Arachnid toxinology in Australia: From clinical toxicology to potential applications

Comprehensive analysis of the global impact and distribution of tick paralysis, a deadly neurological yet fully reversible condition

SUMMARYTick paralysis is a potentially fatal condition caused by neurotoxins secreted by the salivary glands of certain ticks. Documented cases have been reported worldwide, predominantly in the United States, Canada, and Australia, with additional reports from Europe and Africa. This condition also affects animals, leading to significant economic losses and adverse impacts on animal health and welfare. To date, 75 tick species, mostly hard ticks, have been identified as capable of causing this life-threatening condition. Due to symptom overlap with other conditions, accurate diagnosis of tick paralysis is crucial to avoid misdiagnosis, which could result in adverse patient outcomes. This review provides a comprehensive analysis of the current literature on tick paralysis, including the implicated tick species, global distribution, tick toxins, molecular pathogenesis, clinical manifestations, diagnosis, treatment, control, and prevention. Enhancing awareness among medical and veterinary professionals is critical for improving the management of tick paralysis and its health impacts on both humans and animals.

Australian Scorpion Hormurus waigiensis Venom Fractions Show Broad Bioactivity Through Modulation of Bio-Impedance and Cytosolic Calcium

Scorpion venoms are a rich source of bioactive molecules, but characterisation of toxin peptides affecting cytosolic Ca2+, central to cell signalling and cell death, is limited. We undertook a functional screening of the venom of the Australian scorpion Hormurus waigiensis to determine the breadth of Ca2+ mobilisation. A human embryonic kidney (HEK293) cell line stably expressing the genetically encoded Ca2+ reporter GCaMP5G and the rabbit type 1 ryanodine receptor (RyR1) was developed as a biosensor. Size-exclusion Fast Protein Liquid Chromatography separated the venom into 53 fractions, constituting 12 chromatographic peaks. Liquid chromatography mass spectroscopy identified 182 distinct molecules with 3 to 63 components per peak. The molecular weights varied from 258 Da-13.6 kDa, with 53% under 1 kDa. The majority of the venom chromatographic peaks (tested as six venom pools) were found to reversibly modulate cell monolayer bioimpedance, detected using the xCELLigence platform (ACEA Biosciences). Confocal Ca2+ imaging showed 9/14 peak samples, with molecules spanning the molecular size range, increased cytosolic Ca2+ mobilization. H. waigiensis venom Ca2+ activity was correlated with changes in bio-impedance, reflecting multi-modal toxin actions on cell physiology across the venom proteome.

Tick killing in situ before removal to prevent allergic and anaphylactic reactions in humans: a cross-sectional study

BACKGROUND

Tick anaphylaxis is a potentially fatal outcome of improper tick removal and management.

OBJECTIVE

To investigate whether killing ticks in-situ with ether-containing sprays or permethrin cream, before careful removal by the mouthparts could reduce this risk.

METHODS

This was a prospective study at Mona Vale Hospital Emergency Department (ED) in Sydney, New South Wales, over a 6-month period during the peak tick season of 2016. Tick removal methods, allergic/anaphylactic reactions were recorded for patients presenting with ticks in situ or having already removed the ticks themselves. Primary endpoint was allergic/anaphylactic reaction after tick killing/removal.

RESULTS

One hundred twenty-one patients met study inclusion criteria. Sixty-one patients (28 known tick-hypersensitive) had ticks killed with Wart-Off Freeze or Lyclear Scabies Cream (5% w/w permethrin) before removal with fine-tipped forceps or Tick Twister. Three patients (2 known tick-hypersensitive) had allergic reactions (5%), none anaphylactic. The 2 known hypersensitive patients suffered reactions during the killing process and the third patient had a particularly embedded tick meaning it could not be removed solely by mouthparts. Fifty patients presented to the ED posttick removal by various methods, none using either fine-tipped forceps or Tick Twister, of which 43 (86%) experienced allergic reactions - 2 anaphylactic. Five patients suffered allergic reactions before presentation despite no attempt at kill or removal, but ticks had likely been disturbed by some other method. Five patients had live ticks removed in ED - 3 refused killing and had no reaction despite 1 having known hypersensitivity; 2 had ticks on eyelids contraindicating killing, 1 with known hypersensitivity but both had allergic reactions post removal.

CONCLUSION

Results support killing ticks in-situ before careful removal by mouthparts to reduce allergic/anaphylactic reactions although further research is still required.

Scorpion toxin peptide action at the ion channel subunit level

This review categorizes functionally validated actions of defined scorpion toxin (SCTX) neuropeptides across ion channel subclasses, highlighting key trends in this rapidly evolving field. Scorpion envenomation is a common event in many tropical and subtropical countries, with neuropharmacological actions, particularly autonomic nervous system modulation, causing significant mortality. The primary active agents within scorpion venoms are a diverse group of small neuropeptides that elicit specific potent actions across a wide range of ion channel classes. The identification and functional characterisation of these SCTX peptides has tremendous potential for development of novel pharmaceuticals that advance knowledge of ion channels and establish lead compounds for treatment of excitable tissue disorders. This review delineates the unique specificities of 320 individual SCTX peptides that collectively act on 41 ion channel subclasses. Thus the SCTX research field has significant translational implications for pathophysiology spanning neurotransmission, neurohumoral signalling, sensori-motor systems and excitation-contraction coupling. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'

Arachnids of medical importance in Brazil: main active compounds present in scorpion and spider venoms and tick saliva

Arachnida is the largest class among the arthropods, constituting over 60,000 described species (spiders, mites, ticks, scorpions, palpigrades, pseudoscorpions, solpugids and harvestmen). Many accidents are caused by arachnids, especially spiders and scorpions, while some diseases can be transmitted by mites and ticks. These animals are widely dispersed in urban centers due to the large availability of shelter and food, increasing the incidence of accidents. Several protein and non-protein compounds present in the venom and saliva of these animals are responsible for symptoms observed in envenoming, exhibiting neurotoxic, dermonecrotic and hemorrhagic activities. The phylogenomic analysis from the complementary DNA of single-copy nuclear protein-coding genes shows that these animals share some common protein families known as neurotoxins, defensins, hyaluronidase, antimicrobial peptides, phospholipases and proteinases. This indicates that the venoms from these animals may present components with functional and structural similarities. Therefore, we described in this review the main components present in spider and scorpion venom as well as in tick saliva, since they have similar components. These three arachnids are responsible for many accidents of medical relevance in Brazil. Additionally, this study shows potential biotechnological applications of some components with important biological activities, which may motivate the conducting of further research studies on their action mechanisms.

The complexity and structural diversity of ant venom peptidomes is revealed by mass spectrometry profiling

RATIONALE

Compared with other animal venoms, ant venoms remain little explored. Ants have evolved complex venoms to rapidly immobilize arthropod prey and to protect their colonies from predators and pathogens. Many ants have retained peptide-rich venoms that are similar to those of other arthropod groups.

METHODS

With the goal of conducting a broad and comprehensive survey of ant venom peptide diversity, we investigated the peptide composition of venoms from 82 stinging ant species from nine subfamilies using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS). We also conducted an in-depth investigation of eight venoms using reversed-phase high-performance liquid chromatography (RP-HPLC) separation coupled with offline MALDI-TOFMS.

RESULTS

Our results reveal that the peptide compositions of ant venom peptidomes from both poneroid and formicoid ant clades comprise hundreds of small peptides (<4 kDa), while large peptides (>4 kDa) are also present in the venom of formicoids. Chemical reduction revealed the presence of disulfide-linked peptides in most ant subfamilies, including peptides structured by one, two or three disulfide bonds as well as dimeric peptides reticulated by three disulfide bonds.

CONCLUSIONS

The biochemical complexity of ant venoms, associated with an enormous ecological and taxonomic diversity, suggests that stinging ant venoms constitute a promising source of bioactive molecules that could be exploited in the search for novel drug and biopesticide leads.

Venomous and poisonous Australian animals of veterinary importance: a rich source of novel therapeutics

Envenomation and poisoning by terrestrial animals (both vertebrate and invertebrate) are a significant economic problem and health risk for domestic animals in Australia. Australian snakes are some of the most venomous animals in the world and bees, wasps, ants, paralysis ticks, and cane toads are also present as part of the venomous and poisonous fauna. The diagnosis and treatment of envenomation or poisoning in animals is a challenge and can be a traumatic and expensive process for owners. Despite the potency of Australian venoms, there is potential for novel veterinary therapeutics to be modeled on venom toxins, as has been the case with human pharmaceuticals. A comprehensive overview of envenomation and poisoning signs in livestock and companion animals is provided and related to the potential for venom toxins to act as therapeutics.

Scorpion peptides: potential use for new drug development

Several peptides contained in scorpion fluids showed diverse array of biological activities with high specificities to their targeted sites. Many investigations outlined their potent effects against microbes and showed their potential to modulate various biological mechanisms that are involved in immune, nervous, cardiovascular, and neoplastic diseases. Because of their important structural and functional diversity, it is projected that scorpion-derived peptides could be used to develop new specific drugs. This review summarizes relevant findings improving their use as valuable tools for new drugs development.

Distribution, seasonality and risk factors for tick paralysis in Australian dogs and cats

Tick paralysis is a serious and potentially fatal condition of Australian companion animals induced by the paralysis ticks, Ixodes holocyclus and Ixodes cornuatus. Limited published information is available on the distribution, seasonality and risk factors for tick paralysis mortality in dogs and cats. This study describes 3479 cases of canine and feline tick paralysis in Australia using data extracted from a real-time disease surveillance program. Risk factors for mortality were identified, and maps of the distribution of cases were generated. Cluster analysis was performed using a space-time permutation scan statistic. Tick paralysis was found to be distinctly seasonal, with most cases reported during spring. Most cases were located on the eastern coast of Australia with New South Wales and Queensland accounting for the majority of reported cases. A cluster of cases was identified on the south coast of New South Wales. Dogs were found to be at significantly higher risk (P<0.05) of death if less than 6 months of age or if a toy breed. No significant risk factors for mortality were identified for cats. Some animals receiving chemoprophylactic treatment for tick infestation experienced tick paralysis during the products' period of effectiveness. There is a high risk of tick paralysis in dogs and cats on the eastern coast of Australia during the spring months. The risk factors for mortality identified can be used by veterinarians to determine prognosis in cases of canine tick paralysis and potentially to improve the treatment of cases. Daily tick searches of pets - particularly in high risk areas and during high risk periods - are recommended since the prevention of tick paralysis via chemoprophylaxis is not 100% guaranteed across the whole population.

Identification and molecular characterization of three new K+-channel specific toxins from the Chinese scorpion Mesobuthus martensii Karsch revealing intronic number polymorphism and alternative splicing in duplicated genes

K(+)-channel specific toxins from scorpions are powerful probes used in the structural and functional characterization of different subfamilies of K(+)-channels which are thought to be the most diverse ion channels. However, only a limited number of K(+)-channel toxins have been identified from scorpions so far; moreover, little is known about the mechanisms for the generation of a combinatorial peptide library in a venom gland of a scorpion. Here, we identified and characterized three new K(+)-channel toxin-like peptides from the scorpion Mesobuthus martensii Karsch, which were referred to as BmKcug1, BmKcug2 and BmKcugx, respectively. BmKcug1 and BmKcug2 are two new members of α-KTx1 subfamily, and have been classified as α-KTx1.14 and α-KTx1.15, respectively. BmKcugx represents a new subfamily of K(+)-channel specific toxins which was classified into α-KTx22. BmKcugx was thus classified as α-KTx22.1. Genomic analysis demonstrated that BmKcugx gene has two exons interrupted by an intron inserted in the signal peptide encoding region, whereas BmKcug1a (a close homologue of BmKcug1)/BmKcug2 gene was interrupted by two introns, located within the 5'UTR of the gene and in the signal peptide encoding region, respectively. Transcriptomic analysis for the venom glands of M. martensii Karsch indicated that the abundances of the transcripts of BmKcug1a and BmKcug2 are much higher than that of BmKcugx; it suggests that the intron in 5'UTR could markedly increase the expression level of the K(+)-channel toxins. Alignment of the genomic sequences of BmKcug1a and BmKcug2 revealed that an alternative splicing event occurred at the intron 1-exon 2 junction in the 5'UTR of BmKcug2 transcript.

Spider-venom peptides as bioinsecticides

Over 10,000 arthropod species are currently considered to be pest organisms. They are estimated to contribute to the destruction of ~14% of the world's annual crop production and transmit many pathogens. Presently, arthropod pests of agricultural and health significance are controlled predominantly through the use of chemical insecticides. Unfortunately, the widespread use of these agrochemicals has resulted in genetic selection pressure that has led to the development of insecticide-resistant arthropods, as well as concerns over human health and the environment. Bioinsecticides represent a new generation of insecticides that utilise organisms or their derivatives (e.g., transgenic plants, recombinant baculoviruses, toxin-fusion proteins and peptidomimetics) and show promise as environmentally-friendly alternatives to conventional agrochemicals. Spider-venom peptides are now being investigated as potential sources of bioinsecticides. With an estimated 100,000 species, spiders are one of the most successful arthropod predators. Their venom has proven to be a rich source of hyperstable insecticidal mini-proteins that cause insect paralysis or lethality through the modulation of ion channels, receptors and enzymes. Many newly characterized insecticidal spider toxins target novel sites in insects. Here we review the structure and pharmacology of these toxins and discuss the potential of this vast peptide library for the discovery of novel bioinsecticides.

Tick paralysis in Australia caused by Ixodes holocyclus Neumann

Ticks are obligate haematophagous ectoparasites of various animals, including humans, and are abundant in temperate and tropical zones around the world. They are the most important vectors for the pathogens causing disease in livestock and second only to mosquitoes as vectors of pathogens causing human disease. Ticks are formidable arachnids, capable of not only transmitting the pathogens involved in some infectious diseases but also of inducing allergies and causing toxicoses and paralysis, with possible fatal outcomes for the host. This review focuses on tick paralysis, the role of the Australian paralysis tick Ixodes holocyclus, and the role of toxin molecules from this species in causing paralysis in the host.

Neurotoxic and insecticidal properties of venom from the Australian theraphosid spider Selenotholus foelschei

The present study is the first report on the bioactivity of venom from the Australian theraphosid spider Selenotholus foelschei. Venom from female specimens was used in all experiments. Adult spiders yielded an average of 2.2 mg dried venom per milking with a maximum yield of 7.2 mg. To evaluate the activity of pooled S. foelschei venom in invertebrates, a toxicity test in crickets (Acheta domesticus) was used. The results suggest the presence of several insecticidal toxins with different but synergistic modes of action, leading to a fast onset of paralysis as well as persistent paralysis and lethal effects (starting at 4 h after injection) in crickets. Vertebrate activity of S. foelschei venom was tested by using the isolated chick biventer cervicis nerve-muscle preparation. The venom produced a significant reduction in baseline tension (at a concentration of 10 microg/mL) and twitch height (at 0.2-10 microg/mL). Twitches were not restored after repeated washing. The response of the muscle to exogenous acetylcholine (1 mM) and carbachol (0.02 mM) was not reduced by the venom. These results indicate the presence of a vertebrate-active neurotoxin in S. foelschei that irreversibly blocks muscle twitches by acting either on voltage-activated Na(+)-channels or on other pre-synaptically located receptors.

Venomics: unravelling the complexity of animal venoms with mass spectrometry

Animal venoms and toxins are now recognized as major sources of bioactive molecules that may be tomorrow's new drug leads. Their complexity and their potential as drug sources have been demonstrated by application of modern analytical technologies, which have revealed venoms to be vast peptide combinatorial libraries. Structural as well as pharmacological diversity is immense, and mass spectrometry is now one of the major investigative tools for the structural investigation of venom components. Recent advances in its use in the study of venom and toxins are reviewed. The application of mass spectrometry techniques to peptide toxin sequence determination by de novo sequencing is discussed in detail, in the light of the search for novel analgesic drugs. We also present the combined application of LC-MALDI separation with mass fingerprinting and ISD fragmentation for the determination of structural and pharmacological classes of peptides in complex spider venoms. This approach now serves as the basis for the full investigation of complex spider venom proteomes, in combination with cDNA analysis.

An outbreak of tick paralysis in free-ranging mouflon (Ovis ammon musimon)

During November 2006, two live and one dead mouflon (Ovis ammon musimon) were presented with a history of weakness, tremors, and paralysis. After a detailed gross and histologic examination and a bacteriologic, parasitologic, and rabies evaluation, a preliminary diagnosis of tick paralysis was established. A thorough field search revealed 13 affected mouflons found in the open hunting ground "Sveti Juraj" near the town of Senj (Croatia), along with an additional 35 mouflon carcasses. All 13 mouflons were placed in a quiet, semidark stable. All detectable ticks were removed manually, and the animals were topically treated with 250 ppm of Amitraz water emulsion (Taktic 12.5% EC, Intervet International, 5830 Boxmeer, Netherlands). The collected ticks were identified as Ixodes ricinus, Dermacentor marginatus, and Haemaphysalis punctata. In the following 24 hr, all treated animals recovered fully. This report describes a naturally occurring outbreak of tick paralysis in free-ranging mouflons from a karst habitat.

Medical aspects of spider bites

Spiders have been incriminated as causes of human suffering for centuries, but few species worldwide cause medically significant envenomation. Widow spiders (Latrodectus spp.) occur worldwide and cause latrodectism, which is characterized by pain (local and generalized) associated with nonspecific systemic effects, diaphoresis, and less commonly other autonomic and neurological effects. Recluse spiders (Loxosceles spp.) are distributed mostly through the tropical and subtropical Western Hemisphere and can cause severe skin lesions and rarely systemic effects; most bites are unremarkable. Highly dangerous spiders in South America (armed spiders) and Australia (funnel-web spiders) cause rare but severe envenomation requiring medical intervention and sometimes antivenom. Most other spiders involved in verified bites cause minor, transient effects. Many spiders blamed for causing medical mischief have been elevated to medical significance via circumstantial evidence, poor reporting, and repetitive citation in the literature; several species have been shown to be harmless with more stringent scientific evidence involving verified bites in humans.

Twentieth century toxinology and antivenom development in Australia

It was not until the last decade of the 19th century that an experimental approach (led by Bancroft in Queensland and Martin in Sydney and Melbourne) brought a higher plane of scientific objectivity to usher in the modern era of Australian toxinology. This Australia era, 1895-1905, coincided with and in some respects was the result of the new knowledge emerging from Europe and the Americas of the therapeutic effects of antitoxins. The subsequent systematic study of Australian venoms and toxins through to the 1930s and beyond, by Tidswell, Fairley, Ross, Kellaway and Cleland, set the foundation for Australia's leading reputation in venom research. As elsewhere, this development was to revolutionise the medical management of those victims who in the past had died in Australia from our venomous and toxic fauna. Morgan, Graydon, Weiner, Lane and Baxter at the Commonwealth Serum Laboratories emphasised the importance of cooperation between those expert at catching and milking the venomous creatures and those developing the antivenoms. Commercial antivenom manufacture began in Australia in 1930 with the tiger snake antivenom. This was followed by other antivenoms for the other important species (1955: taipan; 1956: brown snake; 1958: death adder; 1959: Papuan black snake; 1961: sea snake; 1962: polyvalent) including the first marine antivenoms in the world (1956: stonefish antivenom; 1970: box jellyfish) culminating, in 1980, with the release of the funnel web spider antivenom. More recent activity has focused on veterinary antivenoms and production of new generation human antivenoms for export (CroFab and ViperaTAB). This paper reviews some of the milestones of Australian toxinology, and antivenom development in particular, during the 20th century.