Several spread disease organisms when feeding on blood- fleas, ticks and mosquitos are 3 that come to mind.
The oxpecker, but it often actually sucks blood out of wounds on the cows as well as eating parasites.
yes i think that is how it goes in a ecological pyramid.
Owl
Spiders and praying mantis do.
there isn't an insect who feeds on fishes.
fleas and other parasites
Parasites.
Yes, a dog can get cow parasites. If a dog eats cow feces, then it could get cow parasites such as, worms.
a lizardfly
grasshopper
Owl
The nightingale eats spiders and ants.