Transfer of Sheep Keds, Melophagus ovinus (L.), from Ewes to their Lambs

Abstract

IT has regularly been stated^1,2 that sheep keds (presumably of all ages) are transferred from ewes to their lambs. To this transfer has been attributed much of the decline in ked populations on ewes during the spring and summer². In detailed studies of behaviour of sheep keds on ewes after parturition, it has been observed at Lethbridge that only newly emerged keds are transferred to the lambs. The older keds on the ewes gradually die off as a result of infection with Trypanosoma melophagium³. These conclusions were drawn from observations that no puparia appeared on lambs until the latter were 4–6 weeks old, and that all keds seen on lambs up to four weeks of age were small ones. Bequaert⁴ has summarized the work of other authors, and claims that the ked deposits its first offspring in 14–30 days after it has emerged. On 10 lambs examined at Lethbridge, there were found an average of 11.6 ± 6.53 keds and no puparia on lambs two weeks of age, 43.3 ± 23.2 keds and 1.5 ± 1.8 puparia at four weeks of age, and 137.3 ± 59.84 keds and 25.5 ± 18.34 puparia at six weeks of age.