Muscular samples of the oesophagus and diaphragm of 335 sheep collected from the slaughterhouse of El Harrach were analyzed by the histopathological method to describe the morphology of two species of Sarcocystis: S. arieticanis and S. tenella. The cysts were counted and measured with a micrometer for their dimensions. A total of 895 cysts were measured. The width, length, shape index (length/width), the thickness of the wall and the length of the projections were recorded. The thick-walled cysts of S. tenella were 10—450 μm long (the mean ± SD value was 50.35 μm ± 1.380) and 1—110 μm (the mean ± SD value was 27.51 μm ± 0.533) wide. The cyst walls were 0.5—4 μm thick (the mean ± SD value was 1.547 μm ± 0.020) and provided with radial striations. The shape index was 1—14 μm (the mean ± SD value was 1.93 ± 0.045). While in the S. arieticanis, the cyst wall was thin and had long hair-like protrusions, the cysts measured 8—780 μm (the mean ± SD value was 123.13 μm ± 12.799) in length and 5—100 μm (the mean ± SD value was 37.00 μm ± 1.68) in width. The hair-like protrusions reached a length of 3—14 μm (the mean ± SD value was 5.428 ± 0.353) and the shape index was 1—17 μm (the mean ± SD value was 3.10 ± 0.281). For the length, the width and the shape index, the differences were statistically significant between thin-walled cysts and thick-walled cysts. The general structural features of the cysts, previously described by other authors, were confirmed.

A total of 10,696 randomly selected sheep have been collected in two slaughterhouses in the north of Algeria (El Harrach and Boufarik) to determine the prevalence of muscular cysticercosis and macroscopic cysts of sarcosporidiosis, to find out the association between prevalence and potential risk factors, as well as to assess the distribution of these parasites in the surface’s muscles of slaughtered sheep. All of the slaughtered sheep carcasses were visually and carefully inspected. Cysticercosis and sarcosporidiosis were found in 220 (2.06 %) and 76 (0.7 %) sheep, respectively. For both diseases, the prevalence was significantly higher in females than males. The prevalence of Cysticercus ovis increased with age, and the difference was statistically significant (P < 0.0001), while all infected animals were old (over 5 years old) for sarcosporidiosis. For C. ovis, it didn’t have significant difference between the seasons, however, all sheep were infected in the spring for sarcosporidiosis. All the detected cysts of C. ovis were non-viable, and were more frequently detected in the heart (51.82 %), followed by the diaphragm (30.77 %) and the oesophagus (17.41 %). This anatomical distribution of C. ovis cysts showed a significant variation (P < 0.001) in different predilection sites. Whereas, for sarcosporidiosis, the species involved was identified as S. gigantea by histology and were distributed in the organs as follows: the skeletal muscles (38.15 %), the oesophagus (31.57 %) and the diaphragm (30.26 %); no significant difference were noted between the 3 sites. The present study has revealed that these parasites are present in Algeria. Appropriate control measures need to be introduced to eradicate these parasites in sheep.