A parasitological survey was carried out on 182 animals from the family Equidae, (110 donkeys, 50 horses
and 22 mules) from different localities in Assiut Governorate, to clear up the prevalence of microfilariae in
March 2008. Out of 182 examined animals the blood of these animals in the period from July 2007 till
25.82 % were harboring microfilariae. The incidence was (28.18 %, 26% and13.63 %) in donkeys, horses and
291
mules respectively (with non significant statistical value). Two types of microfilariae were detected
Onchocerca reticulata (17.58 %) and Setaria equina (10.9%). Examination of thick blood films of some cases
revealed that the microfilariae of Onchocerca reticulata were aggregated together in the form of a bundle
of hair, this may be due to the use of drugs or immunological reactions. Adults of Setaria equina were
detected in the peritoneal cavities of 52.5% of necropsied donkeys. Examination of thick blood films of the
same animals revealed that only 14.28 % harbor microfilariae of Setaria equina in the peripheral blood. It
was concluded that future studies on filarial parasites in equines should be aided with serological
techniques. The highest rate of infection was noticed in Summer (52 %) and Spring (31.8 %), while the
lowest rate was in Winter (4.76%). Seasonal variations were found statistically highly significant and this
may be correlated with the density of the arthropod vector which is affected by climatic variations.