title: Effect of African trypanosomiasis on plasma cortisol and thyroxine concentration in goats.
abstract: Changes in plasma cortisol and thyroxine (T4) levels were measured weekly in female goats experimentally infected with Trypanosoma congolense. Values for plasma cortisol (range 10 to 25 nmol litre-1) and T4 (range 65 to 120 nmol litre-1) were within normal ranges in all goats before infection and in control animals throughout the 24 weeks of study. Cortisol/T4 ratios of 0.23 to 0.15 (or 1:4 to 1:7) were obtained. In the infected goats a significant increase in cortisol and decline in T4 were simultaneously observed within one week of the onset of parasitaemia and fever. A peak cortisol/T4 ratio of 2.0 (2:1) was obtained four weeks after infection when cortisol levels rose to 59.0 +/- 8.9 nmol litre-1 and T4 declined to 29.4 +/- 2.2 nmol litre-1. Thereafter the mean levels fluctuated but remained high (over 30 nmol litre-1) for cortisol and low (under 50 nmol litre-1) for T4 up to 18 weeks after infection. Both hormones tended to return to normal levels towards the end of the study. The changes in mean cortisol levels showed a significant inverse correlation with changes in T4 (r = -0.57, P less than 0.001, n = 26). It is suggested that in trypanosomiasis, hypothalamic stress causes increases in plasma cortisol levels and at the same time suppresses the activity of the thyroid gland.
authors.affiliation: Reproductive Biology Unit, NCRR, Nairobi, Kenya.
authors.forename: B M
authors.initials: BM
authors.lastname: Mutayoba
authors.forename: S
authors.initials: S
authors.lastname: Gombe
mesh_terms: D000818:Animals; D005260:Female; D015511:Goat Diseases / Q000097:blood*; D006041:Goats; D006854:Hydrocortisone / Q000097:blood*; D012044:Regression Analysis; D013974:Thyroxine / Q000097:blood*; D014348:Trypanosoma congolense; D014353:Trypanosomiasis, African / Q000097:blood / Q000662:veterinary*
chemical_list: D013974:Thyroxine; D006854:Hydrocortisone