Membrane interactions and biological activity of antimicrobial peptides from Australian scorpion.

UyCT peptides are antimicrobial peptides isolated from the venom of the Australian scorpion. The activity of the UyCT peptides against Gram positive and Gram negative bacteria and red blood cells was determined. The membrane interactions of these peptides were evaluated by dye release (DR) of the fluorophore calcein from liposomes and isothermal titration calorimetry (ITC); and their secondary structure was determined by circular dichroism (CD). Three different lipid systems were used to mimic red blood cells, Escherichia coli and Staphylococcus aureus membranes. UyCT peptides exhibited broad spectrum antimicrobial activity with low MIC for S. aureus and multi-drug resistant Gram negative strains. Peptide combinations showed some synergy enhancing their potency but not hemolytic activity. The UyCT peptides adopted a helical structure in lipid environments and DR results confirmed that the mechanism of action is by disrupting the membrane. ITC data indicated that UyCT peptides preferred prokaryotic rather than eukaryotic membranes. The overall results suggest that UyCT peptides could be pharmaceutical leads for the treatment of Gram negative multiresistant bacterial infections, especially against Acinetobacter baumanni, and candidates for peptidomimetics to enhance their potency and minimize hemolysis. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.

The Human Health Impacts of the Red Imported Fire Ant in the Western Pacific Region Context: A Narrative Review.

Background: The red imported fire ant (RIFA) is one of the world's most destructive invasive species. RIFA stings are painful and can lead to allergic reactions, including life-threatening anaphylaxis, yet health impacts remain inadequately defined. Methods: We searched MEDLINE (Ovid) and Google Scholar (grey literature) from inception until 20 September 2023 for articles in English using search terms related to red imported fire ants and allergies, including anaphylaxis. Results: Approximately a third of the population in RIFA-infested areas are stung each year. The most frequent reaction is a sterile 1-2 mm pseudo pustule on the skin. Approximately 20% of stings cause a large local reaction and between about 0.5% and 2% stings cause a systemic allergic reaction which can range from skin symptoms to life-threatening anaphylaxis. Local biodiversity is also significantly disrupted by invading RIFA and may lead to complex adverse effects on human health, from agriculture losses to expanded ranges for pathogen vectors. Conclusions: The potential for red imported fire ants to establish themselves as an invasive species in the Western Pacific presents a substantial and costly health issue. Successful eradication and surveillance programs, to identify and eradicate new incursions, would avoid substantial health impacts and costs.

Biology and ecology of Irukandji jellyfish (Cnidaria: Cubozoa).

Irukandji stings are a leading occupational health and safety issue for marine industries in tropical Australia and an emerging problem elsewhere in the Indo-Pacific and Caribbean. Their mild initial sting frequently results in debilitating illness, involving signs of sympathetic excess including excruciating pain, sweating, nausea and vomiting, hypertension and a feeling of impending doom; some cases also experience acute heart failure and pulmonary oedema. These jellyfish are typically small and nearly invisible, and their infestations are generally mysterious, making them scary to the general public, irresistible to the media, and disastrous for tourism. Research into these fascinating species has been largely driven by the medical profession and focused on treatment. Biological and ecological information is surprisingly sparse, and is scattered through grey literature or buried in dispersed publications, hampering understanding. Given that long-term climate forecasts tend toward conditions favourable to jellyfish ecology, that long-term legal forecasts tend toward increasing duty-of-care obligations, and that bioprospecting opportunities exist in the powerful Irukandji toxins, there is a clear need for information to help inform global research and robust management solutions. We synthesise and contextualise available information on Irukandji taxonomy, phylogeny, reproduction, vision, behaviour, feeding, distribution, seasonality, toxins, and safety. Despite Australia dominating the research in this area, there are probably well over 25 species worldwide that cause the syndrome and it is an understudied problem in the developing world. Major gaps in knowledge are identified for future research: our lack of clarity on the socio-economic impacts, and our need for time series and spatial surveys of the species, make this field particularly enticing.

Delayed antivenom for life-threatening tiger snake bite: Lessons learnt.

An adolescent victim of an urban snakebite developed respiratory failure, rhabdomyolysis and consumption procoagulopathy but recovered with two vials of tiger snake antivenom administered after a delay of 48 hours. The clinical significance of a post-bite collapse was not initially appreciated. Tiger snake (Notechis spp.) venom antigen was measurable in blood before antivenom but not after whereas antivenom was measurable in blood for nine ensuing days. This case adds to growing evidence that further pharmacokinetic research of venom-antivenom interaction is required to establish the correct dose and timing of tiger snake antivenom. Antivenom therapy, even when delayed, facilitates recovery from snake envenomation.

Coagulation factor activity patterns of venom-induced consumption coagulopathy in naturally occurring tiger snake (Notechis scutatus) envenomed dogs treated with antivenom.

BACKGROUND: Venom-induced consumption coagulopathy (VICC) from tiger snake (Notechis scutatus) envenomation results in a dose-dependent coagulopathy that is detectable on coagulometry. However, individual coagulation factor activities in dogs with tiger snake envenomation have not been determined. This study aimed to characterise VICC and the time course of recovery in tiger snake envenomed dogs and to investigate an association between tiger snake venom (TSV) concentrations and factor activity. METHODS: This was a prospective, observational, cohort study. The study cohort was 11 dogs of any age, breed, sex, body weight >10 kg, confirmed serum TSV on ELISA and treated with antivenom. Blood was collected at enrolment before antivenom administration, then at 3, 12 and 24 h after antivenom administration. Tiger snake venom concentrations were detected with a sandwich ELISA. Fibrinogen was measured using a modified Clauss method, and coagulation factors (F) II, V, VII, VIII and X were measured with factor-deficient human plasma using a modified prothrombin (PT) and activated partial thromboplastin (aPTT) method. Linear mixed models, with multiple imputations of censored observations, were used to determine the effect of time and TSV concentration on the coagulation times and factor activity. This cohort was compared to 20 healthy controls. RESULTS: At enrolment, there were severe deficiencies in fibrinogen, FV and FVIII, with predicted recovery by 10.86, 11.75 and 13.14 h after antivenom, respectively. There were modest deficiencies in FX and FII, with predicted recovery by 20.57 and 32.49 h after antivenom, respectively. No changes were detected in FVII. Prothrombin time and aPTT were markedly prolonged with predicted recovery of aPTT by 12.58 h. Higher serum TSV concentrations were associated with greater deficiencies in FII, FV and FVIII, and greater prolongations in coagulation times. The median (range) serum TSV concentration was 57 (6-2295) ng/mL. CONCLUSIONS: In tiger snake envenomed dogs, we detected a profound, TSV-concentration-related consumption of select coagulation factors, that rapidly recovered toward normal. These findings allowed further insight into tiger snake VICC in dogs.

Antivenom use, premedication and early adverse reactions in the management of snake bites in rural Papua New Guinea.

OBJECTIVE: To examine antivenom use, premedication, early adverse reactions and patient outcomes after snake bite in rural Papua New Guinea. DESIGN: Retrospective chart analysis of all admissions for snake bite with documented antivenom use at 11 rural health facilities from January 1994 to June 2004. No formal protocol was followed and there was no attempt at randomisation or blinding of prophylaxis. RESULTS: Antivenom use was documented in 136/1881 (7.2%) snake bite admissions and most (121/136: 88.9%) received a single vial. CSL Polyvalent antivenom was administered to 112/136 (82.4%). One hundred and eleven patients (81.6%) happened to have been given premedication with adrenaline and/or promethazine and/or hydrocortisone. Early adverse reactions were reported in 25 patients (18.4%) including 23 treated with polyvalent antivenom. Intravenous test doses of antivenom were given to 32 patients, none of whom had a positive test result. Subsequent adverse reactions occurred in 9 of these 32 (28.1%) patients. One death may have been attributable to anaphylaxis after polyvalent antivenom. Reaction rates were significantly (p < or = 0.005) lower in adrenaline premedicated patients (7.7%) compared to patients premedicated without adrenaline (28.3%) and unpremedicated patients (28.0%). Adrenaline premedication caused no detectable changes in vital signs. The case fatality rate was 9.6% (13/136 patients). CONCLUSIONS: Polyvalent antivenom is the main treatment for envenomation in rural health centres, and early adverse reactions are common. Adrenaline premedication appears to significantly reduce acute adverse reaction rates. Premedication with promethazine and/or hydrocortisone without adrenaline did not reduce early adverse reactions.

Toxinology in Australia's colonial era: a chronology and perspective of human envenomation in 19th century Australia.

The medical management of those envenomed by snakes, spiders and poisonous fish in Australia featured extensively in the writings 19th century doctors, expeditioners and anthropologists. Against the background of this introduced medical doctrine there already existed an extensive tradition of Aboriginal medical lore; techniques of heat treatment, suction, incision and the application of plant-derived pharmacological substances featured extensively in the management of envenomed victims. The application of a hair-string or grass-string ligature, suctioning of the bite-site and incision were practised in a variety of combinations. Such evolved independently of and pre-dated such practices, which were promoted extensively by immigrant European doctors in the late 19th century. Pacific scientific toxinology began in the 17th century with Don Diego de Prado y Tovar's 1606 account of ciguatera. By the end of the 19th century more than 30 papers and books had defined the natural history of Australian elapid poisoning. The medical management of snakebite in Australia was the focus of great controversy from 1860 to 1900. Dogmatic claims of the supposed antidote efficacy of intravenous ammonia by Professor G.B. Halford, and that of strychnine by Dr. Augustus Mueller, claimed mainstream medical attention. This era of potential iatrogenic disaster and dogma was brought to a conclusion by the objective experiments of Joseph Lauterer and Thomas Lane Bancroft in 1890 in Brisbane; and by those of C.J. Martin (from 1893) and Frank Tidswell (from 1898), both of Sydney. The modern era of Australian toxinology developed as a direct consequence of Calmette's discovery, in Paris in 1894, of immune serum, which was protective against snakebite. We review the key contributors and discoveries of toxinology in colonial Australia.

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.

A probable case of Irukandji syndrome in Thailand.

The Irukandji syndrome is a jellyfish envenomation caused by Carukia barnesi or related jellyfish. In literature, the distribution of "Irukandji-like" syndromes is restricted to Australia. We report a case of probable Irukandji syndrome in Thailand. With this report, we hope to promote awareness to aid sting prevention and stimulate research.

Red-bellied black snake (Pseudechis porphyriacus) envenomation in the dog: Diagnosis and treatment of nine cases.

The clinical signs, biochemical changes and serum and urine venom concentrations for a series of nine cases of Red bellied black snake [RBBS] (Pseudechis porphyriacus) envenomation in eight dogs seen in a regional Australian veterinary hospital are described. Although the resulting envenomation syndrome was, in most cases, relatively mild and responded rapidly to intravenous administration of a novel bivalent caprylic acid purified whole IgG equine antivenom for tiger (Notechis scutatus) and brown snake (Pseudonaja textilis), one fatality prior to antivenom treatment was recorded. The latter case occurred within 1 h of envenomation prior to receiving antivenom treatment. Intravascular haemolysis, pigmenturia, bite site swelling, lethargy, and generally mild coagulopathy were present in most cases. Detectable RBBS venom specific components were found in serum, bite site swab or urine using a standard sandwich ELISA approach. Serum levels fell within the range previously reported for human RBBS envenomation cases (6-79 ng/ml) whilst bite site and urine samples varied more markedly (8.2 to >5000 ng/ml and 2.2-1300 ng/ml respectively). No venom was detected from serum after antivenom treatment. The envenomation syndrome in dogs is similar to what is described for humans, with the exception of the presence of potentially severe venom induced consumption coagulopathy in one case (aPTT > 300 s and fibrinogen < 0.43 g/L) and potential for fatal outcomes. This series represents the largest and most detailed examination of RBBS envenomation in animals yet reported. It reinforces the emerging view that the potential severity of this envenomation has been underappreciated by veterinary practitioners and highlights the possibility of severe venom induced consumption coagulopathy in canine cases.

Successful use of camelid (alpaca) antivenom to treat a potentially lethal tiger snake (Notechis scutatus) envenomation in a dog.

This report describes a confirmed clinical case of tiger snake (Notechis scutatus) envenomation in a domestic dog that was successfully treated with a novel polyvalent camelid (alpaca; Llama pacos) antivenom. Samples collected from the dog were assayed for tiger snake venom (TSV) using a highly sensitive and specific ELISA. The TSV concentration in serum and urine at initial presentation was 365 ng/mL and 11,640 ng/mL respectively. At the time of initial presentation whole blood collected from the dog did not clot and the Prothrombin Time was abnormally increased (>300 s). Serum was also visibly hemolysed. The dog was administered antihistamine, dexamethasone and 4000 Units (sufficient to neutralise 40 mg of TSV) of a novel polyvalent alpaca antivenom diluted in 0.9% NaCl. At 4 h post-antivenom treatment the dog's clinical condition had improved markedly with serum TSV concentrations below the limit of detection (<0.015 ng/mL), consistent with complete binding of venom antigens by the alpaca antivenom. Coagulation parameters had begun to improve by 4 h and had fully normalised by 16 h post-antivenom. Venom concentrations in both serum and urine remained undetectable at 16 h post-antivenom. The dog made a complete recovery, without complications, suggesting that the alpaca-based antivenom is both clinically safe and effective.

Fatal presumed tiger snake (Notechis scutatus) envenomation in a cat with measurement of venom and antivenom concentration.

A fatal outcome of a presumed tiger snake (Notechis scutatus) envenomation in a cat is described. Detectable venom components and antivenom concentrations in serum from clotted and centrifuged whole blood and urine were measured using a sensitive and specific ELISA. The cat presented in a paralysed state with a markedly elevated serum CK but with normal clotting times. The cat was treated with intravenous fluids and received two vials of equine whole IgG bivalent (tiger and brown snake) antivenom. Despite treatment the cat's condition did not improve and it died 36 h post-presentation. Serum concentration of detectable tiger snake venom components at initial presentation was 311 ng/mL and urine 832 ng/mL, this declined to non-detectable levels in serum 15-min after intravenous antivenom. Urine concentration of detectable tiger snake venom components declined to 22 ng/mL at post-mortem. Measurement of equine anti-tiger snake venom specific antibody demonstrated a concentration of 7.2 Units/mL in serum at post-mortem which had declined from an initial high of 13 Units/mL at 15-min post-antivenom. The ELISA data demonstrated the complete clearance of detectable venom components from serum with no recurrence in the post-mortem samples. Antivenom concentrations in serum at initial presentation were at least 100-fold higher than theoretically required to neutralise the circulating concentrations of venom. Despite the fatal outcome in this case it was concluded that this was unlikely that is was due to insufficient antivenom.

Prospective assessment of the false positive rate of the Australian snake venom detection kit in healthy human samples.

The Snake Venom Detection Kit (SVDK; bioCSL Pty Ltd, Australia) distinguishes venom from the five most medically significant snake immunotypes found in Australia. This study assesses the rate of false positives that, by definition, refers to a positive assay finding in a sample from someone who has not been bitten by a venomous snake. Control unbroken skin swabs, simulated bite swabs and urine specimens were collected from 61 healthy adult volunteers [33 males and 28 females] for assessment. In all controls, simulated bite site and urine samples [a total of 183 tests], the positive control well reacted strongly within one minute and no test wells reacted during the ten minute incubation period. However, in two urine tests, the negative control well gave a positive reaction (indicating an uninterpretable test). A 95% confidence interval for the false positive rate, on a per-patient rate, derived from the findings of this study, would extend from 0% to 6% and, on a per-test basis, it would be 0-2%. It appears to be a very low incidence (0-6%) of intrinsic true false positives for the SVDK. The clinical impresssion of a high SVDK false positive rate may be mostly related to operator error.

Persistent anosmia and olfactory bulb atrophy after mulga (Pseudechis australis) snakebite.

Loss of sense of smell is an intriguing yet under-recognised complication of snakebite. We report olfactory function testing and neuroimaging of the olfactory bulbs in a 30-year-old man with anosmia persisting for more than 1year after mulga (Pseudechis australis) snakebite. This problem was first noted by the patient 1week after being definitely bitten in Queensland, Australia. He had then presented to a regional hospital where his envenomation was considered mild enough to not warrant antivenom administration. A week later the patient noted a reduction of sense of smell, which progressed to complete inability to smell over the ensuing weeks. On clinical review the patient's neurologic and rhinologic examination did not reveal any structural cause for anosmia. Formal olfactory testing was performed using ''sniffin' sticks" and the patient scored 17 on this test, indicating severe hyposmia (functional anosmia <16.5, normal score >30.3 for men aged 16-35years). MRI of the brain showed no abnormalities. The olfactory bulb volumes were then measured on a volumetric T2-weighted MRI that demonstrated significantly reduced volume of both bulbs, with the right 34.86mm(3) and left 36.25mm(3) (normal volume ⩾58mm(3), 10th centile). The current patient represents a rare instance of a definite, untreated, elapid (mulga snake) envenomation with an intriguing disjunction between the mildness of the systemic features and the severity of the olfactory lesion. It is also unclear if early antivenom use attenuates this condition, and due to the delayed manifestation of the symptoms, awareness of this phenomenon may be lacking amongst physicians.

Ant sting mortality in Australia.

We investigated ant sting related fatalities in Australia over the period 1980-1999. Data was obtained from the Australian Bureau of Statistics and state coronial authorities. Six ant sting-related fatalities were identified, five in Tasmania and one in New South Wales. All were males aged between 40 and 80-years-of-age and most (5/6) had prior histories of jumper or bull ant (Myrmecia spp.) venom allergy. However, none of the deceased carried injectable adrenaline and most died within 20 min of a single sting. Significant cardiopulmonary co-morbidities were identified in all cases and, in addition, moderate-severe laryngeal oedema and coronary atherosclerosis was observed in most (4/6) cases at autopsy. Where ascertained, Myrmecia ant venom specific immunoglobulin E antibodies levels were always elevated and fell into two distinct patterns of immunoreactivity. Adult Tasmanian males with a prior history of ant venom allergy and cardiopulmonary co-morbidities are therefore at highest risk of a fatal outcome from ant stings. Deaths may be avoided by the early recognition of anaphylaxis and self-treatment with adrenaline as well as by the development of purified Myrmecia ant venom immunotherapy.