Continuing EduCation Snakes & Spiders & Toads, Oh My!
Carrie Lohmeyer-Mauzy CVT, BS Objective: A discussion will proceed 3NAKES regarding exposures to snakes, spi- Toxicological exposures are not limited to ders, and toads in dogs. Readers will the ingestion of chocolate, rodenticides, become knowledgeable of the com- plants, or medications. Venomous bites mon species of medical importance from snakes and spiders, along with oral in the United States. Readers will also exposures to poisonous toads can result be able to identify the clinical signs in life threatening symptoms for domestic This program was reviewed and approved associated with these exposures, the animals. There are two groups of venomous by the AAVSB RACE program for 1 hour of common treatments, and the overall snakes that are indigenous to North America continuing education in jurisdictions which rec- ognize AAVSB RACE approval. Please contact prognosis. An understanding of the and the western hemisphere, Crotalidae the AAVSB RACE program if you have any role the technician plays in the out- (pit viper), which include rattlesnakes, water comments/concerns regarding this program’s come of these cases will additionally moccasins and copperheads and Elapidae validity or relevancy to the veterinary profession. be gained. (coral snake).1 The appearance of pit vipers Continuing EduCation
Snakes & Spiders & Toads, continued
between species is very similar.2 Charac- The first signs to develop with pit viper manage hypotension or hypovolemia.3 Cor- teristics that distinguish them from other bites typically include local pain and swell- ticosteroids are not recommended.2,4 The snakes include a heat-sensing pit located ing at the bite site.3 An exception to this is majority of studies have shown that the use between the nostril and eyes, triangular with venom that is neurotoxic. There is very of corticosteroids provides no benefit to shaped heads, retractable fangs, elliptical little tissue involvement with neurotoxic ven- the patient.1 There is either no improvement pupils, and a row of sub-caudal scales distal om from pit vipers.2,4 Other common clinical or clinical signs increase in severity.1 The to the anal plate.1,2,3,4 Venom is stored in signs include hypotension, tachycardia, car- use of corticosteroids in treating pit viper venom glands and is delivered by muscle diac arrhythmias, shock, vomiting, diarrhea, envenomation has also been show to cause contractions that force the venom through lethargy, muscle fasciculations, mental marked increases in mortality rates in some hollow fangs.3 The venom is then injected dullness, cyanosis, petechiae, ecchymosis, studies.1 Platelet and blood transfusions into the victim by downward and forward tissue necrosis, hemorrhage at wound site, should be used to treat coagulopathy.3 stabbing motion.3,4 Bites in response to pain enlarged lymph nodes, hemolysis, throm- Broad- spectrum antibiotics are needed to are the most deadly to dogs and the snake bocytopenia, and coagulopathy.2,3,4 Initial prevent infection at the bite site.1,2,3,4 Signs will deliver the maximum amount of venom first aid measures should include limiting such as GI upset, neurologic signs, cardiac available.1,2 The front legs and head are the patients movements because anxiety arrhythmias, and tachycardia can be man- the most common bite locations in dogs.3,4 and physical activity increase the absorp- aged with standard medical therapies. Pa- Venom is more rapidly absorbed with bites tion of the venom.2 It is also recommended tients should be monitored for a minimum to the thorax, bites to the tongue are compa- to keep the bite location below the heart of 24 hours.3 rable to intravenous envenomation, and bites if possible.1,2,3,5 Tourniquets, suction, and to the muzzle can result in significant facial cold packs should be avoided as they Antivenin is available for pit viper enven- swelling and airway obstruction.2,3 There are are not effective and only increases the omation and is the only proven treatment three main classifications of pit viper venom length of time before the pet receives vet available.1,2 If antivenin is available, it should in North America.3 The first is termed classic care.1 Once in the hospital, the hair or fur be administered as soon as possible.1,3 diamondback venom. It is responsible for around the bite wound should be clipped.3 significant tissue destruction, coagulopa- It is also beneficial to take circumferential thy, and hypotension.3 The second class is measurements to evaluate tissue involve- Mojave A venom which is very neurotoxic.3 ment over time.1,2,3,5 Vital signs should The third class is a combination of both the be monitored including blood pressure.3 classic diamondback and Mojave A venom.3 Crystaloid fluids are recommended IV to Venom toxicity between pit viper species varies significantly.2,5 Generally speaking, rattlesnakes are the most toxic of pit vipers with copperheads being the least toxic.2,3,5
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Antivenin has been effective in reversing Coral snakes are the second major group respiratory paralysis, decreased spinal coagulopathy and thrombocytopenia.3,4 of venomous snake in the US. There are reflexes, muscle weakness, hypotension, There are two main types of antivenin two genera of coral snakes of veterinary muscle fasciculation, tachycardia, dyspnea, available including crotalidae polyvalent medical importance. These include Micru- dysphagia, and hemolysis.1,3 Time of onset antivenin of equine origin and crotalidae roides and Micrurus. Micruroides euryx- of signs could be delayed up to 12 hours.3 polyvalent immune Fab of ovine origin.3 anthus (Sonoran coral snake)is common As with pit viper exposures, the sooner Polyvalent immune Fab is preferable over to central and southeastern Arizona and veterinary care is sought out the better. The antivenin of equine origin. The risk for al- southwestern New Mexico.3 There are three vet clinic must be able to provide ventila- lergic reaction is less, it is more effective at subspecies that make up the Micrurus ge- tory support due the risk of respiratory pa- entering the tissues, and it has a high affin- nus, M. fulvius fulvius (eastern coral snake), ralysis. Patients with pharyngeal paralysis ity for venom antigens.2,3,5 Single vial doses M. fulvius tenere (Texas coral snake), and should be intubated to prevent aspiration.1,2 of antivenin have been shown in studies to M. fulvius barbouri (south Florida coral It is important that radiographs be taken be effective in managing pit viper envenom- snake).1,3,4 The eastern coral snake is typi- frequently to monitor for evidence of aspira- ation in dogs.3 Additional vials should be cally found in eastern North Carolina, South tion pneumonia.2 Maintenance IV fluids are made available and administered if the pets Carolina, Georgia, Florida, Alabama, Mis- recommended for supportive care along condition worsens.3 sissippi, and eastern Louisiana.1 The Texas with broad-spectrum antibiotics to prevent coral snake inhabits southern Arkansas, infection at the bite site.1 Supportive and Prognosis with pit viper envenomation northwestern Louisiana, and south central symptomatic care can be used to treat con- should be made on a case by case basis Texas. 3 As the name suggests the south ditions such as GI signs, neurologic signs, as the likelihood of the pet recovering is Florida coral snake is common to southern hypotension, and hypothermia. Patients dependent on many factors including the Florida.3 Coral snakes are shy, nocturnal, should be monitored for a minimum of 48 severity of envenomation, the length of time and non-aggressive snakes.3,4 Due to these hours.1 Prognosis with coral envenomation between envenomation and the start of characteristics coral snake bites are not is considered to be guarded.2 Coral snake treatment, the species of snake involved, very common.3,4 Coral snakes are identi- venom is available, but it may be very dif- and the aggressiveness of treatment.3 The fied by their bright colors, with alternating ficult to find because production has been administration of antivenin will increase bands of black, red, and yellow.3 Coral discontinued in the US.2,7 The primary the probability that the patient will recover, snakes can be identified from other non- cause of death with coral snake bites is however, it does not guarantee recovery.2 poisonous snakes by the arrangement of respiratory paralysis.3 their color pattern.1 Red bands will always A rattlesnake vaccine has been developed touch yellow bands.3 A common rhyme Spiders: to help decrease the morbidity and mortal- used in identification is “red on yellow, kill Two genera of spiders of veterinary medi- ity of dogs that are bitten by pit vipers.3 a fellow.”2 They have small, non triangular cal importance in the United States are Depending on the weight of the pet the heads, and round pupils.2,3 The fangs of the Latrodectus (widow spiders) and vaccine will be given 2-3 times at four week coral snakes are fixed, short, grooved, and Loxesceles (reculse spiders).2,8 There are intervals.3 4ITERS BEGIN TO DECLINE AFTER partially covered by a membrane. The five species of widow spiders common to months therefore it is recommended that venom duct empties at the base of the the United States including L. mactans dogs be re-vaccinated twice per year.3 The fang and the venom runs down the groove (black widow), L. various (northern black vaccine causes an immune response to the of the fang.3 During the bites the partial widow), L. bishop (red widow), L. hesperus protein fractions of the western diamond- membrane covering the fang pushes away (western black widow), and L. geometri- back rattlesnake.3 The vaccine does not and the snake attaches itself to its victim cus (brown widow).3,9,10 Except for Alaska, protect against the Mojave neurotoxin.3 and chews to deliver additional venom.3 widow spiders inhabit every state in the Dogs who are vaccinated may not develop Coral snake venom is very neurotoxic.2 It US.10 They are identified by a characteristic as severe of clinical signs, but veterinary is composed of polypeptides that cause red, yellow, or orange hourglass-shaped care is still warranted.3 In severe enven- a neuromuscular block resulting in paraly- design on the abdomen of the female.3 omation the use of antivenin may still be sis, as well as enzymes that cause tissue Only female widow spiders are capable needed, however, the amount of antivenin necrosis and hemolysis.3,4 of inflicting an envenomating bite.2,3,10 The required for treatment may be less than in a venom is very potent and a single bite can pet who is unvaccinated.3 Clinical signs associated with coral snake be fatal, with the onset of clinical signs de- bites in dogs include, central nervous veloping within 8 hours of envenomation.3,10 system depression, vomiting, drooling, Local tissue changes and swelling at the
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Snakes & Spiders & Toads, continued
Loxoscelism.12 Systemic signs are not as common.2
Clinical effects typically include redness, swelling, and pain within 3-8 hours, along with a characteristic bulls-eye lesion at the site of envenomation.3,11 A hemorrhagic bul- la is possible within 1-3 days and necrotic tissue around the bite may slough resulting in a slow healing ulcer11. Redness around the bite wound may disburse unevenly due to the effects of gravity.3,11 Hemolytic anemia with pronounced hemoglobinuria is rare, but possible.11 There is no antidote or commercially available antivenin for recluse spider envenomation, therefore treatment is largely supportive and symptomatic.2,3,11 Primary wound care includes debride- ment with aluminum acetate or hydrogen peroxide several times daily.2,5 It is also recommended to bandage and to measure the wound to monitor size increase over- time.2 Pain can be managed with the use of non steroidal anti-inflammatory drugs or opioids.2,3 Antibiotics should also be con- muscle relaxants.3 Antivenin is available sidered to help prevent infection.3 The drug for widow spider envenomation and has dapsone has been used experimentally in the ability to provide rapid and permanent dogs and has been shown to hinder leuko- relief of clinical signs.10 It is of equine origin cyte migration.11 The use of dapsone is a bite site are rare.10 Widow spider venom is and has a low risk of causing anaphylaxis if possible treatment option to help decrease neurotoxic in nature and is responsible for a used properly.10 the severity of the bite lesion.2,3 Complete syndrome called Latrodectism.2 healing of the lesion may take weeks or There are several species of recluse spiders months to occur.2 Common clinical signs include severe in the United States, however, Loxesceles muscle pain, rigidity, and cramping, rest- recluse (brown recluse) is the most impor- Toads lessness, regional numbness, hyperten- tant medically.3 This species is commonly There are two species of toads in the sion, tachycardia, and possible seizures.10 found as far north as Illinois down through United States, Incillius alvarius (Colorado It is not uncommon for patients to lose the southern Gulf states from Texas to Geor- River toad) and Rhinella marina (Marine up to 20% of their body weight within gia.3 Recluse spiders can be identified by a toad), that can cause serious toxicosis in 24 hours of envenomation.10 Respiratory violin-shaped pattern on the dorsum of the domestic animals. The Colorado River toad and cardiovascular collapse is the most cephalothorax along with three pairs of eyes is common to southern Arizona, south- common cause of death.10 Widow spider positioned in a semi-circle on the head.9,11 eastern California, and southwestern treatment should be focused on the control Recluse spiders are non-aggressive and will New Mexico.2,13 The Marine toad is found and alleviation of clinical signs.2,3 Systemic only bite when threatened or when pressure in Hawaii and the southern tips of Texas analgesics, primarily opiates, and muscle is applied to them.9,11 Envenomation from a and Florida.2,13 These toads are equipped relaxants are recommended to control pain recluse spider typically occurs when the pet with parotid glands containing toxins that and to control muscular rigidity.2,3 Calcium accidentally lies on the spider trapping it.11 are secreted on the skin when the toad gluconate is no longer the drug of choice Venom from recluse spiders results in a syn- is attacked or threatened.2,3,13,14 Severity to help alleviate muscle cramping and drome called Loxoscelism.2 Most commonly, of toxicosis is dependent on numerous pain as it is not as effective as opiates and severe tissue necrosis is characteristic of factors. A dog with a low body weight or a
24 Te NAVTA Journal | June/July 2015 Continuing eduCation
dog exposed to a large toad is at greater risk for the development of significant clinical signs. Furthermore, dogs that hold or chew the toad are a greater risk com- pared to dogs that only bite and release.2,14 Geographic location also plays a role in the severity of toxicosis. Dogs exposed to Ma- rine toads in Florida have a higher mortality rate then dogs exposed in Hawaii or Texas.2 Toxins released from the parotid gland are rapidly absorbed across the mucous membranes.3,14
Clinical signs develop within seconds of that has not previously responded to fluid exposure and death can occur within 15 therapy.2 Pets with severe bradycardia can minutes.2,3,13 Drooling, vomiting, retching, be treated with Atropine, however Atro- rubbing face, and head shaking, are char- pine is contraindicated for the control of acteristic after a toad exposure.15 Other hypersalivation due to the increased risk common signs include brick-red mucous of cardiac arrhythmias.13 Supportive and membranes, ataxia, disorientation, vocaliza- symptomatic care should be implemented tion, anxiety, collapse, seizures, mydriasis, until resolution of clinical signs. Prognosis nystagmus, tachypnea, hyperthermia or is dependent on the degree of toxicity. hypothermia, bradycardia or tachycardia, Patients who develop only mild clinical and cardiac arrhythmias.14,15 Veterinary signs have a good prognosis, however, the care should be sought as soon as possible prognosis is more guarded in patients who with any suspected or observed exposure. develop advanced neurologic or cardiovas- mation not being obtained from the client. Flushing of the mouth with water, to pre- cular signs.3 There are seven key elements that should vent further absorption of toxins across the be included in the medical record for a mucous membranes, can be implemented The Role of the Technician: toxicity case including client information, at home.13 If the pet is showing more then The technician plays a very crucial role patient signalment, clinical status, agent in- mild clinical signs (signs other then drool- in the treatment and overall outcome of formation, environmental information, expo- ing or retching) decontamination should patients exposed to spiders, snakes, and sure history, and implemented treatment. take place once the pet has arrived at a toads. One important responsibility of the Client and patient information along with veterinary hospital.13 Dogs who consume technician is obtaining a reliable and ac- clinical status is typically obtained with all a toad in its entirety, will require either curate history from the client. Obtaining a patients regardless of whether the case is decontamination via emesis, multiple doses thorough medical history is important with toxicologic in nature. Information about the of activated charcoal with a cathartic, en- any pet that comes into a veterinary clinic. agent, in this case a spider, snake, or toad, doscopic retrieval of the toad, or surgery.13 It is even more important in toxicological along with environmental information, ex- Management of toad exposures is largely cases, to ensure the patient is treated posure history, and implemented treatment supportive and symptomatic care. There appropriately. For patients arriving to will be additional items in the history. There is no specific antidote or reversal agent. the clinic asymptomatic, obtaining a his- will be some cases where the pet arrives to Maintenance rate of fluids, monitoring car- tory is one of the first items that should the clinic symptomatic and the owner has diovascular system via electrocardiogram, be collected from the client. If the patient no knowledge that an exposure to a spider, monitoring and managing changes in body arrive symptomatic it may be necessary to snake, or toad has occurred, this is where temperature, and monitoring electrolytes stabilize the patient first before obtaining a information on the patient’s environment is recommended.15 Diazepam or pheno- full history from the client. can be useful. A pet that is strictly indoors barbital is recommended for control of sei- is not going be as likely to come in contact zures.13 Propranolol or esmolol is indicated When obtaining a history it is important not with spiders, snakes, or toads compared for treatment of tachycardia, ventricular to make assumptions or pre-judgments, as to pets that have access to several acres arrhythmia, and superventricular arrhythmia doing so could result in vital pieces of infor- of land, garden sheds, ponds, or a fenced
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Snakes & Spiders & Toads, continued
yard. Exposure history will include informa- species of snakes, spiders, and toads, 10. Peterson ME, McNalley J. Black widow tion such as whether the exposure was along with the clinical signs that develop spider envenomation. In: Peterson ME, observed by the owner, the time the expo- and treatments available, will benefit the Talcott PA, eds. Small Animal Toxicology. sure took place, the location of the bite in patients overall chances of survival. Philadelphia, PA: W.B. Saunders Company; 2001: 728-734. regards to spiders and snakes, any clinical signs that developed, and time of onset References 11. Peterson ME, McNalley J. Brown spider envenomation. In: Peterson ME, Talcott PA, of those signs. It will also be important to 1. Peterson ME. Snake bite: pit vipers and eds. Small Animal Toxicology. Philadelphia, note any first aid measures or treatments coral snakes. In: Peterson ME, Talcott PA, PA: W.B. Saunders Company; 2001: 735- implemented by the owner before arriving eds. Small Animal Toxicology. Philadelphia, 740. at the hospital. Besides obtaining a thor- 0! 7" 3AUNDERS #OMPANY ough history, a second role the technician 720. 12. Mullen GR. Spiders. In: Mullen GR, Durden L. eds. Medical and Veterinary plays in the treatment of these cases is 2. Foss T. Zootoxins. In: Poppenga RH, Entomology. Philadelphia, PA: Academic implementing supportive and symptomatic Gwaltney-Brant SM, eds. Small Animal Press; 2002: 427-444 care. These cares may include adjusting IV Toxicology Essentials. West Sussex, UK: fluid rates, administering pain medication John Wiley and Sons; 2011: 171-185. 13. Eubig PA. Bufo species toxicosis: Big toad, big problem. Veterinary Medicine. and antibiotics, obtaining blood samples 3. Gwaltney-Brant SM, Dunayer E, Youssef for labs, and taking radiographs. Depend- H. Terrestrial zootoxins. In: Gupta RC, ed. ing on the severity of toxicosis patients may Veterinary Toxicology: Basic and Clinical 14. Peterson ME, Roberts BK. Amphibian require hospitalization for several days. Principles 2nd ed. Waltham, MA: Academic toxins. In: Peterson ME, Talcott PA, eds. TPR’s will need to be monitored regularly 0RESS Small Animal Toxicology. Philadelphia, PA: 7" 3AUNDERS #OMPANY along with monitoring neurologic and car- 4. Peterson ME. Reptiles. In: Plumlee KH, diac function. Wound care will also be the ed. Clinical Veterinary Toxicology. St. Louis, 15. ASPCA APCC non published data. MO: Mosby; 2004: 104-111. responsibility of the technician. ,OHMEYER # 4AKING A TOXICOLOGIC HIS- 5. Peterson ME. Snake bite: North Ameri- tory In: Poppenga RH, Gwaltney-Brant SM, The veterinary technician’s responsibilities can pit vipers. In: Peterson ME, Talcott eds. Small Animal Toxicology Essentials. are numerous in the treatment of canines PA, eds. Small Animal Toxicology 2nd ed. West Sussex, UK: John Wiley and Sons, exposed to snakes, spiders, and toads. 3T ,OUIS -/ %LSEVIER 3AUNDERS Inc; 2011: 27-32. Depending on the severity of toxicosis, not 1017-1038. all patients will recover. Being knowledge- &OWLER -% 6ETERINARY :OOTOXICOLOGY able about the venomous and poisonous Boca Raton, FL: CRC Press; 1993. About the Author: 7. Peterson ME. Snake bite: coral snakes. #ARRIE ,OHMEYER -AUZY #64 "3 In: Peterson ME, Talcott PA, eds. Small Carrie has been working as a CVT at Animal Toxiciology. 2nd ed. St. Louis, MO: the ASPCA Animal Poison Control cen- %LSEVIER 3AUNDERS ter since 2007. Before coming to poison 8. Graudins A. Venomous arthropods. control, she obtained her associate’s In: Shannon MW, Borron SW, Burns MJ, degree in veterinary technology from eds. Winchester’s Clinical Management Parkland College and also obtained of Poisoning and Drug Overdose 4th ed. her bachelor’s in natural resources and St. Louis, MO: Elsevier Saunders; 2007: environmental science from the Univer- 433-439. sity of Illinois. She worked for 2.5 years at a small animal clinic while in college 9. Goddard J. Physician’s Guide to Arthro- and also assisted with several research pods of Medical Importance. 4th ed. Boca projects in fish and wildlife ecology. Raton, FL: CRC Press; 2003. During her 8 years at animal poison control, Carrie has gained a wealth of knowledge in the field of toxicology and is currently studying to become a board certified toxicologist. She lives in a small town outside Champaign-Urbana with her husband and her two tortoise- shell kittens.
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Snakes & Spiders & Toads Quiz
1. Which statement is not true regarding 6. Which of the following statements 9. A vet hospital must be able to provide venom delivery in pit vipers? is true? what specific treatment in dogs bitten a. Muscle contractions control the amount of a. Neurotoxic venom results in severe BY CORAL SNAKES venom delivered during envenomation tissue necrosis a. Administration of antivenin b. Venom is delivered through hallow fangs b A pet who has been vaccinated with a b. Ventilatory support c. Fangs are retractable rattle snake vaccine will not require c. IV fluid therapy d. A membrane covers the fang antivenin for recovery. d. Intubation c. Respiratory paralysis is the primary cause 2. Corticosteroids are contraindicated of death for recluse spider envenomation 10. Which of the following statements in the treatment of ______. d. Loxoscelism is a condition characterized is true? a. Coral snake envenomation by severe tissue necrosis a. The use of antivenin in the treatment of b. Black widow spider envenomation spider and snake envenomation in dogs c. Pit Viper envenomtaion 7. Which of the following statements is guarantees recovery d. Recluse spider envenomation not true regarding poisonous toads? b. Dogs exposed to toads in Hawaii have a a. The parotid gland is responsible for higher rate of mortality than dogs exposed #ORAL SNAKE ENVENOMATION RESULTS IN secreting toxins when a toad is threatened in Texas or Florida these clinical signs except for ______. b Geographic location of the toad does not c. Atropine is contraindicated for the control a. Coagulopathy play a role in the severity of toxicosis of bradycardia with dogs exposed to b. Respiratory paralysis c. Onset of signs can be observed within poisonous toads c. Hypotension 15 minutes d. Dapsone is a drug that may help decrease d. Muscle weakness d. There is no antidote for toad toxicosis the severity of a bite lesion from a recluse spider 4. Antivenin is available for the 8. Dogs are most commonly bitten by following envomations. pit vipers in what location? a. Widow spider envenomation, coral a. The tongue or oral cavity snake envenomation, and pit viper b. The thorax envenomation c. The front legs and head b. Recluse spider evenomation, widow d. The paws spider envenomation, and pit viper envenomation c. Coral snake envenomation, recluse spider envenomation, and widow spider envomation d. Pit Viper envenomation, coral snake envenomation, and recluse spider envenomation.
5. The following are common clinical signs of widow spider envenomation except for ______. a. Muscle pain b. Tissue necrosis c. Rigidity d. Tachycardia
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