Arachnid Envenomations

Tetracycline protects against dermonecrosis induced by Loxosceles spider venom

Envenomation by spiders belonging to the Loxosceles genus (brown spider) often results in local dermonecrotic lesions. We have previously shown that Loxosceles sphingomyelinase D (SMase D), the venom component responsible for all the pathological effects, induced the expression of matrix metalloproteinases (MMPs) in rabbits and in human keratinocytic cells. We also showed that the SMase D-induced apoptosis and MMP expression of keratinocytes was inhibited by tetracyclines. We have further investigated the ability of tetracyclines to inhibit or prevent the dermonecrotic lesion induced by Loxosceles venom in vivo and in vitro models. Primary cultures of rabbit fibroblasts incubated with increasing concentrations of venom or SMase D showed a decrease in cell viability, which was prevented by tetracyclines. In vivo experiments showed that topical treatments with tetracycline of rabbits, inoculated with crude Loxosceles intermedia venom or recombinant SMase D, significantly reduced the progression of the dermonecrotic lesion. Furthermore, tetracyclines also reduced the expression of MMP-2 and prevented the induction of MMP-9. Our results suggest that tetracycline may be an effective therapeutic agent for the treatment of cutaneous loxoscelism.

Use of prazosin in the treatment of scorpion envenomation

Although scorpion bite is usually lethal in children under 6, sometimes it might cause death for those over 6. Acute lethal systemic seizures (cardiovascular and central nervous systems) have been frequently reported from the countryside of developing countries. Numerous researchers have suggested quite different approaches to the treatment of scorpion bites. In this report, we describe a case brought to the emergency service after the patient had been bitten by a scorpion and had significant sympathetic nervous system symptoms. The patient was treated with prazosin successfully.

Envenomations

Envenomations are uncommon, challenging causes of critical care admissions. This article describes the diagnosis and treatment of envenomations that cause the most critical care admissions in the United States. Most are caused by the following animals: rattlesnakes, copperheads, cottonmouths, coral snakes, brown recluse spiders, and bark scorpions.

Envenomation by a spider, Agelenopsis aperta (family: Agelenidae) previously considered harmless

This is the first report of clinically significant bites by the grass spider (Agelenopsis aperta). Two cases of envenomation in southern California are presented. In the more serious case, a child exhibited several envenomation symptoms. Although this spider may be generally innocuous, it should be considered as a creature of occasional medical importance. Many skin lesions are attributed to spider bites despite insufficient incriminating evidence, and bites that are clinically significant may often erroneously be attributed to the brown recluse spider. Misidentification can lead to undue anxiety in a patient's family.

When to worry about spider bites. Inaccurate diagnosis can have serious, even fatal, consequences

Almost all species of spiders are capable of biting people, but the bites of only a few are medically significant. Physicians need to be able to recognize the clinical signs and symptoms of common venomous spider bites and administer appropriate therapy. This may be difficult, since the offending spider is rarely seen or recovered for identification. Knowledge of life cycles, habits, and toxicity of venomous spiders enables physicians to provide more comprehensive medical care of bite victims. It is hoped that study of immunologic mechanisms and inflammation mediators will lead to the development of new treatments.

Deaths resulting from animal attacks in the United States

The objective of this study was to elucidate the etiology and frequency of deaths in the United States from encounters with animals. The number of deaths from venomous and nonvenomous animals is reported annually to the US Department of Health and Human Services and published in Vital Statistics of the United States. This study is a survey of all animal-related fatalities listed as E-codes 905-906 reported in the Vital Statistics of the United States from 1979 through 1990. Data were extracted uniformly from the annual reports and analyzed using descriptive statistics. From 1979 through 1990, there were 1882 animal-related deaths in the United States. Venomous animals caused 718 deaths; nonvenomous animals caused 1164 deaths. Most deaths occurred among white males. The home site was the location of injury for the majority of deaths. The majority of venomous animal-related deaths were from hymenoptera; "other specified animal" caused the majority of nonvenomous deaths. An annual average of 157 deaths from animal attacks occurred in the United States between 1979 and 1990. Both fatal and nonfatal animal-related injuries are under-recognized public health hazards. Health care providers should educate their patients on exercising caution around animals, seeking medical care after an animal injury, carrying epinephrine kits if they have a history of systemic reactions to insect stings, and wearing helmets and other protective equipment when riding or working around large animals.

Black widow spider bite in a child

An 8-year-old boy who was bitten by a black widow spider was seen in the emergency department twice, as well as by his private family physician, within a 24-hour period of time before being admitted to the hospital. This patient should have been observed for a longer period of time in the emergency department or admitted to the hospital on the day of presentation for observation with conservative management. The current literature is reviewed with special emphasis on the pediatric patient, and management guidelines are recommended.

The scorpion envenoming syndrome

The pathophysiology of the scorpion envenoming syndrome is reviewed with emphasis on the body systems commonly affected. Concepts of the mechanisms underlying venom action, as can be explained by the recently discovered effects on ionic channels, are discussed. The results of clinical analysis of cases of scorpion sting victims and animal experiments with scorpion envenomation supporting these concepts are presented. The pharmacokinetic characteristics of scorpion venoms and their correlation to the magnitude of toxic effects are presented in relation to the potentials of therapeutic intervention. The pharmacological basis of the therapeutic usefulness and toxicities of the drugs commonly used in the treatment of scorpion envenoming is also projected. Finally, the results of a successful nation-wide clinical study with serotherapy of scorpion envenoming are presented and evaluated.