School of Veterinary Science, Massey University, Palmerston North, New Zealand.
School of Agriculture and Environment, Massey University, Palmerston North, New Zealand.
Vet Parasitol. 2021 Mar;291:109391. doi: 10.1016/j.vetpar.2021.109391. Epub 2021 Feb 19.
Theileria orientalis is a tick‒borne intracellular parasite of red blood cells that causes severe and mild infections in various ruminants worldwide. To date there have been 11 types identified within this species, of which 4 types are presently found in New Zealand cattle. Since 2012, New Zealand has suffered a substantial epidemic of infectious bovine anaemia in both dairy and beef cattle associated with the Ikeda type. The speed at which the disease spread through the North Island suggested that other species could have been involved in transmission. The aim of a series of related experiments was to test the null hypothesis that sheep cannot maintain T. orientalis Ikeda type infection or infect ticks that feed on them. Several studies were conducted over 2 years to address this hypothesis which together showed that sheep can have detectable levels of T. orientalis Ikeda type infection in both the acute and chronic phase and that Haemaphysalis longicornis larvae can become infected when feeding on sheep. No anaemia, weight loss or clinical disease was recorded in the sheep in the acute phase of infection. The levels of infection recorded in the sheep were much lower than those found in cattle, consistent with the sheep being asymptomatic carriers of T. orientalis Ikeda type infection.
东方泰勒虫是一种寄生在红细胞内的蜱传寄生虫，可引起世界范围内各种反刍动物的严重和轻度感染。迄今为止，该物种已鉴定出 11 种，其中 4 种目前在新西兰牛群中发现。自 2012 年以来，新西兰在奶牛和肉牛中都遭受了传染性牛贫血的严重流行，这种疾病与 Ikeda 型有关。该疾病在北岛迅速传播的速度表明，可能还有其他物种参与了传播。一系列相关实验的目的是检验一个假设，即绵羊不能维持东方泰勒虫 Ikeda 型感染或感染以其为食的蜱。在两年的时间里进行了几项研究来验证这一假设，这些研究表明，绵羊在急性和慢性阶段都可以检测到东方泰勒虫 Ikeda 型感染，并且在以绵羊为食时，长角血蜱幼虫可以被感染。在感染的急性阶段，绵羊没有出现贫血、体重减轻或临床疾病。绵羊感染的程度远低于牛群中的感染程度，这与绵羊是东方泰勒虫 Ikeda 型感染的无症状携带者一致。
