SUMMARYA rapid method is described for preparing and staining salivary glands of Rhipicephalus appendiculatus ticks infected with Theileria parva. The technique, involving the use of a modified methyl green pyronin stain, minimizes the risk of losing material and allows examination of stained glands within minutes of preparation. The technique was applied in a series of studies in which ticks were either infected with T. parva under different conditions, or maturation of parasites in adult ticks was stimulated by different means. When nymphal ticks were fed on the ears of cattle the subsequent infection rate of the adult ticks showed no correlation with the parasitaemia of the cattle at the time of nymphal engorgement. There was no difference in infection rates between adult ticks in which parasite maturation had been stimulated either by incubation at 37 °C or by feeding on rabbits. However, parasite maturation took about 1 day longer in incubated ticks than in rabbit-fed ticks. Female ticks were consistently more highly infected than males, both in terms of the percentage of ticks infected and the mean number of infected acini/tick. Ticks were infected with T. parva by injection of nymphs with parasitaemic bovine blood, but the resultant adult infection was lower than that in ticks which had been infected naturally by feeding on cattle.

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The acute effects on plasma LH concentrations of an injection of oestradiol\x=req-\ 17\g=b\ were studied in 7 non-cyclic heifers and 19 freemartins. One freemartin showed a normal LH surge due to the positive feedback effect of oestrogen on the hypothalamus. Of the other 18 freemartins, 4 showed positive increases in plasma LH and 6 were unclassified. There was no correlation between the degree of chimaerism and responsiveness to oestrogen. The results also showed that injected oestradiol suppressed the spontaneous fluctuations of plasma LH.