In North American English there isn't a specific term that encompasses desparacitacíon.
If you are referring to internal parasites such as lombrices, amébas or "bichos", you could say "treat for internal parasites".
Other than that the terms are more specific:
for worms: "We treated 4 children for worms", or "we dewormed 4 children".
The terms to worm, and to deworm are slightly pejorative to parents, which is why we often say "treat for worms". For animals we use the term "to worm". i.e. I wormed my cat yesterday.
The medical terminology for worms in general is "treatment for helminthiasis", or more specifically - ascariasis (roundworms), oxyuriasis (pinworms), ankylostomiasis (hookworms), taeniasis (tapeworms).
for "amebas": there´s no specific colloquial term in English. The only way to say it would be "to treat for amebic dysentery".
If you are referring to external parasites like fleas, lice and scabies, you have to use the specific term.
for fleas: deflea, or treat for fleas
for lice (pediculosis): delouse or treat for lice
for scabies: treat for scabies, or medically, use a scabicide.
The terms deflea and delouse, like deworm, are more often used for animals, so to soften the blow for chagrined parents we usually say, "to treat for x".
