Department of Global Health and Bio-Medical Sciences, School of Life Science and Bio-engineering, The Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania.
Tanzania Veterinary Laboratory Agency, Central Veterinary Laboratory, Dar es Salaam, Tanzania.
PLoS Negl Trop Dis. 2023 Apr 5;17(4):e0011199. doi: 10.1371/journal.pntd.0011199. eCollection 2023 Apr.
Smallholder dairy farming is crucial for the Tanzanian dairy sector which generates income and employment for thousands of families. This is more evident in the northern and southern highland zones where dairy cattle and milk production are core economic activities. Here we estimated the seroprevalence of Leptospira serovar Hardjo and quantified potential risk factors associated with its exposure in smallholder dairy cattle in Tanzania.
From July 2019 to October 2020, a cross-sectional survey was carried out in a subset of 2071 smallholder dairy cattle. Information about animal husbandry and health management was collected from farmers, and blood was taken from this subset of cattle. Seroprevalence was estimated and mapped to visualize potential spatial hotspots. The association between a set of animal husbandry, health management and climate variables and ELISA binary results was explored using a mixed effects logistic regression model.
An overall seroprevalence of 13.0% (95% CI 11.6-14.5%) for Leptospira serovar Hardjo was found in the study animals. There was marked regional variations with the highest seroprevalence in Iringa 30.2% (95% CI 25.1-35.7%) and Tanga 18.9% (95% CI 15.7-22.6) with odds ratios of OR = 8.13 (95% CI 4.23-15.63) and OR = 4.39 (95% CI 2.31-8.37), respectively. Multivariate analysis revealed the individual animal factors that were a significant risk for Leptospira seropositivity in smallholder dairy cattle were: animals over 5 years of age (OR = 1.41, 95% CI 1.05-1.9); and indigenous breed (OR = 2.78, 95% CI 1.47-5.26) compared to crossbred animals SHZ-X-Friesian (OR = 1.48, 95% CI 0.99-2.21) and SHZ-X-Jersey (OR = 0.85, 95% CI 0.43-1.63). Farm management factors significantly associated with Leptospira seropositivity included: hiring or keeping a bull for raising purposes (OR = 1.91, 95% CI 1.34-2.71); distance between farms of more than 100 meters (OR = 1.75, 95% CI 1.16-2.64); cattle kept extensively (OR = 2.31, 95% CI 1.36-3.91); farms without cat for rodent control (OR = 1.87, 95% CI 1.16-3.02); farmers with livestock training (OR = 1.62, 95% CI 1.15-2.27). Temperature (OR = 1.63, 95% CI 1.18-2.26), and the interaction of higher temperature and precipitation (OR = 1.5, 95%CI 1.12-2.01) were also significant risk factors.
This study indicated seroprevalence of Leptospira serovar Hardjo, as well as the risk factors driving dairy cattle leptospirosis exposure in Tanzania. The study showed an overall high leptospirosis seroprevalence with regional variations, where Iringa and Tanga represented the highest seroprevalence and risk. The study highlighted the urgent need to understand the human exposures and risks from this important zoonosis to develop control measures and awareness of the problem and quantify the economic and production impacts through abortion and milk loss. In addition, given that the available data was limited to Leptospira serovar Hardjo, the study recommends more studies to identify serologically the most common serovars in cattle for targeted vaccination and risk reduction.
小农户奶牛养殖对坦桑尼亚的奶牛行业至关重要，为成千上万的家庭提供收入和就业机会。在北部和南部高地地区情况更为明显，那里奶牛和牛奶生产是核心经济活动。在这里，我们估计了坦桑尼亚小农户奶牛中感染钩端螺旋体血清型哈迪的血清流行率，并量化了与其接触相关的潜在风险因素。
从 2019 年 7 月到 2020 年 10 月，在坦桑尼亚的一个小农户奶牛亚组中进行了一项横断面调查。从农民那里收集了关于畜牧业和健康管理的信息，并从小农户奶牛亚组中采集了血液。估计了血清流行率，并进行了可视化，以显示潜在的空间热点。使用混合效应逻辑回归模型探索了一组畜牧业、健康管理和气候变量与 ELISA 二进制结果之间的关联。
研究动物的钩端螺旋体血清型哈迪总血清流行率为 13.0%（95%CI 11.6-14.5%）。区域差异显著，伊林加的血清流行率最高为 30.2%（95%CI 25.1-35.7%），坦噶为 18.9%（95%CI 15.7-22.6%），优势比分别为 OR = 8.13（95%CI 4.23-15.63）和 OR = 4.39（95%CI 2.31-8.37）。多变量分析显示，小农户奶牛中钩端螺旋体血清阳性的个体因素是：年龄超过 5 岁的动物（OR = 1.41，95%CI 1.05-1.9）；和本地品种（OR = 2.78，95%CI 1.47-5.26），与杂交品种 SHZ-X-Friesian（OR = 1.48，95%CI 0.99-2.21）和 SHZ-X-Jersey（OR = 0.85，95%CI 0.43-1.63）相比。与钩端螺旋体血清阳性相关的农场管理因素包括：雇用或保留公牛用于繁殖（OR = 1.91，95%CI 1.34-2.71）；农场之间的距离超过 100 米（OR = 1.75，95%CI 1.16-2.64）；牛群广泛放养（OR = 2.31，95%CI 1.36-3.91）；农场没有养猫来控制啮齿动物（OR = 1.87，95%CI 1.16-3.02）；有牲畜培训的农民（OR = 1.62，95%CI 1.15-2.27）。温度（OR = 1.63，95%CI 1.18-2.26）和高温与降水的相互作用（OR = 1.5，95%CI 1.12-2.01）也是重要的危险因素。
本研究表明了坦桑尼亚钩端螺旋体血清型哈迪的血清流行率，以及导致奶牛钩端螺旋体病暴露的风险因素。研究显示，总体钩端螺旋体病血清流行率较高，区域差异较大，伊林加和坦噶的血清流行率和风险最高。该研究强调了迫切需要了解人类接触这种重要人畜共患病的风险，以制定控制措施和提高对该问题的认识，并通过流产和牛奶损失来量化经济和生产影响。此外，由于现有数据仅限于钩端螺旋体血清型哈迪，因此研究建议进行更多研究，以确定牛中最常见的血清型，以便有针对性地接种疫苗和降低风险。
