The Collaborative International Dictionary
Haematozoon
Haematozoon \H[ae]m`a*to*zo"["o]n\ (-t[-o]*z[=o]"[o^]n), n.; pl. H[ae]matozoa (-[.a]). [NL., fr. Gr. a"i^ma, a"i`matos, blood + zw^,on animal.] (Zo["o]l.) A parasite inhabiting the blood; esp.:
Certain species of nematodes of the genus Filaria, sometimes found in the blood of man, the horse, the dog, etc.
The trematode, Bilharzia h[ae]matobia, which infests the inhabitants of Egypt and other parts of Africa, often causing death.
Wiktionary
haematozoon
n. A parasite inhabiting the blood.