BACKGROUND:Ticks(Acari: Ixodidae) have been recognized as important ectoparasites of livestock worldwide, including in Iran. From the point of the pathogen agents' transmission,detection of the distribution of hard ticks in different parts of the country could be useful.OBJECTIVES: This study reports the frequency and diversity of ticks in all age groups of both sexes in the natural habitat of domestic ruminants in Kermanshah province, Iran.METHODS:A total of 600 ruminants (203 cattle,215 sheep,and 182 goats) from 150 flocks (90 in the east and 60 in the west part of the region) of 31 villages (15 in the east and 16 in the western part of the region) were randomly selected and examined from May to September 2012. RESULTS: Of all examined animals,24.63% cattle, 25.12% sheep,and 25.27% goats were infested with a total number of 1031 unfed ixodid ticks.The highest numbers of the hard ticks were collected from 3-4 year-old female cattle and 1-2 year-old female sheep and goats in the region.There was significant difference between age groups and sex of infested animals and prevalence of ixodid ticks.The ixodid tick indices were 4.6,7.9, and 7.1 for cattle, sheep,and goats, respectively.Geographical distribution of ixodid ticks infestations in different parts of Kermanshah province revealed that 12 cattle flocks (8%) and 12 goat flocks (8%) in the Miandarband region of eastern Kermanshah and 20 sheep flocks (13.33%) of Meidandam in western Kermanshah had the highest prevalence.Prevalence of ixodid tick infestation was statistically different between both parts of the region.The highest tick aggregation was found for inner thighs in cattle (46%) and ears in sheep (54%) and goats (43%). There was significant difference between predilection body sites of collected hard ticks from infested animals.Of all examined ticks (1031),three genera including Hyalomma, Rhipicephalus, and Boophilus with eight, nine, and seven species in cattle, sheep, and goats were respectively identified.The predominant infesting ticks were R. sanguinus (26.2% in cattle) and R.turanicus (53.1% in sheep and 40.55% in goats) from the western part of Kermanshah province, which was significantly different.CONCLUSIONS: The results of the current study showed that ixodid ticks infestation was widespread and prevalent in ruminants of the region.