RESUMO
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. Methodology/Principal Findings 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
Assuntos
ToxicologiaRESUMO
Comparisons between venoms from snakes kept under captivity or collected at the natural environment are of fundamental importance in order to obtain effective antivenoms to treat human victims of snakebites. In this study, we compared composition and biological activities of Bothrops atrox venom from snakes collected at Tapajós National Forest (Pará State, Brazil) or maintained for more than 10 years under captivity at Instituto Butantan herpetarium after have been collected mostly at Maranhão State, Brazil. Venoms from captive or wild snakes were similar except for small quantitative differences detected in peaks correspondent to phospholipases A2 (PLA2), snake venom metalloproteinases (SVMP) class PI and serine proteinases (SVSP), which did not correlate with fibrinolytic and coagulant activities (induced by PI-SVMPs and SVSPs). In both pools, the major toxic component corresponded to PIII-SVMPs, which were isolated and characterized. The characterization by mass spectrometry of both samples identified peptides that matched with a single PIII-SVMP cDNA characterized by transcriptomics, named Batroxrhagin. Sequence alignments show a strong similarity between Batroxrhagin and Jararhagin (96%). Batroxrhagin samples isolated from venoms of wild or captive snakes were not pro-coagulant, but inhibited collagen-induced platelet-aggregation, and induced hemorrhage and fibrin lysis with similar doses. Results suggest that in spite of environmental differences, venom variability was detected only among the less abundant components. In opposition, the most abundant toxin, which is a PIII-SVMP related to the key effects of the venom, is structurally conserved in the venoms. This observation is relevant for explaining the efficacy of antivenoms produced with venoms from captive snakes in human accidents inflicted at distinct natural environments.
