Sivakumar Thillaiampalam, Kothalawala Hemal, Weerasooriya Gayani, Silva Seekkuge Susil Priyantha, Puvanendiran Sumathy, Munkhjargal Tserendorj, Igarashi Ikuo, Yokoyama Naoaki
National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan; Veterinary Research Institute, P.O. Box 28, Peradeniya, Sri Lanka.
Veterinary Research Institute, P.O. Box 28, Peradeniya, Sri Lanka.
Vet Parasitol Reg Stud Reports. 2016 Dec;6:20-27. doi: 10.1016/j.vprsr.2016.11.009. Epub 2016 Dec 5.
Throughout the world, infections with the Babesia and Theileria parasites often result in economically significant clinical disease in cattle. We conducted a longitudinal survey of Babesia and Theileria infections in cattle from the Polonnaruwa (n=75; dry zone) and Nuwara Eliya (n=161; wet zone) districts of Sri Lanka. DNA from blood samples collected in June, September, and December 2014 and March 2015 was screened for Babesia bovis, Babesia bigemina, Theileria annulata and Theileria orientalis using specific polymerase chain reactions (PCRs). Additionally, serum samples collected from the animals were screened using enzyme-linked immunosorbent assays (ELISAs) to detect B. bovis- and B. bigemina-specific antibodies. All of the animals surveyed in Polonnaruwa and 150 (93.2%) of the animals surveyed in Nuwara Eliya were PCR-positive for Babesia and/or Theileria at least once during the study period. A greater percentage of the cattle in Polonnaruwa were positive for T. annulata and T. orientalis than B. bovis or B. bigemina at all time points. T. orientalis was the most common infection in Nuwara Eliya. Additionally, more cattle were seropositive for B. bigemina than B. bovis in both districts. Although significant variations were sometimes observed in the rates of animals that were positive for B. bigemina, T. annulata, and T. orientalis at the different sampling time points, the rates of new infections with these parasites (by PCR or ELISA) on second, third, and fourth time points among the parasite-negative samples at the first, second, and third time points, respectively, did not differ between the sampling in either district-suggesting that the parasite species infected cattle at a constant rate in these locations. However, in Polonnaruwa, the rates of new infection with T. annulata were higher than the rates of new infection with T. orientalis. The rates were also higher than those in Nuwara Eliya. In Nuwara Eliya, the rates of new infection with T. orientalis were higher than the rates of new infection with T. annulata. The rates were also higher than those in T. orientalis in Polonnaruwa. These differences might be due to variations in the density and activity of the specific tick vectors within and between the districts. Our findings suggest the need for year-round control measures against bovine Babesia and Theileria infection in Sri Lanka. Further studies to determine the densities of the vector tick species in the different geographical areas of the country are warranted.
在全球范围内，牛巴贝斯虫（Babesia）和泰勒虫（Theileria）寄生虫感染常常会在牛群中引发具有经济重要性的临床疾病。我们对来自斯里兰卡波隆纳鲁沃区（n = 75；干旱地区）和努沃勒埃利耶区（n = 161；湿润地区）的牛群进行了巴贝斯虫和泰勒虫感染的纵向调查。使用特异性聚合酶链反应（PCR）对2014年6月、9月、12月以及2015年3月采集的血液样本中的牛巴贝斯虫（Babesia bovis）、双芽巴贝斯虫（Babesia bigemina）、环形泰勒虫（Theileria annulata）和东方泰勒虫（Theileria orientalis）进行筛查。此外，对从这些动物采集的血清样本使用酶联免疫吸附测定（ELISA）来检测牛巴贝斯虫和双芽巴贝斯虫特异性抗体。在研究期间，波隆纳鲁沃区所有接受调查的动物以及努沃勒埃利耶区150头（93.2%）接受调查的动物至少有一次巴贝斯虫和/或泰勒虫PCR检测呈阳性。在所有时间点，波隆纳鲁沃区的牛群中环形泰勒虫和东方泰勒虫呈阳性的比例高于牛巴贝斯虫或双芽巴贝斯虫。东方泰勒虫是努沃勒埃利耶区最常见的感染类型。此外，在两个区中，双芽巴贝斯虫血清阳性的牛比牛巴贝斯虫血清阳性的牛更多。尽管在不同采样时间点双芽巴贝斯虫、环形泰勒虫和东方泰勒虫呈阳性的动物比例有时会观察到显著差异，但在两个区的采样中，在第一、第二和第三次时间点寄生虫阴性样本中，这些寄生虫在第二、第三和第四次时间点的新感染率（通过PCR或ELISA检测）并无差异——这表明这些寄生虫在这些地区以恒定速率感染牛群。然而，在波隆纳鲁沃区，环形泰勒虫的新感染率高于东方泰勒虫的新感染率。这些比率也高于努沃勒埃利耶区。在努沃勒埃利耶区，东方泰勒虫的新感染率高于环形泰勒虫的新感染率。这些比率也高于波隆纳鲁沃区东方泰勒虫的比率。这些差异可能是由于各区内和各区之间特定蜱虫媒介的密度和活动情况不同所致。我们的研究结果表明，斯里兰卡需要采取全年性的措施来控制牛巴贝斯虫和泰勒虫感染。有必要进一步开展研究以确定该国不同地理区域媒介蜱虫物种的密度。
