of veterinary surgeons, selected at random throughout Australia.
Results The response of 106 veterinary surgeons revealed that snake bite in domestic animals is frequent, with an estimated 6200 cases reported annually. Bites were more prominent in rural (78%) than urban areas (22%) with brown, tiger and black snakes accounting for 76%, 13% and 6% of cases, respectively. Cats and dogs were the most frequently reported victims. Ninety-one percent of cats and 75% of dogs survived following the administration of antivenom whereas 66% of cats and 31% of dogs survived without antivenom. Overall, in 33% of cases antivenom was not used, and venom detection kits were used in only 1% of cases. A number of drugs were used in various combinations with or without antivenom and intravenous fluids in the treatment of animals with snake bite, but their role in reducing the severity of envenomations was not assessed.
Clinical implications Antivenom significantly improves the chances of survival of domestic animals bitten by snakes.     

Some toxicity thresholds for the clinical effects of common tiger snake (Notechis scutatus) envenomation in the dog

SUMMARY Common tiger snake (Notechis scutatus) venom was administered experimentally to dogs at doses from 0.25 lethal dose (LD) to 20 LD. Haemolysis and increased creatine kinase values occurred rapidly after injection of sublethal (subparalytic) doses, but the clotting time of blood was extended and blood became incoagulable only when dogs were dosed with 10 LD or more of venom. Haemolysis, although of a low threshold of toxicity, was not severe and should not greatly affect the lethality of the venom. Coagulopathy is a sign that the dog has been lethally envenomed and will need to be given antivenom if skeletal muscle paralysis is to be overcome.     

SnakeMap: four years of experience with a national small animal snake envenomation registry

SnakeMap is a national cloud-based, veterinary snakebite registry. It was designed to prospectively collect data of the clinical circumstances and temporospatial information on cases of snake envenomation in dogs and cats. We herein introduce the project and summarise the data from the first 4 years of SnakeMap. The registry is a veterinary community-based online database allowing case entry from veterinary hospitals across Australia. Registry data comprise hospital characteristics, patient characteristics, envenoming snake type, treatment and outcome variables, including time and geolocation of the snake bite. We present summative information on select key variables from the SnakeMap registry (1 July 2015 to 30 June 2019). Twenty-eight hospitals from 6 states/territories entered 624 cases into the registry, including 419 dogs (67%) and 205 cats (33%). Bite time was available in 216 animals of which 90 (42%) were reported to be bitten in the 3 hours between 03:00 pm and 05:59 pm; median bite to presentation interval was 60 (interquartile range [IQR] 30, 211) minutes in dogs and 95 (IQR 41, 238) minutes in cats. Bites occurred in the owner's yard in 356 dogs (85%) and 53 cats (26%). A snake venom detection kit was used in 172 cases (28%) and antivenom was administered in 523 cases (85%). Most animals (n = 534, 88%) survived to discharge (median hospitalisation of 25 [IQR 16, 62] hours). SnakeMap effectively collects relevant clinical data from dogs and cats with presumed snake bite and provides locally specific information on the epidemiology of snake envenomation in small animals.     

Myotoxicity and nephrotoxicity of common tiger snake (Notechis scutatus) venom in the dog

SUMMARY The myotoxicity and neurotoxicity of common tiger snake (Notechis scutatus) venom are major factors in the pathogenesis of envenomation in the dog. Histological examination of the tissues of experimentally envenomed dogs has demonstrated the importance of muscle damage in affecting the clinical syndrome of tiger snake envenomation. Within one hour of injection of the venom into dogs, there was selective involvement of some muscles. Cardiac and smooth muscles were not significantly affected. The severity of myofibre damage was influenced by the amount of venom injected. Immobilisation under general anaesthesia resulted in significant protection against the myotoxic effects of high doses of venom. Lesions in the kidneys of experimentally envenomed dogs were acute tubular necrosis and the variable presence of a small amount of proteinaceous material in tubules. These lesions, which were similar to those in cases of natural snake bite, were indicative of a direct nephrotoxic effect, which could be complicated by the effects of myoglobinuria. These findings emphasise the need for supportive treatment aimed at maintenance of renal function in the treatment of dogs suffering from tiger snake envenomation.     

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.     

Spotted black snake (Pseudechis guttatus) envenomation in a maned wolf (Chrysocyon brachyurus).

Envenomation by a spotted black snake (Pseudechis guttatus), following multiple bites on the buccal mucosa of a captive maned wolf (Chrysocyon brachyurus), caused the animal's collapse, hemolysis, rhabdomyolysis, local tissue necrosis, hepatic and renal failure, and subsequent death. The wolf died despite intensive supportive care including antivenom administration, fluid support, and a blood transfusion. Gross necropsy findings included myocardial and intestinal hemorrhage, pulmonary congestion, hepatomegaly, and splenomegaly. Microscopic examination of formalin-fixed tissues demonstrated pulmonary and abdominal visceral hemorrhage, acute nephrosis with casts, multifocal hepatic necrosis, and splenic congestion.     

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 envenomation in cats and its detection by rapid immunoassay

Objective To determine the usefulness of a snake venom detection kit (SVDK) in the management of envenomed cats.
Design A clinical study.  

Animals

Twenty-two cats were investigated.
Procedure Cats injected subcutaneously with approximately 0.25 or 1.0 lethal dose (LD) of tiger snake venom or 1 or 4 LD of brown snake venom were observed for clinical symptoms of envenomation at intervals over the ensuring 24 to 48 hours(h). Blood and urine samples were taken at regular intervals and assayed in a quantitative laboratory assay for snake venoms. Selected samples were assayed in parallel in a rapid, semi-quantitative SVDK.
Results The studies showed that it was important to estimate the elapsed time from envenomation to presentation. If this time was less than 8 h, blood was the most appropriate sample and a negative result should exclude serious envenomation. If the elapsed time exceeded 8 h, it was essential that urine be sampled. Venom levels in urine were high at 8 h and approached the level of test sensitivity over 24 to 48 h; however by this time clinical signs were obvious in endangered cats.  

Conclusions

Careful use of the SVDK is a valuable aid in the management of a potentially envenomed cat.     

A new galago species for South Africa (Primates: Strepsirhini: Galagidae)

The primate fauna of South Africa has historically been viewed as comprising three diurnal cercopithecoid taxa – chacma baboons (Papio ursinus), vervet (Chlorocebus pygerythrus) and samango monkeys (Cercopithecus albogularis) – and two nocturnal lorisoid species – the thick-tailed greater galago (Otolemur crassicaudatus) and the southern lesser galago (Galago moholi). Here we report the positive identification of a third galago species within South Africa’s borders: the Mozambique dwarf galago or Grant’s galago, Galagoides granti (Thomas and Wroughton, 1907). The taxon was previously held to be restricted to Mozambique, eastern Zimbabwe, Malawi and Tanzania, but we have also observed it in the sand forest of Tembe Elephant Park and the Tshanini Community Reserve, near the Mozambique border. The species was formerly mistaken for Galago moholi, erroneously (we believe) extending the range of the latter species into northern KwaZulu-Natal. In South Africa the two small galagos are unlikely to have overlapping ranges: Galago moholi prefers dry savanna woodlands, whereas Galagoides granti is apparently confined to dry sand forest. However, both species may coexist with the larger and more widespread Otolemur crassicaudatus, an inhabitant of moist savanna, forest edge and thicket. The true South African ranges of both small galago species need to be ascertained.     

Common tiger snake envenomation in dogs and mice—relationship between the amount of venom injected and the onset of clinical signs

SUMMARY Common tiger snake (Notechis scutatus) venom was injected into mice and dogs at various dose rates calculated on the known lethal dose (LD) for each species. The larger the dose of venom, the earlier was the onset of clinical signs and the more rapid and severe the course of the disease in both species. In dogs injected with 32 LD of venom, there was sudden collapse and death in about one hour from the time of injection without recovery from premonitory depression and before mydriasis occurred. Dogs given 5 to 16 LD of venom developed preparalytic signs (vomition, salivation or defaecation) in 5 to 30 min, mydriasis in 2 to 4h, became paralysed and died in about 2.5 to 5 h. When doses of venom of about 1 LD were injected, vomition and salivation occurred within 2 h and mydriasis in about 4 h. The dogs were unable to close the mouth completely despite retention of jaw muscle tone. At the site of injection of venom there was occasional but slight erythema and oedema. Sublethally envenomed dogs did not show preparalytic signs nor did they have general skeletal muscle paralysis. Even at the lowest dose tested (0.25 LD), however, they developed mydriasis and photophobia, which persisted for several days.     

A randomized multicenter trial of Crotalidae polyvalent immune Fab antivenom for the treatment of rattlesnake envenomation in dogs

Objective – To determine clinical efficacy of the Crotalidae polyvalent immune F_ab (ovine) antivenom (OPCA) against progressive crotalid envenomation in the dog as reflected in stabilization or improvement of snakebite severity scores (SSS). Additionally, due to the potential decreased half‐life of the F_ab antibodies in dogs we compared SSS between dogs receiving 2 different dosing regimes. Design – Prospective, clinical trial. Setting – Five veterinary emergency and critical care facilities. Animals – One hundred and fifteen client‐owned Crotalid (rattlesnake) snake bitten dogs in whom worsening of the envenomation syndrome was observed before OPCA treatment. Interventions – In a multicenter randomized clinical trial a single dose (1 vial) of OPCA alone was compared with 2 doses (1/2 vial each) administered 6 hours apart. Standard supportive care was provided in all cases. Measurements and Main Results – Data were available for 115 patients, 9 of which were fatalities. All patients' clinical condition was documented with a standardized SSS system accounting for each major body system. Each fatality received maximum severity scores of 20. The mean severity score of the 115 patients decreased from 4.19 to 3.29 points and there was no difference between the 2 treatment groups. The mean severity score of the 107 patients without fatalities decreased from 4.16 to 2.15. Antivenin‐related acute reactions occurred in 6 dogs (6%), and no serum sickness occurred within the 95 cases contacted at the 2‐week posttreatment follow‐up. Conclusions – In the first randomized trial in dogs of antivenin in the United States, OPCA effectively stabilized or terminated venom effects. There were no statistical differences detected between treatment groups within the study time frame.