Parasites, Vectors and Vector-borne Diseases (PVVD), ARC-Onderstepoort Veterinary Institute, Private Bag X05, 100 Old Soutpan Road, Onderstepoort 0110, Pretoria, South Africa.
Vet Parasitol. 2010 May 28;170(1-2):30-6. doi: 10.1016/j.vetpar.2010.02.008. Epub 2010 Feb 18.
Serological responses of field cattle (260) on a farm in KwaZulu-Natal, South Africa were determined before and after vaccination with the commercial Babesia bovis live-blood vaccine, using the indirect fluorescent antibody test (IFAT). All the cattle tested negative for B. bovis antibodies before vaccination while 83% of them had significant antibody titres (>or=1/80) to Babesia bigemina, indicating a high degree of natural exposure to the latter parasite. By Day 60 post-vaccination only 53% of the cattle had seroconverted to B. bovis. This raised the question as to why only half of the vaccinated cattle had seroconverted. The possibility of previous exposure to B. bigemina infection interfering with the development of detectable antibodies to B. bovis was therefore investigated under controlled conditions. It was found that simultaneous vaccination with B. bigemina and B. bovis (n=6), and B. bigemina vaccination followed by B. bovis vaccination (n=12), had no effect on the animals' immune responses to B. bovis vaccination. All of these cattle developed a significant antibody response. However, only 58% of cattle (n=12) which had previously been inoculated with the B. bigemina field isolate, obtained from the trial farm, seroconverted (>or=1/80) after B. bovis vaccination, yet parasites for B. bovis could be demonstrated microscopically in all of the animals in this group. These findings confirmed the serology results from the field trial. When challenged with a B. bovis field isolate, cattle in this group did not show clinical reactions compared with an unvaccinated control group. The judicious use of IFAT to establish vaccination success obtained with the current South African B. bovis vaccine is indicated.
在南非夸祖鲁-纳塔尔省的一个农场里，对 260 头野外牛进行了血清学反应测定，在接种商业性巴贝斯虫 live-blood 疫苗前后使用间接荧光抗体试验（IFAT）进行了测定。所有牛在接种前均检测出 B. bovis 抗体阴性，而 83%的牛对巴贝斯虫二联苗有显著的抗体滴度（≥1/80），表明它们曾高度自然感染后者寄生虫。接种后第 60 天，只有 53%的牛对 B. bovis 发生血清转化。这就提出了一个问题，为什么只有一半的接种牛发生了血清转化。因此，在控制条件下，研究了先前感染巴贝斯虫二联苗感染是否会干扰对 B. bovis 的可检测抗体的发展。结果发现，同时接种巴贝斯虫二联苗和 B. bovis（n=6），以及先接种巴贝斯虫二联苗后接种 B. bovis（n=12），对动物对 B. bovis 疫苗接种的免疫反应没有影响。所有这些牛都产生了显著的抗体反应。然而，仅有 58%（n=12）的牛之前曾接种过来自试验农场的巴贝斯虫二联苗野外分离株，在接种 B. bovis 后血清转化（≥1/80），但在该组所有动物中均可以显微镜观察到 B. bovis 寄生虫。这些发现证实了田间试验的血清学结果。当用 B. bovis 野外分离株进行攻毒时，与未接种对照组相比，该组中的牛没有出现临床反应。明智地使用 IFAT 来确定当前南非 B. bovis 疫苗的接种成功率是必要的。
