Arthropod Envenomations

Treatments for Latrodectism-A Systematic Review on Their Clinical Effectiveness

Latrodectism or envenomation by widow-spiders is common and clinically significant worldwide. Alpha-latrotoxin is the mammalian-specific toxin in the venom that results in toxic effects observed in humans. Symptoms may be incapacitating and include severe pain that can persist for days. The management of mild to moderate latrodectism is primarily supportive while severe cases have variously been treated with intravenous calcium, muscle relaxants, widow-spider antivenom and analgesic opioids. The object of this systematic review is to examine the literature on the clinical effectiveness of past and current treatments for latrodectism. MEDLINE, EMBASE and Google Scholar were searched from 1946 to December 2016 to identify clinical studies on the treatment of latrodectism. Studies older than 40 years and not in English were not reviewed. There were only two full-publications and one abstract of placebo-controlled randomised trials on antivenom use for latrodectism. Another two randomised comparative trials compared the route of administration of antivenom for latrodectism. There were fourteen case series (including two abstracts), fourteen case reports and one letter investigating drug treatments for latrodectism with the majority of these also including antivenom for severe latrodectism. Antivenom with opioid analgesia is often the major treatment reported for latrodectism however; recent high quality evidence has cast doubt on the clinical effectiveness of this combination and suggests that other treatments need to be investigated.

Papular urticaria and things that bite in the night

Whether we are hiking in the back country or playing in our backyard, we run the risk of exposure to offending arthropods. Papular urticaria is a very common hypersensitivity reaction to the bites, stings, and contact with critters such as mites, ticks, spiders, fleas, mosquitoes, midges, flies, and even caterpillars. Children seem to be at greatest risk, although adults are also vulnerable. The classic presentation of papular urticaria includes recurrent pruritic papules or vesicles and varying degrees of local edema. Severity is often related to the host response to the salivary or contactant proteins. Our understanding of the immune mechanism continues to improve; however, our approach to therapy has remained essentially unchanged. Although this review admittedly reaches beyond papular urticaria, it is with the intention of improving the reader's recognition of the offending arthropods, the characteristics of reactions, and the current therapeutic approaches.

Red-back spider envenomation in children in Central Australia

OBJECTIVE

To describe the clinical spectrum of Red-back spider (RBS) envenomation in children up to 12 years of age.

METHODS

Retrospective case notes review of children with a discharge diagnosis of RBS bite from January 1992 to June 2001. The setting was Alice Springs Hospital, the main paediatric hospital for the whole region of Central Australia. The patients were 54 children, comprising 39 Aboriginal and 15 non-Aboriginal children.

RESULTS

Forty-six (85%) children had systemic envenomation. The three most common systemic features are irritability, hypertension and sweating; 35 (65%) children had all three systemic features. Forty-five (83%) received antivenom therapy. The clinical characteristics and outcomes showed no significant difference between children 4 and > 4 years of age.

CONCLUSIONS

There is a high incidence of systemic envenomation due to RBS bite in children in Central Australia. The triad of irritability, hypertension and sweating in a previously well child is highly suggestive of latrodectism.

Red-back spider bites to Perth children, 1979-1988

The aim of this study was to describe the pattern of illness caused by red-back spider bites to children in Perth, Western Australia, over a 10 year period, and to compare it with that in adults. The case-notes of 241 (89%) of the 271 children admitted to Princess Margaret Hospital and Fremantle Hospital with suspected red-back spider bite from 1979 to 1988 were available for analysis. A definite bite was defined as a definite bite by a positively identified red-back spider, positive identification of a red-back spider with no definite bite but the later development of typical symptoms or no definite history of red-back spider bite but strong clinical evidence and complete recovery after administration of antivenom. Systemic envenomation was accepted if there were symptoms of vomiting, generalized pain or sweating, or abdominal pain. Sixty-five per cent of children were definitely bitten. As found in previous adult and mixed studies, there was a peak incidence in the warmer months with a male preponderance (68%); 81% of bites were to the extremities and 83% of bites occurred in the daytime. The syndrome produced in children was usually similar to that seen in adults. Twenty-one per cent of children received antivenom, a rate comparable to previous studies in older age groups; however, no child received more than one ampoule. Compared with data extracted from a previously published study at Fremantle Hospital, in which 37% of adults treated with antivenom received more than one ampoule, these findings suggest that contrary to current opinion children may not be at an increased risk of morbidity from latrodectism.

Acute arthropod envenomation. Incidence, clinical features and management

Black widow spider (Latrodectus mactans) envenomation is found throughout both the temperate and tropical latitudes, and is one of the leading causes of death from arthropod envenomations worldwide. The venom is highly neurotoxic, affecting the presynaptic motor endplate to allow massive noradrenaline (norepinephrine) and acetylcholine release into synapses causing excessive stimulation and fatigue of the motor end plate and muscle. Clinically, patients develop a bite site lesion and pain, abdominal pain and tenderness, and lower extremity pain and weakness within minutes to hours of envenomation. Symptoms progress over several hours, then subside over 2 to 3 days. The recommended treatment of 'common' envenomation is calcium gluconate 10% intravenously, titrated to relief of symptoms; antivenin, although effective, may cause hypersensitivity and serum sickness reactions, and should be restricted to life-threatening envenomations only. Brown recluse spider (Loxosceles reclusa) envenomations are seen in the Americas and in Europe, and are endemic to the south and central United States. The venom contains at least 8 enzymes, consisting of various lysins (facilitating venom spread) and sphingomyelinase D, which causes cell membrane injury and lysis, thrombosis, local ischaemia, and chemotaxis. Local envenomations begin as pain and itching that progresses to vesiculation with violaceous necrosis and surrounding erythema, and ultimately ulcer formation. Systemic envenomations may be life threatening, and present with fever, constitutional symptoms, petechial eruptions, thrombocytopenia, and haemolysis with haemoglobinuric renal failure. Treatment of local envenomations is conservative (local wound care, cryotherapy, elevation, tetanus prophylaxis, and close follow-up); systemic envenomation requires supportive care and treatment of arising complications, corticosteroids to stabilise red blood cell membranes, and support of renal function. Dapsone 100mg daily has emerged as a promising therapeutic agent in both animal studies and clinical trials. Over 650 species of scorpions are known to cause envenomation (mostly in children under 10 years); they are endemic mostly in arid and tropical areas. Different venoms and clinical presentations are seen across the different species. Most commonly, an inflammatory local reaction occurs with envenomation, which is treated with wound debridement and cleaning, tetanus prophylaxis, and antihistamines. Occasionally the venom is allergenic, and the resultant allergic reaction is treated in a standard fashion.(ABSTRACT TRUNCATED AT 400 WORDS)