Veterinary Parasitology 102 (2001) 133–141 Sheep oestrosis (Oestrus ovis Linné 1761, Diptera: Oestridae) in Sardinia, Italy A. Scala a , G. Solinas a , C.V. Citterio b , L.H. Kramer c , C. Genchi b,∗ a Section of Parasitology, Department of Animal Biology, University of Sassari, via Vienna 2, 07100 Sassari, Italy b Department of Animal Pathology, Hygiene and Veterinary Public Health, University of Milan, via Celoria 10, 20133 Milano, Italy c Department Veterinary Pathology, University of Parma, Parma, Italy Received 7 February 2001; received in revised form 1 June 2001; accepted 17 July 2001 Abstract Oestrosis, the nasal myiasis of sheep and goats, is caused by the larvae of Oestrus ovis L. 1758 (Diptera, Oestridae) that develop from the first to the third stage larva in the nasal cavities and frontal sinuses of affected animals. The authors report the results of an epidemiological study of oestrosis of sheep in Sardinia, Italy. Heads of 6-month to 10-year-old Sardinian sheep (n = 566) from 124 free-ranging flocks were examined for the presence and location O. ovis larvae from December 1996 to November 1997. Larvae were collected, counted, and larval stages were identified. O. ovis larvae were found in 100% of examined flocks and in 91% (514/566) of examined sheep. The monthly prevalence ranged from 69% in May to 100% in July. First stage larvae were found in 82% (463) of all heads examined, second stage larvae in 65% (367) and third stage larvae in 10% (56). The majority of sheep harboured first stage larvae, with prevalences of over 80% throughout most of the study period. The prevalence of O. ovis found in this study of Sardinian sheep is the highest reported in the Mediterranean area. The high percentage of first stage larvae found throughout the entire study period may be due to a brief period of decreased rate of larval maturation, in particular in December 1996 (96%) and January–October 1997 (94%). Third stage larvae were consistently present, often however, with extremely low prevalences compared to total larval burden. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Arthropoda; Oestrus ovis; Sheep arthropoda; Epidemiology; Italy ∗ Corresponding author. Tel.: +39-2-2666079; fax: +39-2-2364470. E-mail address: claudio.genchi@unimi.it (C. Genchi). 0304-4017/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0304-4017(01)00515-5