Eimeria  sp.  is  one  of  the  most  important  parasites  that  cause  very  high  economic  loss  in 
poultry farms in Egypt. It causes a disease called coccidiosis.  This study aimed to detect the 
prevalence of  Eimeria  species in chicken and detection of its pathological effect  within the 
intestinal  mucosa.  The  present  study  investigate  the  prevalence  of  Eimeria  sp.  in  chicken 
through  fecal  examination  and  the  diagnosis  was  based  on  direct  fecal  sample  examination 
(unstained  wet  mount  technique)  and  concentration  techniques,  followed  by  sporulation  of 
unsporulated  oocyst  for  identification  of  Eimeria  spp.  and  finally  studying  the  pathological 
effect of this parasite in the intestinal mucosa of infected chicken. The total prevalence rate of
Eimeria spp. was (66%). The incidence rate in Broiler chickens was (70%) and in Balady was 
(58%).  The highest percent of infection was at the age of (15-30) day  (54.3% in Broiler and 
72.4% for Balady), and the disease was more prevalent in winter than in summer. The species 
that  were  detected  are  E.acovullina  (the  highest  prevalence  rate)  followed  by  E.tenella, 
E.necatrix  followed  by  E.mitis  (lowest  prevelance  rate).  These  results  indicate  that  the 
coccidiosis  is  a  serious  parasitic  disease  that  effect  on  the  poultry  production  in  Egypt  and 
control measures should be put in consideration to overcome this disease. 
Keyswords: Eimeria - prevalence- coccidiosis- oocyst