[Seasonal cycle of strongylus in cattle on Réunion Island]

An experiment with tracer calves was conducted in Reunion island to determine the seasonal fluctuations of parasites in one of the most important rearing area, and to provide basis for a drenching programme. After being exposed to infestation for 28-31 days, two calves are slaughtered each month and their worms identified and counted. Four genera area prevalent : Trichostrongylus and Ostertagia rise in late winter--early summer; Cooperia and Oesophagostomum in early summer and again in late summer--early winter. Based on this seasonal incidence, three treatments in July, January and April or May are proposed--The effects of the cyclone Hyacinthe on the dynamic of infesting larvae are discussed.