The toxin is not secreted in detectable amounts until 3 days of attachment.
Clinical signs of the animal being sick are often seen at day 3-4 with peak toxicity on days 5-6. These 3 days gives us a chance to find and to remove ticks before they inject large amounts of toxin.
Not every animal will paralyse or get really sick. Weight, age and immune competence counts – smaller and younger animals such as puppies, kittens, foals, calves, lambs and kids are more affected.
Tick infested areas may continuously expose dogs so they develop immune resistance however it only lasts for a couple of months and not until the next season. However, infestation by adults can occur at any time of the year when conditions are suitable, even in mid winter.
In my experience if an animal is already “wobbly on it’s legs”, tick antiserum administration will be required for recovery.