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Loxosceles deserta
General Details, Taxonomy and Biology, Venom, Clinical Effects, Treatment, First Aid , Antivenoms
Loxosceles deserta ( Desert Loxosceles  )  [ Original photo copyright © Marshal_Hedin-2010-CC BY-SA-2.0 ]
Suborder: Araneomorphae
Family: Sicariidae
Genus: Loxosceles
Species: deserta
Common Names
Desert Loxosceles
Region
North America + Central America
Countries
Mexico, United States of America
 
Taxonomy and Biology
Size: Male : Total length about 7.5 mm. Legs I to IV with lengths about 26.30, 29.45, 24.05 and 27.45 mm respectively. Palp about 3.90 mm in length.

Female : Total length about 7.5 mm. Legs I to IV with lengths about 15.85, 17.25, 14.35 and 18.00 mm respectively. Palp about 3.35 mm in length.
Description
Male : Total length about 7.5 mm. Legs I to IV with lengths about 26.30, 29.45, 24.05 and 27.45 mm respectively. Palp about 3.90 mm in length.

Female : Total length about 7.5 mm. Legs I to IV with lengths about 15.85, 17.25, 14.35 and 18.00 mm respectively. Palp about 3.35 mm in length.

Males and Females : Carapace is plain, yellowish, pale brownish yellow, pale orange yellow or sand coloured. Abdomen is uniform pale brownish grey. Legs pale near the body becoming darker ( particularly metatarsus and tarsus ). There is a faint or very indistinct, dark violin-shaped marking on the cephalothorax in some specimens, but it is usually absent.
Habitat
Up to about 1650 metres in the Mohave and Sonoran desert, usually in rocky regions, especially rocky foothill terrain, abandoned mines, talus slopes, under debri, abandoned buildings, rodent burrows or any other natural or man-made structure offering protection from the harsh environment. Most often encountered in the winter months.
Species Map
Small (Approx 20k) version
 
Venom
General: Venom Neurotoxins
Possibly present but not clinically significant
General: Venom Myotoxins
Possibly present but not clinically significant
General: Venom Procoagulants
Possibly present but not clinically significant
General: Venom Anticoagulants
Not present
General: Venom Haemorrhagins
Not present
General: Venom Nephrotoxins
Not present
General: Venom Cardiotoxins
Not present
General: Venom Necrotoxins
Primary necrotoxins
General: Venom Other
Not present or not significant
 
Clinical Effects
General: Dangerousness
Clinical effects uncertain, but related to medically important species, therefore major envenoming cannot be excluded.
General: Rate of Envenoming: Unknown but likely to be low
General: Untreated Lethality Rate: Unknown but lethal potential cannot be excluded
General: Local Effects
Insufficient case reports to know, but related species cause initially trivial bite, progressing to local pain, erythema, discolouration, blistering, ulceration & necrosis.
General: Local Necrosis
Insufficient case reports to know, but related species cause significant local necrosis.
General: General Systemic Effects
Insufficient case reports to know, but related species, may develop 2-3 days of fever, malaise, rash.
General: Myotoxicity
Does not occur, based on current clinical evidence
General: Coagulopathy & Haemorrhages
Insufficient case reports to know, but related species, potential in severe cases for haemolysis, thrombocytopenia, DIC.
General: Renal Damage
Insufficient case reports to know, but related species can cause secondary renal failure (rare; viscero cutaneous loxoscelism only).
General: Cardiotoxicity
Does not occur, based on current clinical evidence
General: Other
Insufficient case reports to know, but related species can cause shock (rare; viscero cutaneous loxoscelism only).
 
First Aid
Description: First aid for Recluse Spider Bites (includes fiddleback spiders)
Details
1. Most bites go unnoticed at the time, only becoming evident later, once local tissue injury commences, by which time first aid is useless.
2. If the bite is witnessed, capture the spider and take it with the victim to a hospital or doctor.
3. Most traditional, and many of the more recently fashionable, first aid measures are useless and potentially dangerous. These include local cauterization, incision, excision, amputation, suction by mouth, vacuum pump or syringe, combined incision and suction ("venom-ex" apparatus), injection or instillation of compounds such as potassium permanganate, phenol (carbolic soap) and trypsin, application of electric shocks or ice (cryotherapy), use of traditional herbal, folk and other remedies including the ingestion of emetic plant products and parts of the snake, multiple incisions, tattooing and so on.
 
Treatment
Treatment Summary
The treatment of loxoscelism is controversial. Except for Brazil, no antivenom is available and even in Brazil, its role is uncertain. Good wound care, targeted treatment of secondary infection, avoidance of early surgical intervention and pain relief are important. Hyperbaric oxygen therapy remains an unproven treatment, though some experts believe it can assist pain relief and healing. Patients should be aware that local skin necrosis may take many weeks or months to heal. Patients with viscerocutaneous loxoscelism require urgent medical attention and full supportive therapy.
Key Diagnostic Features
Bite usually minor or not noticed; progressive local erythema, pain, mottled haemorrhagic colour, blisters, eschar formation (5-7 days), systemically unwell.
General Approach to Management
While most cases will be minor, not requiring admission, some cases will be more severe, requiring admission and treatment, so assess carefully before early discharge.
Antivenom Therapy
The role of antivenom in treating loxoscelism is uncertain, but where available (eg parts of Sth America) it should be used.
Antivenoms
1. Antivenom Code: IAmIBB01
Antivenom Name: Soro antiarachnidico
Manufacturer: Instituto Butantan
Phone: +55-11-3726-7222
Address: Av. Vital Brasil, 1500 Butanta
05503-900
Sao Paulo - SP
Country: Brazil
2. Antivenom Code: IAmINP04
Antivenom Name: Suero Antiloxoscelico
Manufacturer: Instituto Nacional de Salud
Phone: ++51-1-467-4499
Address: Centro Nacional de Produccion de Biologicos
Av. Defensores del Morro 2268
Chorrillos
Lima 9
Country: Peru
3. Antivenom Code: IAmIBM07
Antivenom Name: Aracmyn
Manufacturer: Instituto Bioclon
Phone: ++56-65-41-11
Address: Calzada de Tlalpan No. 4687
Toriello Guerra
C.P. 14050
Mexico, D.F.,
Country: Mexico
Loxosceles deserta ( Desert Loxosceles ) [ Original photo copyright © Marshal_Hedin-2010-CC BY-SA-2.0 ]
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Loxosceles deserta ( Desert Loxosceles ) [ Original photo copyright © Tony_Iwane-CC BY-NC-SA 3.0 ]
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