Venomous spider bites in south africa: epidemiology and clinical features

Du Plessis, Catharina Elizabeth (2019-04)

Thesis (MSc)--Stellenbosch University, 2019.

Thesis

Introduction: Worldwide the number of spider bite calls to poison centres comprises less than 2.5% of calls. Only a small proportion of spiders cause serious envenomation in humans. The known medically important spiders of South Africa include the Latrodectus (button), Cheiracanthium (sac) and Loxosceles (violin) species. The button spiders can cause neurotoxicity called latrodectism while violin and sac spider bites can cause necrotic skin lesions. The clinical syndrome of latrodectism is well defined and an effective antivenom is available. The diagnosis of necrotic arachnidism on the other hand is more difficult, especially if the spider bite is not painful. The necrotic skin lesions are not specific and have a wide differential diagnosis. Aim: The main aim of the study was to perform a retrospective assessment of poison centre data regarding spider bites from January 2005 to December 2017 and to develop an algorithm for the diagnosis of spider bites. Results: From a total of 83 974 calls, 1917 (2.3%) were related to suspected spider bites. The majority of these calls were from the Western Cape Province. The majority of bites occurred during the warmer months of the year, peaking in January and February. Adults were involved more frequently than children, 1497 versus 420, respectively. In 138 (48.6%) of the 284 reported button spider bites, the spider was positively identified. Of these, 80 (28.1%) patients were treated with antivenom. The most common clinical features were generalised pain (n = 89, 31.3%), muscle pain and cramps (n = 88, 31.0%) and sweating (n = 58, 20.4%). In the cytotoxic spider group only 5 spiders were positively identified. In the majority of calls the spider was not seen or could not be identified (n = 1301, 68%). Discussion: The number of spider bite calls to poison centres are low when compared to the total number of calls received. Bites usually involved adults and occurred mostly during the warmer months of the year. There has not been a single death associated with spider bites. In terms of a Poison Information Centre helpline data collection suggested categories for the diagnosis of spider bites include definite, probable and unlikely. Based on the clinical presentation it is possible to diagnose neurotoxic spider bites caused by button spiders with confidence and advise the use of the antivenom when indicated. A positive response to the antivenom supports the presumed diagnosis. It is more difficult to diagnose cytotoxic spider bites and the majority reported skin lesions are unlikely to be caused by spiders. We have developed a diagnostic algorithm that incorporates the most important clinical features and the distribution of spiders to assist with the diagnosis. Conclusion: In the majority of spider bites it is unlikely that serious effects will develop, however the early identification of a spider as well as the recognition of a clinical syndrome associated with certain spider bites, would assure safe and effective treatment. The helpline data is insufficient to fully describe necrotic arachnidism and further prospective studies are warranted.

Inleiding: Wêreldwyd behels die getal spinnekopbyt-oproepe na gifsentrums minder as 2,5% van die totale oproepe. Slegs ’n klein aantal spinnekoppe veroorsaak ernstige envenomasie by die mens. Die spinnekoppe van Suid-Afrika wat van mediese belang is, sluit die Latrodectus (knopie)-, Cheiracanthium (sak)- en Loxosceles (viool)-spesie in. Die knopiespinnekop kan neurotoksisiteit bekend as latrodektisme veroorsaak, terwyl viool- en sakspinnekopbyte tot nekrotiese velletsels kan lei. Die kliniese sindroom van latrodektisme is goed omskryf en ’n doeltreffende teengif is daarvoor beskikbaar. Die diagnose van nekrotiese arachnidisme daarenteen is egter moeiliker, veral as die spinnekopbyt nie waargeneem is nie. Die nekrotiese velletsels is nie spesifiek nie en het ’n wye differensiële diagnose. Doel: Die hoofdoel van die studie was om ’n retrospektiewe assessering van gifsentrumdata, vanaf Januarie 2005 tot Desember 2017, oor spinnekoppe uit te voer en om ’n algoritme vir die diagnose van spinnekopbyte te ontwikkel. Resultate: Uit altesaam 83 974 oproepe wat ontvang is, het 1 917 (2,3%) vermoedelik met spinnekopbyte verband gehou. Die meerderheid van hierdie oproepe was van die Wes-Kaap. Die byte het meestal gedurende die warmer maande van die jaar plaasgevind en in Januarie en Februarie ’n hoogtepunt bereik. Volwassenes het meer gereeld deurgeloop as kinders, onderskeidelik 1 497 teenoor 420. In 138 (48,6%) van die 284 aangemelde knopiespinnekopbyte is die spinnekop positief geïdentifiseer. Hiervan is 80 (28,1%) pasiënte met teengif behandel. Die algemeenste kliniese kenmerke was algemene pyn (n = 89; 31,3%), spierpyn en krampe (n = 88; 31,0%), en sweet (n = 58; 20,4%). In die sitotoksiese spinnekopgroep is slegs 5 spinnekoppe positief geïdentifiseer. In die meeste oproepe is die spinnekop nie opgemerk nie of kon dit nie geïdentifiseer word nie (n = 1 301; 68%). Bespreking: Die aantal spinnekopbyt-oproepe na gifsentrums is laag vergeleke met die totale aantal oproepe wat ontvang is. Dit was gewoonlik volwassenes wat gebyt is en dit het meestal gedurende die warm maande van die jaar plaasgevind. Daar was nie ’n enkele sterfte wat met spinnekoppe verband gehou het nie. Die insameling van data by ʼn gifinligtingsentrum het dit laat blyk dat voorgestelde kategorieë vir die diagnose van spinnekopbyte “beslis”, “waarskynlik” en “onwaarskynlik” moet insluit. Op grond van die kliniese presentasie is dit moontlik om neurotoksiese spinnekopbyte wat deur knopiespinnekoppe veroorsaak word, met sekerheid te diagnoseer en die gebruik van die teengif aan te beveel wanneer dit as gewens aangedui word. ’n Positiewe reaksie op die teengif ondersteun die veronderstelde diagnose. Dit is moeiliker om sitotoksiese spinnekopbyte te diagnoseer, en die meerderheid gerapporteerde velletsels is waarskynlik nie deur spinnekoppe veroorsaak nie. Ons het ’n diagnostiese algoritme ontwikkel wat die belangrikste kliniese kenmerke en die verspreiding van spinnekoppe insluit om diagnosering te vergemaklik. Gevolgtrekking: By die meeste spinnekopbyte is dit onwaarskynlik dat ernstige gevolge sal ontwikkel, maar die vroeë identifisering van ’n spinnekop, asook die herkenning van ’n kliniese sindroom wat met sekere spinnekopbyte verband hou, verseker veilige en effektiewe behandeling. Die hulplyndata is onvoldoende om nekrotiese arachnidisme volledig te beskryf en verdere prospektiewe studies is geregverdig.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106053
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