Arthropod Envenomation
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Arthropod Envenomation Michael R. Loomis, DVM, MA, DACZM North Carolina Zoological Park Hymenoptera Envenomation Order Hymenoptera Family Vespidae- wasps Family Formicidae- ants Familt Mutillidae- velvet ants Family Apidae- bees • Stinger is a modified ovipositor Bee and Wasp Venom Components • Proteins, peptides and • Apitoxin – 52% Melitten (potent anti- amines inflammatory agent that – Phospholipase increases production of cortisol) – Histamine – 10-12% Phospholipase A2 – Bradykinin – 2-5% Aldolapin (blocks – cyclooxygenase) Acetylcholine – 1-3% Hyuronidase – Dopamine – 0.5-2% Histamine – Seratonin – 1-2% Dopamine and noradrenaline – Mast cell degranulating – 2% Protease-inhibitors peptide – Apamine increases cortisol – Mastoparan production, mild neurotoxin Ant Venom Components • Fire ants- 95% alkaloid (Unique among ants) • Most other ants, similar to bee and wasp venom • Harvester ant venom contains a hemolysin Venom Toxicity Family Common Name LD 50 (mg/kg) Apidae Honey bee 2.8 Mutillidae Velvet ant 71.0 Vespidae Paper wasp 2.4 Vespidae Yellowjacket 3.5 Formicidae Harvester ant 0.66 Formicidae Maricopa Harvester ant 0.12 Morbidity and Mortality Bees and Wasps • In US, 9.3 million ant • 17-56% produce local stings and 1 million reactions stings of other • Hymenoptera/year 1-2% produce generalized reactions • More deaths/year than any other type of • 5% seek medical care envenomation • 30-120 deaths from • Most deaths are the wasp and bee result of Anaphylaxis stings/year Local Reactions • Pain • Edema which may extend 10 cm from sting • +/- bleeding • Pruritis • Sensation of warmth due to vasodilation • Nausea/vomiting Generalized Reactions- Anaphylaxis • Urticaria • Target organs (IgE-mediated • Confluent red rash allergic reaction) • Shortness of breath or – Skin- urticaris wheezing – Respiratory System • Bronchospasm • Weakness, syncope • Laryngospasm • Anxiety, confusion – Vascular system • Chest pain • Vasodilation • Angioedema • Twice as many anaphylactic reactions from wasps than bees • Possible DIC Generalized Reactions- Toxic • Can result from 30 • Melittin, phospholipase vespid stings or 200 A2 and hyluronidase honey bee stings responsible for most • Massive envenomations toxic signs in adults results in > – Vomiting 15% mortality – Diarrhea • 20 honey bee stings/kg – Shock lethal for humans – Hemoglobinuria – Rhabdomyolysis – Multiorgan failure Generalized Reactions- Toxic • Acute renal failure • Kounis syndrome – Acute tubular necrosis (allergic myocardial – Direct nephrotoxic ischemia and infarction) effects – Inferior ST-segment – Interstitial nephritis from elevation hypersensitivity reaction – Pigment nephropathy (Rhabdoymolysis or intravascular hemolysis) Fire ants • 1989- 32 deaths from fire ants • “Pathnpneumonic” sterile pustules • Little protein so anaphylaxis uncommon • Can survive as many as 5000 stings Harvester Ants Maricopa harvester ant has the most toxic insect venom Single sting of harvester ant Treatment- Generalized- Anaphylaxis • Antihistamines – Diphenhydramine – Cimetadine (IV) if unresponsive to Diphenhydramine • Bronchodilators – Epinephrine – Albuterol – Theophylline • Corticosteroids Treatment- Local • Remove stinger • Diphrenhydramine • Ice or cool pack • Elevate extriminity Centiped Envenomation Class Chilopoda • 3000 species • Single pair of legs/body segment • Predominately nocturnal • Warm temperate and tropical regions • Scolopendra most dangerous genus • Venom delivered by forcipuels, modified pair of legs behind the mandibles • Venom components: – 5-hydroxytryptamine – hemolytic phospholipase A – a cardiotoxic protein – a cytolysin • Unknown frequency of stings Morbidity and Mortality • Systemic reactions – ECG changes suggestive of Ischimia – Rhabdomyalysis – Proteinuria • Fatalities extremely rare – 7 year old Phillipino girl stung by S. subspinipes – 5 fatalities reported in U.S from 1991-2001 Symptoms and Signs of Envenomation • Severe pain • Local tissue swelling • Redness • Swollen, painful lymph nodes • Headache • Palpitations • Nausea and/or vomiting • Anxiety • Local puritis Treatment • Systemic analgesics as needed • Local injectable anesthetics (e.g. lidocaine) • Update tetanus vaccination • Monitor for local infection • Symptomatic treatment for systemic signs Milliped Envenomation Class Diplopoda • 7000 species • 2 pairs of legs/body segment • Do not have biting mouthparts or fangs Morbidity and Mortality • No documented deaths • Secrete defensive irritating liquid from pores along sides • Secretions contain – Benzoquinones – Aldehydes – Hydrocyanic acid – Phenols – Terpenoids – Nitroethylbenzenes Signs and Symptoms • Local erythema • Mild edema • Vessicles • Rarely, cracked skin that may slough and heal • Conjunctivitis Treatment Scorpion Envenomation • 1500 species • 50 species dangerous to humans • Flattened, elongated body • 1 pair of claws • 4 pairs of legs • Segmented tail with poisonous spike at end • Most dangerous species belong to family Buthidae Scorpions Known to be Lethal to Humans Genus Geographical Location • Buthus Mediterranean area • Parabuthus Western and Southern Africa • Mesobuthus Throughout Asia • Buthotus Southern Africa and SE Asia • Tityus Central and South America • Leiurus North Africa and Middle East • Androctonus North Africa to SE Asia • Centruroides SW U.S., Mexico, Central America, Caribbean Frequency of Stings • Occur in temperate and tropical regions (50°N to 50°S latitude) • In 2006 16,231 reported stings in U.S. • Only 1 of 30 species of scorpions in U.S. dangerous to humans (Centruroides) Lethal Stings • Most fatalities within 24 hours of sting from respiratory and/or cardiovascular failure – < 1% Centuroides stings in adults are fatal – 25% children under 5 die if not treated • Mexico 1000 deaths /year • U.S. 4 deaths in 11 years Venom • Contains multiple toxins and other compounds – Neurotoxins -Glycosaminoglycans – Cardiotoxins -Histamine – Nephrotoxins s -Serotonin – Hemolytic toxins -Tryptophan – Phosphodiesterases -Cytokine releasers – Phospholipases – Hyaluronidases Neurotoxins • Most Potent toxin components • Cause impairment in nerves, muscles and heart by altering ion channel permeability • 2 classes – Long-chain polypeptide • Stabilizes sodium channels in open position causing prolonged firing of somatic, sympathetic and parasympathetic neurons • Release of excessive neurotransmitters – Short polyprptide • Blocks potassium channels Venom Toxicity SPECIES LD50 (mice) mg/kg Leiurus quinquestriatus (Middle East) 0.25 Androctonus crassicauda (Saudi Arabia) 0.08-0.5 Centruroides noxius (Mexico 0.26 Tityus serrulatus (Brazil) 0.43 Centruroides sculpturatus (SW U.S.) 1.12 Mesobuthus eupeus (Iran) 1.45 Mouse LD50 of < 1.5mg/kg considered potentially lethal for humans Signs and Symptoms • Most common are: – Mydriasis – Nystagmus – Hypersalivation – Dysphagia – Restlessness Signs and Symptoms • Sympathetic Override • Parasympathetic – Tachycardia Symptoms – Hypertension – Hypotension – Hyperthermia – Bradycardia – Pulmonary Edema – Salivation – Lacrimation – Urination – Defecation – Gastric Emptying Signs and Symptoms • Cranial Nerve Effects • Somatic effects – Roving or rotary eye – Restlessness movements – Muscle jerking – Blurred vision – True seizures – Tongue fasciculations (Centruroides) – Loss of pharyngeal muscle control Treatment • Local RX – Negative-pressure extractor – Ice bags (first 2 hours) – Local wound care – Immobilize affected body part below level of heart – Calm the patient – Lymphatic-venous compression wrap if medical RX is delayed – Topical or local anesthetic – Muscle relaxers for severe spasms – =/- tetanus prophylaxis, antibiotics Treatment • Systemic Treatment – ABC’s – O2 – IV fluids – Cardiac drugs as necessary – Atropine (counters venom-induced parasympathetic effects) Treatment • Antivenom – Treatment of choice Spider Envenomation Over 3000 Species of Spiders • 98-99% of spider bites are harmless • 4 Genera have produced lethal bites • 3 additional genera are probably capable of producing lethal bites • Symptoms can include: – Necrotic wounds – Systemic toxicity – Death Lethal Genera • Atrax- Australian funnel-web spiders • Latrodectes- Widow spiders • Loxosceles- Recluse spiders • Phoneutria- Wandering spiders Potentially Lethal Genera • Hadronyche- Australian funnel-web spiders • Missulena- Mouse spiders • Sicaritus- Six-eyed sand spider Types of Venom • Neurotoxic – Widow spiders- Latrotoxins – Australian funnel web and mouse spiders- open sodium channels – Brazilian wondering spiders- attacks multiple types of ion channels, serotonin • Necrotic venom – Family Sciariidae –recluse and six-eyed sand spiders. Produce dermonecrotic compound sphingomyelinase Venom Delivery • Two chelicerae, each with two segments, the fang and the basal portion. – Fang penetrates the skin – Basal portion includes all or part of the spider's venom glands, which can be squeezed under voluntary control by the spider to force venom out of the glands and into the wound Widow spiders • Genus Latrodectus Black widow spider Large geographical range Widow spiders • Genus Latrodectus – Latrotoxins-cause release of acetylcholine • Stimulates muscle contractions • painful abdominal cramps • interfering with respiration Katipo spider • 5% death rate prior to development of antivenom • 63 deaths in US from 1950- 1989 Widow spiders • Local pain may be followed by localized or generalized severe muscle cramps, abdominal pain, weakness, and tremor • Large muscle groups (such as shoulder or back) are often affected, resulting