Prevalence of nasopharyngeal myiasis in roe deer (Capreolus capreolus) from an area with high sympatry between wild and domestic ungulates in Central Spain

Abstract

Abstract Infection by the sheep bot flyOestrus ovis was firstly reported in a single roe deer from Central Spain in 2023. In order to confirm whether that finding was an isolated event or a spillover of O. ovis to a new host, nasopharyngeal cavities of 184 roe deer hunted in Central Spain between January-June 2023 were examined. All larvae were recovered and morphologically identified; in addition, species identification was molecularly confirmed in a subset of specimens. Forty-four roe deer (23.9%; CI 95 17.95-30.74) were positive for different Oestrinae larval stages. Twenty-six animals (14.1%; CI 95 9.44-20.02%) were infested by the roe deer nasal bot fly (Cephenemyia stimulator) with a mean intensity of 35.2 (SD 49.71) larvae/infested animal,and eighteen (9.8%; CI 95 5.90-15.02%) roe deer harboured the sheep bot fly (O. ovis), with a mean intensity of 2.0 (SD 1.33) larvae/infested animal. No mixed infestations by both Oestrinae were found in a single animal. All larval instars (L1, L2 and L3) of both species were identified. Most C. stimulator specimens were located at the nasal turbinates, and a small percentage (3.2%) at the pharynx; however, all O. ovislarvae were found at the nasal turbinates. Since O. ovis is highly prevalent in sheep and goats from Central Spain, the high sympatry between roe deer populations and small ruminant flocks in the studied area may have increased the risk of cross-infection. Moreover, the finding of mature third stage larvae of O. ovis suggests that this species can complete its life cycle in roe deer. Therefore, monitoring bot flies in sheep and goat flocks as well as in sympatric wild ruminants is strongly recommended for achieving an optimum control of nasal myiasis.