A cross-sectional study was conducted to estimate the prevalence, larval burden, associated risk factors and co-existence of both Coenurus cerebralis and Oestrus ovis in small ruminants slaughtered at ELFORA export abattoir which located in Bishoftu, Ethiopia from December 2016 to March 2017. A total of 384 heads of small ruminants (180 sheep and 204 goats) were examined for the presence of both C.cerebralis and O.ovis larvae in their predilection site according to standard procedures. Results of the present study showed an overall prevalence of 6.8% and 77.9% of C. cerebralis and O. ovis, respectively. Of the examined animals, 11.7% sheep and 2.5% goats were positive for C. cerebralis (P<0.05) and 90% sheep and 67.2% goats were positive for O. ovis (P<0.05). Higher prevalence of C.cerebralis was observed in young (P<0.05) than adult but vice-versa for O.ovis. Significantly (P<0.05) higher prevalence of C. cerebralis was recorded in animals from Bale (11.1%) than those animals from Somali (0.00%). Similarly, significantly (P<0.05) higher prevalence of O.ovis was recorded in small ruminants from Bale (90.3%) than those animals from Jinka and Somali (66.7%). Significantly (P<0.05) higher prevalence of O.ovis was recorded in small ruminants with medium body condition than those with good body condition animals. The overall monthly prevalence of C. cerebralis ranged from 13.7% January to 1.8% March which is statistically significant (P<0.05) whereas monthly prevalence of O. ovis ranged from 84.2% in January to 74.7% in February (P>0.05). An overall proportion of 28.5%, 36.3% and 35.2% were recorded for L1, L2 and L3 larval stages, respectively and maximum of 37 and 35 larvae were recovered from sheep and goats, respectively. Significant association (P<0.05) was observed on cyst burden, maximum number of cyst encounter in animals who infest only with C.cerebralis. out of 17 concurrently infected young animals 9, 7 and 1 head have 1, 2 and 3 cyst per brain respectively but the remaining young animal infect only with C.cerebralis 2, 2 and 1 head contain 3, 4 and 5 cyst per brain respectively.

Keywords: prevalence, sympatry, C.cerebralis and O.ovis.