title: Low Health System Performance, Indigenous Status and Antivenom Underdosage Correlate with Spider Envenoming Severity in the Remote Brazilian Amazon.
abstract: BACKGROUND
  A better knowledge of the burden and risk factors associated with severity due to spider bites would lead to improved management with a reduction of sequelae usually seen for this neglected health problem, and would ensure proper use of antivenoms in remote localities in the Brazilian Amazon. The aim of this study was to analyze the profile of spider bites reported in the state of Amazonas in the Western Brazilian Amazon, and to investigate potential risk factors associated with severity of envenomation.
  
  
  RESULTS
  We used a case-control study in order to identify factors associated with spider bite severity in the Western Brazilian Amazon from 2007 to 2014. Patients evolving to any severity criteria were considered cases and those with non-severe bites were included in the control group. All variables were retrieved from the official Brazilian reporting systems. Socioeconomical and environmental components were also included in a multivariable analysis in order to identify ecological determinants of incidence and severity. A total of 1,181 spider bites were recorded, resulting in an incidence of 4 cases per 100,000 person/year. Most of the spider bites occurred in males (65.8%). Bites mostly occurred in rural areas (59.5%). The most affected age group was between 16 and 45 years old (50.9%). A proportion of 39.7% of the bites were related to work activities. Antivenom was prescribed to 39% of the patients. Envenomings recorded from urban areas [Odds ratio (OR) = 0.40 (95%CI = 0.30-0.71; p<0.001)] and living in a municipality with a mean health system performance index (MHSPI >median [OR = 0.64 (95%CI = 0.39-0.75; p<0.001)] were independently associated with decreased risk of severity. Work related accidents [OR = 2.09 (95%CI = 1.49-2.94; p<0.001)], Indigenous status [OR = 2.15 (95%CI = 1.19-3.86; p = 0.011)] and living in a municipality located >300 km away from the state capital Manaus [OR = 1.90 (95%CI = 1.28-2.40; p<0.001)] were independently associated with a risk of severity. Living in a municipality located >300 km away from the state capital Manaus [OR = 1.53 (95%CI = 1.15-2.02; p = 0.003)] and living in a municipality with a MHSPI <median [OR = 1.91 (95%CI = 1.28-2.47; p = 0.002)] increased the odds of antivenom underdosage.
  
  
  CONCLUSIONS
  Spider bites is prevalent across the study region with a higher incidence in the rainy season in rural areas. Spider bites can be painful and lead to local manifestations but rarely result in life-threatening envenoming. Major local complications were dermonecrosis and secondary infection in cases diagnosed as Loxosceles bites. Based on the correlations shown here, envenomings occurring in remote rural areas, Indigenous status and living in a municipality located >300 km away from the state capital Manaus could be contributing factors to higher severity of spider envenomings in this area, as well as to antivenom underdosage.
authors.affiliation: Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.|Escola Superior de Ciências da Saúde, Universidade do Estado do Amazonas, Manaus, Brazil.|Núcleo de Sistemas de Informação, Fundação de Vigilância em Saúde do Amazonas, Manaus, Brazil.
authors.forename: Vanderson Souza
authors.initials: VS
authors.lastname: Sampaio
authors.affiliation: Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.|Escola Superior de Ciências da Saúde, Universidade do Estado do Amazonas, Manaus, Brazil.
authors.forename: André Alexandre
authors.initials: AA
authors.lastname: Gomes
authors.affiliation: Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.|Escola Superior de Ciências da Saúde, Universidade do Estado do Amazonas, Manaus, Brazil.
authors.forename: Iran Mendonça
authors.initials: IM
authors.lastname: Silva
authors.affiliation: Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.|Escola Superior de Ciências da Saúde, Universidade do Estado do Amazonas, Manaus, Brazil.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Sachett
authors.affiliation: Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.|Escola Superior de Ciências da Saúde, Universidade do Estado do Amazonas, Manaus, Brazil.
authors.forename: Luiz Carlos Lima
authors.initials: LC
authors.lastname: Ferreira
authors.affiliation: Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.|Escola Superior de Ciências da Saúde, Universidade do Estado do Amazonas, Manaus, Brazil.
authors.forename: Sâmella
authors.initials: S
authors.lastname: Oliveira
authors.affiliation: Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.|Department of Medical Sciences, Faculty of Medicine, Universitat de Girona, Catalunya, Spain.
authors.forename: Meritxell
authors.initials: M
authors.lastname: Sabidò
authors.affiliation: Curso de Ciências Biológicas, Faculdades Integradas do Tapajós, Santarém, Pará, Brazil.
authors.forename: Hipócrates
authors.initials: H
authors.lastname: Chalkidis
authors.affiliation: Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.|Escola Superior de Ciências da Saúde, Universidade do Estado do Amazonas, Manaus, Brazil.
authors.forename: Maria Graças Vale
authors.initials: MG
authors.lastname: Barbosa Guerra
authors.affiliation: Department of Medicine, Emory University, Atlanta, Georgia, United States of America.
authors.forename: Jorge Luis
authors.initials: JL
authors.lastname: Salinas
authors.affiliation: Instituto Butantan, Secretaria de Estado da Saúde de São Paulo, São Paulo, Brazil.
authors.forename: Fan Hui
authors.initials: FH
authors.lastname: Wen
authors.affiliation: Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.|Instituto de Pesquisas Leônidas & Maria Deane, FIOCRUZ, Manaus, Brazil.
authors.forename: Marcus Vinícius Guimarães
authors.initials: MV
authors.lastname: Lacerda
authors.affiliation: Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.|Escola Superior de Ciências da Saúde, Universidade do Estado do Amazonas, Manaus, Brazil.
authors.forename: Wuelton Marcelo
authors.initials: WM
authors.lastname: Monteiro
mesh_terms: D000293:Adolescent; D000328:Adult; D000997:Antivenins / Q000008:administration & dosage*; D001938:Brazil / Q000453:epidemiology; D016022:Case-Control Studies; D003695:Delivery of Health Care; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012308:Risk Management; D001098:Spider Bites / Q000188:drug therapy* / Q000453:epidemiology*
chemical_list: D000997:Antivenins