Abstract. Changes in plasma T4 levels were investigated in prepubertal and adult female goats during the course of an experimental Trypanosoma congolense infection. A significant decline in the T4 levels was observed within 1 week of trypanosome challenge. The levels remained low up to the end of the 7th weeks when prepubertal goats received a trypanocidal treatment, whereafter the values started to rise to normal pre-infection values. The post-infection plasma T4 values in the untreated adult goats did not return to normal except in one resistant goat which recovered naturally after 16 weeks of the infection. The thyroid glands of chronically infected and untreated adult goats revealed marked atrophy, fibrosis and colloidopathy. It is concluded that trypanosomiasis rapidly impairs thyroid gland function in susceptible animals, but these changes can be reversed by early trypanocidal treatment before marked degenerative changes become evident or following self cure in resistant animals.
B. M. Mutayoba, H. B. O'hara-Ireri and S. Gombe
B. M. Mutayoba, S. Gombe, E. N. Waindi and G. P. Kaaya
Abstract. Adult normocyclic female goats experimentally infected with Trypanosoma congolense developed irregular and shorter estrous cycles before complete cessation at the fourth cycle post-infection. This was followed within a month by a decline in the mean plasma progesterone and estradiol-17β levels. The peak luteal progesterone as well as pre-ovulatory estradiol-17β level declined progressively from the second to the fourth cycle post-infection. The ovaries became atretic with reduced numbers of primordial and primary follicles. The larger follicles became atretic at the tertiary stage with subsequent lack of corpora lutea formation. The rapidity of ovarian dysfunction appeared to be related to the degree of susceptibility of the individual infected goats.
B. M. Mutayoba, H. H. D. Meyer, D. Schams and E. Schallenberger
Using the biotin-streptavidin amplification technique, highly sensitive specific second-antibody enzyme immunoassays for determining LH in bovine plasma with long (48 h) and short (4 h) incubation periods were developed. Biotin was linked to bLH by the N-hydroxysuccimidine method and the product (biotinyl-bLH) used to bridge between streptavidin-peroxidase and the immobilised bLH antibody in competitive tests. The assays were validated and their performance compaired with a radioimmunoassay currently in use. The sensitivities of the long and short incubation enzyme immunoassays (8 pg and 15 pg/well, respectively) were superior to that of 5-day incubation radioimmunoassay (100 pg/tube). Plasma interference in both assays were acceptable and volumes of 5 to 40 μl gave parallel standard curves and comparable LH levels, 10–20 μl plasma was sufficient to measure LH baseline levels by the long incubation enzyme immunoassay. The mean recovery of added standard bLH to plasma samples containing different endogenous LH was >90% (range 91.7–112) in both assays. The intra- and inter-assay variations of both assays were less than 10 and 17%, respectively. When both enzyme immunoassay and radioimmunoassay were used to measure LH in cyclic cows, the basal levels measured by enzyme immunoassay were lower than that measured by radioimmunoassay. Enzyme immunoassay offers an attractive alternative to the lengthy radioimmunoassay in current usage, with an added advantage of employing non-isotopic label.