Jongejan F, Vogel S W, Gueye A, Uilenberg G
Department of Parasitology and Tropical Veterinary Medicine, University of Utrecht, Pays-Bas.
Rev Elev Med Vet Pays Trop. 1993;46(1-2):223-7.
Sequential passage of Cowdria ruminantium (Senegal isolate) in cultures of bovine umbilical endothelial cells has resulted in loss of virulence without loss of immunogenicity, as previously demonstrated. We have carried out further immunization of 39 Dutch sheep using in vitro attenuated rickettsiae of passage 21 and challenged these animals either with the homologous or with heterologous Cowdria stocks. After vaccination several sheep developed elevated rectal temperatures for a maximum of 2 days, but no further clinical response to the vaccine was observed. All sheep developed high titres of antibodies to Cowdria. Challenge of 10 sheep with the homologous virulent stock did not provoke any clinical reaction, demonstrating that these animals were solidly immune. Reactions to heterologous challenge varied from virtually no reaction to fatal heartwater depending on the stock of Cowdria used. These results are discussed in relation to currently available vaccination methods against cowdriosis. In Senegal 30 susceptible sahelian sheep were immunized with attenuated rickettsiae of passage 21. Hyperthermia was seen in 13, the only other clinical symptom was a temporary diarrhoea. The immunized animals are at present exposed, together with 30 controls, to field challenge in the Niayes, the area where the Senegal isolate was originally isolated.
如先前所示，反刍动物考德里氏体（塞内加尔分离株）在牛脐静脉内皮细胞培养物中连续传代已导致毒力丧失但免疫原性未失。我们用第21代体外减毒立克次氏体对39只荷兰绵羊进行了进一步免疫，并分别用同源或异源考德里氏体毒株攻击这些动物。接种疫苗后，几只绵羊的直肠温度升高，最长持续2天，但未观察到对疫苗的进一步临床反应。所有绵羊均产生了高滴度的抗考德里氏体抗体。用同源强毒株攻击10只绵羊未引发任何临床反应，表明这些动物具有牢固的免疫力。根据所用考德里氏体毒株的不同，对异源攻击的反应从几乎无反应到致命的心脏水病不等。结合目前可用的抗牛心水病疫苗接种方法对这些结果进行了讨论。在塞内加尔，用第21代减毒立克次氏体对30只易感萨赫勒绵羊进行了免疫。13只绵羊出现体温过高，唯一的其他临床症状是暂时性腹泻。目前，这些免疫动物与30只对照动物一起，在最初分离出塞内加尔分离株的尼亚耶地区接受野外攻击。
