Konnai Satoru, Imamura Saiki, Nakajima Chie, Witola William Harold, Yamada Shinji, Simuunza Martin, Nambota Andrew, Yasuda Jun, Ohashi Kazuhiko, Onuma Misao
Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan.
Acta Trop. 2006 Aug;99(1):34-41. doi: 10.1016/j.actatropica.2006.06.008. Epub 2006 Aug 8.
In order to investigate the transmission dynamics of Theileria parva (T. parva) by the brown ear tick, Rhipicephalus appendiculatus (R. appendiculatus), under experimental conditions, detection of T. parva in ticks and cattle was performed by a quantitative real-time PCR assay. A calf inoculated with a T. parva mixture became PCR-positive for T. parva infection on day 8 post-inoculation, and subsequently, nymphal ticks were introduced and maintained to feed on the infected calf for 6 days. Engorged nymphs were collected daily and allowed to molt into adults, and overall, 70.8% (121/171) of the adult ticks acquired the T. parva infection. Furthermore, the T. parva infection rate in ticks under field conditions was monitored by real-time PCR in R. appendiculatus ticks collected from a traditionally managed pastoral land of Zambia, on which Sanga breed cattle are traditionally reared and the area has endemic East Coast fever (ECF). A total of 70 cattle were randomly selected in the same area and 67 (95.7%) were found to be serologically positive for R. appendiculatus tick antigen (RIM36). Twenty-nine (43.3%) of the 67 serologically positive cattle were real-time PCR-positive for T. parva, although no piroplasms could be detected in the blood smears. Unexpectedly, out of 614 R. appendiculatus nymphal and adult ticks collected by flagging vegetation, 4.1% were positive for T. parva DNA. However, since the rate of transmission of T. parva from infected cattle to ticks and vice versa and the serological evidence of exposure to R. appendiculatus ticks in naturally exposed cattle were relatively high, it would be wise in such a case to consider vector control as well as vaccination against ECF as control measures.
为了在实验条件下研究微小泰勒虫(Theileria parva,T. parva)通过褐耳蜱(Rhipicephalus appendiculatus,R. appendiculatus)的传播动力学,采用定量实时荧光定量PCR检测蜱和牛体内的T. parva。一头接种T. parva混合物的小牛在接种后第8天PCR检测呈T. parva感染阳性,随后引入若蜱并使其在感染的小牛身上取食6天。每天收集饱血若蜱并使其蜕变为成蜱,总体而言,70.8%(121/171)的成蜱感染了T. parva。此外,通过实时荧光定量PCR监测赞比亚传统管理的牧场土地上采集的R. appendiculatus蜱在野外条件下的T. parva感染率,该牧场传统上饲养桑加品种的牛,该地区有东海岸热(ECF)地方病。在同一地区随机选择了70头牛,发现其中67头(95.7%)对R. appendiculatus蜱抗原(RIM36)血清学呈阳性。在67头血清学阳性的牛中,有29头(43.3%)T. parva实时荧光定量PCR检测呈阳性,尽管在血涂片中未检测到梨形虫。出乎意料的是,在通过拍打植被收集的614只R. appendiculatus若蜱和成蜱中,4.1%的蜱T. parva DNA呈阳性。然而,由于T. parva从感染牛到蜱以及反之亦然的传播率,以及自然暴露牛中接触R. appendiculatus蜱的血清学证据相对较高,在这种情况下,将媒介控制以及针对ECF的疫苗接种作为控制措施是明智的。