Characterization of Trypanosoma congolense serodemes in stocks isolated from cattle introduced onto a ranch in Kilifi, Kenya.

A herd of 20 cattle was introduced on a ranch in Kilifi, Coast Province of Kenya, where they were in contact with Glossina austeni for 6 months. In total, 65 trypanosome isolates were made from these animals. Examination of the isolates revealed that 61 were Trypanosoma congolense and 4 were T. theileri. Out of the 61 T. congolense isolates, 55 were successfully passaged and cloned in mice to provide trypanosome populations for further analyses. The stocks and their clones were inoculated into goats on which teneral G. morsitans centralis were later fed in order to provide metacyclics for use in serodeme analysis. Identification of serodemes was carried out by indirect immunofluorescence and neutralization using antimetacyclic hyperimmune sera prepared in mice against metacyclics of cloned trypanosome populations. So far 4 serodemes have been identified in 8 stocks and 7 clones. Each of the 9 stocks contained a mixture of at least 2 of the 4 serodemes identified. Furthermore, stocks isolated sequentially from individual animals contained the same serodemes despite repeated treatment with a curative dose (6 mg/kg body weight) of Berenil between isolations. From the latter finding, it can be inferred that the 4 serodemes were present on the ranch throughout the study period.

Prolactin and hypertension.

Progesterone (2.5 mg per kilogram) caused sustained hypertension in rabbits. When the same dose of progesterone was administered together with prolactin (1.25 mg. per kilogram), there was no increase in the blood pressure. In rabbits with progesterone-induced hypertension, the addition of prolactin caused a sharp drop in blood pressure. It is suggested that prolactin acts by reducing the sensitivity of the blood vessels to circulating pressor substances and further that a reduced prolactin response may be the cause of heightened sensitivity to pressor substances observed in pre-eclampsia.