Influences on venom yield in Australian tigersnakes (Notechis scutatus) and brownsnakes (Pseudonaja textilis: Elapidae, Serpentes)

The rates at which venomous animals produce venoms are of obvious biological and medical importance, but factors influencing those rates remain poorly understood. We gathered data on venom yield (wet mass of venom) and percentage solids (dry mass of the venom divided by wet mass) for 53 eastern brownsnakes (Pseudonaja textilis) and 36 mainland tigersnakes (Notechis scutatus) over a 4-year period at Venom Supplies Pty. Ltd, a commercial venom production facility in South Australia. Tigersnakes yielded about threefold more venom (by wet mass) than brownsnakes, but with slightly lower percentage solids. Both species showed significant geographic variation in percentage solids. Venom yields varied as a function of the snake's sex and geographic origin, but these effects were secondary consequences of geographic and sex-based differences in body size. Relative head size affected venom yield in brownsnakes but not tigersnakes. Overall, the amount of venom that a snake produced during milking was affected by its species, its geographic origin, its body size and relative head size, and by the time of year that it was milked, as well as by interactions among these factors. Body size was the most important effect on venom yield, with yields increasing more rapidly with size in brownsnakes than in tigersnakes. Research at the intersection of snake ecology and venom characteristics has great potential, but will require a genuinely interdisciplinary approach.

Neutralisation of the clotting activity of Australian snake venoms by snake plasma

Plasmas from Pseudonaja textilis and Notechis scutatus were tested in vitro for their ability to neutralise the procoagulant activity, in human plasma, of nine elapid venoms. Pseudonaja textilis plasma inhibited the procoagulant activity of all Pseudonaja species and in one taipan (Oxyuranus scutellatus). However there was no inhibitory activity against any from the Notechis species. Plasma from Notechis scutatus exhibited no inhibitory activity against any Notechis species, including self, only weak inhibition against the Pseudonaja species and, again, total inhibition of Oxyuranus scutellatus. Thus, protection of a species from the effects of its own venom does not appear to be universal.

Brown snakes (Pseudonaja genus): venom yields, prothrombin activator neutralization and implications affecting antivenom usage

The recent high prevalence of fatal bites by Brown snakes (Pseudonaja genus) has led to this study of venom yields from 66 brown snake milkings over 15 months. The amount of venom obtained from all species was higher than reported previously. Electrophoretic and Western blotting analyses of their venoms showed significantly lower avidity of Brown snake antivenom (BS-AV) for the prothrombin activator (PA) component (190 kD) than for other venom components, including the neurotoxins. The LD50 of P. inframacula has been determined for the first time. SDS-PAGE (sodium dodecyl sulphate-polyacrylamide gel electrophoresis) and Western blotting studies have shown that the Pseudonaja venoms contained proportionately more PA component than venoms of the Taipan (Oxyuranus scutellatus) or the Fierce snake (O. microlepidotus). Neutralization of the prothrombin activator of the Common Brown snake (P. textilis) (Pt-PA) by BS-AV was found to be time dependent and 40% remained unneutralized after 30 minutes incubation. Adult rats administered quantities of Pt-PA (IV) died with acute disseminated intravascular coagulation. Rats were made resistant to Pt-PA by preheparinization or by induction of tolerance to increasing quantities of Pt-PA. There is no evidence that Pt-PA has intrinsic toxicity apart from being a procoagulant. The improvement of BS-AV by addressing its deficiencies should be canvassed.

Snake bites recorded by veterinary practices in Australia

OBJECTIVE

To determine the extent of the snake bite problem in domestic animals, its regional significance and the effects of antivenom treatment.

DESIGN

A questionnaire was designed seeking information on the number and type of domestic animals referred, whether treated or untreated, type of snakes and management of the bite.

PROCEDURE

The survey form was sent to 10% of veterinary surgeons, selected at random throughout Australia.

RESULTS

The response of 106 veterinary surgeons revealed that snake bite in domestic animals is frequent, with an estimated 6200 cases reported annually. Bites were more prominent in rural (78%) than urban areas (22%) with brown, tiger and black snakes accounting for 76%, 113% and 6% of cases, respectively. Cats and dogs were the most frequently reported victims. Ninety-one percent of cats and 75% of dogs survived following the administration of antivenom whereas 66% of cats and 31% of dogs survived without antivenom. Overall, in 33% of cases antivenom was not used, and venom detection kits were used in only 1% of cases. A number of drugs were used in various combinations with or without antivenom and intravenous fluids in the treatment of animals with snake bite, but their role in reducing the severity of envenomations was not assessed.

CLINICAL IMPLICATIONS

Antivenom significantly improves the chances of survival of domestic animals bitten by snakes.

Sphero-echinocytosis of human red blood cells caused by snake, red-back spider, bee and blue-ringed octopus venoms and its inhibition by snake sera

It was found that bee (Apis mellifera) venom, red-back spider (Latrodectus mactans) venom, blue-ringed octopus (Hapalochlaena maculosa) venom, ten different snake venoms, phospholipase A2 and four snake toxins caused sphero-echinocytosis of human red blood cells at 200 ng/ml. Most venoms and toxins lost the ability to deform human red blood cells when their components of less than mol. wt 10,000 were applied. In a number of cases the sphero-echinocytotic effect was also inhibited by blood sera of Notechis scutatus and Pseudonaja textilis.

Comparative study on the procoagulant from the venom of Australian brown snakes (Elapidae; Pseudonaja spp.)

The procoagulant was isolated from the venom of four clinically significant species of brown snake; Pseudonaja affinis, P. inframacula, P. nuchalis, and P. textilis. HPLC elution profiles and PAGE showed a high degree of homology between the procoagulants from the four species. Antiserum from the CSL Ltd (Brown Snake Antivenom) produced a single band against all four procoagulants. The specific activity of the procoagulant varied between species, while inhibitory studies indicated that the procoagulants were serine proteases with a sialic acid component which also contributes to the coagulant action.

A comparative study on the biological properties of venoms from juvenile and adult common tiger snake (Notechis scutatus) venoms

1. The biological properties of venoms from juvenile and adult common tiger snakes (Notechis scutatus) were compared. 2. The lethality, procoagulant activity and enzymatic activities of the juvenile venom were not substantially different from those of the adult venom. 3. Electrophoretic studies, however, indicated some minor differences in the protein composition of the juvenile and adult venoms.

Neutralization of tiger snake (Notechis scutatus) venom by serum from other Australian elapids

Sera from four Australian elapids and one boidid (python) were tested for their ability to protect neonatal mice against the toxic action of tiger snake (Notechis scutatus) venom. Of the five serum samples tested, only serum from Pseudechis australis and Pseudechis porphyriacus were capable of neutralizing the tiger snake venom. In addition, neutralization was shown to be highly variable within serum taken from individual snakes of the same species (P. porphyriacus). Previously, only viperid and colubrid snakes have been shown to possess neutralizing factors against snake venoms.

A comparative study of the biological properties of venoms from juvenile and adult inland taipan (Oxyuranus microlepidotus) snake venoms

The biological properties of adult and juvenile inland taipan (Oxyuranus microlepidotus) snake venoms were examined. The enzymatic activities, intravenous median lethal dose and procoagulant activity of the juvenile venom samples were not significantly different from those of the adult venom samples. Also, the juvenile and adult venoms exhibited similar electrophoretic patterns, indicating that they possessed similar protein composition.

The biological properties of venoms from juvenile and adult taipan (Oxyuranus scutellatus) snakes

1. The biological properties of four venom pooled samples from adult taipan (Oxyuranus scutellatus) snakes and one pooled venom sample from six juvenile taipan snakes (11 months old) were compared. 2. The intravenous LD50 (median lethal dose), procoagulant activity and enzymatic activities of the juvenile venom were not significantly different from those of the adult venoms. 3. The juvenile and adult venoms exhibited similar polyacrylamide gel electrophoretic (PAGE) and SDS-PAGE patterns, indicating that they possessed a similar protein composition. 4. The results suggest that there is no significant age-dependency in the biological properties of taipan venom.

Envenomation by the inland taipan, Oxyuranus microlepidotus

A case of envenomation by a three-week-old inland taipan (Oxyuranus microlepidotus)-the second recorded case of a bite by possibly the most venomous snake in the world - is reported. Evidence which supports the use of the term "inland taipan", and confirms the effectiveness of taipan antivenom in the treatment of bites by this snake, is presented.