Effect of the time to antivenom administration on recovery from snakebite envenoming-related coagulopathy in French Guiana

A murine experimental model of the pulmonary thrombotic effect induced by the venom of the snake Bothrops lanceolatus

BACKGROUND

The venom of Bothrops lanceolatus, a viperid species endemic to the Lesser Antillean Island of Martinique, induces thrombosis in a number of patients. Previous clinical observations indicate that thrombotic events are more common in patients bitten by juvenile specimens. There is a need to develop an experimental model of this effect in order to study the mechanisms involved.

METHODOLOGY/PRINCIPAL FINDINGS

The venoms of juvenile and adult specimens of B. lanceolatus were compared by (a) describing their proteome, (b) assessing their ability to induce thrombosis in a mouse model, and (c) evaluating their in vitro procoagulant activity and in vivo hemostasis alterations. Venom proteomes of juvenile and adult specimens were highly similar, albeit showing some differences. When injected by the intraperitoneal (i.p.) route, the venom of juvenile specimens induced the formation of abundant thrombi in the pulmonary vasculature, whereas this effect was less frequent in the case of adult venom. Thrombosis was not abrogated by the metalloproteinase inhibitor Batimastat. Both venoms showed a weak in vitro procoagulant effect on citrated mouse plasma and bovine fibrinogen. When administered intravenously (i.v.) venoms did not affect classical clotting tests (prothrombin time and activated partial thromboplastin time) but caused a partial drop in fibrinogen concentration. The venom of juvenile specimens induced partial alterations in some rotational thromboelastometry parameters after i.v. injection. When venoms were administered i.p., only minor alterations in classical clotting tests were observed with juvenile venom, and no changes occurred for either venom in rotational thromboelastometry parameters. Both juvenile and adult venoms induced a marked thrombocytopenia after i.p. injection.

CONCLUSIONS/SIGNIFICANCE

An experimental model of the thrombotic effect induced by B. lanceolatus venom was developed. This effect is more pronounced in the case of venom of juvenile specimens, despite the observation that juvenile and adult venom proteomes are similar. Adult and juvenile venoms do not induce a consumption coagulopathy characteristic of other Bothrops sp venoms. Both venoms induce a conspicuous thrombocytopenia. This experimental model reproduces the main clinical findings described in these envenomings and should be useful to understand the mechanisms of the thrombotic effect.

Capacity of community health centers to treat snakebite envenoming in indigenous territories of the Brazilian Amazon

INTRODUCTION

The deaths from and morbidities associated with snakebites - amputations, loss of function in the limb, visible scarring or tissue damage - have a vast economic, social, and psychological impact on indigenous communities in the Brazilian Amazon, especially children, and represent a real and pressing health crisis in this population. Snakebite clinical and research experts have therefore proposed expanding antivenom access from only hospitals to include the community health centers (CHC) located near and within indigenous communities. However, there are no studies examining the capacity of CHCs to store, administer, and manage antivenom treatment. In response to this gap, the research team calling for antivenom decentralization developed and validated an expert-based checklist outlining the minimum requirements for a CHC to provide antivenom.

METHODS

The objective of this study was thus to survey a sample of CHCs in indigenous territories and evaluate their capacity to provide antivenom treatment according to this accredited checklist. The checklist was administered to nurses and doctors from 16 CHCs, two per indigenous district in Amazonas/Roraima states.

RESULTS

Our results can be conceptualized into three central findings: 1) most CHCs have the capacity to provide antivenom treatment, 2) challenges to capacity are human resources and specialized items, and 3) antivenom decentralization is feasible and appropriate in indigenous communities.

CONCLUSION

Decentralization would provide culturally and contextually appropriate care accessibility to a historically marginalized and underserved population of the Brazilian Amazon. Future studies should examine optimal resource allocation in indigenous territories and develop an implementation strategy in partnership with indigenous leaders. Beyond the indigenous population, the checklist utilized could be applied to community health centers treating the general population and/or adapted to other low-resource settings.

Development and validation of a minimum requirements checklist for snakebite envenoming treatment in the Brazilian Amazonia

BACKGROUND

Currently, antivenoms are the only specific treatment available for snakebite envenoming. In Brazil, over 30% of patients cannot access antivenom within its critical care window. Researchers have therefore proposed decentralizing to community health centers to decrease time-to-care and improve morbidity and mortality. Currently, there is no evidence-based method to evaluate the capacity of health units for antivenom treatment, nor what the absolute minimum supplies and staff are necessary for safe and effective antivenom administration and clinical management.

METHODS

This study utilized a modified-Delphi approach to develop and validate a checklist to evaluate the minimum requirements for health units to adequately treat snakebite envenoming in the Amazon region of Brazil. The modified-Delphi approach consisted of four rounds: 1) iterative development of preliminary checklist by expert steering committee; 2) controlled feedback on preliminary checklist via expert judge survey; 3) two-phase nominal group technique with new expert judges to resolve pending items; and 4) checklist finalization and closing criteria by expert steering committee. The measure of agreement selected for this study was percent agreement defined a priori as ≥75%.

RESULTS

A valid, reliable, and feasible checklist was developed. The development process highlighted three key findings: (1) the definition of community health centers and its list of essential items by expert judges is consistent with the Brazilian Ministry of Health, WHO snakebite strategic plan, and a general snakebite capacity guideline in India (internal validity), (2) the list of essential items for antivenom administration and clinical management is feasible and aligns with the literature regarding clinical care (reliability), and (3) engagement of local experts is critical to developing and implementing an antivenom decentralization strategy (feasibility).

CONCLUSION

This study joins an international set of evidence advocating for decentralization, adding value in its definition of essential care items; identification of training needs across the care continuum; and demonstration of the validity, reliability, and feasibility provided by engaging local experts. Specific to Brazil, further added value comes in the potential use of the checklist for health unit accreditation as well as its applications to logistics and resource distribution. Future research priorities should apply this checklist to health units in the Amazon region of Brazil to determine which community health centers are or could be capable of receiving antivenom and translate this expert-driven checklist and approach to snakebite care in other settings or other diseases in low-resource settings.

Bothrops venom-induced hemostasis disorders in the rat: Between Scylla and Charybdis

Hemostasis impairment represents the most threatening consequence of Viperidae envenoming, notably with Bothrops genus. In the French departments of America, B. atrox envenomation in French Guiana may lead to bleeding while B. lanceolatus envenomation in Martinique to thrombosis. Bleeding related to B. atrox envenomation is attributed to vascular damage mediated by venom metalloproteinases and blood uncoagulable state resulting from thrombocytopenia and consumptive coagulopathy. Thrombosis related to B. lanceolatus envenomation are poorly understood. We aimed to compare the effects of B. atrox and B. lanceolatus venoms in the rat to identify the determinants of the hemorrhagic versus thrombotic complications. Viscoelastometry (ROTEM), platelet count, plasma fibrinogen, thrombin generation assay, fibrinography, endothelial (von Willebrand factor, ADAMTS13 activity, ICAM-1, and soluble E-selectin), and inflammatory biomarkers (IL-1β, IL-6, TNF-α, MCP-1, and PAI-1) were determined in blood samples obtained at H3, H6, and H24 after the subcutaneous venom versus saline injection. In comparison to the control, initial fibrinogen consumption was observed with the two venoms while thrombocytopenia and reduction in the clot amplitude only with B. atrox venom. Moreover, we showed an increase in thrombin generation at H3 with the two venoms, an increase in fibrin generation accompanied with hyperfibrinogenemia at H24 and an increase in inflammatory biomarkers with B. lanceolatus venom. No endothelial damage was found with the two venoms. To conclude, our data support two-sided hemostasis complications in Bothrops envenoming with an initial risk of hemorrhage related to platelet consumption and hypocoagulability followed by an increased risk of thrombosis promoted by the activated inflammatory response and rapid-onset fibrinogen restoration.

Bothrops atrox and Bothrops lanceolatus Venoms In Vitro Investigation: Composition, Procoagulant Effects, Co-Factor Dependency, and Correction Using Antivenoms

Bothrops venoms are rich in enzymes acting on platelets and coagulation. This action is dependent on two major co-factors, i.e., calcium and phospholipids, while antivenoms variably neutralize venom-related coagulopathy effects. Our aims were (i) to describe the composition of B. atrox and B. lanceolatus venoms; (ii) to study their activity on the whole blood using rotational thromboelastometry (ROTEM); (iii) to evaluate the contribution of calcium and phospholipids in their activity; and (iv) to compare the effectiveness of four antivenoms (Bothrofav™, Inoserp™ South America, Antivipmyn™ TRI, and PoliVal-ICP™) on the procoagulant activity of these two venoms. Venom composition was comparable. Both venoms exhibited hypercoagulant effects. B. lanceolatus venom was completely dependent on calcium but less dependent on phospholipids than B. atrox venom to induce in vitro coagulation. The four antivenoms neutralized the procoagulant activity of the two venoms; however, with quantitative differences. Bothrofav™ was more effective against both venoms than the three other antivenoms. The relatively similar venom-induced effects in vitro were unexpected considering the opposite clinical manifestations resulting from envenomation (i.e., systemic bleeding with B. atrox and thrombosis with B. lanceolatus). In vivo studies are warranted to better understand the pathophysiology of systemic bleeding and thrombosis associated with Bothrops bites.