The Collaborative International Dictionary of English v.0.48:

Haematozoon \H[ae]m`a*to*zo"on\ (-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.] (Zool.)
   A parasite inhabiting the blood; esp.:
   (a) Certain species of nematodes of the genus Filaria,
       sometimes found in the blood of man, the horse, the dog,
       etc.
   (b) The trematode, Bilharzia h[ae]matobia, which infests
       the inhabitants of Egypt and other parts of Africa, often
       causing death.
       [1913 Webster]