Leelahapongsathon Kansuda, Schukken Ynte Hein, Pinyopummintr Tanu, Suriyasathaporn Witaya
Department of Food Animal Clinics, Faculty of Veterinary Medicine, Chiang Mai University, Mae Hea, Chiang Mai, Chiang Mai Province 50100, Thailand.
Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY 14853; GD Animal Health, 7418EZ Deventer, the Netherlands.
J Dairy Sci. 2016 Feb;99(2):1418-1426. doi: 10.3168/jds.2015-9950. Epub 2015 Dec 10.
The objectives of study were to determine the transmission parameters (β), durations of infection, and basic reproductive numbers (R0) of both Streptococcus agalactiae and Streptococcus uberis as pathogens causing mastitis outbreaks in dairy herds. A 10-mo longitudinal study was performed using 2 smallholder dairy herds with mastitis outbreaks caused by Strep. agalactiae and Strep. uberis, respectively. Both herds had poor mastitis control management and did not change their milking management during the entire study period. Quarter milk samples were collected at monthly intervals from all lactating animals in each herd for bacteriological identification. The durations of infection for Strep. uberis intramammary infection (IMI) and Strep. agalactiae IMI were examined using Kaplan-Meier survival curves, and the Kaplan-Meier survival functions for Strep. uberis IMI and Strep. agalactiae IMI were compared using log rank survival-test. The spread of Strep. uberis and Strep. agalactiae through the population was determined by transmission parameter, β, the probability per unit of time that one infectious quarter will infect another quarter, assuming that all other quarters are susceptible. For the Strep. uberis outbreak herd (31 cows), 56 new infections and 28 quarters with spontaneous cure were observed. For the Strep. agalactiae outbreak herd (19 cows), 26 new infections and 9 quarters with spontaneous cure were observed. The duration of infection for Strep. agalactiae (mean=270.84 d) was significantly longer than the duration of infection for Strep. uberis (mean=187.88 d). The transmission parameters (β) estimated (including 95% confidence interval) for Strep. uberis IMI and Strep. agalactiae IMI were 0.0155 (0.0035-0.0693) and 0.0068 (0.0008-0.0606), respectively. The R0 (including 95% confidence interval) during the study were 2.91 (0.63-13.47) and 1.86 (0.21-16.61) for Strep. uberis IMI and Strep. agalactiae IMI, respectively. In conclusion, the transmission parameter and R0 values were not different between both pathogens; however, the duration of infection for Strep. agalactiae was longer than Strep. uberis. These suggest that Strep. uberis may have a different transmission dynamic compared with Strep. agalactiae.
本研究的目的是确定无乳链球菌和乳房链球菌作为导致奶牛群乳腺炎暴发的病原体的传播参数（β）、感染持续时间和基本繁殖数（R0）。对两个分别暴发由无乳链球菌和乳房链球菌引起的乳腺炎的小农户奶牛群进行了为期10个月的纵向研究。两个牛群的乳腺炎控制管理都很差，并且在整个研究期间没有改变挤奶管理方式。每月从每个牛群的所有泌乳动物中采集一次乳区奶样进行细菌学鉴定。使用Kaplan-Meier生存曲线检查乳房链球菌乳房内感染（IMI）和无乳链球菌IMI的感染持续时间，并使用对数秩生存检验比较乳房链球菌IMI和无乳链球菌IMI的Kaplan-Meier生存函数。无乳链球菌和乳房链球菌在群体中的传播由传播参数β决定，β是指在假定所有其他乳区均易感的情况下，一个感染乳区在单位时间内感染另一个乳区的概率。对于乳房链球菌暴发的牛群（31头奶牛），观察到56例新感染和28个乳区自然治愈。对于无乳链球菌暴发的牛群（19头奶牛），观察到26例新感染和9个乳区自然治愈。无乳链球菌的感染持续时间（平均=270.84天）显著长于乳房链球菌的感染持续时间（平均=187.88天）。估计的乳房链球菌IMI和无乳链球菌IMI的传播参数（β）（包括95%置信区间）分别为0.0155（0.0035 - 0.069）和0.0068（0.0008 - 0.0606）。研究期间，乳房链球菌IMI和无乳链球菌IMI的R0（包括95%置信区间）分别为2.91（0.63 -）和1.86（0.21 - 16.61）。总之，两种病原体的传播参数和R0值没有差异；然而，无乳链球菌的感染持续时间比乳房链球菌长。这些表明乳房链球菌与无乳链球菌相比可能具有不同的传播动态。
