Final answer:
Fleas inject hemorrhagic saliva that prevents blood clotting and damages tissue, which is similar to the mechanisms of spider and snake venoms that also affect the clotting process and can cause more severe symptoms.
Step-by-step explanation:
Fleas inject a hemorrhagic saliva which damages tissue and causes bleeding. Flea saliva contains anticoagulants and enzymes that disrupt the blood clotting process and can cause tissue damage. This biological mechanism is similar to how certain species of spiders and snakes employ their venom.
For example, the brown recluse spider venom has hemotoxins and cytotoxins affecting red blood cells and clotting, leading to symptoms such as redness, pain, and in severe cases, necrosis.
In another example, components of snake venom can prevent blood from clotting and have potential medical applications, such as developing new drugs or other therapeutic approaches.