Poisoning spiders

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* Introduction

* Morphology

* Latrodectus mactans (habitat, toxicity, effects, etc.)

* Loxoscelism (poison, clinical, treatment)

* References


True spiders medical interest in the world belong to the genera Phoneutria, Loxosceles and Latrodectus and Atrax, the first of which is distributed from Costa Rica to Bolivia. The genus Atrax is in Australia, New Guinea and the Solomon Islands. Loxosceles spp and spiders Latrodectus spp are cosmopolitan. The accident aracndico in America is a public health problem in countries such as Chile, the U.S. and Brazil, with Loxosceles spp bites more frequent in the first two countries and in Brazil Phoneutria spp. In Colombia we know publications by Loxosceles spp accident but by Latrodectus spp in the first half of the twentieth century, and recent stories (1990s) of accidents in Antioquia Phoneutria spp.

The human spider bite occurs in most cases by accident often goes unnoticed the first time since he immediately accidentando it relates to an insect bite. In our country it is estimated that there are over 1700 different species of spiders among the three most aggressive Latrodectus mactans is better known as Black Widow, casampulga, capulina spider, spider flax, wheat, deathwatch. Over 20,000 are poisonous.

In South America the main poisonous spiders are

* Latrodectus mactans (wheat spider, black widow)

* Loxosceles laeta (spider corner)


Spiders have an exoskeleton composed primarily of chitin and its body is divided into two regions or tagmas.

The prosoma or cephalothorax which are chelicerae externally and internally hooks inoculants and poison gland, eyes are between 1 and 4 and pairs according to their position and number can be used to classify the genera spiders. The 2 pedipalps possessing six segments each, the last of which is the male copulatory organ and externally 4 pairs of jointed legs with seven segments each.

Hooks inoculants on spiders in the infraorder Araneomorphae are folded like a pair of pincers and venomous gland is a party to the cephalothorax and elsewhere in the chelicerae, while in the infraorder Mygalomorphae inoculators hooks are located vertically oblique and venom gland is totalmenteen the chelicerae. The poison gland is a structure composed of a muscular part, a secretory layer and a conduit which leads to the hook secretory inoculator. Soumalainen3 studied the structure of the venom gland of 16 different families of spiders concluding that there are no major differences between these.

The second region is the opisthosoma or abdomen, which is usually not segmented and her stigmata are lung, the genital slit, reproductive organs, the spinners (usually six) and post them, anus. All spiders are considered poisonous except for a few genres. However, the World Health Organization (WHO) considers four kinds of spiders real medical interest for clinical manifestations and lethality of their poisons, three of which belong to the infraorder Araneomorphae well: Latrodectus, Theridiidae family; Loxosceles, family Loxoscelidae; Phoneutria, Ctenidae family. The fourth genus belongs to the infraorder Mygalomorphae (Atrax, family Hexathelidae).



External morphology of a spider. Adapted from Luke S. Aranhas of medical interest. Offset Butantan Institute, Sao Paulo, 1992.

Ocular formula for identification of the genre. A: Formula Phoneutria eyepiece spp B: Formula eyepiece Latrodectus spp. C: Formula Eye of Loxosceles spp. Adapted from Luke S. Aranhas of medical interest. Offset Butantan Institute, Sao Paulo, 1992.




Latrodectus mactans

Until recently, it was believed that the only species of the genus Latrodectus medically important Latrodectus mactans was, but after studying some researchers in the field, it was considered a set of four species mactans group members. In recent work on this subject is quoted Uruguay Latrodectus mirabilis, a member of this group mactans. According to current studies of the systematics of this genus, it seems that this group should be checked, which is estimated at more convenient designate Latrodectus specimens found in Uruguay as belonging to that group, until further studies to identify clearly of the species present.

Geographic distribution:

The black widow distributed through almost everyone even in extreme climate zones.


They live in dark, moist areas live outdoors, at ground level, on the flats can live on pasture or in some crops (hence the name in some places) + + – in stony areas can be found under loose stones , can also be installed in the vicinity of the houses, window borders, debris.


Family comes Thriddidae Genre Lactrodetus

Species: mactans, hespeus, variolus, bishopi, geometricus.

The localized species from Canada to Patagonia and in most of our country, especially in humid climates and ends: L. mactans.

Black Widow’s name comes from the custom post-nuptial females to attack and eat the male after mating, build irregular webs dense and very sticky threads. The brood sack (ootheca) is light brown and has a small pear-shaped, which can contain up to 150 eggs unhatched it takes about 21 -25 days. These spiders in middle age, with glossy black color, with the abdomen globose highly developed which is in the back one or several red spots, and belly of reddish, yellowish or whitish with cupped or hourglass.

At the time of the attack on wing guard position, time of day of the attack, season, and physical characteristics of the spider tell us about the risk of developing symptoms of varying severity.

The spider’s body (carapace) has a length of about 13-15 mm in females and their venom is responsible for the symptoms of poisoning in humans, while the male fails to measure up to 5 mm; less robust and its color is lighter than the female, their venom is harmless.

A fluid inoculated venom yellowish, oily containing 6 different active substances, in varying amounts, from 0.1 to 0.5 mg over a long nail located in the chelicerae.



The latrotoxin its main component that acts on nerve endings causing pain at the site of injury, in the regional lymph nodes. It also contains polypeptides, enzymes such as hyaluronidase and D-aminobutyric acid acting on the action neuromuscular plate, alternating kinetics of sodium and potassium ions in the synopsis adrenergic, increasing their permeability, allowing for greater release of catecholamines specifically, motor condition by acetylcholine depletion effect.

The neurotoxic alfalatrotexina which causes the release of acetylcholine in cerebral cortex, neuronal and ganglionic system plate, with respect to calcium metabolism alteration thereof.


In general it can take up more than one hour in symptoms ranging from local pain, to muscle spasms, tremors fine body, delirium, cramps, tachycardia, arrhythmias and called wood abdomen or belly.


Diffuse, with little immediate skin reaction, with irritability. , Restlessness, localized pain.

In the regional lymph nodes, malaise, fever, sweating and epiphora significant, important data home without a flash, with a pale area circumscribed by a line which presents erythematous hypoesthesia or anesthesia. Nausea, vomiting, constipation bowel.


Such as restlessness, irritability, anxiety, psychosis can reach muscle contractures, described by Maretic latrodectsmica facie, facial flushing, wince, muscle spasm with trismus and blepharitis. Localized pain in pelvic girdle and intense muscle contractions.


Changes in heart rate at both ends, and alteration tension, acute urinary retention and / or crushing chest pain.


Grade I or mild:

Injury site pain, erythema, sweating, aches lumbosacral spine, lower limb muscle and joint pain and muscle pain in legs, diaphoresis sialorrhea dizziness, fatigue, weakness, hyperreflexia.

Grade II or moderate

This accented with more data, more designs, epiphora, diaphoresis, headache, mild respiratory insufficiency, spasticity. Stiff limbs, chills, abdominal cramps, extremities with presence of spasms and muscle contractions, priapism.

GRADE III or severe

The above data more intense, mydriasis, or miosis, confusion, delirium, hallucinations, urinary retention, severe bronchoconstriction, generalized muscle spasticity in abdomen (belly wood) lactrodectsmica facies, diaphoresis, respiratory failure more importantly, hemolysis, dysautonomia with abnormal tension and heart and respiratory rate.

Immediate effects:

Local irritation, pain discreet, and / or go unnoticed.


Punctate lesions 1-2 mm apart, with pain, local erythema, whitish area distrmico discreetly.


Under 5 years

Weight less than 15 kg

Heart disease, hypertension, other diseases complicated Carriers

Respiratory failure, circulatory previous.


None specific. Systemic pathologies it were added, metabolic, but there we specifically indicate any lesion progression, evolution is oriented so that the stage progression.


Acute abdomen, pancreatitis, perforated viscus, Tetanus, acute myocardial infarction, renal colic, food poisoning, tresticular torque.


* ABC (aeration, ventilation, circulation) Metamizole 10 mg / kg daily.

Paracetamol 10-15 mg / Kg

Naproxen disodium.

Meperidine (1-2 mg / kg / day)

Morphine (0.01-0.02 mcg / kg / day) IM

* Analgesics (pain control) methocarbamol 10 mg / kg IV in 5 -30 min to every 6 hrs.

Diazepam (0.2-0.4 mg / Kg)

* Muscle relaxants

* Calcium Gluconate (1-2 ml / kg) not to exceed 10 ml slowly and watch FC.

* Antihypertensives nitropresiato PRN from nifedipine up. tetanus toxoid. (0.5 ml IM DU).

* Protection Scheme and tetanus as age

* Antibiotic: lactam derivatives.

* Fabotherapic: Serum Polyvalent Faboterpico antiarcnido: Modified by enzymatic digestion, albumin-free lyophilized with neutralizing capacity of 6000 LD 50 (spider venom glands 1 dose)


Ideal direct IV and diluted. From the way we possibly an alternative IM is not optimal, minimizes effectiveness.

The dose in children tends to be higher due to the higher concentration of venom per kg body weight or m2sc.


Dosage varies according to the degree of injury, patient age but mostly depending on the symptoms.

Reserved primarily for patients with symptoms present from mild to moderate to severe respiratory distress and symptoms that management does not revert to calcium, muscle relaxants and painkillers.

General measures:

* It is always important to identify the issue, concerned corroborate black widow.

* Reassure the victim and / or family

* Keep patient at rest and in a comfortable position

* If required by states of anxiety or nervousness immobilize the affected area in a functional position.

* Before the swelling or edema of the affected limb raise

* Wash the affected area with soap and water.

* Remove rings, bracelets, just clothes that may compromise circulation.

* Injury Delimiting measuring the rise and subsequent control thereof and continuous sign-symptomatology.


* Do not use disinfectants or antiseptics to color AFFECTED AREA

* DO NOT USE TURNSTILES of the affected limb.

If the patient has a tourniquet should be loosened slowly while administering retirrsele fabotherapy.

* Not to cut or suck on the area bitten.

* Not useful and could condition ADDED INFECTIONS.




* Spiders are widely distributed throughout the world, several species exist. The most widespread in South America and Chile is the Loxosceles laeta, whose bite is high pathogenicity.

* The body of Loxosceles laeta or “corner spider” or “house spider” is between 8-12mm long with legs outstretched reaching up to 45mm, 4-6mm wide.

* It is dark brown or tan, with lighter cephalothorax relating to the abdomen, with a dark violin-shaped, with base directed forward.

* The cephalothorax has piriform look at its front end and are located 3 pairs of simple eyes, two lateral and one anterior, forming a triangle.

* Females are larger and more corpulent than males, which also differ by the expansion sacciforme easily presented in the distal segment of the pedipalps, seminal receptacle corresponding to or spermatheca.

* It has been found in 41% of urban households and 24% of rural central Chile.


* Son of residential and rural habits, sedentary, solitary, and nocturnal activity.

* They are found cohabiting human habitation behind furniture, boxes or other objects that move occasionally and in closets or even in cracks in the walls. At these sites, weaves a loose fabric, cottony and dirty, that serves as shelter during the day and where drag to capture prey. Overnight fabric leaves and hunts walking cautiously towards the walls of flies and other insects that rest at this hour.

* Accidents occur when dressing, when you are inside clothing, sleeping when the bed is in contact with the wall or put your hand behind furniture or other objects.




* It’s part and thermolabile protein.

* Has owned necrotizing, hemolytic, vasculitic and coagulant.

* On average 0.1 mg of venom produced by electrical stimulation in the cephalothorax.

* In the skin causes severe vascular alterations vasoconstriction and other areas of hemorrhage, rapidly leading to local ischemia and the formation of a plaque gangrenous.

* Laeta Loxosceles venom induces and regulatory kinases such as Expressed and Secreted activation normal T lymphocytes (RANTES), monoliths chemoattractant protein 1 (MCP-1), IL-8 and the oncogene related to growth of a (GRO-a) which are probably involved in the onset of dermonecrosis mediated by neutrophils and lymphocytes T. Furthermore, complement activation leads to release of C5b which is chemotactic for neutrophils and this causes cell damage in the bite site.

* The venom of Loxosceles spp. It produces platelet aggregation by binding of serum amyloid P-glycoprotein to the platelet membrane in the presence of calcium ions, ultimately leading to disseminated intravascular coagulation. All this contributes to local damage by vascular obstruction, as well as serotonin secretion by activated platelets and induction for PMN chemotaxis towards the bite site.

* Another mechanism that may explain the platelet activation is the damage to the membranes of endothelial cells by the action of the poison containing mataloproteinasa, and this leads to activation of coagulation with a consumption of not only as coagulation factors fibrinogen, but platelets.

* Renal failure can be induced by CID, but also appears to be linked to the action of metalloproteinases which degrade the extracellular matrix and damage the integrity of the basement membranes of blood vessels resulting in hemorrhages and kidney in Acute Renal Insufiencia.




* The spider’s bite only in self-defense. Can occur throughout the year, but more frequent in spring and summer. It usually occurs to compress against the skin at night when you sleep (38%) or dressing (32%) with long clothes hanging in closets.

* The bite is common on the face and extremities.

* The spider is seen in 80% of cases and identified by 13%.

* The pictures produced adopts two clinical forms:

* Cutaneous loxoscelism

* With a frequency of 85%.

* It is usually abrupt onset and in three quarters of cases there is burning pain, itching or pain Local indefinite in the remaining appears as volume increased. During the hours acquires characteristics frank pain and increasing.

* There are two types of skin loxoscelism: the necrotic (more common) and edema (rare).

* The necrotic skin loxoscelism occurs in 75% of cases and appears in the first 24 hours. It manifests as a purplish plaque “livedoid” irregular contour and color, length and depth of variables, with pale ischemic areas and hemorrhagic areas, surrounded by a halo of intense edema and erythema. The sign “red”, “white” and “blue” is typical of loxoscelism. Vesicles can be installed and / or hemorrhagic bullae. Is defined during the first 24 hrs. evolution and transformation, depending on the damage, in a crust or a scab, which is apparent within 3 to 6 weeks, giving rise to an ulcer, which ends to heal with or without sequelae, depending on initial damage, in variable periods (4-71 days).

Loxoscelism: Plate settle livedoid in which blisters and sore in training


Loxoscelism: Extensive partial detachment scar edges.


* Sometimes a plate is not the first manifestation of livedoid loxoscelism but an erythematous (20%), which may lead to more frequent loxoscelism necrotic and terminates in a scaly process. A poor prognostic sign is the appearance of a diffuse scarlatiniform eruption, morfiliforme, urticarial or petechial over the affected area, trunk or flexural areas.

* The prevalence loxoscelism edematous skin occurs in about 4% of the bites. It is characterized by a large disfiguring edema in the area of the bite, which is habitulamente in the face. It has the best prognosis of all injuries. Usually in both general symptoms are minor and frequent. There may be febrculas, malaise and anxiety. In general there is no regional lymphadenopathy.

* Complications include cellulitis, lymphangitis, skin lesions similar to PG, venous thrombosis, loss of function, graft rejection. Apparently unrelated to the bite site.



* Loxoscelism cutaneous and visceral

* With a frequency of 15%.

* It is serious and highly fatal if not treated.

* Starts similarly to cutaneous loxoscelism pure, but around 12-24 hrs. after the bite, symptoms begin, signs and complications arising mainly from massive intravascular hemolysis: sustained high fever, violent and progressive anemia, icterus, hematuria, hemoglobinuria that can lead to acute renal insuficiciencia (nephrosis blackwater), metabolic acidosis, electrolyte imbalance, hypertensive crisis, arrhythmias.

* It worsens with multisystem involvement, sensory and death.

* Laboratory tests showed anemia, thrombocytopenia, and TTPK TP increased, liver involvement, hematuria, hemoglobinuria.

* It is very important to control any loxoscelism during the first 24 to 48 hrs.y be alert to the appearance of symptoms and signs suggestive of visceral box.

According to the thesis Loxoscelism in children: clinical manifestations between 1964-1980 found that have been classified according to age, place of origin, both clinical Simple Skin Type and the cutaneous and visceral, among others, as we shall show below.


Distribution Loxoscelism cases for age and sex. Department of Pediatrics 1964-1980 HGBRDT


Distribution Loxoscelism cases by origin. Department of Pediatrics 1964-1980 HGBRDT


Distribution of cases according to the circumstances Loxoscelism the bite occurred. Department of Pediatrics 1964-1980 HGBRDT


Distribution of cases according to the body area Loxoscelism compromised. Department of Pediatrics 1964-1980 HGBRDT


(…) The thesis Reference Data: Trujillo Loxoscelism in Hospitals 1980-1989: epidemiological and clinical aspects.


Distribution of cases according Loxoscelism local manifestations. Department of Pediatrics 1964-1980 HGBRDT


Distribution of cases according Loxoscelism Simple Cutaneous Manifestations. Department of Pediatrics 1964-1980 HGBRDT


Distribution of cases of cutaneous and visceral Loxoscelism as general statements. Department of Pediatrics 1964-1980 HGBRDT


Distribution of cases in different hospitals Loxoscelism Trujillo between 1980-1989


* Of 120 cases registered only took into account the above because they were identified by both clinical and spider identification of complete clinical history.



* Sting or bite other arthropods.

* Steven Johnson Syndrome.

* Toxic epidermal necrosis.

* Erythema nodosum or multiforme.

* Herpes simplex infected chronic.

* Herpes zoster.

* Diabetic Ulcer.


* There are no laboratory tests to confirm the diagnosis.

* It is important to determine and monitor:


  • Hemolysis, hemoglobinuria (CBC with platelet count).

    * Hematuria (urinalysis).

    * Prothrombin time, thromboplastin time and renal function test (urea / creatinine).


    * The use of serum antiloxosceles should be the treatment of choice. The antidote is an injectable solution of specific immunoglobulins, purified and concentrated, obtained from hyperimmune equine serum Loxosceles venom However, in practice there are significant limitations: the serum must be used as quickly as possible, during 2 to 4 hours following the accident, which is not always easy. The action of the poison is so fast and powerful that nothing or very little is obtained with the late application of serum therapy, because all the damage is already established and the subsequent evolution of the lesions will progress simply its aftermath.

    * In its place antihistamines are used as background therapy in cutaneous cases cigars, and antihistamines, corticosteroids, and all measures and restoration antishock erythrocyte, where visceral.

    * Pain management with analgesics.

    * In pure cutaneous cases, we recommend starting treatment with injectable antihistamines (such as clorofenamina maleate 0.4 mg / kg / day in 4 doses or dextroclorofenamina, in doses of 0.15 mg / kg / day) for the time necessary to the desaparici6n pain and edema and the demarcation of the necrosis.

    * Local treatment with injuries cleaning and removal of necrotic fragments, is any skin ulcers. In cutaneous-visceral cases, treatment involves inpatient and emergency antishock therapy. Blood transfusions, oxygen, hydration, correction and blocking renal anuria are often necessary. As antitoxic treatment, has advocated the use of corticosteroid urgent injectable dose of 200 to 400 mg hydrocortisone, followed by 40 to 60 mg of prednisone per day for 4 to 7 days and then antihistamines. Among the emergency treatment is successfully used exchange transfusion, which serves to remove cellular debris and toxins caused by hemolysis, thereby locks the mechanism of base around the cutaneous-visceral process.

    * Dapsone: The sulfones are potent inhibitors of the chemotaxis of neutrophils. Its application has reduced local tissue mass destruction affected by the bite of Loxosceles spp, but his strong side reactions such as hemolysis, agranulocytosis and drug hypersensitivity symptoms (fever, nausea, vomiting, lymphadenopathy, leukopenia, and mononucleosis syndrome ), limit their use. The dose is 50-100 mg / day, maximum 200 mg 2 times / day for 10-25 days.

    * Colchicine 1.2 mg orally, followed by 0.6 mg c / 2 hours for 2 days and then 0.6 mg C / 4 hours for two days. Inhibits PMN infiltration, and can be effective in stopping the rapid progression of skin necrosis.

    * Hyperbaric oxygen: The use of hyperbaric oxygen has also been suggested that local damage is secondary to PMN adhesion to the blood vessel wall. The treatment involves the application of oxygen at 2 atmospheres pressure for 60 to 90 minutes twice daily (6 sessions) being observed an improvement in skin necrosis in both humans and animals.

    * Surgical excision: As in other types of accidents that produce poisonous animals necrosis at the site of the bite, early surgical excision of the ulcerated lesion is one of the recommended treatments. It seems that the healing is better with conservative management, posterior debridement and grafting.



    Loxoscelism: Ulcer at three weeks




    * HERMOZA Mogollon, Miguel Angel. Thesis: clinical manifestations in children Loxoscelism 1964-1980. UNT.

    * JAVE GLVEZ, Luis Manuel. Thesis: Hospitals Loxoscelism Trujillo in 1980-1989. Epidemiological and clinical aspects. UNT.

    * QUINTANA CASTILLO, Juan Carlos. PATIO OTERO, Rafael. Aracndico Poisoning in the Americas. Topics Review, Vol.5, Issue 13, May 2002, one-9pp.

    * Thomas P. Forks, DO, PhD, From the Department of Family Medicine, The University of Mississippi Medical Center, Jackson. (J Am Board Fam Pract 13 (6) :415-423, 2000).

    Sites visited

    [URL 01]:

    ida / frames / medioFrame.html


    [URL 02]: http://www.aps.org.ar/Contenidos/Publicaciones.htm

    [URL 03]: http://www.umm.edu/surgeries_spanish/presentations/10013815024.htm

    [URL 04]: http://pcs.adam.com/imagepage/2582.htm

    [URL 05]:

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    Job Submitted by:

    David Rodriguez Diaz 1, July Mogollon Rodrguez1, Johany Zavaleta1 Guevara, Angela Rodriguez Daz1, Cynthia Alzamora1 Eslava, Dr. Fausto Valdivia Mestanza2.

    January Students of the Year VI of the Faculty of Medicine of the Universidad Privada “Antenor Orrego”. Trujillo – Peru.

    2 Pediatrician. Assistant Hospital Paediatric Department IV “Victor Lazarte Echegaray”. Professor of the Faculty of Medicine of the Universidad Privada “Antenor Orrego”. Trujillo – Peru.

    Correspondence to: