Animal Health
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Browsing Animal Health by Author "Amrein, Y. U.,"
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Item On the Reacquisition of Virulence in Trypanosomes of the Brucei-group(1965) Amrein, Y. U., ; Geigy, R.; Kauffmann, M. ; Swiss Tropical Institute, BasleThe authors began by attempting to extend earlier observations [this Bulletin, 1964, v. 61, 1127] which appeared to show that the addition of the sugars inositol and arabinose sporadically induced a re-acquisition of infectivity to mice in cultures of Trypanosoma brucei and T. rhodesiense. With the same or similar stabilates of recently isolated strains of these 2 species, grown in Weinman's medium at 25 °C, the present work showed that the re-acquisition of infectivity was not due to the addition of sugars, but occurred also in control cultures. It was concluded that the most important variable was the donor of the (human) blood used in preparing the medium. Among 5 donors tested, cultures grown in medium prepared from the blood of 1 were consistently uninfective to mice. Media prepared from 2 other donors always produced a proportion of infective cultures, while media prepared from the remaining 2 donors gave rise to infective forms only when stored at 4°C for 6 weeks before being inoculated with trypanosomes. However, under these conditions, all of 10 cultures prepared with blood from one of the latter 2 donors became infective to mice, producing fairly acute infections in 19 out of 20 mice to which they were inoculated. In contrast, only 1-5 of the 10 cultures prepared from each of the other 3 suitable donors became infective, and the resulting infections in mice were very chronic. Recognizable metacyclic trypanosomes were seen only rarely in any of these cultures. The authors found that no cultures became infective before 8 days after inoculation, and the majority of those which became infective did so around the 18th day: thereafter infectivity declined rapidly. They compare this with the fact that infected tsetse flies become infective about 18 days after ingesting trypanosomes, and speculate that the nature of the blood on which the tsetse feed may play an important part in determining whether infective trypanosomes develop in a particular fly. The authors also record observations that cultivated forms of T. brucei and T. rhodesiense, when suspended in tissue culture fluid no. 199 with pieces of organs removed from tsetse flies, were attracted to midgut, salivary gland and muscle tissue, but not to Malpighian tubes, gonads or fat cells. Such cultures declined after 6-7 days, and none became infective to mice, in contradistinction to the results obtained by TRAGER with T. viva
