Venom Ophthalmia and Ocular Complications Caused by Snake Venom

Composition, pharmacology, and pathophysiology of the venom of monocled cobra (Naja kaouthia)- a medically crucial venomous snake of southeast Asia: An updated review

The Monocled Cobra (Naja kaouthia), a category one medically significant snake from the Elapidae family, inflicts severe envenomation in South and Southeast Asian countries. N. kaouthia is distributed throughout the eastern and northeastern parts of India, Nepal, Bangladesh, Myanmar, Thailand, Vietnam, Malaysia, and southwestern China. Envenomation by N. kaouthia is a medical emergency, and the primary clinical symptoms are neurotoxicity and localized tissue destruction. Unfortunately, data on the actual magnitude of N. kaouthia envenomation is scarce due to poor record keeping, lack of diagnostic kits, and region-wise well-coordinated epidemiological surveys. The present review highlights the diversity in the composition of N. Kaouthia venom (NKV) across various geographical regions, as revealed through biochemical and proteomic analyses. The qualitative and quantitative differences in the toxin isoforms result in differences in lethality and pathophysiological manifestation that may limit the effectiveness of antivenom therapy. Studies on commercial polyvalent antivenom (PAV) effectiveness against distinct NKV samples have revealed varying toxicity and enzymatic activity neutralization. Additionally, the identification of snake venom's poorly immunogenic toxins by mass spectrometry, quantification of venom-specific antibodies, and implications for antivenom therapy against snakebites are highlighted. Future directions involve clinical studies on NK envenomation where the snake is frequently encountered and the correlation of this data with NKV composition in that region. For more efficient and superior hospital management of NK envenomation, research should enhance the current immunization procedure to boost the development of antibodies against less immunogenic venom components of this snake.

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.

A review study on forensic optometry: new insights in forensic science to solve crime scenes, domestic violence and sexual assaults

Forensic science has made a lot of progress in the medical field, but still ocular signs are not so well known to forensic scientists, whereas ocular signs play a very important role in forensic science. The major goal of this study to describe the importance of eye related clues in forensic science to solve the crime scenes and know the actual cause of death for the conviction of the criminals and save an innocent persons. Narrative review was done to review the articles available on the PubMed, Google Scholar, Research Gate, Web of Science and Medline related to the forensic optometry about the various methods of identification and strategies to deal with the forensic cases. The review covered studies that focused on interventions for forensic optometry and eye-related clues to the current study target. Twenty-seven of the 54 studies that met the inclusion criteria yielded good results, and all examined the significance of eye-related clues in forensic optometry. Peer reviewed articles/studies were referred to ascertain the eye related clues in the forensic science. Some authors suggest that eye related clues are very important aspects towards the forensic science and done the clinical research on that aspects. Criminal cases, domestic abuse and sexual assault affect people of all socioeconomic backgrounds. As a result, these traits would be highly valuable in determining the way of death and the chronological history of events leading up to a crime.

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.

miRNAs derived from cobra venom exosomes contribute to the cobra envenomation

Currently, there is an increasing amount of evidence indicating that exosomes and the miRNAs they contain are crucial players in various biological processes. However, the role of exosomes and miRNAs in snake venom during the envenomation process remains largely unknown. In this study, fresh venom from Naja atra of different ages (2-month-old, 1-year-old, and 5-year-old) was collected, and exosomes were isolated through ultracentrifugation. The study found that exosomes with inactivated proteins and enzymes can still cause symptoms similar to cobra envenomation, indicating that substances other than proteins and enzymes in exosomes may also play an essential role in cobra envenomation. Furthermore, the expression profiles of isolated exosome miRNAs were analyzed. The study showed that a large number of miRNAs were co-expressed and abundant in cobra venom exosomes (CV-exosomes) of different ages, including miR-2904, which had high expression abundance and specific sequences. The specific miR-2094 derived from CV-exosomes (CV-exo-miR-2904) was overexpressed both in vitro and in vivo. As a result, CV-exo-miR-2904 induced symptoms similar to cobra envenomation in mice and caused liver damage, demonstrating that it plays a crucial role in cobra envenomation. These results reveal that CV-exosomes and the miRNAs they contain play a significant regulatory role in cobra envenomation. Our findings provide new insights for the treatment of cobra bites and the development of snake venom-based medicines.

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.

Bilateral Simultaneous Optic Neuritis Following Envenomations by Indian Cobra and Common Krait

In India, most snakebite envenomation (SBE) incidents are caused by the "Big Four" snakes which include Russell's viper, common krait, Indian cobra, and saw-scaled viper. Their common envenomation effects include neurotoxicity, myotoxicity, and coagulopathy. However, they also induce rare complications such as priapism, pseudoaneurysm, and sialolithiasis. Ocular manifestations such as optic neuritis develop rarely following envenomations by non-spitting snakes and they may cause temporary vision changes and blindness if untreated. While optic neuritis following Indian cobra envenomation has been reported previously, this was not encountered in victims of common kraits. Hence, for the first time, we report optic neuritis developed in a victim following envenomation by a common krait and compare its clinical features and diagnostic and therapeutic methods used with another case of optic neuritis in a victim of an Indian cobra bite. Both patients received antivenom treatment and made an initial recovery; however, optic neuritis developed several days later. The condition was diagnosed using ophthalmic examination together with computed tomography and/or magnetic resonance imaging methods. Due to very similar clinical features, both patients received intravenous corticosteroids which restored their vision and successfully treated optic neuritis. This case report suggests that the optic neuritis developed in a common krait envenomation is comparable to the one developed following a cobra bite, and therefore, the same diagnostic and therapeutic approaches can be used. This study also raises awareness of this rare complication and provides guidance for the diagnosis and treatment of SBE-induced optic neuritis.

Central retinal artery occlusion as an ophthalmic complication after snakebite

Snakebite causes 421.000-1.200.000 poisonings per year due to and hematotoxicity, neurotoxicity y vasculotoxicity. Ophthalmological manifestations secondary to snake bites are rare. If the snake belongs to the Viperidae family, the most frequent ophthalmologic manifestations are macular infarction, chronic open-angle glaucoma, and retinal or vitreous hemorrhage. Central retinal artery occlusion is an extremely rare ocular complication. We report the case of a 30-year-old patient, who consulted due to poor vision in her left eye weeks after suffering a snake bite (Bothrops atrox) in her left lower limb. The diagnosis was a central retinal artery occlusion in the left eye with abnormal findings in the ophthalmological physical examination and in complementary retinal and neuro-ophthalmological tests.

In Vitro neurotoxicity and myotoxicity of Malaysian Naja sumatrana and Naja kaouthia venoms: Neutralization by monovalent and Neuro Polyvalent Antivenoms from Thailand

Naja sumatrana and Naja kaouthia are medically important elapids species found in Southeast Asia. Snake bite envenoming caused by these species may lead to morbidity or mortality if not treated with the appropriate antivenom. In this study, the in vitro neurotoxic and myotoxic effects N. sumatrana and N. kaouthia venoms from Malaysian specimens were assessed and compared. In addition, the neutralizing capability of Cobra Antivenom (CAV), King Cobra Antivenom (KCAV) and Neuro Polyvalent Antivenom (NPAV) from Thailand were compared. Both venoms produced concentration-dependent neurotoxic and myotoxic effects in the chick biventer cervicis nerve-muscle preparation. Based on the time to cause 90% inhibition of twitches (i.e. t₉₀) N. kaouthia venom displayed more potent neurotoxic and myotoxic effects than N. sumatrana venom. All three of the antivenoms significantly attenuated venom-induced twitch reduction of indirectly stimulated tissues when added prior to venom. When added after N. sumatrana venom, at the t₉₀ time point, CAV and NPAV partially restored the twitch height but has no significant effect on the reduction in twitch height caused by N. kaouthia venom. The addition of KCAV, at the t₉₀ time point, did not reverse the attenuation of indirectly stimulated twitches caused by either venom. In addition, none of the antivenoms, when added prior to venom, prevented attenuation of directly stimulated twitches. Differences in the capability of antivenoms, especially NPAV and CAV, to reverse neurotoxicity and myotoxicity indicate that there is a need to isolate and characterize neurotoxins and myotoxins from Malaysian N. kaouthia and N. sumatrana venoms to improve neutralization capability of the antivenoms.

Cerebral Complications of Snakebite Envenoming: Case Studies

There are an estimated 5.4 million snakebite cases every year. People with snakebite envenoming suffer from severe complications, or even death. Although some review articles cover several topics of snakebite envenoming, a review of the cases regarding cerebral complications, especially rare syndromes, is lacking. Here, we overview 35 cases of snakebite by front-fanged snakes, including Bothrops, Daboia, Cerastes, Deinagkistrodon, Trimeresurus, and Crotalus in the Viperidae family; Bungarus and Naja in the Elapidae family, and Homoroselaps (rare cases) in the Lamprophiidae family. We also review three rare cases of snakebite by rear-fanged snakes, including Oxybelis and Leptodeira in the Colubridae family. In the cases of viper bites, most patients (17/24) were diagnosed with ischemic stroke and intracranial hemorrhage, leading to six deaths. We then discuss the potential underlying molecular mechanisms that cause these complications. In cases of elapid bites, neural, cardiac, and ophthalmic disorders are the main complications. Due to the small amount of venom injection and the inability to deep bite, all the rear-fanged snakebites did not develop any severe complications. To date, antivenom (AV) is the most effective therapy for snakebite envenoming. In the six cases of viper and elapid bites that did not receive AV, three cases (two by viper and one by elapid) resulted in death. This indicates that AV treatment is the key to survival after a venomous snakebite. Lastly, we also discuss several studies of therapeutic agents against snakebite-envenoming-induced complications, which could be potential adjuvants along with AV treatment. This article organizes the diagnosis of hemotoxic and neurotoxic envenoming, which may help ER doctors determine the treatment for unidentified snakebite.

Black-necked spitting cobra (Naja nigricollis) phospholipases A2 may cause Trypanosoma brucei death by blocking endocytosis through the flagellar pocket

African trypanosomes, such as Trypanosoma brucei, are flagellated protozoa which proliferate in mammals and cause a variety of diseases in people and animals. In a mammalian host, the external face of the African trypanosome plasma membrane is covered by a densely packed coat formed of variant surface glycoprotein (VSG), which counteracts the host's adaptive immune response by antigenic variation. The VSG is attached to the external face of the plasma membrane by covalent attachment of the C-terminus to glycosylphosphatidylinositol. As the trypanosome grows, newly synthesised VSG is added to the plasma membrane by vesicle fusion to the flagellar pocket, the sole location of exo- and endocytosis. Snake venoms contain dozens of components, including proteases and phospholipases A2. Here, we investigated the effect of Naja nigricollis venom on T. brucei with the aim of describing the response of the trypanosome to hydrolytic attack on the VSG. We found no evidence for VSG hydrolysis, however, N. nigricollis venom caused: (i) an enlargement of the flagellar pocket, (ii) the Rab11 positive endosomal compartments to adopt an abnormal dispersed localisation, and (iii) cell cycle arrest prior to cytokinesis. Our results indicate that a single protein family, the phospholipases A2 present in N. nigricollis venom, may be necessary and sufficient for the effects. This study provides new molecular insight into T. brucei biology and possibly describes mechanisms that could be exploited for T. brucei targeting.

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.

Elucidating the Venom Diversity in Sri Lankan Spectacled Cobra (Naja naja) through De Novo Venom Gland Transcriptomics, Venom Proteomics and Toxicity Neutralization

Inadequate effectiveness of Indian antivenoms in treating envenomation caused by the Spectacled Cobra/Indian Cobra (Naja naja) in Sri Lanka has been attributed to geographical variations in the venom composition. This study investigated the de novo venom-gland transcriptomics and venom proteomics of the Sri Lankan N. naja (NN-SL) to elucidate its toxin gene diversity and venom variability. The neutralization efficacy of a commonly used Indian antivenom product in Sri Lanka was examined against the lethality induced by NN-SL venom in mice. The transcriptomic study revealed high expression of 22 toxin genes families in NN-SL, constituting 46.55% of total transcript abundance. Three-finger toxins (3FTX) were the most diversely and abundantly expressed (87.54% of toxin gene expression), consistent with the dominance of 3FTX in the venom proteome (72.19% of total venom proteins). The 3FTX were predominantly S-type cytotoxins/cardiotoxins (CTX) and α-neurotoxins of long-chain or short-chain subtypes (α-NTX). CTX and α-NTX are implicated in local tissue necrosis and fatal neuromuscular paralysis, respectively, in envenomation caused by NN-SL. Intra-species variations in the toxin gene sequences and expression levels were apparent between NN-SL and other geographical specimens of N. naja, suggesting potential antigenic diversity that impacts antivenom effectiveness. This was demonstrated by limited potency (0.74 mg venom/ml antivenom) of the Indian polyvalent antivenom (VPAV) in neutralizing the NN-SL venom. A pan-regional antivenom with improved efficacy to treat N. naja envenomation is needed.

[Haemorrhagic Stroke after Snakebite Envenomation Resulting in Irreversible Blindness in a 6-Year-Old Child in Mali]

Introduction

Snakebite envenomation can cause serious damage. Here, we report the case of a six-year-old male child bitten by a snake.

Clinical description

The child presented a gingivorrhagia, abdominal pain, bloody vomiting and severe headache from a snakebite. Neurological examination showed paralysis of the III cranial nerve associated with bilateral blindness and mydriasis, unreactive on the right. The brain scan revealed a left frontal hematoma. The course on antivenom was marked by the disappearance of clinical signs except blindness which remained 18 months after discharge.

Discussion - Conclusion

The hemorrhagic syndrome evoked viper bite. Blindness is rarely seen as a result of viperine envenomation. In our case, the presence of intracranial hypertension, absence of ocular lesions and scanner were in favor of compression of the optic nerves which resulted in permanent blindness.

Effects of Sodium Silicate Complex against Hemorrhagic Activities Induced by Protobothrops mucrosquamatus Venom

Protobothrops mucrosquamatus poses a serious medical threat to humans in Southern and Southeastern Asia. Hemorrhage is one of the conspicuous toxicities related to the pathology of P. mucrosquamatus envenoming. Previous in vitro and in vivo studies showed that a silica-derived reagent, sodium silicate complex (SSC), was able to neutralize hemorrhagic and proteolytic activities induced by pit viper venoms, including Crotalus atrox, Agkistrodon contortrix contortrix and Agkistrodon piscivorus leucostoma. In this study, we validated that SSC could neutralize enzymatic and toxic effects caused by the venom of P. mucrosquamatus. We found that SSC inhibited the hemolytic and proteolytic activities induced by P. mucrosquamatus venom in vitro. In addition, we demonstrated that SSC could block intradermal hemorrhage caused by P. mucrosquamatus venom in a mouse model. Finally, SSC could neutralize lethal effects of P. mucrosquamatus venom in the mice. Therefore, SSC is a candidate for further development as a potential onsite first-aid treatment for P. mucrosquamatus envenoming.

A Neurotoxic Snake Venom without Phospholipase A2: Proteomics and Cross-Neutralization of the Venom from Senegalese Cobra, Naja senegalensis (Subgenus: Uraeus)

The Senegalese cobra, Naja senegalensis, is a non-spitting cobra species newly erected from the Naja haje complex. Naja senegalensis causes neurotoxic envenomation in Western Africa but its venom properties remain underexplored. Applying a protein decomplexation proteomic approach, this study unveiled the unique complexity of the venom composition. Three-finger toxins constituted the major component, accounting for 75.91% of total venom proteins. Of these, cardiotoxin/cytotoxin (~53%) and alpha-neurotoxins (~23%) predominated in the venom proteome. Phospholipase A₂, however, was not present in the venom, suggesting a unique snake venom phenotype found in this species. The venom, despite the absence of PLA₂, is highly lethal with an intravenous LD₅₀ of 0.39 µg/g in mice, consistent with the high abundance of alpha-neurotoxins (predominating long neurotoxins) in the venom. The hetero-specific VINS African Polyvalent Antivenom (VAPAV) was immunoreactive to the venom, implying conserved protein antigenicity in the venoms of N. senegalensis and N. haje. Furthermore, VAPAV was able to cross-neutralize the lethal effect of N. senegalensis venom but the potency was limited (0.59 mg venom completely neutralized per mL antivenom, or ~82 LD₅₀ per ml of antivenom). The efficacy of antivenom should be further improved to optimize the treatment of cobra bite envenomation in Africa.