Venom ophthalmia caused by venoms of spitting elapid and other snakes: Report of ten cases with review of epidemiology, clinical features, pathophysiology and management

A comparison of the venom proteomes and potential therapeutics of 3 African naja subgenera

African cobras (Naja species) represent one of the most encountered medically important snakes in Africa. They are classified as African spitting (Afronaja subgenus) and non-spitting cobras (Uraeus and Boulengerina subgenera) with similar and different characteristics. Snake venom toxins including three-finger toxin (3FTx), phospholipase A2 (PLA2), and snake venom metalloproteinase (SVMP) cause snakebite envenomation leading to morbidity and mortality. The profile of the proteome of African cobra venoms will help to develop safer and more effective antivenoms. The approval of Captopril by the US Food and Drug Administration (FDA) for the treatment of cardiovascular diseases, has led to intensified research towards possible use of venom toxins as therapeutics. In this review, we compare the venom proteome profile of 3 African Naja subgenera. In both Afronaja and Boulengerina subgenera, 3FTx (Afronaja-69.79%; Boulengerina-60.56%) followed by PLA2 (Afronaja-21.15%; Boulengerina-20.21%) dominated the venoms compared to the Uraeus subgenus dominated by 3FTx (84.55%) with little to no PLA2 abundance (0.8%). The venom of subgenus Uraeus was distinct from the other two subgenera by the almost total absence of PLA2, thus indicating little or no contribution of PLA2 in the envenomation caused by Uraeus compared to Afronaja and Boulengerina. Furthermore, we report studies on the experimental testing of African cobra venoms and toxins against diseases including anti-cancer properties.

Snake eyes: Characterization of topical ocular exposures from rattlesnakes in Arizona

Patients occasionally present with reports of ocular exposure to fluids from rattlesnakes, claiming or suspecting the substance to be venom. This study set out to evaluate and characterize reported cases of suspected venom-induced ophthalmia in humans. A retrospective review of rattlesnake exposures reported to the Arizona Poison and Drug Information Center over a 24-year period was conducted for ocular exposures. Recorded information included patient demographics, clinical course, laboratory results, and treatments. Documentation regarding interactions between patients and snakes was reviewed by Arizona Poison and Drug Information Center herpetologists to evaluate what substance was expelled from the snake resulting in ocular exposure. Our review of rattlesnake encounters found a total of 26 ocular exposure cases. Patient demographics were largely intentional interactions and involved the male sex. Symptoms ranged from asymptomatic to minor effects with 46.2% managed from home and treated with fluid irrigation. A review of cases by herpetologists concluded the exposure patients commonly experienced was to snake musk. Kinematics of venom expulsion by rattlesnakes conclude the venom gland must be compressed, fangs erected to ≥60o, and fang sheath compressed against the roof of the mouth for venom expulsion. Evidence suggests the chance of venom "spitting" by rattlesnakes is close to zero. Rattlesnakes are documented to forcefully expel airborne malodorous "musk" defensively. An important distinction to remember is musk has a foul odor and is usually colorless, while venom is comparatively odorless and yellow. Rattlesnake venom-induced ophthalmia is a rare event as venom expulsion requires the kinematics of feeding or defensive bites. If the rattlesnake is not in the process of biting or otherwise contacting some other object with its mouth, it is more biologically plausible patients are being exposed to snake musk as a deterrent. Whether it's venom or musk, topical exposure to the eyes should prompt immediate irrigation.

Wilderness Medical Society Clinical Practice Guidelines for Treatment of Eye Injuries and Illnesses in the Wilderness: 2024 Update

A panel convened to develop an evidence-based set of guidelines for the recognition and treatment of eye injuries and illnesses that may occur in the wilderness. These guidelines are meant to serve as a tool to help wilderness providers accurately identify and subsequently treat or evacuate for a variety of ophthalmologic complaints. Recommendations are graded based on the quality of their supporting evidence and the balance between risks and benefits according to criteria developed by the American College of Chest Physicians.

A Retrospective Cohort Study of Cobra Envenomation: Clinical Characteristics, Treatments, and Outcomes

This study investigated the clinical characteristics, treatments, and outcomes of envenomation involving cobra species in Thailand (Naja kaouthia, Naja siamensis, and Naja sumatrana). Data of patients who had been bitten by a cobra or inoculated via the eyes/skin in 2018-2021 were obtained from the Ramathibodi Poison Center. There were 1045 patients admitted during the 4-year study period (bite, n = 539; ocular/dermal inoculation, n = 506). Almost all patients with ocular/dermal inoculation had eye involvement and ocular injuries, but none had neurological effects. Most of the patients bitten by a cobra had local effects (69.0%) and neurological signs and symptoms (55.7%). The median interval between the bite and the onset of neurological symptoms was 1 h (range, 10 min to 24 h). Accordingly, patients should be observed closely in hospitals for at least 24 h after a bite. Intubation with ventilator support was required in 45.5% of patients and for a median duration of 1.1 days. Antivenom was administered in 63.5% of cases. There were nine deaths, most of which resulted from severe infection. Neurological effects and intubation were significantly more common after a monocled cobra bite than after a spitting cobra bite. The administration of antivenom with good supportive care, including the appropriate management of complications, especially wound infection, might decrease fatality.

A rare case of Panophthalmitis due to cobra bite

PURPOSE

Ocular manifestations of snake bite are rare, ranging from direct injury to the eye from snake venom or indirect injury due to antivenom. We report a rare case of cobra bite causing panophthalmitis due to indirect injury as a result of snake venom toxin related tissue necrosis and susceptibility to secondary infections.

METHODS

Observational case report. External photographs, slit lamp photos, ultrasonography of the eye and histopathology of the eviscerated eye were used to characterize and describe the clinical findings. Thirty-nine-years-old male farmer presented with history of cobra snake bite on his right index finger and developed right eye sudden onset pain and redness 3 days later. On examination, features were suggestive of panophthalmitis and the eye had to be eviscerated with scleral excision.

CONCLUSION

It is important for ophthalmologist to be aware of such grave consequences of snake bite to be prepared for the emergency management of such cases.

Bites by Non-Native Reptiles in France: Species, Circumstances and Outcome

We aimed to make an exhaustive assessment of circumstances of bites by exotic reptiles bred in France. A retrospective observational study was conducted in all the reported cases from 2000 to 2020 in French poison control centers (PCCs). Two hundred and eighteen cases of bites were recorded. The sex ratio (M/F) of the patients was 1.79 and the mean age of the patients was 29.0 ± 15.8 years. Twenty-two cases (10.1%) occurred during the deep night. One hundred and eighty-six bites (85.7%) occurred in a private context; however, there were more cases of high severity when it occurred in a professional setting (60.0% vs. 11.2%, p < 0.01). The feeding/nursing activity accounted for 54.7% cases. Forty-three species of snake were identified; 28 were considered venomous. There were no deaths among the patients in the study. Most of the cases (85.8%) were of mild severity. All of the patients bitten by a venomous reptile were hospitalized: 10 patients received an antivenom; and 2 required surgery. Bites occurred at home and by a small number of popular non-venomous reptile species (pythons and boas, colubrids). These occurred mainly when handling the animals. The rare envenomations were mainly by Asian and American crotalids, followed by elapids. One-third of them were treated with antivenom when available.

Cytotoxicity of Venoms and Cytotoxins from Asiatic Cobras (Naja kaouthia, Naja sumatrana, Naja atra) and Neutralization by Antivenoms from Thailand, Vietnam, and Taiwan

Envenoming by cobras (Naja spp.) often results in extensive local tissue necrosis when optimal treatment with antivenom is not available. This study investigated the cytotoxicity of venoms and purified cytotoxins from the Monocled Cobra (Naja kaouthia), Taiwan Cobra (Naja atra), and Equatorial Spitting Cobra (Naja sumatrana) in a mouse fibroblast cell line, followed by neutralization of the cytotoxicity by three regional antivenoms: the Thai Naja kaouthia monovalent antivenom (NkMAV), Vietnamese snake antivenom (SAV) and Taiwanese Neuro bivalent antivenom (NBAV). The cytotoxins of N. atra (NA-CTX) and N. sumatrana (NS-CTX) were identified as P-type cytotoxins, whereas that of N. kaouthia (NK-CTX) is S-type. All venoms and purified cytotoxins demonstrated varying concentration-dependent cytotoxicity in the following trend: highest for N. atra, followed by N. sumatrana and N. kaouthia. The antivenoms moderately neutralized the cytotoxicity of N. kaouthia venom but were weak against N. atra and N. sumatrana venom cytotoxicity. The neutralization potencies of the antivenoms against the cytotoxins were varied and generally low across NA-CTX, NS-CTX, and NK-CTX, possibly attributed to limited antigenicity of CTXs and/or different formulation of antivenom products. The study underscores the need for antivenom improvement and/or new therapies in treating local tissue toxicity caused by cobra envenomings.

Review of the Mechanisms of Snake Venom Induced Pain: It's All about Location, Location, Location

Pain—acute, chronic and debilitating—is the most feared neurotoxicity resulting from a survivable venomous snake bite. The purpose of this review is to present in a novel paradigm what we know about the molecular mechanisms responsible for pain after envenomation. Progressing from known pain modulating peptides and enzymes, to tissue level interactions with venom resulting in pain, to organ system level pain syndromes, to geographical level distribution of pain syndromes, the present work demonstrates that understanding the mechanisms responsible for pain is dependent on “location, location, location”. It is our hope that this work can serve to inspire the molecular and epidemiologic investigations needed to better understand the neurotoxic mechanisms responsible for these snake venom mediated diverse pain syndromes and ultimately lead to agent specific treatments beyond anti-venom alone.

Snake Venom Proteomics of Samar Cobra (Naja samarensis) from the Southern Philippines: Short Alpha-Neurotoxins as the Dominant Lethal Component Weakly Cross-Neutralized by the Philippine Cobra Antivenom

The Samar Cobra, Naja samarensis, is endemic to the southern Philippines and is a WHO-listed Category 1 venomous snake species of medical importance. Envenomation caused by N. samarensis results in neurotoxicity, while there is no species-specific antivenom available for its treatment. The composition and neutralization of N. samarensis venom remain largely unknown to date. This study thus aimed to investigate the venom proteome of N. samarensis for a comprehensive profiling of the venom composition, and to examine the immunorecognition as well as neutralization of its toxins by a hetero-specific antivenom. Applying C₁₈ reverse-phase high-performance liquid chromatography (RP-HPLC) and tandem mass spectrometry (LC-MS/MS), three-finger toxins (3FTx) were shown to dominate the venom proteome by 90.48% of total venom proteins. Other proteins in the venom comprised snake venom metalloproteinases, phospholipases A_2, cysteine-rich secretory proteins, venom nerve growth factors, L-amino acid oxidases and vespryn, which were present at much lower abundances. Among all, short-chain alpha-neurotoxins (SαNTX) were the most highly expressed toxin within 3FTx family, constituting 65.87% of the total venom proteins. The SαNTX is the sole neurotoxic component of the venom and has an intravenous median lethal dose (LD₅₀) of 0.18 μg/g in mice. The high abundance and low LD₅₀ support the potent lethal activity of N. samarensis venom. The hetero-specific antivenom, Philippine Cobra Antivenom (PCAV, raised against Naja philippinensis) were immunoreactive toward the venom and its protein fractions, including the principal SαNTX. In efficacy study, PCAV was able to cross-neutralize the lethality of SαNTX albeit the effect was weak with a low potency of 0.20 mg/ml (defined as the amount of toxin completely neutralized per milliliter of the antivenom). With a volume of 5 ml, each vial of PCAV may cross-neutralize approximately 1 mg of the toxin in vivo. The findings support the potential para-specific use of PCAV in treating envenomation caused by N. samarensis while underscoring the need to improve the potency of its neutralization activity, especially against the highly lethal alpha-neurotoxins.

The Relative Efficacy of Chemically Diverse Small-Molecule Enzyme-Inhibitors Against Anticoagulant Activities of African Spitting Cobra (Naja Species) Venoms

African spitting cobras are unique among cobras for their potent anticoagulant venom activity arising from strong inhibition of Factor Xa. This anticoagulant effect is exerted by venom phospholipase A₂ (Group I PLA₂) toxins whose activity contributes to the lethality of these species. This anticoagulant toxicity is particularly problematic as it is not neutralized by current antivenoms. Previous work demonstrated this trait for Naja mossambica, N. nigricincta, N. nigricollis, and N. pallida. The present work builds upon previous research by testing across the full taxonomical range of African spitting cobras, demonstrating that N. ashei, N. katiensis, and N. nubiae are also potently anticoagulant through the inhibition of Factor Xa, and therefore the amplification of potent anticoagulant activity occurred at the base of the African spitting cobra radiation. Previous work demonstrated that the enzyme-inhibitor varespladib was able to neutralize this toxic action for N. mossambica, N. nigricincta, N. nigricollis, and N. pallida venoms. The current work demonstrates that varespladib was also able to neutralize N. ashei, N. katiensis, and N. nubiae. Thus varespladib is shown to have broad utility across the full range of African spitting cobras. In addition, we examined the cross-reactivity of the metalloprotease inhibitor prinomastat, which had been previously intriguingly indicated as being capable of neutralizing viperid venom PLA₂ (Group II PLA₂). In this study prinomastat inhibited the FXa-inhibiting PLA₂ toxins of all the African spitting cobras at the same concentration at which it has been shown to inhibit metalloproteases, and thus was comparably effective in its cross-reactivity. In addition we showed that the metalloprotease-inhibitor marimastat was also able to cross-neutralize PLA₂ but less effectively than prinomastat. Due to logistical (cold-chain requirement) and efficacy (cross-reactivity across snake species) limitations of traditional antivenoms, particularly in developing countries where snakebite is most common, these small molecule inhibitors (SMIs) might hold great promise as initial, field-based, treatments for snakebite envenoming as well as addressing fundamental limitations of antivenom in the clinical setting where certain toxin effects are unneutralized.

Proteomic characterization of Naja mandalayensis venom

Background

Naja mandalayensis is a spitting cobra from Myanmar. To the best of our knowledge, no studies on this venom composition have been conducted so far. On the other hand, few envenomation descriptions state that it elicits mainly local inflammation in the victims’ eyes, the preferred target of this spiting cobra. Symptoms would typically include burning and painful sensation, conjunctivitis, edema and temporary loss of vision.

Methods

We have performed a liquid-chromatography (C18-RP-HPLC) mass spectrometry (ESI-IT-TOF/MS) based approach in order to biochemically characterize N. mandalayensis venom.

Results

A wide variety of three-finger toxins (cardiotoxins) and metallopeptidases were detected. Less abundant, but still representative, were cysteine-rich secretory proteins, L-amino-acid oxidases, phospholipases A₂, venom 5'-nucleotidase and a serine peptidase inhibitor. Other proteins were present, but were detected in a relatively small concentration.

Conclusion

The present study set the basis for a better comprehension of the envenomation from a molecular perspective and, by increasing the interest and information available for this species, allows future venom comparisons among cobras and their diverse venom proteins.

Animal Venoms-Curse or Cure?

An estimated 15% of animals are venomous, with representatives spread across the majority of animal lineages. Animals use venoms for various purposes, such as prey capture and predator deterrence. Humans have always been fascinated by venomous animals in a Janus-faced way. On the one hand, humans have a deeply rooted fear of venomous animals. This is boosted by their largely negative image in public media and the fact that snakes alone cause an annual global death toll in the hundreds of thousands, with even more people being left disabled or disfigured. Consequently, snake envenomation has recently been reclassified by the World Health Organization as a neglected tropical disease. On the other hand, there has been a growth in recent decades in the global scene of enthusiasts keeping venomous snakes, spiders, scorpions, and centipedes in captivity as pets. Recent scientific research has focussed on utilising animal venoms and toxins for the benefit of humanity in the form of molecular research tools, novel diagnostics and therapeutics, biopesticides, or anti-parasitic treatments. Continued research into developing efficient and safe antivenoms and promising discoveries of beneficial effects of animal toxins is further tipping the scales in favour of the “cure” rather than the “curse” prospect of venoms.

Unexpected lack of specialisation in the flow properties of spitting cobra venom

Venom spitting is a defence mechanism based on airborne venom delivery used by a number of different African and Asian elapid snake species ('spitting cobras'; Naja spp. and Hemachatus spp.). Adaptations underpinning venom spitting have been studied extensively at both behavioural and morphological level in cobras, but the role of the physical properties of venom itself in its effective projection remains largely unstudied. We hereby provide the first comparative study of the physical properties of venom in spitting and non-spitting cobras. We measured the viscosity, protein concentration and pH of the venom of 13 cobra species of the genus Naja from Africa and Asia, alongside the spitting elapid Hemachatus haemachatus and the non-spitting viper Bitis arietans By using published microCT scans, we calculated the pressure required to eject venom through the fangs of a spitting and a non-spitting cobra. Despite the differences in the modes of venom delivery, we found no significant differences between spitters and non-spitters in the rheological and physical properties of the studied venoms. Furthermore, all analysed venoms showed a Newtonian flow behaviour, in contrast to previous reports. Although our results imply that the evolution of venom spitting did not significantly affect venom viscosity, our models of fang pressure suggests that the pressure requirements to eject venom are lower in spitting cobras than in non-spitting cobras.

Comparative venomics and preclinical efficacy evaluation of a monospecific Hemachatus antivenom towards sub-Saharan Africa cobra venoms

Cobras are the most medically important elapid snakes in Africa. The African genera Naja and Hemachatus include snakes with neurotoxic and cytotoxic venoms, with shared biochemical, toxinological and antigenic characteristics. We have studied the antigenic cross-reactivity of four sub-Saharan Africa cobra venoms against an experimental monospecific Hemachatus haemachatus antivenom through comparative proteomics, preclinical assessment of neutralization, and third generation antivenomics. The venoms of H. haemachatus, N. annulifera, N. mossambica and N. nigricollis share an overall qualitative family toxin composition but depart in their proportions of three-finger toxin (3FTxs) classes, phospholipases A₂ (PLA₂s), snake venom metalloproteinases (SVMPs), and cysteine-rich secretory proteins (CRISPs). A monospecific anti-Hemachatus antivenom produced by Costa Rican Instituto Clodomiro Picado neutralized the lethal activity of the homologous and heterologous neuro/cytotoxic (H. haemachatus) and cyto/cardiotoxic (N. mossambica and N. nigricollis) venoms of the three spitting cobras sampled, while it was ineffective against the lethal and toxic activities of the neurotoxic venom of the non-spitting snouted cobra N. annulifera. The ability of the anti-Hemachatus-ICP antivenom to neutralize toxic (dermonecrotic and anticoagulant) and enzymatic (PLA₂) activities of spitting cobra venoms suggested a closer kinship of H. haemachatus and Naja subgenus Afrocobra spitting cobras than to Naja subgenus Uraeus neurotoxic taxa. These results were confirmed by third generation antivenomics. BIOLOGICAL SIGNIFICANCE: African Naja species represent the most widespread medically important elapid snakes across Africa. To gain deeper insight into the spectrum of medically relevant toxins, we compared the proteome of three spitting cobras (Hemachatus haemachatus, Naja mossambica and N. nigricollis) and one non-spitting cobra (N. annulifera). Three finger toxins and phospholipases A₂ are the two major protein families among the venoms analyzed. The development of antivenoms of broad species coverage is an urgent need in sub-Saharan Africa. An equine antivenom raised against H. haemachatus venom showed cross-reactivity with the venoms of H. haemachatus, N. mossambica and N. nigricollis, while having poor recognition of the venom of N. annulifera. This immunological information provides clues for the design of optimum venom mixtures for the preparation of broad spectrum antivenoms.

Convergent evolution of pain-inducing defensive venom components in spitting cobras

Convergent evolution provides insights into the selective drivers underlying evolutionary change. Snake venoms, with a direct genetic basis and clearly defined functional phenotype, provide a model system for exploring the repeated evolution of adaptations. While snakes use venom primarily for predation, and venom composition often reflects diet specificity, three lineages of cobras have independently evolved the ability to spit venom at adversaries. Using gene, protein, and functional analyses, we show that the three spitting lineages possess venoms characterized by an up-regulation of phospholipase A2 (PLA2) toxins, which potentiate the action of preexisting venom cytotoxins to activate mammalian sensory neurons and cause enhanced pain. These repeated independent changes provide a fascinating example of convergent evolution across multiple phenotypic levels driven by selection for defense.

Venom Ophthalmia and Ocular Complications Caused by Snake Venom

Little is known about the detailed clinical description, pathophysiology, and efficacy of treatments for ocular envenoming (venom ophthalmia) caused by venom of the spitting elapid and other snakes, as well as ocular complications caused by snake venom injection. In this paper, we review clinical information of case reports regarding venom ophthalmia and snake venom injection with associated ocular injuries in Asia, Africa, and the United States. We also review the literature of snake venom such as their compositions, properties, and toxic effects. Based on the available clinical information and animal studies, we further discuss possible mechanisms of venom ophthalmia derived from two different routes (Duvernoy's gland in the mouth and nuchal gland in the dorsal neck) and the pathophysiology of snake venom injection induced ocular complications, including corneal edema, corneal erosion, cataract, ocular inflammation, retinal hemorrhage, acute angle closure glaucoma, as well as ptosis, diplopia, and photophobia. Finally, we discuss the appropriate first aid and novel strategies for treating venom ophthalmia and snake envenoming.

Clinical importance of the Mandalay spitting cobra (Naja mandalayensis) in Upper Myanmar - Bites, envenoming and ophthalmia

Examination of 18 cobras brought to three hospitals in the Mandalay Region by patients bitten or spat at by them distinguished 3 monocled cobras (Naja kaouthia) and 15 Mandalay spitting cobras (N. mandalayensis), based on their morphological characteristics. We confirm and extend the known distributions and habitats of both N. mandalayensis and N. kaouthia in Upper Myanmar. Clinical symptoms of local and systemic envenoming by N. mandalayensis are described for the first time. These included local swelling, blistering and necrosis and life-threatening systemic neurotoxicity. More information is needed about the clinical phenotype and management of bites by N. mandalayensis, the commoner of the two cobras in Upper Myanmar. Since the current cobra antivenom manufactured in Myanmar has lower pre-clinical efficacy against N. mandalayensis than N. kaouthia, there is a need for more specific antivenom therapy.

Naja atra venom-spit ophthalmia in Taiwan: An epidemiological survey from 1990 to 2016

BACKGROUND

Venomous snakebites are common during hot seasons in Taiwan. However, rarely is venom spat directly into the subject's eyes, causing eye injury. Despite being uncommon, analytical data regarding venom-spit ophthalmia in Taiwan have been lacking. This study thus aimed to conduct an epidemiological survey on Naja atra venom-spit ophthalmia in Taiwan during the past decades to improve future care of such patients.

METHODS

Registered records of cases with snake venom injuries at the Taiwan National Poison Control Center from 1990 to 2016 were retrospectively reviewed, enrolling those with records of cobra venom-spit eye injuries and excluding exotic species. Demographic data, clinical symptoms, snake species, ocular conditions, management, and outcomes were recorded and analyzed.

RESULTS

A total of 39 cases suffering from Naja atra venom-spit ophthalmia were enrolled. The overall incidence rate was 1.6 cases per million people from 1990 to 2016. Among the included cases, most were unilaterally injured (82%), male (95%), aged 18 to 59 years (90%), injured during catching (51%), and injured in spring and summer (92%). Ocular symptoms occurred in 90% of the cases, majority of which included ocular pain (90%) and redness (85%). Conjunctivitis (67%) and corneal injury (59%) of involved eyes were common. Immediate water irrigations were done in all cases, most of whom received further topical eye drops, including antibiotics, corticosteroids, and vasoconstrictors. Although topical or intravenous antivenoms were administered in 11 cases, no obviously superior outcome was observed. Most cases (77%) were symptom free after the acute stage.

CONCLUSION

Although Naja atra venom-spit ophthalmia in Taiwan is uncommon, the risk for transient ocular symptoms and corneal/conjunctival injury does exists. Prompt ocular irrigation and professional ophthalmic care after envenomation help prevent serious ocular sequelae. Moreover, superior outcomes were not achieved with the use of antivenom. Nonetheless, further studies are required to clarify the role antivenoms play in venom-spit ophthalmia.

Venomous Bites, Stings, and Poisoning: An Update

This article discusses the epidemiology, prevention, clinical features, and treatment of venomous bites by snakes, lizards, and spiders; stings by fish, jellyfish, echinoderms, insects, and scorpions; and poisoning by ingestion of fish, turtles, and shellfish. Invertebrate stings cause fatalities by anaphylaxis, secondary to acquired hypersensitivity (Hymenoptera, such as bees, wasps, and ants; and jellyfish), and by direct envenoming (scorpions, spiders, jellyfish, and echinoderms). Simple preventive techniques, such as wearing protective clothing, using a flashlight at night, and excluding venomous animals from sleeping quarters, are of paramount importance to reduce the risk of venomous bites and stings.

Proteomic insights into short neurotoxin-driven, highly neurotoxic venom of Philippine cobra (Naja philippinensis) and toxicity correlation of cobra envenomation in Asia

The Philippine cobra, Naja philippinensis, is a WHO Category 1 venomous snake of medical importance responsible for fatal envenomation in the northern Philippines. To elucidate the venom proteome and pathophysiology of envenomation, N. philippinensis venom proteins were decomplexed with reverse-phase high-performance liquid chromatography, and protein fractions were subsequently digested with trypsin, followed by nano-liquid chromatography-tandem mass spectrometry analysis and data mining. Three-finger toxins (3FTX, 66.64% of total venom proteins) and phospholipases A₂ (PLA₂, 22.88%) constitute the main bulk of venom proteome. Other proteins are present at low abundances (<4% each); these include metalloproteinase, serine protease, cobra venom factor, cysteine-rich secretory protein, vespryn, phosphodiesterase, 5' nucleotidase and nerve growth factor. In the three-finger toxin family, the alpha-neurotoxins comprise solely short neurotoxins (SNTX, 44.55%), supporting that SNTX is the principal toxin responsible for neuromuscular paralysis and lethality reported in clinical envenomation. Cytotoxins (CTX) are the second most abundant 3FTX proteins in the venom (21.31%). The presence of CTX correlates with the venom cytotoxic effect, which is more prominent in murine cells than in human cells. From the practical standpoint, SNTX-driven neuromuscular paralysis is significant in N. philippinensis envenomation. Antivenom production and treatment should be tailored accordingly to ensure effective neutralization of SNTX. BIOLOGICAL SIGNIFICANCE: The venom proteome of Naja philippinensis, the Philippine cobra, is unravelled for the first time. Approximately half the protein bulk of the venom is made up of short neurotoxins (44.55% of the total venom proteins). As the only alpha-neurotoxins present in the venom, short neurotoxins are the causative toxins of the post-synaptic blockade and fast-onset neuromuscular paralysis in N. philippinensis envenomation. A substantial amount of cytotoxins (21.31%) was also detected in N. philippinensis venom, supporting that the venom can be cytotoxic although the effect is much weaker in human cells compared to murine cells. The finding is consistent with the low incidence of local tissue necrosis in N. philippinensis envenomation, although this does not negate the need for monitoring and care of bite wound in the patients.

A Review of Corneal Endotheliitis and Endotheliopathy: Differential Diagnosis, Evaluation, and Treatment

The corneal endothelium plays an integral role in regulating corneal hydration and clarity. Endotheliitis, defined as inflammation of the corneal endothelium, may disrupt endothelial function and cause subsequent visual changes. Corneal endotheliitis is characterized by corneal edema, the presence of keratic precipitates, anterior chamber inflammation, and occasionally limbal injection, neovascularization, and co-existing or superimposed uveitis. The disorder is classified into four subgroups: linear, sectoral, disciform, and diffuse. Its etiology is extensive and, although commonly viral, may be medication-related, procedural, fungal, zoological, environmental, or systemic. Not all cases of endothelial dysfunction leading to corneal edema are inflammatory in nature. Therefore, it is imperative that practitioners consider a broad differential for patients presenting with possible endotheliitis, as well as familiarize themselves with appropriate diagnostic and therapeutic modalities.

Long-term Effects of Snake Envenoming

Long-term effects of envenoming compromise the quality of life of the survivors of snakebite. We searched MEDLINE (from 1946) and EMBASE (from 1947) until October 2018 for clinical literature on the long-term effects of snake envenoming using different combinations of search terms. We classified conditions that last or appear more than six weeks following envenoming as long term or delayed effects of envenoming. Of 257 records identified, 51 articles describe the long-term effects of snake envenoming and were reviewed. Disability due to amputations, deformities, contracture formation, and chronic ulceration, rarely with malignant change, have resulted from local necrosis due to bites mainly from African and Asian cobras, and Central and South American Pit-vipers. Progression of acute kidney injury into chronic renal failure in Russell's viper bites has been reported in several studies from India and Sri Lanka. Neuromuscular toxicity does not appear to result in long-term effects. Endocrine anomalies such as delayed manifestation of hypopituitarism following Russell's viper bites have been reported. Delayed psychological effects such as depressive symptoms, post-traumatic stress disorder and somatisation have been reported. Blindness due to primary and secondary effects of venom is a serious, debilitating effect. In general, the available studies have linked a clinical effect to a snakebite in retrospect, hence lacked accurate snake authentication, details of acute management and baseline data and are unable to provide a detailed picture of clinical epidemiology of the long-term effects of envenoming. In the future, it will be important to follow cohorts of snakebite patients for a longer period of time to understand the true prevalence, severity, clinical progression and risk factors of long-term effects of snake envenoming.

Snake Eyes: Coral Snake Neurotoxicity Associated With Ocular Absorption of Venom and Successful Treatment With Exotic Antivenom

BACKGROUND

Coral snake bites from Micrurus fulvius and Micrurus tener account for < 1% of all snake bites in North America. Coral snake envenomation may cause significant neurotoxicity, including respiratory insufficiency, and its onset may be delayed up to 13 h.

CASE REPORT

We present a unique patient encounter of M. tener venom exposure through the ocular mucous membranes and a small cutaneous bite, resulting in neurotoxicity. To our knowledge, this is the first reported case of systemic neurotoxicity associated with ocular contact with coral snake venom. Our patient developed rapid-onset skeletal muscle weakness, which is very uncommon for M. tener, along with cranial nerve deficits. Acquisition of antivenom was challenging, but our patient provides a rare report of resolution of suspected M. tener neurotoxicity after receiving Central American coral snake (Micrurus nigrocinctus) antivenom. Our patient subsequently developed serum sickness, a known delayed complication of antivenom. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The emergency physician should be aware that coral snake venom may be absorbed through different routes. Neurotoxicity and respiratory insufficiency may be fatal and onset may be delayed up to 13 h. North American Coral Snake Antivenom is in very limited supply, so non-Food and Drug Administration-approved alternative coral snake antivenoms may be used for patients demonstrating neurotoxicity. Emergency physicians should be proactive in contacting a toxicologist to procure antivenom, as well as consideration of adjunctive treatments, such as neostigmine. Furthermore, whole immunoglobulin G products, such as antivenom, may result in immediate and delayed reactions.

Canine ocular and periocular snakebites requiring enucleation: A report of 19 cases

PURPOSE

To describe the clinical and histopathologic features secondary to ocular and periocular snakebites in dogs requiring enucleation.

METHODS

Retrospective review of patients with recorded snakebite envenomation from the archives of the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) and Texas A&M Veterinary Medical Teaching Hospital (1997-2017). The cases included in this study required witnessed snakebites to the dog by the owner, clinical signs supportive of periocular or ocular envenomation, and/or histopathologic lesions compatible with snakebites. Two groups were established: ocular bites (OB) and periocular bites (PB).

RESULTS

Nineteen cases were included in the study (OB = 16/19; PB = 3/19). Dogs affected were typically older (median 8 years; range 1-18), and both sexes were equally represented. Left eyes (14/19) were more likely to sustain snake-induced trauma compared to right eyes (5/19). Fifteen breeds were identified, with terriers (9/19) commonly represented. Snakes bites occurred in six US states, with the majority of cases from Texas (7/19), California (5/19), and Arizona (4/19). Common clinical signs included facial edema, corneal ulceration, keratomalacia, uveitis, hyphema, and secondary glaucoma. All eyes demonstrated vision loss prior to enucleation. Histologically, the ocular and periocular tissues contained extensive necrosis associated with envenomation. Retinal detachment, lens capsule rupture, and intraocular hemorrhage/inflammation were commonly found.

CONCLUSIONS

Snakebite envenomation is a largely necrotizing disease process that can result in profound infiltrative and destructive ocular changes presumed to be related to the proteolytic factors and necrotoxins in venom. Ocular alterations secondary to snakebites may be irreversible regardless of supportive therapy instituted.

The Ex vivo Eye Irritation Test (EVEIT) model as a mean of improving venom ophthalmia understanding

Snakes belonging to the genus Naja (Elapid family), also known as "spitting cobras", can spit venom towards the eyes of the predator as a defensive strategy, causing painful and potentially blinding ocular envenoming. Venom ophthalmia is characterized by pain, hyperemia, blepharitis, blepharospasm and corneal erosions. Elapid venom ophthalmia is not well documented and no specific treatment exists. Furthermore, accidental ejection of venom by non-spitting vipers, as Bothrops, also occurs. The Ex vivo Eye Irritation Test model (EVEIT) has enabled important progress in the knowledge of chemical ocular burns. Considering the lack of experimental animal model, we adapted the EVEIT to study venom ophthalmia mechanisms. Ex vivo rabbit corneas were exposed to venoms from spitting (Naja mossambica, Naja nigricollis) and non-spitting (Naja naja, Bothrops jararaca and Bothrops lanceolatus) snakes, and rinsed or not with water. The corneal thickness and the depth of damage were assessed using high-resolution optical coherence tomography (HR-OCT) imaging and histological analysis. All Naja venoms induced significant corneal edema, collagen structure disorganization and epithelial necrosis. Corneas envenomed by African N. mossambica and N. nigricollis venoms were completely opaque. Opacification was not observed in corneas treated with venoms from non-spitting snakes, such as the Asian cobra, N. naja, and the vipers, B. jararaca and B. lanceolatus. Moreover, Bothrops venoms were able to damage the epithelium and cause collagen structure disorganization, but not edema. Immediate water rinsing improved corneal status, though damage and edema could still be observed. In conclusion, the present study shows that the EVEIT model was successfully adapted to set a new experimental ex vivo animal model of ophthalmia, caused by snake venoms, which will enable to explore new therapies for venom ophthalmia.

Snakebites in Africa and Europe: a military perspective and update for contemporary operations

Snakebite envenoming is rare among military patients, with few cases reported in recent years. Increasingly, however, military operations are taking place in remote parts of Africa, which are inhabited by numerous species of venomous snake, and in Europe, where dangerous species exist but are less common. Bites from a venomous snake may prove fatal, and therefore military medics must be adequately prepared to manage them. This paper reviews the most medically significant species of venomous snake present in Africa and Europe, before suggesting an evidence-based approach to snakebite prevention and management, including possible changes to the UK's Clinical Guidelines for Operations.

Case of venom ophthalmia following contact with Naja pallida: the red spitting cobra

Venom ophthalmia is a condition that can be eyesight threatening. This article describes a case of venom ophthalmia due to the Naja pallida (red spitting cobra) and is aimed to educate readers regarding the management of an uncommon, yet important, pathology that deployed military personnel may encounter. Simple first steps can reduce the impact of the injury with copious irrigation of the eye being the key management step. Each step of the management, including what not to do, is discussed in order to educate and act as a guide to all deployed healthcare professionals.

Ophthalmia Secondary to Cobra Venom Spitting in the Volta Region, Ghana: A Case Report

Purpose

To report the first case of ophthalmia due to contact with cobra venom in the Volta Region, Ghana.

Methods

An ointment containing vitamin A was applied to treat the patient's unilateral defects in the corneal epithelium and the consequent diminished visual acuity.

Results

Healing of the corneal epithelium and improvement of visual acuity were observed after only 1 day.

Conclusions

This case suggests that consequences of cases of cobra venom spitting in the eyes can be minimal if immediate treatment is provided.

Prospective, consecutive case series of 158 snakebite patients treated at Savannakhet provincial hospital, Lao People's Democratic Republic with high incidence of anaphylactic shock to horse derived F(ab')2 antivenom

Snakebites are a seriously neglected public health problem in Lao PDR. Community-based cross-sectional surveys in two districts of Savannakhet province in Southern Laos revealed an incidence of up to 1105 snakebites per 100,000 persons per year. In contrast the number of snakebite patients treated in district and provincial hospitals are low. In order to improve health care for snakebite victims, antivenom was introduced to Savannakhet provincial hospital in July 2013 and medical staff has been trained in management of venomous snakebites at the same time. After the intervention the number of snakebite patients treated at the provincial hospital increased significantly from 4 patients in 2012 to 158 snakebite patients between July 2013 and November 2015. They were included into a prospective, consecutive case series. Median age was 32 years (range 1.5-70 years) and male-to-female ratio 2.2:1. Forty patients were bitten by Malayan pit vipers, 26 by green pit vipers, 24 by cobras, including 3 cases of venom ophthalmia, 5 by kraits, 8 by non-venomous species and in 55 cases the snake could not be identified. Forty-three out of 158 patients received horse derived F(ab')2 antivenom from Queen Saovabha Memorial Institute (QSMI) in Bangkok. Twenty-three patients (53%) developed early adverse reactions (EARs) within one hour after antivenom administration, including 13 patients (30%) with severe anaphylaxis. This extremely high rate of severe EARs turns the use of antivenom into a risky intervention. In contrast a retrospective chart review from Chulalongkorn University in Bangkok found only 3.5% early reactions including 1.2% severe anaphylactic reactions using the same antivenom from QSMI between 1997 and 2006. The reason for this enormous difference remains unclear. A better understanding of the aetiology and pathophysiology behind antivenom induced anaphylaxis is crucial in order to identify patients at risk and to improve safety of antivenom administration.

Ocular Manifestations of Venomous Snake Bite over a One-year Period in a Tertiary Care Hospital

Purpose

Ocular manifestations in snake-bite injuries are quite rare. However, the unusual presentations, diagnosis and their management can pose challenges when they present to the ophthalmologist. Early detection of these treatable conditions can prevent visual loss in these patients who are systemically unstable and are unaware of their ocular condition. To address this, a study was conducted with the aim of identifying the various ocular manifestations of snake bite in a tertiary care center.

Methods

This is a one-year institute-based prospective study report of 12 snake bite victims admitted to a tertiary hospital with ocular manifestations between June 2013 to June 2014, which provides data about the demographic characteristics, clinical profiles, ocular manifestations, and their outcomes.

Results

Twelve cases of snake bite with ocular manifestations were included of which six were viper bites, three were cobra bites and three were unknown bites. Six patients presented with bilateral acute angle closure glaucoma (50%), two patients had anterior uveitis (16.6%) of which one patient had concomitant optic neuritis. One patient had exudative retinal detachment (8.3%), one patient had thrombocytopenia with subconjunctival hemorrhage (8.3%) and two patients had external ophthalmoplegia (16.6%).

Conclusions

Bilateral angle closure glaucoma was the most common ocular manifestation followed by anterior uveitis and external ophthalmoplegia. Snake bite can result in significant ocular morbidity in a majority of patients but spontaneous recovery with anti-snake venom, steroids and conservative management results in good visual prognosis.

Venomics, lethality and neutralization of Naja kaouthia (monocled cobra) venoms from three different geographical regions of Southeast Asia

Previous studies showed that venoms of the monocled cobra, Naja kaouthia from Thailand and Malaysia are substantially different in their median lethal doses. The intraspecific venom variations of N. kaouthia, however, have not been fully elucidated. Here we investigated the venom proteomes of N. kaouthia from Malaysia (NK-M), Thailand (NK-T) and Vietnam (NK-V) through reverse-phase HPLC, SDS-PAGE and tandem mass spectrometry. The venom proteins comprise 13 toxin families, with three-finger toxins being the most abundant (63-77%) and the most varied (11-18 isoforms) among the three populations. NK-T has the highest content of neurotoxins (50%, predominantly long neurotoxins), followed by NK-V (29%, predominantly weak neurotoxins and some short neurotoxins), while NK-M has the least (18%, some weak neurotoxins but less short and long neurotoxins). On the other hand, cytotoxins constitute the main bulk of toxins in NK-M and NK-V venoms (up to 45% each), but less in NK-T venom (27%). The three venoms show different lethal potencies that generally reflect the proteomic findings. Despite the proteomic variations, the use of Thai monovalent and Neuro polyvalent antivenoms for N. kaouthia envenomation in the three regions is appropriate as the different venoms were neutralized by the antivenoms albeit at different degrees of effectiveness.

BIOLOGICAL SIGNIFICANCE

Biogeographical variations were observed in the venom proteome of monocled cobra (Naja kaouthia) from Malaysia, Thailand and Vietnam. The Thai N. kaouthia venom is particularly rich in long neurotoxins, while the Malaysian and Vietnamese specimens were predominated with cytotoxins. The differentially expressed toxin profile accounts for the discrepancy in the lethal dose of the venom from different populations. Commercially available Thai antivenoms (monovalent and polyvalent) were able to neutralize the three venoms at different effective doses, hence supporting their uses in the three regions. While dose adjustment according to geographical region seems possible, changes to standard recommended dosage should only be made if further study validates that the monocled cobras within a population do not exhibit remarkable inter-individual venom variation.

Venom-spraying behavior of the scorpion Parabuthus transvaalicus (Arachnida: Buthidae)

Many animals use chemical squirting or spraying behavior as a defensive response. Some members of the scorpion genus Parabuthus (family Buthidae) can spray their venom. We examined the stimulus control and characteristics of venom spraying by Parabuthus transvaalicus to better understand the behavioral context for its use. Venom spraying occurred mostly, but not always, when the metasoma (tail) was contacted (usually grasped by forceps), and was absent during stinging-like thrusts of the metasoma apart from contact. Scorpions were significantly more likely to spray when contact was also accompanied by airborne stimuli. Sprays happened almost instantaneously following grasping by forceps (median=0.23s) as a brief (0.07-0.30s, mean=0.18s), fine stream (<5° arc) that was not directed toward the stimulus source; however, rapid independent movements of the metasoma and/or telson (stinger) often created a more diffuse spray, increasing the possibility of venom contact with the sensitive eyes of potential scorpion predators. Successive venom sprays varied considerably in duration and velocity. Collectively, these results suggest that venom spraying might be useful as an antipredator function and can be modulated based on threat.

Venom ophthalmia from Naja mossambica in KwaZulu Natal, South Africa: a reminder to all that for ocular chemical injury, dilution is the solution

Venom ophthalmia caused by venoms of spitting elapids such as the Mozambique Spitting Cobra (Naja mossambica) is seen in regions where people live in close proximity to elapids, such as in the KwaZulu Natal region of South Africa. We report such a case in a 43-year-old woman who presented to Mosvold Hospital, a district hospital in South Africa. Clinical features and best practice management of venom ophthalmia will be discussed.

Ophthalmia due to spitting cobra venom in an urban setting--a report of three cases

To describe three presentations of spitting cobra venom induced ophthalmia in urban Singapore. Case notes and photographs of three patients with venom ophthalmia who presented to our clinic between 2007 and 2012 were reviewed. Two patients encountered the spitting cobra while working at a job site while the third patient had caught the snake and caged it. The venom entered the eyes in all 3 cases. Immediate irrigation with tap water was carried out before presenting to the Accident and Emergency department. All patients were treated medically with topical antibiotic prophylaxis and copious lubricants. The use of anti-venom was not required in any case. All eyes recovered with no long-term sequelae. If irrigation is initiated early, eyes can recover with no significant complications or sequelae.

Adder bite on eyelid along with retained intraorbital fangs

PURPOSE

Snake bite to the eye is a rare event. Most cases reported in the literature are due to boa constrictor bites. This is a rare case of snake bite from a common adder (Vipera berus) to the ocular adnexa along with a retained intraorbital tooth.

METHOD

A 57-year-old man presented with a history of being bitten by an adder in the left eye upper lid 12 days previously while bending down to pick up a log at his farm. He developed a firm, tender lump in the medial part of his left upper eyelid.

RESULT

A CT scan revealed an extraconal curved calcific dense foreign body, about 5 mm in length consistent with adder's tooth in the superomedial part of left orbit.

CONCLUSION

There are few reports of adder bites on face, ear and neck. We report a rare case of adder bite on eyelid along with retained intraorbital fangs and its clinical outcome.

Poisons, toxungens, and venoms: redefining and classifying toxic biological secretions and the organisms that employ them

Despite extensive study of poisonous and venomous organisms and the toxins they produce, a review of the literature reveals inconsistency and ambiguity in the definitions of 'poison' and 'venom'. These two terms are frequently conflated with one another, and with the more general term, 'toxin.' We therefore clarify distinctions among three major classes of toxins (biological, environmental, and anthropogenic or man-made), evaluate prior definitions of venom which differentiate it from poison, and propose more rigorous definitions for poison and venom based on differences in mechanism of delivery. We also introduce a new term, 'toxungen', thereby partitioning toxic biological secretions into three categories: poisons lacking a delivery mechanism, i.e. ingested, inhaled, or absorbed across the body surface; toxungens delivered to the body surface without an accompanying wound; and venoms, delivered to internal tissues via creation of a wound. We further propose a system to classify toxic organisms with respect to delivery mechanism (absent versus present), source (autogenous versus heterogenous), and storage of toxins (aglandular versus glandular). As examples, a frog that acquires toxins from its diet, stores the secretion within cutaneous glands, and transfers the secretion upon contact or ingestion would be heteroglandular-poisonous; an ant that produces its own toxins, stores the secretion in a gland, and sprays it for defence would be autoglandular-toxungenous; and an anemone that produces its own toxins within specialized cells that deliver the secretion via a penetrating wound would be autoaglandular-venomous. Adoption of our scheme should benefit our understanding of both proximate and ultimate causes in the evolution of these toxins.