Seasonal infestation of Oestrus ovis larvae in sheep heads in central region of Saudi Arabia.

During a period of 12 months, 544 sheep heads were examined for infestation with Oestrus ovis larvae in Riyadh abattoir, Central Region of Saudi Arabia. The tested animals were males, less than one year old. The prevalence of infestation was 5.9%. The peak of infestation reached 23.3% in March 2000. The highest mean number of larva per infested sheep head in first, second and third instars larvae were 5, 7, and 5.3 respectively in spring months. A total for all instars being 4.3 larva per sheep head. All three stages disappeared in summer and winter months probably due to the very hot and dry weather.