Snakes & Spiders & Toads, Oh
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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 22 Te NAVTA Journal | June/July 2015 Continuing EduCation 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.34ITERSBEGINTODECLINEAFTER 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.