Snakes are a valuable yet understudied taxon for investigating evolutionary adaptations in the vertebrate retina. They possess up to three visual pigments: a short-wavelength-sensitive opsin (SWS1), a medium/long-wavelength-sensitive opsin (LWS), and rhodopsin (RH1). Nocturnal snakes have duplex retinas containing both rod and cone photoreceptors, whereas diurnal caenophidian ("advanced") snakes exhibit simplex "all-cone" retinas, lacking morphologically typical rods. In this study, we analyzed photoreceptor morphology in the retinas of caenophidian snakes using high-resolution scanning electron microscopy (SEM) and examined visual-opsin expression patterns with immunohistochemistry (IHC). Our analyses revealed remarkable interspecific variability in visual-cell morphology. Light microscopy showed that in all sampled diurnal caenophidians, photoreceptors expressing RH1 exhibit a gross cone-like morphology. However, SEM analysis revealed a subset of photoreceptors with distinct features-thinner inner segments and rod-like synaptic terminals-suggesting they are transmuted, cone-like rods. In retinal sections from nocturnal caenophidian snakes, coexpression of the cone opsins SWS1 and LWS in individual cones was observed, whereas rhodopsin expression remained restricted to morphologically typical rods and showed no coexpression. In contrast, diurnal caenophidians commonly coexpress rhodopsin and SWS1 in single cones, with some instances of triple coexpression (SWS1, RH1, and LWS) in single cones. We evaluated the patterns of spatial distribution of RH1- and SWS1-expressing photoreceptors, as well as SWS1 + RH1 multiopsin cones, in wholemounted retinas of ten species. Our findings revealed considerable species-specific variation in photoreceptor density, topography, and opsin coexpression patterns. IHC results suggest that in some species, rhodopsin is not only expressed in transmuted, cone-like rods but may also be co-opted by UV/violet-sensitive (SWS1-expressing) cones. These findings underscore the exceptional diversity and adaptive innovation in snake visual systems. The unique features and striking interspecific differences in their photoreceptors highlight snakes as an outstanding taxon for studying vertebrate visual-system function and evolution.

In Eswatini, bites from snakes with cytotoxic venoms inflict substantial morbidity on humans through blistering, swelling, and tissue necrosis. Despite its widespread use, there is little evidence regarding the efficacy of antivenom in preventing snakebite-induced tissue damage. We conducted a prospective observational study in nine hospitals in Eswatini to describe and quantify symptoms of local tissue toxicity. Our secondary aim was to examine the use of antivenom. Data from 125 snakebite patients with extensive or rapidly progressive swelling were analyzed. The median increase in circumference of envenomed limbs was 12%. Necrosis developed in 31 (25%) patients, primarily in distal extremities. Seventy patients (56%) received South African Institute for Medical Research (SAIMR) Polyvalent antivenom (South African Vaccine producers, Johannesburg South Africa), which was administered for indications related to local tissue damage. Upon hospital presentation, patients treated with antivenom exhibited slightly more severe swelling. Ten out of 11 patients with necrosis upon admission received antivenom. At least seven patients developed necrosis after admission despite previous antivenom therapy. In this nonrandomized observational study, no relationship was observed between the rate at which swelling receded and antivenom treatment. Adverse reactions to antivenom occurred in 49% of patients. Although our analysis has its limitations, it emphasizes the compelling need for research into the indications for and outcomes of antivenom treatment for local tissue damage.

The variation in venom between and within snake species has significant implications for snakebite treatment. This highlights the critical importance of studying venom composition and its variations, not only for medical purposes but also from an evolutionary perspective. This study explores analytics for characterizing venom variability, focusing on venom toxin accurate masses, and emphasizes how the complexity of studying snake venom variability can be addressed by using liquid chromatography mass spectrometry (LC-MS) analysis with bioinformatics tools. This was demonstrated by investigating LC-MS data obtained from the venoms of 15 true cobras (Naja spp.), 5 mambas (Dendroaspis spp.) and 28 vipers (Crotalus and Bothrops spp.; total of 20 Elapidae and 28 Viperidae venoms), with newly developed bioinformatics tools. The measured LC-MS data was processed in an automated fashion and sorted based on the monoisotopic accurate masses of all toxins found, their peak intensities, and their retention times in LC. The data was then investigated using bioinformatic tools, before the toxin data available in open-source databases was used to predict the class of a toxin by means of its mass. This study highlights the importance of studying venom variability, which is performed by our combinatorial approach of intact-toxin analysis and toxin grouping by accurate mass.

BACKGROUND:Snakebites are problematic in many developing regions, including India, where over half of global snakebite deaths occur. Antivenoms are currently the only licensed treatment for snakebites. However, their use causes several challenges, most notably geographical limitations in efficacy and adverse side effects. Therefore, therapeutic alternatives are urgently needed. Recently, several studies have evaluated small molecule inhibitors (SMIs) and highlighted their promise as safe and effective alternatives to antivenoms. We investigate their potential use against Indian snakes, particularly Russell's viper (Daboia russelii), responsible for over half of India's snakebite cases. METHODS:Here, we explored the effectiveness of two phase-2-approved SMIs in countering the diverse and variable toxicities of D. russelii from across India. RESULTS:The phospholipase inhibitor varespladib and the metalloproteinase inhibitor marimastat, individually or in combination, effectively counter the toxicities of D. russelii venoms in vitro. Specific drug efficacy varies across geographic regions. These SMIs and their combination prevent lethality caused by the pan-Indian D. russelii, even in rescue experiments where treatment is delayed, in mice. CONCLUSIONS:Our findings support the potential use of SMIs as effective, affordable, and accessible future therapies for treating bites from the world's most medically important snake species.

A considerable number of patients present to hospitals in Eswatini each year following bites by venomous snakes. Effectively diagnosing and treating patients with snakebite envenoming requires healthcare workers to have a variety of generic and snakebite-specific medical skills. In several countries, however, healthcare workers have been found to have limited skills in managing snakebite patients. We used the Delphi method to adapt the Hennessy-Hicks training needs analysis questionnaire to the context of snakebite envenoming and subsequently used the adapted questionnaire to assess the self-perceived training needs of 90 healthcare workers from ten hospitals in Eswatini. Two-thirds (63%) of participants were nursing staff and one third (34%) medical doctors. Overall, 74% of healthcare workers had previously received training on snakebite. Although a training need was reported for all skills included in the survey, the extent of the training need varied between different skills and groups of healthcare workers. The highest average training need was registered in the domains ‘research and audit’ and ‘clinical tasks’ with the latter accounting for nine of the ten skills with the highest training need. Nurses reported a higher training need than doctors, especially for clinical tasks. Receiving snakebite training before as well as after obtaining the primary qualification was associated with the lowest average training need, particularly in clinical skills. Ninety-three percent of interviewed healthcare workers would welcome more frequent training opportunities on the clinical management of snakebite patients. This newly developed snakebite training needs analysis tool can aid in adapting training initiatives to a dynamic and evolving healthcare workforce and it is designed to be transferrable to snakebite endemic settings worldwide.

Snakebite is a significant public health concern in Africa, with the viperid species Echis ocellatus being responsible for the majority of snakebite deaths in West Africa. Recently E. ocellatus underwent taxonomic revision and was split into two species, E. ocellatus sensu stricto and E. romani, leading to questions regarding differences in venom bioactivities and the efficacy of antivenoms indicated for treatment of 'E. ocellatus' envenoming against the two redefined species. Using a range of in vitro assays we compared the toxin activities of the two species and the venom-neutralising efficacy of three antivenoms (EchiTAbG, SAIMR Echis and Echiven) raised against 'E. ocellatus'. We then used murine preclinical assays to compare the in vivo efficacy of these antivenoms against E. romani and E. ocellatus s. str venoms. Mitochondrial barcoding of snake skins and venom revealed that E. romani, and not E. ocellatus, is used in the manufacture of several antivenoms raised against 'E. ocellatus'. There were also a number of differences in specific toxin activity between the venoms of the two species in the three in vitro assays utilised in this study.; E. ocellatus (Ghana) had the strongest phospholipase A2 (PLA2) activity, followed by weak PLA2 activity for E. romani (Cameroon) and insignificant activity by E. romani (Nigeria). E. ocellatus (Ghana) and E. romani (Nigeria) demonstrated comparable snake venom metalloproteinase activity, whilst E. romani (Cameroon) had reduced, albeit still significant, activity in comparison. However no differences were observed in a plasma clotting assay measuring coagulopathy between the venoms and localities. Venoms from E. ocellatus (Ghana) and E. romani (Cameroon and Nigeria) were all recognised comparably by the three antivenoms, and there were only modest differences between antivenoms in neutralising the various in vitro toxin effects. In murine preclinical assays, each antivenom could neutralise the lethal effects of E. romani (Nigeria), but differences were seen in their comparative potency when the same antivenom doses were tested against E. romani (Cameroon) and E. ocellatus (Ghana). In these comparative potency assays, all three antivenoms were unable to confer 100% survival when tested against E. romani (Cameroon), but SAIMR Echis provided the best protection with 80% survival. When tested against E. ocellatus (Ghana), the comparative doses of SAIMR Echis and Echiven provided 100% protection whereas EchiTAbG failed to prevent lethality beyond three hours. This represents the first detailed analysis of differences between E. ocellatus and E. romani venom bioactivities and the efficacy of existing antivenoms against these two species. Our findings demonstrate that EchiTAbG, SAIMR Echis and Echiven antivenoms are preclinically efficacious against the lethal effects of E. ocellatus and E. romani venom across a number of localities.

In the UK, exotic reptiles are increasingly popular as pets, and housed in zoological collections, whilst venomous snakes of medical importance have long been the focus of herpetological studies. As all reptiles can harbour protist and helminth parasites, some of these may carry tangible zoonotic risk. This study utilised traditional and molecular diagnostic techniques, including sedimentation-flotation, real-time polymerase chain reaction (rtPCR), and necropsy, to investigate endoparasite infections in captive-bred (CB) and wild-caught (WC) reptiles. Representative animals originated from pet shops, zoological and private collections as well as those housed in research herpetariums. Parasitic infections were detected in 21.1% (n = 109) of samples from 58 reptile species across 12 families. The most prevalent infections included nematodes (17.4%), cestodes (0.9%) and protists (3.7%). The nematodes, particularly strongylid (9.3%) and ascarid (5.6%) species, being the most common. Of particular interest, zoonotic genera, Ophidascaris and Giardia were identified. When possible, necropsy revealed latent infections, including prepatent stages of the hookworm Kalicephalus sp. and pentastomid larvae in Echis ocellatus snakes. These accounted for 55.6% of all parasitic infections. Real-time-PCR methods detected additional co-infection overlooked by microscopy, whilst necropsy provided additional insights. These findings highlight the need in the UK for better parasitic screening protocols to enhance captive reptile welfare, mitigate zoonotic risks and safeguard public health.

Elapid snakebites cause severe toxicity, predominantly neurotoxicity and general cytotoxicity. However, the specific cellular impacts of individual venom toxins remain largely underexplored. This study developed a high-throughput platform for profiling cytotoxicity from elapid venoms, focusing on nanofractionation analytics to enhance selectivity and toxin identification. Elapid Venoms were tested on four human cell lines, representing kidney (RPTEC/TERT1), liver (HepaRG), endothelial (iPSC-EC), and skin (HaCaT) tissues. Cytotoxic effects were assessed through cell coverage, viability, and metabolic assays in both crude and nanofractionated venom samples. Nanofractionation revealed selective cytotoxicity in venom components, notably phospholipases A2 (PLA2s) and three-finger toxins (3FTxs), which impaired membrane integrity and cellular metabolism. Crude B. multicinctus venom displayed specific cytotoxicity toward liver and skin cells but not kidney or endothelial cells. Cytotoxicity of nanofractionated B. multicinctus venom was lost, likely due to denaturing conditions of the reversed-phase separation. Fractionation after size exclusion chromatography (SEC) for post-column bioassaying to avoid toxin denaturation yielded bioactive fractions, with 3FTxs, PLA2s, and Kunitz-type serine protease (KUNs) likely responsible for the observed cell permeability disruption, extracellular matrix (ECM) degradation, and metabolic loss. This integrated analytical workflow, combining nanofractionation with high-throughput cytotoxicity assays and venomics, enabled rapid identification of venom components with cell type-specific toxicity. Our findings contribute to understanding elapid venom toxicity and can aid in developing targeted snakebite treatments focusing on cytotoxicity responsible for tissue-specific damage.

Snakebite envenoming constitutes a significant global health issue, particularly in Africa, where venomous species such as Echis vipers and Dendroaspis mambas pose substantial risks to human health. This study employs a standardized venomics workflow to comprehensively characterize and comparatively quantify the venom composition of nine medically relevant snake species chosen from among the deadliest in Africa. Utilizing shotgun venom proteomics and venom gland transcriptomics, we report detailed profiles of venom complexity, highlighting the relative abundance of dominant toxin families such as three-finger toxins and Kunitz-type proteins in Dendroaspis, and metalloproteinases and phospholipases A2 in Echis. We delineate here the relative abundance and structural diversity of venom components. Key to our proteomic approach is the implementation of Multi-Enzymatic Limited Digestion (MELD), which improved protein sequence coverage and enabled the identification of rare toxin families such as hyaluronidases and renin-like proteases, by multiplying the overlap of generated peptides and enhancing the characterization of both toxin and non-toxin components within the venoms. The culmination of these efforts resulted in the construction of a detailed toxin database, providing insights into the biological roles and potential therapeutic targets of venom proteins and peptides. The findings here compellingly validate the MELD technique, reinforcing its reproducibility as a valuable characterization approach applied to venomics. This research significantly advances our understanding of venom complexity in African snake species, including representatives of both Viperidae and Elapidae families. By elucidating venom composition and toxin profiles, our study paves the way for the development of targeted therapies aimed at mitigating the morbidity and mortality associated with snakebite envenoming globally.

Snake venoms are complex bioactive mixtures designed to paralyse, kill, or digest prey. These venoms are of pharmacological interest due to their ability to modulate molecular targets such as ion channels and receptors with high specificity and potency. Traditional studies often focus on in vitro molecular analysis or in vivo behavioural effects, limiting comprehensive understanding. Here, we present a high-throughput screening platform that combines in vitro ion channel assays with in vivo zebrafish larval bioassays using nanofractionation analytics. This method integrates post-column calcium flux assays, zebrafish paralytic bioassays, toxin mass spectrometry, and proteomics to link bioactivity with toxin identification. Using elapid snake venoms (genus Dendroaspis, Naja, and Hemachatus) as a proof of concept, we identified several toxins modulating ion channels with paralytic effects on zebrafish larvae. Our approach enables parallel acquisition of in vitro and in vivo data, offering a robust guide for identifying and characterising ion channel modulators with defined molecular targets.

Snakebite claims 138,000 lives a year with an additional 400,000 patients left permanently disabled or disfigured. Morbidity following envenoming includes the development of chronic wounds around the bite site. The understanding of the underlying pathophysiology of chronic snakebite wounds has been severely limited by the historical reliance on a preclinical model that only captures acute local envenoming pathology. Through the application of three medically important snake venoms (Echis ocellatus, Bothrops atrox and Naja nigricollis) to a recently developed preclinical model of chronic wounds, we have been able to characterise key features of venom wounds. We have been able to show that venom wounds share consistencies with non-venom induced preclinical wounds, and also display unique characteristics such as extracellular matrix degradation and eosinophilic infiltrate. This model will not only serve to increase our understanding the underlying pathophysiology of venom wounds, but will also provide a platform for exploring therapeutic interventions to reduce or resolve snakebite wounds. ### Competing Interest Statement JC has provided consultancy to BioTherapy Services Ltd and received research funds from Mitsubishi Tanabe Pharma for an unrelated project.

Snakebite envenoming remains a devastating and neglected tropical disease, claiming over 100,000 lives annually and causing severe complications and long-lasting disabilities for many more1,2. Three-finger toxins (3FTx) are highly toxic components of elapid snake venoms that can cause diverse pathologies, including severe tissue damage3 and inhibition of nicotinic acetylcholine receptors (nAChRs) resulting in life-threatening neurotoxicity4. Currently, the only available treatments for snakebite consist of polyclonal antibodies derived from the plasma of immunized animals, which have high cost and limited efficacy against 3FTxs5,6,7. Here, we use deep learning methods to de novo design proteins to bind short- and long-chain α-neurotoxins and cytotoxins from the 3FTx family. With limited experimental screening, we obtain protein designs with remarkable thermal stability, high binding affinity, and near-atomic level agreement with the computational models. The designed proteins effectively neutralize all three 3FTx sub-families in vitro and protect mice from a lethal neurotoxin challenge. Such potent, stable, and readily manufacturable toxin-neutralizing proteins could provide the basis for safer, cost-effective, and widely accessible next-generation antivenom therapeutics. Beyond snakebite, our computational design methodology should help democratize therapeutic discovery, particularly in resource-limited settings, by substantially reducing costs and resource requirements for development of therapies to neglected tropical diseases.

Background Across North America an estimated 3,800–6,500 snakebite envenomings occur annually, resulting in 7–15 deaths and an unknown number of disfigurements and disabilities. Most bites are caused by Crotalid snake species. The variable diversity and toxin complexity of crotalid venoms presents a considerable challenge to developing broadly effective small molecule therapeutics to better treat snakebite in this region. Methods We evaluated the ability of three small molecule, toxin inhibiting, repurposed drugs to inhibit the venom activities of six medically important crotalid snake species ( Agkistrodon contortrix, Crotalus atrox, C. adamanteus, C. horridus, C. scutulatus and Sistrurus miliarius ). These drugs target two pathologically relevant venom toxin families, the snake venom metalloproteinases (SVMPs; marimastat and DMPS) and phospholipases A2 (PLA2s; varespladib), and venom inhibition was measured using in vitro enzymatic and phenotypic plasma coagulation assays. Thereafter we evaluated the efficacy of individual drugs and dual drug combinations in in vivo preclinical models of snakebite envenoming, using both preincubation and rescue model formats. Results In vitro bioassays demonstrated that the selected small molecules showed potent inhibition of the enzymatic activity of different toxin families to the nanomolar (varespladib vs PLA2 and marimastat vs SVMP) or micromolar (DMPS vs SVMP) level. Three of the venoms had anticoagulant activity, which varespladib restored to normal coagulation profiles, suggesting this activity is mostly driven by PLA2 toxins. Preclinical experiments revealed that pre-incubation of representative venoms with single drugs was insufficient to completely protect against lethality, except for varespladib against C. scutulatus . Superior efficacy was observed when drugs were used in a combination approach, with the combination of marimastat and varespladib providing greatest protection against lethality in both pre-incubation and rescue models. Conclusions Venom variation among snake species makes the development of generic snakebite therapeutics challenging. In this study we showed that while SVMP and PLA2 inhibiting drugs show inhibitory potency against diverse North American snake venoms, drug combinations consisting of an SVMP inhibitor together with a PLA2 inhibitor are required to confer broad in vivo protection against lethality caused by envenoming. This study highlights the potential long-term value of drug combinations as next-generation therapeutics for snakebite envenoming. ### Competing Interest Statement NRC is named as an inventor on a patent application describing the use of the DMPS and varespladib drug combination as a therapeutic for snakebite indication. * WHO : World Health Organisation FDA : Food and Drug Administration SVMP : Snake Venom Metalloproteinase PLA2 : Phospholipase A2 CLPs : C-type lectin-like proteins LMIC : Low and Middle-Income Country DMPS : 2,3-dimercaptopropane-1-sulfonic acid Wellcome Trust, , 221712/Z/20/Z Medical Research Council, , MC/PC/15040

Snakebite envenoming is a persistent cause of mortality and morbidity worldwide due to the logistical challenges and costs of current antibody-based treatments. Their persistence motivates a broad interest in the discovery of inhibitors against multispecies venom phospholipase A2 (PLA2), which are underway as an alternative or supplemental treatment to improve health outcomes. Here, we present new computational strategies for improved inhibitor classification for challenging metalloenzyme targets across many species, including both a new method to utilize existing molecular docking, and subsequent data normalization. These methods were improved to support experimental screening efforts estimating the broader efficacy of candidate PLA2 inhibitors against diverse viper and elapid venoms.

The scientific study of animal venoms covers a broad phylogenetic domain. We argue that the true extent of this domain has been obscured by researchers having overlooked the biological essence of venom. Venoms manipulate the physiological functioning of recipients to produce extended phenotypes that are beneficial to the venom producer and detrimental to its victim. The ability to produce extended phenotypes in living victims, such as prey paralysis, distinguishes venom from saliva. Understanding venom from this perspective substantially broadens the phylogenetic domain of venom to include taxa that use toxic secretions to feed on plants and manipulate sexual partners, and it paves the way for unifying the field of venomics with the fields that study invertebrate-plant interactions and sexual conflict.

Snake venoms contain variable mixtures of toxins that evolved to incapacitate prey but cause extensive pathology in snakebite patients. In viper venom, the most potent toxins are the haemorrhagic and coagulopathic snake venom metalloproteinases (SVMPs). SVMP research has been hampered by the lack of an efficient generic recombinant production protocol. Using baculovirus/insect cell expression, we produced and functionally validated enzymes from all three structurally variable SVMP classes (PI, PII and PIII). Incorporating the native N-terminal prodomain, which blocks the active site via a cysteine-switch motif, overcame the cytotoxicity of SVMPs. Incubation with Zn2+ activated the SVMP zymogens, resulting in proteolysis of the PIII prodomain. Functional validation of the recombinant SVMPs was performed using protein substrate degradation, platelet aggregation and blood coagulation assays, benchmarked to native venom-purified SVMP. Our study provides a potent generic platform for the expression of SVMPs of value, for bioprospecting and discovery of novel snakebite therapeutics. ### Competing Interest Statement The authors have declared no competing interest. Source data are provided with this paper. European Council, 899670, 101149867 Wellcome Trust, https://ror.org/029chgv08, 221708/Z/20/Z Biotechnology and Biological Sciences Research Council, BB/Y007581/1 Engineering and Physical Sciences Research Council, EP/Z002613/1

Snakebite envenoming is a neglected tropical disease that causes high mortality and morbidity. The current treatment, intravenous antivenom, comes with numerous disadvantages making new therapeutics important. Optimised small molecules offer the possibility for oral use at the onset of envenoming, and the highly pathogenic, zinc-dependent, snake venom metalloproteinase toxin family represents an attractive target for drug discovery. Through systematic chemical modification guided by molecular modelling, we describe the development of hydroxamic acid DC-174, a molecule that displays potent broad spectrum metalloproteinase inhibition and neutralises the procoagulant activities of multiple snake venoms. In oral-dosing studies, DC-174 showed preclinical efficacy in a mouse model of severe envenoming, with efficacy boosted by a pharmacokinetically-informed multiple dosing regimen. This rationally designed metalloproteinase inhibitor offers a potential paradigm shift from delayed treatment with antivenom in tertiary hospitals to a contemporary approach using oral drugs amenable for rapid use in snakebite-affected communities. ### Competing Interest Statement The authors have declared no competing interest. Wellcome Trust, 221712/Z/20/Z

BACKGROUND:Venoms and their associated glands and delivery structures have evolved numerous times among animals. Within these venom systems, the molecular, cellular, and morphological components interact and co-evolve to generate distinct, venom phenotypes that are increasingly recognized as models for studying adaptive evolution. However, toxins are often unevenly distributed across venom-producing tissues in patterns that are not necessarily adaptive but instead likely result from constraints associated with protein secretion. RESULTS:We generate a high-quality draft genome of the Cape coral snake (Aspidelaps lubricus) and combine analyses of venom gland single-cell RNA-seq data with spatial venom gland in situ toxin distributions. Our results reveal that while different toxin families are produced by distinct populations of cells, toxin expression is fine-tuned by regulatory modules that result in further specialization of toxin production within each cell population. We also find that the evolution of regulatory elements closely mirrors the evolution of their associated toxin genes, resulting in spatial association of closely related and functionally similar toxins in the venom gland. While this compartmentalization is non-adaptive, the modularity of the underlying regulatory network likely facilitated the repeated evolution of defensive venom in spitting cobras. CONCLUSIONS:Our results provide new insight into the variability of toxin regulation across snakes, reveal the molecular mechanisms underlying the heterogeneous toxin production in snake venom glands, and provide an example of how constraints can result in non-adaptive character states that appear to be adaptive, which may nevertheless facilitate evolutionary innovation and novelty.

Target product profiles for animal plasma-derived antivenoms: antivenoms for treatment of snakebite envenoming in sub-Saharan Africa [Internet].

INTRODUCTION:The puff adder (Bitis arietans) is a medically important snake species found across much of Africa, yet there is limited literature on the clinical features and pathophysiology of envenoming after a puff adder bite. METHODS:We conducted a case-series study to describe the clinical features of patients with puff adder bites who were treated in two primary healthcare facilities in Kenya and complemented our case-series with a scoping review of all published cases of puff adder envenoming that contained sufficient clinical details to highlight the major features. RESULTS:Between December 2020 and September 2021, 15 patients were admitted with a suspected puff adder bite (based on the patient's description of the biting snake or confirmed in patients who brought the dead snake or a picture of the biting snake for identification) at the Chemolingot and Mwingi sub-county hospitals in Baringo and Kitui counties, central Kenya. Common local and systemic features on admission included pain (n=15, 100%), swelling (n=14, 93%), and haemorrhage (n=9, 60%). Coagulopathy (n=2, 13%), blistering (n=1, 8%) and shock (n=1, 8%) were less common. In addition, we conducted a literature review and identified 23 studies with detailed descriptions of the clinical features of puff adder envenoming from 37 patients. Local features were common and consistent across cases-swelling (100%, n=37) and pain (95%, n=35). Systemic features were less consistent, with 10 (27%) patients exhibiting hypotension on admission, 10 (27%) patients reporting a fever, and 13 (35%) developing anaemia. Some complications were more common in patients with bites by captive snakes (amputations), compared to patients with bites by wild snakes (hypotension). Snake identification was easier and more accurate after bites by captive snakes, but more challenging for patients bitten in community settings. CONCLUSION:We combined clinical cases and a literature review to describe the common and less common clinical features of puff adder envenoming. Further clinical research incorporating serial laboratory assays of patients with definitively identified puff adder bites is crucial to better understand the pathophysiology of envenoming by this medically important snake species.