Chamboko T, Mukhebi A W, Callaghan C J, Peter T F, Kruska R L, Medley G F, Mahan S M, Perry B D
UF/USAID/SADC Heartwater Research Project, Harare, Zimbabwe.
Prev Vet Med. 1999 Apr 9;39(3):191-210. doi: 10.1016/s0167-5877(98)00144-5.
As part of a series of studies associated with the development of improved vaccines for heartwater (a tick-borne disease of ruminant livestock caused by Cowdria ruminantium), field surveys were carried out to assess losses associated with the disease and the costs associated with controlling it in the two main agro-ecological zones of Zimbabwe (lowveld and highveld) where heartwater is believed to be endemic and epidemic, respectively. In each zone, a cross-sectional study was performed in the main farming systems (smallholder (SH) and large-scale commercial (LSC) beef and dairy), followed by longitudinal studies in the same sectors to improve data accuracy for some parameters. Suspected heartwater-specific mortality in cattle was similar in all LSC sectors (p = 0.72) accounting for a median 1% mortality risk. Heartwater-specific mortality in SH areas was not assessed due to poor diagnostic ability of the farmers. Few LSC farms and SH households kept sheep; suspected heartwater-specific mortality in LSC sheep was 0.8% in the lowveld and 2.4% in the highveld. Goats were a major enterprise in SH areas but not on LSC farms. Suspected heartwater mortality in LSC goats was 0.8% at one site in the highveld and 17.5% on a farm in the lowveld. Application of acaricides was the major control method for heartwater and other tick-borne diseases on both SH and LSC farms. On LSC farms, plunge dipping was used most frequently and the number of acaricide applications ranged widely between 3 and 52 per year. The total cost of acaricides per head per annum was higher in highveld dairies than in highveld and lowveld beef enterprises (p = 0.03). In SH areas, cattle plunge dipping was conducted by the government with an average frequency of 8 +/- 2 (sd) immersions per annum in both the lowveld and highveld. The type of tick control on sheep and goats in all production systems was highly variable (ranging from none to hand removal or intensive acaricide treatment). Suspected heartwater cases on LSC farms were treated with tetracyclines; treatment was not reported in SH areas. Reported treatment costs were high (median Z$ 120) and highly variable (range Z$-833). Vaccination against heartwater with the live, blood-based vaccine was reported on only one LSC farm. LSC farms applying acaricide 30 or more times per year reported higher morbidity (p < 0.0001) and mortality (p < 0.0001) than farms applying acaricides less than 30 times a year. This finding supports the use of reduced tick control in the management of heartwater in Zimbabwe.
作为与开发改良型心水病疫苗（一种由反刍动物立克次氏体引起的反刍家畜蜱传疾病）相关的一系列研究的一部分，开展了实地调查，以评估津巴布韦两个主要农业生态区（低地和高地）与该疾病相关的损失以及控制该疾病的成本，据信心水病在这两个地区分别为地方病和流行病。在每个区域，对主要养殖系统（小农户（SH）以及大规模商业（LSC）肉牛和奶牛养殖）进行了横断面研究，随后在同一部门进行纵向研究，以提高某些参数的数据准确性。所有LSC部门的牛疑似心水病特异性死亡率相似（p = 0.72），中位死亡风险为1%。由于农民的诊断能力较差，未对SH地区的心水病特异性死亡率进行评估。很少有LSC农场和SH家庭饲养绵羊；LSC绵羊疑似心水病特异性死亡率在低地为0.8%，在高地为2.4%。山羊是SH地区的主要养殖对象，但LSC农场不养殖。LSC山羊疑似心水病死亡率在高地的一个养殖场为0.8%，在低地的一个农场为17.5%。使用杀螨剂是SH和LSC农场控制心水病及其他蜱传疾病的主要方法。在LSC农场，药浴最为常用，每年使用杀螨剂的次数在3至52次之间差异很大。高地奶牛场每头牛每年的杀螨剂总成本高于高地和低地的肉牛企业（p = 0.03）。在SH地区，政府进行牛药浴，低地和高地每年平均药浴频率为8±2（标准差）次。所有生产系统中绵羊和山羊的蜱虫控制方式差异很大（从无到手工清除或强化杀螨剂处理）。LSC农场的疑似心水病病例用四环素治疗；SH地区未报告有治疗情况。报告的治疗成本很高（中位数为120津巴布韦元）且差异很大（范围为833津巴布韦元）。仅在一个LSC农场报告了使用基于血液的活疫苗预防心水病的情况。每年使用杀螨剂30次或更多次的LSC农场报告的发病率（p < 0.0001）和死亡率（p < 0.0001）高于每年使用杀螨剂次数少于30次的农场。这一发现支持在津巴布韦的心水病管理中减少蜱虫控制措施的使用。
