A study of the major australian snake venoms in the monkey (Macaca fascicularis): I. the movement of injected venom, methods which retard this movement, and the response to antivenoms

Abstract

<h2>Summary</h2> Conscious monkeys were comfortably restrained for several hours whilst the movement and effects of injected snake venom was studied. Routine clinico-pathological studies were carried out on blood samples obtained at regular intervals and a solid phase radioimmunoassay was used to assay plasma levels of snake venoms and an individual neurotoxin. When snake venom was injected subcutaneously into the lower limb of a monkey and no first aid was applied, venom could be detected in the plasma of the animals within 15 min of the injection. Plasma venom and neurotoxin levels peaked about 60 min after the injection but signs of neurotoxicity were usually not seen until 120 min after injection. Post mortem studies showed that very little Tiger snake venom remained at the injection site, but high concentrations were found in the regional lymph nodes. Tiger snake venom components including the neurotoxin, notexin, were excreted in both the bile and urine of monkeys. The high levels of venom and neurotoxin found in the urine of monkeys parallel those found in some human snake bite victims. Recently developed first aid measures were applied to the envenomed limb of a number of monkeys. These measures consisted of the application of a firm crepe bandage to the length of the injected limb which was then immobilized with a splint. The first aid measures were found to delay the movement of all the major Australian land snake venoms and also the venom of the beaked sea snake (<i>Enhydrina schistosa</i>). A number of envenomed monkeys infused with antivenom immediately neurotoxic signs developed, barely survived even when given 10 times the amount of antivenom required to neutralize <i>in vitro</i> the dose of venom they had received. Surviving monkeys had persistent ptosis and lethargy for up to 5 d after envenoming. Failure to respond to antivenom was more likely if no effective first aid measure had been employed.