Dr. Murai Éva szerk.: Parasitologia Hungarica 23. (Budapest, 1990)
most valuable method for recognizing early and latent infection and is said to have had a major role in that infection was twice eradicated from North America (GEORGI and THEODORIDES 1980; LEVINE 1985). In Hungary, the horse population has been maintained free from dourine since 1951. The complement fixation test is still the officially approved method of checking horse sera for dourine. At present T. equiperdum is maintained only in a few institutes by continuous passage in mice. In the United States of America, after repeated unsuccessful attempts MÖHLER (1911) eventually succeeded in maintaining a T. equiperdum strain on a slant blood agar culture prepared as described by Novy and McNeal; as, however, only a single strain could be adapted to the medium, this cultivating procedure is used only for the laboratory maintenance of other Trypanosoma species (MÖHLER 1911). During our studies on rodents two questions arose, namely (i) whether T. equiperdum passaged in horses twice can produce disease in the guinea pig at all; and (ii) how long trypanosomes can be demonstrated from guinea pigs. MATERIALS AND METHODS The T. equiperdum strain used in this study was obtained from the Pasteur Institute, Paris. The properties of this strain were described in our two previous papers (KEMENES and HORVÁTH 1986, HORVÁTH et al. 1987). The trypanosomes were maintained by continuous passage in mice. The blood of agonizing mice was collected in 3.3 % sodium citrate solution to prevent blood clotting. One ml of the blood dilution containing 1-1.5 x 10 trypanosomes was inoculated intraperitoneally into guinea pigs. Thirty spotted, male and female guinea pigs (body mass: 350-400 g), derived from the same stock, were used. The guinea pigs were divided into three groups of 10 and placed into three previously flamesterilized, large metal cages for an observation period of 38 weeks. Two groups contained only male and the third one comprised female guinea pigs. All three groups contained an additional control, uninoculated guinea pig. The guinea pigs were fed a rodent diet, oats and, twice a week, vegetables. Drinking water was available ad libitum. The mice used in the study were NMRI (Swiss) SPF albino mice (LATI, Gödöllő; body mass: 17-21 g). Blood samples were taken from the infected guinea pigs initially at one-week, then at 2- to 3-week intervals, by incising the animals' ear and, occasionally, from the heart. The fresh and Giemsa-stained blood smears were examined by light microscopy. Six mice each were inoculated intraperitoneally with 0.5 ml of blood from guinea pigs judged negative for trypanosoma infection. Of them, three mice were killed after an observation period of 10 days and another three were challenged with citrated murine blood containing T. equiperdum to determine whether the previous infection had induced immunity. The killed mice were necropsied after checking their blood for the presence of trypanosomes. Guinea pigs that were negative by microscopic examination of the blood were killed at 2-3 weeks, 8-12 weeks or 38 weeks PI. After necropsy, with their spleen homogenate mice were inoculated to enable detection of trypanosomes possibly present in the tissues as latent infection. The same was done with the spleen homogenate of guinea pigs that died during the experimental period.
