Abstract
Coccidiosis in chickens is one of the major problems in the poultry industry, caused by protozoan parasites of the genus Eimeria. The current study used morphological and molecular characteristics to identify Eimeria spp. infecting domestic chickens (Gallus gallus) in the Riyadh region of Saudi Arabia. In this study, 120 domestic poultry were examined and 30 were found to be infected with oocysts of Eimeria spp. (25%). According to the morphology of the recorded oocysts, five species were found. Eimeria necatrix was the first species discovered, and it was distinguished by oblong, ovoid-shaped oocysts with double-layered walls that measured 20 (23-23) and 17 (16-20) μm. The second species was Eimeria maxima, which had oval- to egg-shaped oocysts with double-layered walls and measurements of 28 (26-29) and 23 (20-24) μm. The third species was Eimeria tenella, characterized by oval-shaped oocysts with double-layered walls and measurements of 21 (20-24) × 17 (16-20) μm. Eimeria praecox was the fourth species that was characterized by spherical-shaped oocysts with single-layered walls and measurements of 21 (19-23) × 20 (19-20) μm. Eimeria acervulina was the last species to have oval-shaped oocysts with double-layered walls and measurements of 20 (18-25) and 17 (14-20) μm. The percentages of infection with Eimeria species were as follows: E. tenella, 10.84%; E. necatrix, 5.84%; E. acervulina, 4.16%; E. maxima, 2.5%; and E. praecox, 1.66%. Nested PCR based on the amplification of internal transcribed spacer I (ITS-I) regions confirmed the presence of the five Eimeria species in the examined fecal samples with their specific amplicon sizes: E. necatrix (383 bp), E. maxima (145 bp), E. tenella (278 bp), E. praecopx (116 bp), and E. acervulina (321 bp).