Used for neutralising systemic envenoming by members of the Australian paralysis tick group. It is made from dog IgG. Each ampoule contains 1,000 units of neutralising capacity against the target venoms. This is a freeze dried preparation. Re-constitute with approximately 6.3mL of Water for Injections BP. The immunising venom is common paralysis tick (Ixodes holocyclus) venom (salivary gland extract).
Current experience suggests that all Ixodes paralysis tick venoms will respond to CSL Tick Antivenom, though it was principally developed for bites by the common paralysis tick. These are robust "hard bodied" ticks.
The common paralysis tick is found in eastern Australia.
The saliva contains a presynaptic neurotoxin, holocyclotoxin, active at the skeletal neuromuscular junction causing progressive flaccid paralysis.
Paralysis is not the most common effect of bites by paralysis ticks, which more usually cause local skin irritation. Multiple bites may leave an effect like a rash. Particularly in children, an adult female tick feeding over several days may cause the classical paralysis, usually first noticed as an ataxic gait with general malaise. Untreated, this can progress to full respiratory paralysis, the cause of most fatalities. Once the tick is removed, it might be expected that the effects of the toxin would quickly dissipate, but this is not the case. Indeed, the extent of paralysis may worsen for up to 48 hours after removal of all ticks.
As with most antivenoms, CSL Tick Antivenom should only be given if there is clear evidence of envenoming. See potential contraindications. It should be given intravenously, through a drip set. If possible, dilute antivenom up to 1 in 10, with an isotonic crystaloid solution (eg saline, Hartmans or dextrose). In general, each ampoule/dose should be run over 15-30 minutes. Prior to commencing antivenom therapy, make sure everything is ready to treat anaphylaxis, should this occur. Specifically, have adrenaline ready to give.
The use of adrenaline as pre-treatment when using antivenoms is still being debated. The risk of anaphylaxis varies from antivenom to antivenom. It is recommended that the Product Information be read before use and if necessary contact be made with a specialist in the field.
CSL Tick Antivenom should be considered in every case of significant systemic envenoming by paralysis ticks in Australia, the hallmark of which will be progressive and major paralysis. If paralytic features are only minor, then removal of the tick will usually be sufficient.
If there is either a sudden fall in blood pressure or bronchospasm, after starting the antivenom infusion, then temporarily stop the antivenom and give adrenaline by subcutaneous injection, give 100% O2 and IV fluids (Haemaccel®).
If there is an infusion pump set up, then commence cautious IV infusion of 6mg/100mL adrenaline dilution, (at about 10mL/hr), increasing the rate if there is no response in a few minutes, and decreasing the rate as soon as a sufficient response is obtained. Once the untoward antivenom reaction is thus controlled, cautiously recommence antivenom infusion.
If adrenaline is to be given (by subcutaneous injection), use a 1:1000 solution. For adults give 0.5mL (0.5mg) initially. For children give 0.01mg/kg initially. Repeat as necessary and try IM injection if no response to SC injection.
If bronchospasm is the major problem, try nebulised adrenaline, 2mL of 1:1000 solution.
Any patient who has received antivenom may develop serum sickness, from 4 to 14 days later. Before leaving hospital, they should be advised of the symptoms of serum sickness, such as rash, fever, joint aches and pains, malaise, and told to return immediately for review and probable commencement of oral steroid therapy. If there was major envenoming, organise follow up. This is usually not necessary for minor envenoming.