Mbassa G K, Kweka L E, Dulla P N
Department of Veterinary Anatomy, Faculty of Veterinary Medicine, Sokoine University of Agriculture, Morogoro, Tanzania.
Vet Parasitol. 1998 May;77(1):41-8. doi: 10.1016/s0304-4017(97)00138-6.
Two Theileria parva sporozoite stabilates stored at -196 degrees C, then at -70 degrees C for six weeks (stabilate 1) and more than six months (stabilate 2) were inoculated into four eight-month old male calves, 1 and 2 (stabilate 1), and 3 and 4 (stabilate 2). Calves 1 and 2 developed pyrexia, enlargement of lymph nodes, and the former died of East Coast Fever. Calves 3 and 4 showed slight enlargement of lymph nodes without fever. Lymph node smears from all calves (from day 10 to 20 post-inoculation) showed lymphoblasts, phagocytic macrophages, and schizonts. Piroplasms were detected in erythrocytes in blood smears from calves 1 and 2 but not in calves 3 and 4. Calves 2, 3 and 4 recovered without any treatment while calf 1 died of East Coast Fever on day 20. Serum samples from recovered calves taken on day 30 of the experiment were positive for antischizont antibodies to T. parva at 1:640 dilution, but pre-inoculation serum samples were negative. Stabilate 2 was used to immunize 64 Boran, Friesian, Ayrshire and crosses with Zebu cattle in four herds with 25% reduction of oxytetracycline dose. All the animals except one calf recovered without any severe reactions. The latter died of disease other than ECF after the monitoring period was over (day 24). Day 30 post-inoculation serum samples were positive for T. parva antischizont antibodies. A follow-up of the remaining animals for over one year revealed no further ECF incidences in these herds. This experiment shows the loss of infectivity of the vaccine stored at temperatures higher than -196 degrees C. dependent on the duration. However, despite the lack of clinical signs in calves 3 and 4, there was cellular response and antibody production, and the stabilate for vaccine against East Coast fever can thus be stored prior to use at higher than -196 degrees C and still maintain capability to produce antibodies in field cattle, eliminating the use of oxytetracycline and monitoring. The vaccine will be cheaper and easier to use and the requirement for liquid nitrogen in the field reduced and the scale of application of the vaccine widened.
将保存在-196℃，然后在-70℃保存六周（保种1）和六个多月（保种2）的两个泰勒虫孢子虫稳定株接种到四头八个月龄的雄性犊牛中，1号和2号犊牛接种保种1，3号和4号犊牛接种保种2。1号和2号犊牛出现发热、淋巴结肿大，前者死于东海岸热。3号和4号犊牛淋巴结稍有肿大但无发热。所有犊牛（接种后第10天至20天）的淋巴结涂片显示有淋巴母细胞、吞噬性巨噬细胞和裂殖体。在1号和2号犊牛的血液涂片红细胞中检测到梨形虫，但3号和4号犊牛未检测到。2号、3号和4号犊牛未经任何治疗而康复，而1号犊牛在第20天死于东海岸热。在实验第30天采集的康复犊牛血清样本在1:640稀释度下对泰勒虫抗裂殖体抗体呈阳性，但接种前血清样本为阴性。保种2用于免疫四个牛群中的64头博拉恩牛、弗里斯兰牛、艾尔郡牛以及与瘤牛的杂交牛，土霉素剂量减少25%。除一头犊牛外，所有动物均康复且无任何严重反应。后者在监测期结束（第24天）后死于非东海岸热的疾病。接种后第30天的血清样本对泰勒虫抗裂殖体抗体呈阳性。对其余动物进行一年多的随访发现，这些牛群中未再发生东海岸热病例。该实验表明，保存在高于-196℃温度下的疫苗的感染力会随保存时间而丧失。然而，尽管3号和4号犊牛没有临床症状，但仍有细胞反应和抗体产生，因此，用于预防东海岸热的疫苗稳定株在使用前可保存在高于-196℃的温度下，并且仍能在田间牛群中产生抗体，从而无需使用土霉素和进行监测。该疫苗将更便宜且更易于使用，减少了田间对液氮的需求，并扩大了疫苗的应用规模。
