Snakebites are a serious public health problem and, in the Amazon, the Bothrops atrox snake is the most frequent cause of envenomation. B. atrox venom (BaV) causes pathophysiological changes with intense, local inflammatory processes, such as severe tissue complication (STC). However, mechanisms associated with the inflammatory process in humans are still poorly understood. Thus, in this study, we sought to describe the profile of local and systemic immunological soluble molecules in Bothrops envenomation patients treated at a specialist tertiary healthcare unit in the Brazilian Amazon. An analytical and prospective study was performed with patients who had snakebites with different clinical outcomes (STC and Mild Tissue Complication—MTC) using venous blood and blister exudate in order to measure immunological soluble molecules present in the response process. Twenty STC patients and 20 MTC patients were eligible for the study. In addition, 20 healthy donors (HD) who had never been bitten by a snake were used as controls. The biomarkers CXCL-8, CCL-5, CXCL-9, CCL-2 and CXCL-10; C3a, C4a, and C5a; IL-1, IL-2, IL-4, IL-5, IL-6, IL-10, TNF, IFN-γ and IL-17A were quantified using flow cytometry and ELISA. The circulating response profile differs between the studied groups, with MTC patients presenting a mixed profile and STC patients presenting a more polarized profile for Th1 response. In addition, individuals who develop STC have a more intense local immune response, because the tissue response differs from the circulating immunological soluble molecules and presents Th1/Th2/Th17 response polarization. Furthermore, these results suggest that CCL-2 and CXCL-10 are biomarkers for STC and the response profile they assume against Bothrops snakebite should reflect in the clinical practice for the patient.

BackgroundA 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 FindingsWe 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 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.

Snakebites are considered a major public health problem worldwide. In the Amazon region of Brazil, the snake Bothrops atrox ( B. atrox ) is responsible for 90% of the bites. These bites may cause local and systemic signs from acute inflammatory reaction and hemostatic changes, and present common hemorrhagic disorders. These alterations occur due the action of hemostatically active and immunogenic toxins which are capable of triggering a wide range of hemostatic and inflammatory events. However, the crosstalk between coagulation disorders and inflammatory reaction still has gaps in snakebites. Thus, the goal of this study was to describe the relationship between the consumption of fibrinogen and the profile of inflammatory molecules (chemokines and cytokines) in evenomations by B. atrox snakebites. A prospective study was carried out with individuals who had suffered B. atrox snakebites and presented different levels of fibrinogen consumption (normal fibrinogen [NF] and hypofibrinogenemia [HF]). Seventeen patients with NF and 55 patients with HF were eligible for the study, in addition to 50 healthy controls (CG). The molecules CXCL-8, CCL-5, CXCL-9, CCL-2, CXCL-10, IL-6, TNF, IL-2, IL-10, IFN-γ, IL-4, and IL-17A were quantified in plasma using the CBA technique at three different times (pre-antivenom therapy [T0], 24 h [T1], and 48 h [T2] after antivenom therapy). The profile of the circulating inflammatory response is different between the groups studied, with HF patients having higher concentrations of CCL-5 and lower IFN-γ. In addition, antivenom therapy seems to have a positive effect, leading to a profile of circulating inflammatory response similar in quantification of T1 and T2 on both groups. Furthermore, these results suggest that a number of interactions of CXCL-8, CXCL-9, CCL-2, IL-6, and IFN-γ in HF patients are directly affected by fibrinogen levels, which may be related to the inflammatory response and coagulation mutual relationship induced by B. atrox venom. The present study is the first report on inflammation-coagulation crosstalk involving snakebite patients and supports the better understanding of envenomation's pathophysiology mechanisms and guides in the search for novel biomarkers and prospective therapies.