School of Veterinary Science, Massey University, Palmerston North, New Zealand.
Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, Uppsala, Sweden.
N Z Vet J. 2021 Mar;69(2):83-92. doi: 10.1080/00480169.2020.1830867. Epub 2020 Nov 25.
To estimate animal-level seroprevalence of serovar Copenhageni and serovars Ballum and Tarassovi, in beef cattle, sheep and deer on New Zealand farms, and herd/flock-level seroprevalence of any serovar when existing same-sera data for serovars Hardjobovis and Pomona were included, and to determine associations between risk factors and animal-level seroprevalence.
Banked sera from sheep (n=82), beef (n=54) and deer (n=62) herds/flocks (n=3,878 animals) from seven regions were analysed using the microscopic agglutination test. Titres of ≥48 were designated positive. Herds/flocks were considered positive if either ≥1, ≥2 or ≥3 animals were positive. Existing same-sera data for serovars Hardjobovis and Pomona were included to establish farm-level any-serovar seropositivity. Factors associated with serological status were analysed using generalised estimating equations.
Animal-level seroprevalence for serovars Ballum, Copenhageni, and Tarassovi, respectively, was 13.7 (95% CI=11.7-16.0)%, 12.6 (95% CI=10.6-14.7)% and 18.0 (95% CI=15.7-20.5)% for beef cattle, 10.5 (95% CI=9.0-12.1)%, 16.7 (95% CI=14.9-18.6)% and 14.0 (95% CI=12.4-15.8)% for sheep and 6.6 (95% CI=5.3-8.2)%, 15.5 (95% CI=13.5-17.7)% and 3.6 (95% CI=2.7-4.8)% for deer, respectively. Herd/flock-level seroprevalence for Ballum was 86.6, 52.4 and 39.0% for sheep, 85.2, 52.7 and 33.3% for beef cattle and 50.8, 27.9 and 21.3% for deer at definitions ≥1, ≥2 and ≥3 seropositive animals per species, respectively. For Copenhageni, corresponding data were 95.1, 73.2 and 56.1% for sheep, 68.5, 48.2 and 29.6% for beef cattle and 73.8, 57.4 and 41.0% for deer, and for Tarassovi, 80.5, 59.7 and 45.1% for sheep, 83.3, 68.5 and 61.1% for beef cattle, and 42.6, 16.4 and 4.9% for deer. Seropositivity to all serovars was observed from all regions, with some differences in seroprevalence observed between species and regions, but not between islands. Combining with Hardjobovis and Pomona data, herd/flock-level seropositivity for all animal species and all five serovars was 100% at definition ≥1 animal positive, and 97.5 and 96.3% for sheep flocks, 87.8 and 97.8% for beef cattle herds, and 89.3 and 75% for deer herds at ≥2 and ≥3 animals positive, respectively.
Seropositivity to serovars Ballum, Copenhageni and Tarassovi is common in sheep, beef cattle and deer New Zealand and most, or all farms have ≥1 livestock species seropositive to ≥1 serovar.
Serovars Ballum, Tarassovi and Copenhageni should be considered when clinical or subclinical signs of leptospirosis are observed in sheep, beef cattle or deer. Livestock sector workers are potentially at risk of exposure.
估计新西兰农场牛、羊和鹿的血清学 Copenhageni 血清型和血清型 Ballum、Tarassovi 的动物水平血清阳性率，以及包含 Hardjobovis 和 Pomona 血清型现有相同血清数据时任何血清型的畜群/羊群水平血清阳性率，并确定与动物水平血清阳性率相关的风险因素。
使用显微镜凝集试验分析来自七个地区的 82 只绵羊、54 只牛和 62 只鹿的畜群/羊群的血清（3878 只动物）。将滴度≥48 判定为阳性。如果至少有 1、2 或 3 只动物呈阳性，则将畜群/羊群判定为阳性。包含 Hardjobovis 和 Pomona 血清型的现有相同血清数据用于建立农场水平的任何血清型血清阳性率。使用广义估计方程分析与血清学状态相关的因素。
牛、羊和鹿的血清型 Ballum、Copenhageni 和 Tarassovi 的动物水平血清阳性率分别为 13.7（95%CI=11.7-16.0）%、12.6（95%CI=10.6-14.7）%和 18.0（95%CI=15.7-20.5）%、10.5（95%CI=9.0-12.1）%、16.7（95%CI=14.9-18.6）%和 14.0（95%CI=12.4-15.8）%、6.6（95%CI=5.3-8.2）%、15.5（95%CI=13.5-17.7）%和 3.6（95%CI=2.7-4.8）%。血清型 Ballum 的畜群/羊群水平血清阳性率在绵羊、牛和鹿中分别为 86.6、52.4 和 39.0%、85.2、52.7 和 33.3%、50.8、27.9 和 21.3%；对于 Copenhageni，相应的数据分别为 95.1、73.2 和 56.1%，68.5、48.2 和 29.6%，73.8、57.4 和 41.0%；对于 Tarassovi，分别为 80.5、59.7 和 45.1%，83.3、68.5 和 61.1%，42.6、16.4 和 4.9%。所有地区均观察到对所有血清型的血清阳性，不同物种和地区之间存在血清阳性率差异，但岛屿之间无差异。结合 Hardjobovis 和 Pomona 数据，所有动物物种和所有五个血清型的畜群/羊群水平血清阳性率在定义为≥1 只动物阳性时为 100%，在绵羊群中，≥2 只和≥3 只动物阳性时分别为 97.5%和 96.3%，在牛群中，≥2 只和≥3 只动物阳性时分别为 87.8%和 97.8%，在鹿群中，≥2 只和≥3 只动物阳性时分别为 89.3%和 75%。
血清型 Ballum、Copenhageni 和 Tarassovi 在新西兰绵羊、牛和鹿中普遍存在，大多数或所有农场的≥1 种牲畜对≥1 种血清型呈血清阳性。
在绵羊、牛或鹿中观察到钩端螺旋体病的临床或亚临床症状时，应考虑血清型 Ballum、Tarassovi 和 Copenhageni。牲畜部门的工作人员可能有接触的风险。
