arthropod envenomation - cyclotis.org

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 amines – Phospholipase

– Histamine

– Bradykinin

– Acetylcholine

– Dopamine

– Seratonin

– Mast cell degranulating peptide

– Mastoparan

• Apitoxin – 52% Melitten (potent anti-

inflammatory agent that increases production of cortisol)

– 10-12% Phospholipase A2 – 2-5% Aldolapin (blocks

cyclooxygenase) – 1-3% Hyuronidase – 0.5-2% Histamine – 1-2% Dopamine and

noradrenaline – 2% Protease-inhibitors – Apamine increases cortisol

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 stings and 1 million stings of other Hymenoptera/year

• More deaths/year than any other type of envenomation

• Most deaths are the result of Anaphylaxis

• 17-56% produce local reactions

• 1-2% produce generalized reactions

• 5% seek medical care

• 30-120 deaths from wasp and bee 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

• Confluent red rash

• Shortness of breath or wheezing

• Weakness, syncope

• Anxiety, confusion

• Chest pain

• Target organs (IgE-mediated allergic reaction) – Skin- urticaris

– Respiratory System • Bronchospasm

• Laryngospasm

– Vascular system • Vasodilation

• Angioedema

• Twice as many anaphylactic reactions from wasps than bees

• Possible DIC

Generalized Reactions- Toxic

• Can result from 30 vespid stings or 200 honey bee stings

• Massive envenomations in adults results in > 15% mortality

• 20 honey bee stings/kg lethal for humans

• Melittin, phospholipase A2 and hyluronidase responsible for most toxic signs

– Vomiting

– Diarrhea

– Shock

– Hemoglobinuria

– Rhabdomyolysis

– Multiorgan failure

Generalized Reactions- Toxic

• Acute renal failure

– Acute tubular necrosis

– Direct nephrotoxic effects

– Interstitial nephritis from hypersensitivity reaction

– Pigment nephropathy (Rhabdoymolysis or intravascular hemolysis)

• Kounis syndrome (allergic myocardial ischemia and infarction)

– Inferior ST-segment elevation

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

• Buthus

• Parabuthus

• Mesobuthus

• Buthotus

• Tityus

• Leiurus

• Androctonus

• Centruroides

Geographical Location

Mediterranean area

Western and Southern Africa

Throughout Asia

Southern Africa and SE Asia

Central and South America

North Africa and Middle East

North Africa to SE Asia

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

– Tachycardia

– Hypertension

– Hyperthermia

– Pulmonary Edema

• Parasympathetic Symptoms

– Hypotension

– Bradycardia

– Salivation

– Lacrimation

– Urination

– Defecation

– Gastric Emptying

Signs and Symptoms

• Cranial Nerve Effects

– Roving or rotary eye movements

– Blurred vision

– Tongue fasciculations

– Loss of pharyngeal muscle control

• Somatic effects

– Restlessness

– Muscle jerking

– True seizures (Centruroides)

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

Large geographical range

Black widow spider

Widow spiders

• Genus Latrodectus – Latrotoxins-cause release of

acetylcholine

• Stimulates muscle contractions

• painful abdominal cramps

• interfering with respiration

• 5% death rate prior to development of antivenom

• 63 deaths in US from 1950-1989

Katipo spider

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 in considerable pain.

• In severe cases, nausea, vomiting, fainting, dizziness, chest pain, and respiratory difficulties may follow.

European black widow spider

Widow spiders

• In some cases, abdominal pain may mimic such conditions as appendicitis or gallbladder problems. Chest pain may be mistaken for a heart attack.

• Blood pressure and heart rate may be elevated. The elevation of blood pressure can lead to one of the most severe complications.

• Life-threatening reactions are generally seen only in small children and the elderly.

Redback spider

Widow spiders

Treatment

• Pain management (Narcotics may be required for severe pain)

• Muscle relaxants

• Antivenom in severe cases

Black widow spider with egg case

Australian funnel-web spiders

• Genera Atrax and Hadronyche

• All are Australian except 1 species of Hadronyche from Chile

• Produce atracotoxins- very toxic to primates

Sydney funnel-web spider,

Atrax robustus

Australian funnel-web spiders

Symptoms of systemic envenoming include:

• Tingling around the mouth and tongue

• Facial muscle twitching • Nausea • Vomiting • Profuse sweating • Salivation • Shortness of breath.

Sydney funnel-web spider

Australian funnel-web spiders

Patients may rapidly develop:

• Agitation

• Confusion and coma associated with hypertension

• Metabolic acidosis

• Dialation of the pupils

• Generalized muscle twitching

• Pulmonary edema.

Sydney funnel-web spider

Australian funnel-web spiders

• Death results from progressive hypotension or possibly raised intracranial pressure resulting from cerebral edema

• 13 deaths 1927-1980 from A. robustus

Hydronyche cerberea,

Southern tree funnel-

web spider

Australian funnel-web spiders

Treatment:

– Supportive care

– Applying a pressure immobilization bandage

– Antivenom

H. infensa, Toowoomba

funnel-web spider

Mouse spiders

• Genus Missulena

• Similar venom to Australian funnel-web spiders

Brazilian wandering spider

• Genus Phoneutria

• Found throughout Central and South America

• Aggressive

• In addition to neurotoxins, venom contains serotonin

Brazilian wandering spider

• Symptoms from mild envenomation

– Pain

– Edema

– Hyperemia

– Sweating

Brazilian wandering spider

• Symptoms from severe envenomation – Local pain – Tachycardia – Prostration – Profuse sweating – Poor peripheral profusion – Muscle fasciculation – Diarrhea – Vomiting – Priapism – Pulmonary edema

Brazilian wandering spider

• Treatment – Pain management – Supportive care – Antivenom – Mechanical ventilation

• 2.3% of cases required antivenom in a series of 422 patients

• Deaths from bites have been drastically reduced since introduction of antivenom in 1996

Recluse spiders

• Genus Loxosceles

• Worldwide distribution, but most common in the new world

• Venom contains the dermonecrotic agent sphingomyelinase D Brown recluse spider

Recluse spiders

• Symptoms – Severe pain at bite site after

about four hours

– Severe itching

– Nausea

– Vomiting

– Fever

– Myalgias (muscle pain)

Brown recluse spider

Recluse spiders

• Symptoms may progress to:

– Blistering (common)

– Necrosis (death) of skin and subcutaneous fat (less common)

– Severe destructive necrotic lesions with deep wide borders (rare)

Brown recluse spider bite

Recluse spiders

• First Aide – Apply ice to decrease pain and

swelling.

– Elevate area if possible above the level of the heart.

– Wash the area thoroughly with cool water and mild soap.

– Avoid any strenuous activity because this can spread the spider's venom in the skin.

– Use acetaminophen for pain relief.

Brown recluse spider bite

Recluse spiders

• Medical RX

– Tetanus immunization

– Pain medication

– Antibiotics if signs of infection are present in the wound

– Antihistamines such as diphrenhydramine (Benadryl) for itch relief

Brown recluse spider

Recluse spiders

• May form a necrotising ulcers that destroys soft tissue and may take months and very rarely years to heal, leaving deep scars

• Damaged tissue may become gangrenous and eventually slough away Brown recluse spider bite

Recluse spiders

• Systemic effects – Mild symptoms include

nausea, vomiting, fever, rashes, and muscle and joint pain

– Rarely more severe symptoms occur including hemolysis, thrombocytopenia, and DIC

Brown recluse spider

Recluse spiders

• Treatment

– Routine treatment should include elevation and immobilization of the affected limb, application of ice, local wound care, and tetanus prophylaxis

– In almost all cases, bites are self-limited and typically heal without any medical intervention

Brown recluse spider

Recluse spiders

• An antivenom is available in South America

• Chilean recluse-systemic reactions in 15% of cases and fatalities in 3-4%

Chilean recluse spider

Six-eyed sand spider

• Genus Sicaritus

• Found in southern hemisphere

• Same family as recluse spiders (Sicariidae)

• Considered by some as worlds most venomous spiders

• Death and loss of limbs reported

Other Spiders Causing Necrosis

• Hobo spider

• Yellow sac spider

Hobo spider Yellow sac spider