National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080‒8555, Hokkaido, Japan; Department of Microbiology and Parasitology, Sher‒e‒Bangla Agricultural University, Sher‒e‒Bangla Nagar, Dhaka, 1207, Bangladesh.
Department of Microbiology and Parasitology, Sher‒e‒Bangla Agricultural University, Sher‒e‒Bangla Nagar, Dhaka, 1207, Bangladesh.
Acta Trop. 2024 Aug;256:107244. doi: 10.1016/j.actatropica.2024.107244. Epub 2024 May 19.
Questing ticks carry various tick-borne pathogens (TBPs) that are responsible for causing tick-borne diseases (TBDs) in humans and animals around the globe, especially in the tropics and sub-tropics. Information on the distribution of ticks and TBPs in a specific geography is crucial for the formulation of mitigation measures against TBDs. Therefore, this study aimed to survey the TBPs in the questing tick population in Bangladesh. A total of 2748 questing hard ticks were collected from the pastures in Sylhet, Bandarban, Sirajganj, Dhaka, and Mymensingh districts through the flagging method. After morphological identification, the ticks were grouped into 142 pools based on their species, sexes, life stages, and collection sites. The genomic DNA extracted from tick specimens was screened for 14 pathogens, namely Babesia bigemina (AMA-1), Babesia bovis (RAP-1), Babesia naoakii (AMA-1), Babesia ovis (18S rRNA), Theileria luwenshuni (18S rRNA), Theileria annulata (Tams-1), Theileria orientalis (MPSP), Anaplasma marginale (groEL), Anaplasma phagocytophilum (16S rRNA), Anaplasma bovis (16S rRNA), Anaplasma platys (16S rRNA), Ehrlichia spp. (16S rRNA), Rickettsia spp. (gltA), and Borrelia (Bo.) spp. (flagellin B) using genus and species-specific polymerase chain reaction (PCR) assays. The prevalence of the detected pathogens was calculated using the maximum likelihood method (MLE) with 95 % confidence interval (CI). Among 2748 ixodid ticks, 2332 (84.86 %) and 416 (15.14 %) were identified as Haemaphysalis bispinosa and Rhipicephalus microplus, respectively. Haemaphysalis bispinosa was found to carry all the seven detected pathogens, while larvae of R. microplus were found to carry only Bo. theileri. Among the TBPs, the highest detection rate was observed in A. bovis (20/142 pools, 0.81 %, CI: 0.51-1.20), followed by T. orientalis (19/142 pools, 0.72 %, CI: 0.44-1.09), T. luwenshuni (9/142 pools, 0.34 %, CI: 0.16-0.62), B. ovis (4/142 pools, 0.15 %, CI: 0.05 - 0.34) and Bo. theileri (4/142 pools, 0.15 %, CI: 0.05-0.34), Ehrlichia ewingii (3/142 pools, 0.11 %, CI: 0.03-0.29), and Babesia bigemina (1/142, 0.04 %, CI: 0.00 - 0.16). This study reports the existence of T. luwenshuni, E. ewingii, and Bo. theileri in Bangladesh for the first time. The novel findings of this study are the foremost documentation of transovarian transmission of B. bigemina and E. ewingii in H. bispinosa and also provide primary molecular evidence on the presence of E. ewingii and Bo. theileri in H. bispinosa. Therefore, this study may shed light on the circulating TBPs in ticks in the natural environment and thereby advocate awareness among physicians and veterinarians to control and prevent TBDs in Bangladesh.
本研究旨在调查孟加拉国游离寄生蜱种群中的蜱传病原体（TBP）。通过旗标法从锡尔赫特、班达尔班、锡拉杰甘杰、达卡和迈门辛地区的牧场中采集了 2748 只游离硬蜱。在形态学鉴定后，根据其物种、性别、生活阶段和采集地点将蜱分为 142 个池。从蜱标本中提取基因组 DNA，采用种属特异性聚合酶链反应（PCR）方法检测 14 种病原体，即双芽巴贝斯虫（AMA-1）、牛巴贝斯虫（RAP-1）、纳氏巴贝斯虫（AMA-1）、绵羊巴贝斯虫（18S rRNA）、卢氏泰勒虫（18S rRNA）、环形泰勒虫（Tams-1）、东方泰勒虫（MPSP）、边缘无浆体（groEL）、嗜吞噬细胞无形体（16S rRNA）、牛无形体（16S rRNA）、平角无浆体（16S rRNA）、埃立克体属（16S rRNA）、罗卡体属（gltA）和伯氏疏螺旋体（Bo.）（鞭毛蛋白 B）。采用最大似然法（MLE）计算检测病原体的流行率，置信区间（CI）为 95%。在 2748 只蜱中，2332 只为双斑血蜱（84.86%），416 只为微小牛蜱（15.14%）。双斑血蜱携带所有七种检测到的病原体，而微小牛蜱幼虫仅携带博氏疏螺旋体。在这些 TBP 中，检测率最高的是牛无形体（20/142 池，0.81%，CI：0.51-1.20），其次是东方泰勒虫（19/142 池，0.72%，CI：0.44-1.09）、卢氏泰勒虫（9/142 池，0.34%，CI：0.16-0.62）、牛巴贝斯虫（4/142 池，0.15%，CI：0.05-0.34）和博氏疏螺旋体（4/142 池，0.15%，CI：0.05-0.34）、埃立克体属（3/142 池，0.11%，CI：0.03-0.29）和双芽巴贝斯虫（1/142，0.04%，CI：0.00-0.16）。本研究首次在孟加拉国报告了卢氏泰勒虫、埃立克体属和博氏疏螺旋体的存在。本研究的新发现是双斑血蜱中双芽巴贝斯虫和埃立克体属经卵传递的首次报道，也为双斑血蜱中埃立克体属和博氏疏螺旋体的存在提供了初步的分子证据。因此，本研究可能揭示了游离寄生蜱在自然环境中传播的蜱传病原体，从而倡导孟加拉国的医生和兽医提高对控制和预防 TBD 的认识。
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