Al-Fahdi Amira, Alqamashoui Badar, Al-Hamidhi Salama, Kose Onur, Tageldin Mohammed H, Bobade Patrick, Johnson Eugene H, Hussain Abdel-Rahim, Karagenc Tulin, Tait Andy, Shiels Brian, Bilgic Huseyin Bilgin, Babiker Hamza
Department of Biochemistry, College of Medicine and Health Sciences, Sultan Qaboos University, Oman.
A'Sharqiyah University, Oman.
Ticks Tick Borne Dis. 2017 Aug;8(5):741-748. doi: 10.1016/j.ttbdis.2017.05.008. Epub 2017 May 21.
Theileriosis is one of the most prevalent infectious diseases of livestock in the Arabian Peninsula, and causes high rates of mortality and morbidity in sheep and cattle. However, there is a paucity of information on the distribution of Theileria spp. over the whole region and their impact on different hosts. The present study carried out a country-wide molecular survey for Theileria spp. of livestock in Oman across four governorates. The aim of the survey was to define the prevalence of Theileria spp. in cattle, sheep and goats, highlight risk factors for infection and identify the main tick species involved in parasite transmission.
A total of 2020 animals were examined in the survey consisting of sheep [n=592], goats [n=981] and cattle [n=447]. All three species were raised and co-grazed on the same farms. Theileria parasites were detected using PCR-RFLP and RLB of the 18S rRNA gene. Cloning and sequencing of the 18S rRNA was carried out on 11 T. lestoquardi isolates from Ash-Sharqiyah, and Ad-Dhahira governorates, and phylogenetic relationships were inferred using additional sequences of T. lestoquardi, T. annulata and T. ovis available in GenBank.
Theileria spp. prevalence was 72.3%, 36.7% and 2.7% among cattle, sheep and goats, respectively. Strong similarity in results was obtained using RLB and PCR-RFLP for detection of Theileria spp. however, RLB detected a higher rate of mixed infection than PCR-RFPL (P<0.001). Theileria annulata was the only parasite detected in cattle, while sheep and goats carried T. ovis, T. lestoquardi and T. annulata as well as Theileria spp. OT1. Of the four Theileria spp. detected in small ruminants, overall T. ovis was most prevalent (sheep [33.4%], goats [2.0%]), whereas T. lestoquardi was less prevalent (sheep [22.0%], goats [0.5%]). A large proportion of infected sheep (19%) carried mixed infection of T. ovis and T. lestoquardi. However, single T. lestoquardi infections (3.0%) were less prevalent than T. ovis infections (14.5%). Risk of Theileria spp. infection was significantly higher for exotic breeds, relative to native breeds, of cattle (p=0.00002) and sheep (p=0.005). Phylogenetic analysis placed T. lestoquardi in Oman in the same clade as other T. lestoquardi strains isolated from the same regional area (Iraq and Iran). The main tick species, identified on the examined animals, Hyalomma anatolicum, was widely distributed and was found in all of the surveyed governorates.
Theileria spp. are widespread in Oman with variable prevalence detected in different regions. Two economically important hosts, cattle and sheep are at high risk from virulent T. annulata and T. lestoquardi, respectively. The survey indicates extensive exposure to ticks and transmission of infection that has a significant economic impact. The higher prevalence of T. lestoquardi as mixed rather than single infection requires further investigation.
泰勒虫病是阿拉伯半岛最普遍的家畜传染病之一，在绵羊和牛中导致高死亡率和发病率。然而，关于泰勒虫属在整个地区的分布及其对不同宿主的影响的信息匮乏。本研究在阿曼全国四个省份对家畜的泰勒虫属进行了分子调查。该调查的目的是确定牛、绵羊和山羊中泰勒虫属的流行率，突出感染的风险因素，并识别参与寄生虫传播的主要蜱种。
在该调查中总共检查了2020只动物，包括绵羊[n = 592]、山羊[n = 981]和牛[n = 447]。所有这三个物种在同一农场饲养和共同放牧。使用18S rRNA基因的PCR-RFLP和RLB检测泰勒虫寄生虫。对来自佐法尔省和艾哈迈德省的11个莱氏泰勒虫分离株进行了18S rRNA的克隆和测序，并使用GenBank中可获得的莱氏泰勒虫、环形泰勒虫和绵羊泰勒虫的其他序列推断系统发育关系。
泰勒虫属的流行率在牛、绵羊和山羊中分别为72.3%、36.7%和2.7%。使用RLB和PCR-RFLP检测泰勒虫属时结果有很强的相似性；然而，RLB检测到的混合感染率高于PCR-RFPL（P < 0.001）。环形泰勒虫是在牛中检测到的唯一寄生虫，而绵羊和山羊携带绵羊泰勒虫、莱氏泰勒虫和环形泰勒虫以及泰勒虫属OT1。在小反刍动物中检测到的四种泰勒虫属中，总体上绵羊泰勒虫最普遍（绵羊[33.4%]，山羊[2.0%]），而莱氏泰勒虫较不普遍（绵羊[22.0%]，山羊[0.5%]）。很大一部分受感染的绵羊（19%）携带绵羊泰勒虫和莱氏泰勒虫的混合感染。然而，单一莱氏泰勒虫感染（3.0%）比绵羊泰勒虫感染（14.5%）更不普遍。相对于本地品种的牛（p = 0.00002）和绵羊（p = 0.005），外来品种感染泰勒虫属的风险显著更高。系统发育分析将阿曼的莱氏泰勒虫置于与从同一地区（伊拉克和伊朗）分离的其他莱氏泰勒虫菌株相同的进化枝中。在检查的动物身上鉴定出的主要蜱种，小亚璃眼蜱，分布广泛，在所有调查省份都有发现。
泰勒虫属在阿曼广泛分布，不同地区流行率不同。两个具有经济重要性的宿主，牛和绵羊分别面临来自致病性环形泰勒虫和莱氏泰勒虫的高风险。该调查表明广泛接触蜱以及感染传播具有重大经济影响。莱氏泰勒虫作为混合感染而非单一感染的较高流行率需要进一步调查。
