畜牧兽医学报  2023, Vol. 54 Issue (8): 3183-3194. DOI: 10.11843/j.issn.0366-6964.2023.08.006    PDF    
近十年PCR技术在寄生虫病诊断中的应用
杨富升, 古小彬     
四川农业大学动物医学院, 成都 611130
摘要:寄生虫病给全球畜牧养殖业造成了严重的经济损失,有些寄生虫病可引发公共卫生问题,因此,及时准确的诊断寄生虫病对疾病的防治至关重要。PCR技术具有灵敏、快速、特异性强等优势,可以有效提高诊断的准确性,从而给寄生虫病的防控提供可靠的技术支持。本文对近十年(2012—2022)在寄生虫病诊断中使用的PCR技术和靶基因进行综述,以期为寄生虫病的诊断提供参考。
关键词PCR技术    靶基因    寄生虫病诊断    
A Review on Applications of PCR Technology in the Diagnosis of Parasitic Diseases in the Past 10 Years
YANG Fusheng, GU Xiaobin     
College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China
Abstract: Parasitic diseases cause significant economic losses in breeding industry worldwide, and some parasitic diseases pose major public health threats. Thus, it is crucial to make a timely and accurate diagnosis of parasitic diseases for disease prevention and control. Polymerase chain reaction (PCR) technology can effectively improve the accuracy of diagnosis for its advantages of high sensitivity, specificity and convenience, so this technology can provide reliable technical support for the prevention and control of parasitic diseases. In this review, the categories of PCR techniques and their target genes used in the diagnosis of parasitic diseases in the past 10 years (2012-2022) were summerized, in the hope of providing a reference for the diagnosis of parasitic diseases.
Key words: PCR technology    target gene    diagnosis of parasitic diseases    

寄生虫病是威胁全球动物养殖业的一类重要疾病,可引起动物生产性能降低,造成动物生长发育受阻甚至死亡,给养殖业带来巨大的经济损失,同时有些寄生虫病还可感染人类,引起公共卫生问题。利用可靠的检测技术准确诊断寄生虫病是制定针对性防控措施的前提,对有效防控寄生虫疾病具有重大意义[1]

目前,多数寄生虫病的诊断是依靠显微镜检测法,该方法常作为寄生虫病的诊“金标准”,但显微镜检测法对于虫体形态学特征不明显、感染早期虫体数量较少而呈现亚临床症状的病例极易漏检[2],而这些漏检病例常成为动物群体寄生虫病传播的重要隐形传染源,所以需要可靠的检测技术在寄生虫病大量传播前进行及时准确的诊断。聚合酶链式反应技术(PCR)作为现代分子生物技术,具有操作简单、特异性强、灵敏性高等优点,能较好地解决传统显微镜检测法易漏检早期感染病例的“卡脖子”问题[3]。选择合适的靶基因设计引物能提高检测的特异性,对PCR检测也至关重要。随着核酸技术的成熟和寄生虫基因组序列的深入研究,PCR检测方法在寄生虫病的诊断上发挥着越来越重要的作用,给寄生虫病的有效防控提供技术支持。因此,本文针对近十年(2012—2022)PCR技术在寄生虫病诊断上的应用和相关报道进行综述。

1 常用PCR检测技术

近十年内,用于寄生虫病诊断的常用PCR技术包括常规PCR、巢氏PCR、多重PCR、荧光定量PCR和数字PCR等(表 1)。

表 1 近十年各类PCR技术在寄生虫病诊断中的应用 Table 1 The application of various PCR techniques in the diagnosis of parasitic diseases in the past ten years
1.1 常规PCR

常规PCR通过外部合成寄生虫特异性DNA片段,再经电泳检测是否含有该目的条带,从而判断检测样品的阳性或阴性。

研究发现,利什曼原虫、类圆线虫和布氏锥虫的常规PCR方法灵敏度高于传统镜检法,但该方法的检出率会因靶基因不同而存在差异。皮肤型利什曼原虫的常规HSP20-PCR(热休克蛋白基因)最低可检测到10 fg虫体DNA,灵敏度高于显微镜检测法[4]kDNA-PCR(动基体基因)和ITS-1-PCR证实了上述观点,这两种方法对疑似患病皮肤样品的检出率均高于显微镜检测法(kDNA-PCR:98.7%;ITS-1-PCR:91%;镜检:74.4%)[5];内脏型利什曼原虫kDNA-PCR检测也得到类似结论,该方法的检出率(67%)明显优于显微镜检测法(54%)[6]。应用于马场的普通类圆线虫ITS-2-PCR检测方法明显优于传统培养检测,且适合大量样本的检测[7]。布氏锥虫mtDNA-PCR检测方法在血液中最低可检测出虫体1个·mL-1,具有较好的重复性[8]。然而,在一项皮肤型利什曼原虫的检测中得到了相反的结论,该研究中的kDNA-PCR方法的检出率(56.2%)低于显微镜检测法(76.2%)[9]。除此之外,近十年内还有研究者建立常规PCR方法用于猫胞裂虫[10]、疥螨[11]、贾第鞭毛虫[12]、曼氏血吸虫[13]等的诊断,但未与其他检测方法进行比较。

综上,常规PCR的灵敏度常高于显微镜检测法,然而常规PCR无法进行定量检测和多种寄生虫的混合感染检测等,因此,研究者们利用常规PCR衍生出的其他PCR技术对寄生虫病进行更深入的检测。

1.2 巢氏PCR

为提高PCR扩增的特异性和灵敏度,研究者发明了巢式PCR(nested PCR,nPCR)。nPCR是指利用外引物和内引物依次进行PCR扩增,将两次特异性扩增后的最终产物进行电泳检测。

疟原虫、牛巴贝斯虫和利什曼原虫的nPCR诊断方法的检测灵敏度高于传统镜检法,适用于低荷虫数样品的检测。疟原虫的显微镜检测法对虫体的最低检测限度约20个·μL-1,而间日疟原虫18S rRNA-nPCR对虫体的最低检测限度达到了6个·μL-1[14],优化后甚至可达0.2个·μL-1[15],在恶性疟原虫、卵形疟原虫、三日疟原虫的nPCR检测限度亦被证实高于镜检法[16-19]。牛巴贝斯虫18S rRNA-nPCR对临床血样的整体检出率(54.4%)高于显微镜检测法(20.4%)[20];利什曼原虫kDNA-nPCR对隐形感染样本的检出率(79%)高于显微镜检测法(58%)[21]。虾肝肠胞虫、眼部弓形虫和利什曼原虫的nPCR方法的检测灵敏高于常规PCR,其中虾肝肠胞虫β-tubulin-nPCR的灵敏度较常规PCR方法提高100倍[22],眼部弓形虫B1-nPCR检出率较常规PCR提高30%[23],利什曼原虫ITS-1-nPCR可检出常规PCR为“假阴性”的样品[24]。研究还发现,nPCR方法比免疫组化和免疫色谱法更灵敏。利什曼原虫kDNA-nPCR对显性感染样本的检出率(100%)高于免疫组化方法(97%),而两种方法对隐性感染样本的检出率相当(均为94%)[25];疟原虫18S rRNA-nPCR对隐形感染者的检测比快速免疫色谱法更有效[26]。此外,nPCR还被用于马泰勒虫[27]、肝片吸虫[28]等的流行病学调查。

综上,nPCR较常规PCR、显微镜检测法等有更高的灵敏度,适用于检测低荷虫数的样品,也可以作为流行病学调查的工具。

1.3 多重PCR

相较于常规PCR,多重PCR(multiplex PCR,mPCR)是在反应体系中加入1对以上引物,最终扩增出多条DNA片段进行检测,适合用于诊断多种寄生虫的混合感染。

疟原虫等原虫和美洲板口线虫等土源性线虫的mPCR灵敏度高于传统“金标准”方法(显微镜检测法、福尔马林乙酸乙酯浓集法等)。cox3-mPCR对卡氏住白细胞虫、沙氏住白细胞虫、并核疟原虫和鸡疟原虫的最低检测限度分别为105、105、106、107copies·μL-1,该方法对临床样品的检出率高于显微镜检测法[29];然而在疟原虫属、住白细胞虫属、变形血原虫属等混合感染样品的检测中得到不同的结论,在检测其中1个混合感染的样品时,显微镜检测法检测出了混合感染样品的所有虫种,而Cytb-mPCR未检出疟原虫属[30]。以人蛔虫的ITS-1基因、美洲板口线虫和粪类圆线虫18S rRNA基因建立的mPCR对混合感染样品的最低检测限度均为1 pg虫体DNA,其检测灵敏度是福尔马林乙酸乙酯浓集法的5倍[31]。另外,mPCR较其他PCR方法的灵敏度在不同寄生虫中存在差异。Cytb-mPCR对疟原虫属、住白细胞虫属、变形血原虫属等混合感染样品的总体检出率(52.7%)高于Cytb-nPCR(48.8%)[30]cox1-mPCR对卡普拉疟原虫、吕氏泰勒虫和羊巴贝斯虫的灵敏度与常规PCR一致[32];而羊泰勒虫和无浆体18S rRNA-mPCR对泰勒虫的最低检测限度(29.4×10-3 ng·μL-1)低于18S rRNA-PCR(29.4×10-6 ng·μL-1)[33],类似的结果在以环形泰勒虫Cytb基因和瑟根泰勒虫ITS-1基因的mPCR方法中得到证实,该方法对瑟根泰勒虫的最低检测限度(10-7 ng·μL-1)低于常规PCR(10-8ng·μL-1)[34],造成上述差异的原因可能与mPCR体系中多对引物之间的影响有关。近十年内,mPCR方法还用于鸡异刺线虫、贝拉异刺线虫和印度异刺线虫的混合检测[35],东方次睾吸虫和华支睾吸虫的混合检测[36]

综上,mPCR可用于多种寄生虫混合感染的诊断,该方法对于引物和反应条件的设计上较常规PCR更加严格,否则会产生非特异性条带或产生的条带不能准确区分虫种,也会影响该方法的灵敏性。

1.4 荧光定量PCR

荧光定量PCR(quantitative real-time PCR,qPCR)是指在PCR反应体系中加入荧光基团,通过检测荧光基团在扩增中的荧光信号发射情况,在一定范围内定量分析样本中的基因含量。

巴贝斯虫、利什曼原虫和派琴虫qPCR的灵敏度高于传统显微镜检法和巯基醋酸盐培养基检测。微小巴贝斯虫18S rRNA-qPCR检测灵敏度是染色镜检的20倍[37];利什曼原虫ITS-1-qPCR可以定量检测所有的急性与慢性病例的寄生虫荷虫量,而显微镜检测法只能对其中部分样品中进行定量检测[38]kDNA-qPCR对内脏型利什曼原虫显性、隐形感染病例以及婴儿利什曼原虫感染病例的检出率均高于显微镜检法[6, 39],派琴虫ITS-1-qPCR最低检测限度(1个虫体)远高于标准方法——巯基醋酸盐培养基检测(RFTM,>1 000个虫体),且在临床样本检测中亦发现其检出率(82.22%)高于RFTM(57.5%)[40]。另外,在其他寄生虫的qPCR检测中证实其灵敏度高于常规PCR、nPCR。kDNA-qPCR在婴儿利什曼原虫感染病例的检出率高于ITS-1-PCR[39];包拉米虫和马尔太虫18S rRNA-qPCR可检测出稀释至10 copies·μL-1的标准样品,其临床样品的检出率(87.2%)高于ITS-1-PCR(60.7%)[41];微小孢子虫18S rRNA-qPCR最低检测限度(0.1个卵囊)明显高于18S rRNA-nPCR的检测限度(100个卵囊)[42]。然而,在一项曼氏血吸虫的检测中却发现121 bp-qPCR对低荷虫数感染人群的检出率与其标准检测方法(改良加藤厚涂片法)相当[43],亦有发现kDNA-qPCR对婴儿利什曼原虫的检出率略低于直接凝集实验(direct agglutination test,DAT),不过DAT方法无法区分既往感染和现症感染[6]。此外,需要注意的是qPCR只能在一定范围内定量检测,多房棘球绦虫和加拿大棘球绦虫qPCR方法的最低检测限度分别为2×10-5、2×10-4 ng·μL-1浓度的DNA,超过该限度只能定性检测[44]。qPCR反应中探针类型对检测结果也有一定影响。在皮肤利什曼原虫和黏膜利什曼原虫的qPCR检测中,以SYBRGreen为探针的kDNA-qPCR的检出率均高于TaqMan探针[45],不过使用TaqMan探针能同时对多个寄生虫的混合感染进行定量检测,通常应用于原虫混合感染和蠕虫混合感染的流行病学调查[46-48]。近十年内qPCR还被报道用于克氏锥虫[49]、隐孢子虫[50]、恶性疟原虫[51]等的检测。

综上,qPCR的检出率通常高于传统的标准方法,且能够在一定范围内准确的检测出待检样品中的寄生虫含量,但检测结果受到探针和样本类型的影响。

1.5 数字PCR

数字PCR(digital PCR,dPCR)是一种新型PCR技术,其原理是将整体反应体系分解成大量反应单元进行PCR扩增,最终通过统计学分析,计算出原始DNA浓度。

研究发现,dPCR检测灵敏度高于显微镜检测法,可检出寄生虫的隐形和早期感染。巴贝斯虫ITS-1-dPCR最低检测下限是10 copies·μL-1,能检测出镜检呈阴性的低荷虫数样本,该方法适用于检测巴贝斯虫的隐性感染[52]。dPCR也可检出小鼠日本血吸虫的早期感染[53-55]SjR2-dPCR最低可以检测到0.05 fg虫体DNA,远远低于1对成虫(约3 000 ng)或1个卵(约50 pg)的DNA含量[53]。人蛔虫卵的检测发现dPCR较qPCR具有更高的灵敏度,在相同的待检样品中,ITS-1-dPCR方法检出的人蛔虫卵DNA量大于qPCR的检出量(ITS-1-dPCR:5个虫卵DNA量;ITS-1-qPCR:1个虫卵DNA量)[56]。然而针对粪便中隐孢子虫的检测时,却得出相反的结果,其18S rRNA-dPCR的检测效果不如18S rRNA-qPCR,前者对阳性粪便中不同浓度隐孢子虫的DNA拷贝数始终低于qPCR,且随着DNA浓度降低,dPCR的精准度降低,而18S rRNA-qPCR定量检测却不受DNA浓度的影响[50],类似的结果在慢性锥虫病的检测中亦得到证实[49]

综上,dPCR可用于低荷虫数的定量检测,灵敏度会因检测对象不同而存在差异。对比qPCR的相对定量,dPCR不需要参考基因及建立标准曲线,是一种绝对定量检测,但是dPCR技术成本较高、操作复杂,尚未得到广泛应用和推广。

2 常用分子靶基因

近十年内,已报道用于寄生虫病诊断的常用分子靶标包括核糖体基因、线粒体基因、蛋白编码基因和其他高拷贝的基因(表 2)。

表 2 近十年各类靶基因在寄生虫病PCR诊断中的应用 Table 2 The application of various target genes in PCR diagnosis of parasitic diseases in the past ten years
2.1 核糖体基因

核糖体基因(ribosomal DNA,rDNA)与核糖体蛋白形成核糖体,其中18S rRNA、28S rRNAITS-1、ITS-2等基因常作为靶基因应用到PCR检测中。

近十年,以18S rRNA基因建立了检测贾第鞭毛虫、包拉米虫、马尔太虫、泰勒虫、巴贝斯虫、疟原虫等的PCR方法,被证实18S rRNA基因具有良好的特异性。以该基因设计引物检测贾第鞭毛虫,其特异性片段大小为130 bp,发现在相同类型的PCR方法中,18S rRNA基因的检出率(100%)高于磷酸丙糖异构酶(TPI)基因(92.6%)[12];在检测包拉米虫和马尔太虫时,该基因引物产生的特异性条带大小分别为118、199 bp,对牡蛎其他常见寄生虫的DNA检测结果为阴性[41];在检测环形泰勒虫、分离泰勒虫、吕氏泰勒虫、尤氏泰勒虫等时,产生的特异性条带在298 bp左右,特异性良好,不会与吉氏巴贝斯虫、立克次氏体等产生反应[33];在微小巴贝斯虫中产生的特异性片段长238 bp,对双芽巴贝斯虫、驽巴贝斯虫、分离巴贝斯虫和恶性疟原虫等检测结果为阴性[37];在多种疟原虫中以18S rRNA靶基因建立了多种PCR检测方法,扩增出的片段约为157~165 bp,对利什曼原虫、巴贝斯虫和弓形虫等检测结果为阴性[57],还可通过18S rRNA靶基因同时鉴别恶性疟原虫、间日疟原虫、三日疟原虫、卵形疟原虫,它们所扩增的条带大小分别为250、120、144、800 bp[16-18]。近十年内18S rRNA还用做检测美洲板口线虫[31]、粪类圆线虫[31]、隐孢子虫[42]、猫胞裂虫[10]等的靶基因。

近十年,ITS靶基因已用于利什曼原虫、异刺线虫、肝片吸虫、奥尔森派琴虫的PCR诊断。以利什曼原虫的ITS-1基因设计了多种特异性引物,在皮肤型利什曼原虫中产生的ITS-1特异性条带大小在300~350 bp[24],而内脏型利什曼原虫的特异性条带为360[6]和100 bp[58]ITS-2在检测不同种类的异刺线虫时产生的特异性条带大小不同,鸡异刺线虫为396 bp、贝拉异刺线虫为272 bp、印度异刺线虫为482 bp,它们的引物不会与鸡蛔虫、孟氏尖旋线虫、回饰带线虫、唇饰带线虫等寄生虫产生反应[35];以肝片吸虫ITS-2设计引物得到的条带大小为208 bp,其引物特异性强,对同盘吸虫、华支睾吸虫、东毕吸虫等虫体DNA检测为阴性[28]。除单独使用ITS-1、ITS-2基因外,还可将两种基因联合建立PCR诊断方法,其可有效检测组织中的奥尔森派琴虫,该方法特异性强,不会在其他类型的派琴虫中扩增出特异性片段[40]。近十年内ITS还用作检测人蛔虫[31]、瑟根泰勒虫[34]、微小巴贝斯虫[52]、邓肯巴贝斯虫[52]等的靶基因。

与上述核糖体基因相比,28S rRNA基因在寄生虫PCR检测的研究相对较少。以枯氏住肉孢子虫的检测中,该引物产生的特异性条带为580 bp,该基因在同为常规PCR方法的检测中最低检测限度(0.01 ng·μL-1)高于cox1靶基因(1 ng·μL-1),然而该基因的引物特异性不强,可从刚地弓形虫、微小孢子虫、欧猥迭宫绦虫中扩增到杂条带,无法很好地区分上述寄生虫[59]

2.2 线粒体基因

线粒体DNA(mtDNA)存在于线粒体中,其中包括细胞色素b基因(Cytb)、细胞色素c氧化酶基因(cox)、烟酰胺腺嘌呤二核苷酸脱氢酶基因(nad)和16S rRNA,上述基因常被用做分子靶标应用到寄生虫的PCR检测中。

Cytb基因已用于细粒棘球绦虫和环形泰勒虫的检测。其中以细粒棘球绦虫Cytb基因设计引物产生的条带为121 bp[60],引物对肝片吸虫、莫尼茨绦虫DNA检测的结果都为阴性;在环形泰勒虫的检测中,扩增出的条带大小为393 bp,不会与双芽巴贝斯虫、卵形巴贝斯虫、中华泰勒虫等产生反应[34]cox1基因已用于犬恶丝虫、疥螨、卡普拉疟原虫、吕氏泰勒虫、巴贝斯虫、枯孢子虫的检测中,具有良好的特异性。在犬恶丝虫的检测时扩增出的特异性条带大小为502 bp,在阴性血清样本中不会出现目的条带[25];检测疥螨所扩增的cox1特异性条带大小为121 bp,对于痒螨、蠕形螨和金黄色葡萄球菌等病原DNA检测为阴性[11];对于卡普拉疟原虫、吕氏泰勒虫和巴贝斯虫,特异性引物产生的片段大小分别是320、664、555 bp,引物之间不会产生非特异性条带,与无浆体、锥氏虫属等不会产生反应[32]cox3基因已用于猫胞裂虫(252 bp)和沙氏住白细胞虫(294 bp)的检测,在同为常规PCR的检测中,猫胞裂虫cox3基因在早期感染病例检测中的敏感度高于18S rRNA[10],而在沙氏住白细胞虫的检测中,发现cox3基因的敏感性低于Cytb基因[61]。以16S rRNA为靶基因建立了检测疥螨的多种PCR方法,产生的特异性条带大小为135 bp,两种方法中引物都不会与痒螨、耳螨等虫体DNA产生反应[62]。以线粒体基因nad6建立了检测细粒棘球绦虫的PCR方法,产生的特异性条带为558 bp,对多房棘球绦虫、孟氏迭宫绦虫、犬复孔绦虫、多头带绦虫及犬弓首蛔等虫体DNA为阴性[63]。除使用单个线粒体基因外,还可联合2种线粒体基因设计引物检测虫体。以多房棘球绦虫nad基因(126 bp)和加拿大棘球绦虫cox1基因(143 bp)建立了检测上述两者虫体的mPCR检测方法[44];以及东方次睾吸虫nad1基因(508 bp)和华支睾吸虫nad5基因(311 bp)建立了mPCR检测方法,两对引物不会与鸭对体吸虫、横川后殖吸虫和卷棘口吸虫产生反应[36]。除上述线粒体基因外,还可用线粒体上的其他基因序列,如以位于线粒体非编码区和cytb5′末端之间的序列、线粒体DNA的非编码区之间的序列设计引物建立疟原虫属、变形血原虫属等的PCR诊断方法[30]

2.3 蛋白编码基因

除上述核糖体基因和线粒体基因外,一些编码特定功能蛋白的基因也能作为靶基因。这类基因相对保守,在染色体上的拷贝数较多,它们的功能包括协助寄生虫运动、维持寄生虫形态、使寄生虫逃逸宿主免疫功能。近十年内已被报道用于寄生虫PCR诊断的蛋白编码基因有β-微管蛋白基因、红细胞膜蛋白1基因(EMP1)、精氨酸转运蛋白基因(AAP3)、热休克蛋白基因(HSP)、磷酸丙糖异构酶(TPI)基因、顶膜抗原基因(AMA-1)、伴侣素基因(CCT)等。

以β-微管蛋白基因为靶基因检测虾肝肠胞虫,产生的特异性条带237 bp,该引物特异性强,对该虫的多种宿主DNA检测为阴性[22]。有研究发现恶性疟原虫的EMP1基因丰度显著高于18S rRNA基因,以EMP1基因设计引物得到的目的条带为260 bp,结果也显示该基因在PCR检测中的敏感性高于18S rRNA[51]。以AAP3基因为靶基因检测环孢子虫,扩增出的目的条带大小为74 bp,该方法对布氏锥虫、克氏锥虫、人或小鼠的DNA的检测为阴性,具有良好的特异性[64]。以TPI基因为靶基因检测贾第鞭毛虫,产生的特异性条带大小为530 bp,在同类型的PCR方法中,该基因在同一批样本的检出率低于18S rRNA基因[12]。以利什曼原虫HSP20基因分别设计了长为107和370 bp的两种引物检测该虫,发现前者的灵敏度高于后者[4];以利什曼原虫HSP70基因设计的引物产生的条带大小为1 422 bp,在同类型的PCR检测中,对同一批样本的检出率低于18S rRNA基因[65]。研究发现在利什曼原虫中HSP基因的拷贝数相对较少,所以HSP为靶基因的PCR检测中效果不如18S rRNAITS-1、ITS-2基因等[66]。在牛卵形巴贝斯虫的PCR检测中发现蛋白编码基因AMA-1基因和CCT基因的敏感性不如18S rRNA基因,其临床样本的检出率低[67]

2.4 其他基因序列

除上述基因外,近十年内还用于寄生虫PCR诊断的靶基因还包括其他的一些高拷贝数基因,比如日本血吸虫SjR2、曼氏血吸虫121 bp高度重复序列、利什曼原虫的动基体基因kDNA、疟原虫的Pvr47和Pf364、弓形虫的B1和529 bp的高度重复序列等。

以日本血吸虫的逆转录座子SjR2为靶基因建立了两种PCR方法,在常规PCR中的引物扩增的片段大小为191 bp,不会与曼氏血吸虫、埃及血吸虫等产生反应[53];在qPCR中的引物扩增的片段大小为230 bp,不会与华支睾吸虫、卫氏并殖吸虫产生反应[68]。以曼氏血吸虫全基因组中的一段高度重复序列“121 bp”建立了多种PCR检测方法[13, 69-70],在同类型的PCR方法中,该基因的敏感度比线粒体基因nad5、核糖体基因28S rRNA[71]。动基体基因kDNA是利什曼原虫诊断中敏感性高、特异性强的靶基因序列[46, 72],以该基因设计的引物产生的条带为100~150 bp[9, 21, 39, 73-77],在同类型的PCR方法下,该基因的敏感性均高于ITS-1基因、18S rRNA基因[39, 78]。间日疟原虫的高拷贝数基因Pvr47和恶性疟原虫的高拷贝数基因Pf364也常作为靶基因建立了多种PCR检测方法,产生的特异性条带分别为104、88 bp,在同类型PCR方法下,Pvr47、Pf364基因较18S rRNA基因更灵敏[79-83]。在弓形虫的全基因组中,以B1基因(193 bp)和一段高度重复序列529 bp设计引物建立PCR方法,对利什曼原虫属、疟原虫属、细粒棘球蚴、阿米巴原虫和人类染色体DNA检测为阴性[84-87]

3 展望

寄生虫病的传统诊断方法在形态相似的虫体样本和亚临床病症样本的诊断上不如PCR快速准确。随PCR技术日渐成熟,已衍生出多种PCR检测方法,如nPCR、mPCR、qPCR、dPCR等,这些方法部分已经广泛应用于多种寄生虫病的检测,在实际使用中可结合经济条件、试验条件、研究策略等合理选择适宜的PCR检测方法。另外,PCR方法也有待改进的地方,如进一步提高检测的特异性、准确性和敏感性、减少试验过程中的污染、减少实际应用的成本投入等。PCR诊断方法的准确性与靶基因的选择密不可分,现核糖体基因、线粒体基因、编码蛋白基因以及其他特有的高拷贝数基因等靶基因已被广泛应用于寄生虫病的PCR检测,但不同的寄生虫病所适用的靶基因不同,而随组学技术的发展,可挖掘更多的靶基因来提高PCR技术的准确性,因此,未来还需要更多的研究来确定检测各类寄生虫的最优特异性靶基因。

参考文献
[1]
陈家旭, 蔡玉春, 艾琳, 等. 我国重要人体寄生虫病防控现状与挑战[J]. 检验医学, 2021, 36(10): 993-1000.
CHEN J X, CAI Y C, AI L, et al. Epidemic status and challenges of important human parasitic diseases in China[J]. Laboratory Medicine, 2021, 36(10): 993-1000. (in Chinese)
[2]
严俊, 胡桃, 雷正龙. 全国重点寄生虫病的防控形势与挑战[J]. 中国寄生虫学与寄生虫病杂志, 2015, 33(6): 412-417.
YAN J, HU T, LEI Z L. The Endemic situation and challenges of major parasitic diseases in China[J]. Chinese Journal of Parasitology and Parasitic Diseases, 2015, 33(6): 412-417. (in Chinese)
[3]
周晓农. 开展精准防治实现消除血吸虫病的目标[J]. 中国血吸虫病防治杂志, 2016, 28(1): 1-4.
ZHOU X N. Implementation of precision control to achieve the goal of schistosomiasis elimination in China[J]. Chinese Journal of Schistosomiasis Control, 2016, 28(1): 1-4. (in Chinese)
[4]
MONTALVO A M, ALBA A, FRAGA J, et al. Improving the sensitivity of an hsp20-based PCR for genus detection of Leishmania parasites in cutaneous clinical samples: A proof of concept[J]. Parasitol Res, 2020, 119(1): 345-349. DOI:10.1007/s00436-019-06520-6
[5]
BAFGHI A F, ESLAMI G, NIAZJORJANI O, et al. Isolation and molecular identification of Leishmania spp. in patients with cutaneous leishmaniasis in Golestan province, Iran[J]. Int J Epidemiol Res, 2019, 6(1): 8-13. DOI:10.15171/ijer.2019.02
[6]
MOHAMMADIHA A, HAGHIGHI A, MOHEBALI M, et al. Canine visceral leishmaniasis: A comparative study of real-time PCR, conventional PCR, and direct agglutination on sera for the detection of Leishmania infantum infection[J]. Vet Parasitol., 2013, 192(1-3): 83-90. DOI:10.1016/j.vetpar.2012.10.013
[7]
BRACKEN M K, WØHLK C B M, PETERSEN S L, et al. Evaluation of conventional PCR for detection of Strongylus vulgaris on horse farms[J]. Vet Parasitol, 2012, 184(2-4): 387-391. DOI:10.1016/j.vetpar.2011.08.015
[8]
GUMMERY L, JALLOW S, RAFTERY A G, et al. Comparison of loop-mediated isothermal amplification (LAMP) and PCR for the diagnosis of infection with Trypanosoma brucei ssp. in equids in The Gambia[J]. PLoS One, 2020, 15(8): e0237187. DOI:10.1371/journal.pone.0237187
[9]
RASTI S, GHORBANZADEH B, KHEIRANDISH F, et al. Comparison of molecular, microscopic, and culture methods for diagnosis of cutaneous leishmaniasis[J]. J Clin Lab Anal, 2016, 30(5): 610-615. DOI:10.1002/jcla.21910
[10]
SCHREEG M E, MARR H S, GRIFFITH E H, et al. PCR amplification of a multi-copy mitochondrial gene (cox3) improves detection of Cytauxzoon felis infection as compared to a ribosomal gene (18S)[J]. Vet Parasitol, 2016, 225: 123-130. DOI:10.1016/j.vetpar.2016.06.013
[11]
CHNG L, HOLT D C, FIELD M, et al. Molecular diagnosis of scabies using a novel probe-based polymerase chain reaction assay targeting high-copy number repetitive sequences in the Sarcoptes scabiei genome[J]. PLoS Negl Trop Dis, 2021, 15(2): e0009149. DOI:10.1371/journal.pntd.0009149
[12]
PUEBLA L E J, NÚÑEZ F A, SANTOS L P, et al. Molecular analysis of Giardia duodenalis isolates from symptomatic and asymptomatic children from La Habana, Cuba[J]. Parasite Epidemiol Control, 2017, 2(3): 105-113. DOI:10.1016/j.parepi.2017.05.003
[13]
FERRER E, PÉREZ F, BELLO I, et al. Polymerase chain reaction for the amplification of the 121-bp repetitive sequence of Schistosoma mansoni: a highly sensitive potential diagnostic tool for areas of low endemicity[J]. J Helminthol, 2015, 89(6): 769-773. DOI:10.1017/S0022149X14000595
[14]
FUEHRER H P, NOEDL H. Recent advances in detection of Plasmodium ovale: implications of separation into the two species Plasmodium ovale wallikeri and Plasmodium ovale curtisi[J]. J Clin Microbiol, 2014, 52(2): 387-391. DOI:10.1128/JCM.02760-13
[15]
YENTUR DONI N, YILDIZ ZEYREK F, SEYREK A. Detection of Plasmodium using filter paper and nested PCR for patients with malaria in Sanliurfa, in Turkey[J]. Malar J, 2016, 15(1): 299. DOI:10.1186/s12936-016-1334-2
[16]
LI P P, ZHAO Z J, WANG Y, et al. Nested PCR detection of malaria directly using blood filter paper samples from epidemiological surveys[J]. Malar J, 2014, 13: 175. DOI:10.1186/1475-2875-13-175
[17]
WANG B, HAN S S, CHO C, et al. Comparison of microscopy, nested-PCR, and real-time-PCR assays using high-throughput screening of pooled samples for diagnosis of malaria in asymptomatic carriers from areas of endemicity in Myanmar[J]. J Clin Microbiol, 2014, 52(6): 1838-1845. DOI:10.1128/JCM.03615-13
[18]
UGAH U I, ALO M N, OWOLABI J O, et al. Evaluation of the utility value of three diagnostic methods in the detection of malaria parasites in endemic area[J]. Malar J, 2017, 16(1): 189. DOI:10.1186/s12936-017-1838-4
[19]
ZHANG X J, KADIR K A, QUINTANILLA-ZARIÑAN L F, et al. Distribution and prevalence of malaria parasites among long-tailed macaques (Macaca fascicularis) in regional populations across Southeast Asia[J]. Malar J, 2016, 15(1): 450. DOI:10.1186/s12936-016-1494-0
[20]
AMORIM L S, WENCESLAU A A, CARVALHO F S, et al. Bovine babesiosis and anaplasmosis complex: Diagnosis and evaluation of the risk factors from Bahia, Brazil[J]. Rev Bras Parasitol Vet, 2014, 23(3): 328-336. DOI:10.1590/S1984-29612014064
[21]
SHIRIAN S, ORYAN A, HATAM G R, et al. Comparison of conventional, molecular, and immunohistochemical methods in diagnosis of typical and atypical cutaneous leishmaniasis[J]. Arch Pathol Lab Med, 2014, 138(2): 235-240. DOI:10.5858/arpa.2013-0098-OA
[22]
HAN J E, TANG K F J, KIM J H. The use of beta-tubulin gene for phylogenetic analysis of the microsporidian parasite Enterocytozoon hepatopenaei (EHP) and in the development of a nested PCR as its diagnostic tool[J]. Aquaculture, 2018, 495: 899-902. DOI:10.1016/j.aquaculture.2018.06.059
[23]
FARHADI A, HANILOO A, FAZAELI A, et al. PCR-based diagnosis of Toxoplasma parasite in ocular infections having clinical indications of toxoplasmosis[J]. Iran J Parasitol, 2017, 12(1): 56-62.
[24]
YEHIA L, ADIB-HOUREIH M, RASLAN W F, et al. Molecular diagnosis of cutaneous leishmaniasis and species identification: Analysis of 122 biopsies with varied parasite index[J]. J Cutan Pathol, 2012, 39(3): 347-355. DOI:10.1111/j.1600-0560.2011.01861.x
[25]
OI M, SATO Y, NAKAGAKI K, et al. Detection of Dirofilaria immitis DNA in host serum by nested PCR[J]. Parasitol Res, 2015, 114(10): 3645-3648. DOI:10.1007/s00436-015-4591-z
[26]
TURKI H, RAEISI A, MALEKZADEH K, et al. Efficiency of nested-PCR in detecting asymptomatic cases toward malaria elimination program in an endemic area of Iran[J]. Iran J Parasitol, 2015, 10(1): 39-45.
[27]
BAPTISTA C, LOPES M S, TAVARES A C, et al. Diagnosis of Theileria equi infections in horses in the Azores using cELISA and nested PCR[J]. Ticks Tick Borne Dis, 2013, 4(3): 242-245. DOI:10.1016/j.ttbdis.2012.11.008
[28]
HUANG S Y, GONG J Z, YANG B, et al. Development of a nest-PCR for detection of Fasciola hepatica DNA in the intermediate snail host, Radix cucunorica, and the prevalence in northwestern China[J]. Infect Genet Evol, 2019, 75: 103984. DOI:10.1016/j.meegid.2019.103984
[29]
XUAN M N T, KAEWLAMUN W, SAIWICHAI T, et al. Development and application of a novel multiplex PCR assay for the differentiation of four haemosporidian parasites in the chicken Gallus gallus domesticus[J]. Vet Parasitol, 2021, 293: 109431. DOI:10.1016/j.vetpar.2021.109431
[30]
CILOGLU A, ELLIS V A, BERNOTIENE· R, et al. A new one-step multiplex PCR assay for simultaneous detection and identification of avian haemosporidian parasites[J]. Parasitol Res, 2019, 118(1): 191-201. DOI:10.1007/s00436-018-6153-7
[31]
SANPRASERT V, KERDKAEW R, SRIRUNGRUANG S, et al. Development of conventional multiplex PCR: a rapid technique for simultaneous detection of soil-transmitted helminths[J]. Pathogens, 2019, 8(3): 152. DOI:10.3390/pathogens8030152
[32]
TU H L C, NUGRAHENI Y R, TIAWSIRISUP S, et al. Development of a novel multiplex PCR assay for the detection and differentiation of Plasmodium caprae from Theileria luwenshuni and Babesia spp. in goats[J]. Acta Trop, 2021, 220: 105957. DOI:10.1016/j.actatropica.2021.105957
[33]
CUI Y Y, ZHANG Y, JIAN F C, et al. Development of duplex PCR for simultaneous detection of Theileria spp. and Anaplasma spp. in sheep and goats[J]. Exp Parasitol, 2017, 176: 1-7. DOI:10.1016/j.exppara.2017.01.011
[34]
JUNLONG L, LI Y Q, LIU A H, et al. Development of a multiplex PCR assay for detection and discrimination of Theileria annulata and Theileria sergenti in cattle[J]. Parasitol Res, 2015, 114(7): 2715-2721. DOI:10.1007/s00436-015-4478-z
[35]
BISWAS P G, OHARI Y, MOHANTA U K, et al. Development of a multiplex PCR method for discriminating between Heterakis gallinarum, H. beramporia, and H. indica parasites of poultry[J]. Vet Parasitol, 2021, 295: 109463. DOI:10.1016/j.vetpar.2021.109463
[36]
高俊峰, 王鑫, 毛瑞锋, 等. 淡水鱼中3种吸虫囊蚴多重PCR检测方法的建立[J]. 中国预防兽医学报, 2022, 44(2): 157-161.
GAO J F, WANG X, MAO R F, et al. Establishment of multiplex PCR for detection of three kinds of Trematode metacercariae in freshwater fish[J]. Chinese Journal of Preventive Veterinary Medicine, 2022, 44(2): 157-161. (in Chinese)
[37]
TEAL A E, HABURA A, ENNIS J, et al. A new real-time PCR assay for improved detection of the parasite Babesia microti[J]. J Clin Microbiol, 2012, 50(3): 903-908. DOI:10.1128/JCM.05848-11
[38]
FEKRI-SOOFIABADI M, FEKRI M, MORADABADI A, et al. Ability of real-time PCR for differential diagnosis of various forms of cutaneous leishmaniasis: A comparative study with histopathology[J]. BMC Res Notes, 2019, 12(1): 615. DOI:10.1186/s13104-019-4666-5
[39]
MOHAMMADIHA A, MOHEBALI M, HAGHIGHI A, et al. Comparison of real-time PCR and conventional PCR with two DNA targets for detection of Leishmania (Leishmania) infantum infection in human and dog blood samples[J]. Exp Parasito, 2013, 133(1): 89-94. DOI:10.1016/j.exppara.2012.10.017
[40]
RÍOS R, ARANGUREN R, GASTALDELLI M, et al. Development and validation of a specific real-time PCR assay for the detection of the parasite Perkinsus olseni[J]. J Invertebr Pathol, 2020, 169: 107301. DOI:10.1016/j.jip.2019.107301
[41]
CANIER L, DUBREUIL C, NOYER M, et al. A new multiplex real-time PCR assay to improve the diagnosis of shellfish regulated parasites of the genus Marteilia and Bonamia[J]. Prev Vet Med, 2020, 183: 105126. DOI:10.1016/j.prevetmed.2020.105126
[42]
宋悦, 赵权, 黄燕, 等. 隐孢子虫三种实时荧光定量PCR检测方法的比较[J]. 中国动物传染病学报, 2017, 25(6): 48-55.
SONG Y, ZHAO Q, HUANG Y, et al. Comparison of three real-time PCR assays for Cryptosporidium[J]. Chinese Journal of Animal Infectious Diseases, 2017, 25(6): 48-55. (in Chinese)
[43]
SIQUEIRA L M V, SENRA C, DE OLIVEIRA Á A, et al. A real-time PCR assay for the diagnosis of intestinal schistosomiasis and cure assessment after the treatment of individuals with low parasite burden[J]. Front Immunol, 2021, 11: 620417. DOI:10.3389/fimmu.2020.620417
[44]
SANTA M A, PASTRAN S A, KLEIN C, et al. Detecting co-infections of Echinococcus multilocularis and Echinococcus canadensis in coyotes and red foxes in Alberta, Canada using real-time PCR[J]. Int J Parasitol Parasites Wildl, 2018, 7(2): 111-115. DOI:10.1016/j.ijppaw.2018.03.001
[45]
GOMES C M, CESETTI M V, DE PAULA N A, et al. Field validation of SYBR green- and TaqMan-based real-time PCR using biopsy and swab samples to diagnose American Tegumentary Leishmaniasis in an area where Leishmania braziliensis (Viannia) is endemic[J]. J Clin Microbiol, 2017, 55(2): 526-534. DOI:10.1128/JCM.01954-16
[46]
DA SILVA SALES K G, DE OLIVEIRA MIRANDA D E, PAIVA M H S, et al. Fast multiplex real-time PCR assay for simultaneous detection of dog and human blood and Leishmania parasites in sand flies[J]. Parasit Vectors, 2020, 13(1): 131. DOI:10.1186/s13071-020-3994-6
[47]
LLEWELLYN S, INPANKAEW T, NERY S V, et al. Application of a multiplex quantitative PCR to assess prevalence and intensity of intestinal parasite infections in a controlled clinical trial[J]. PLoS Negl Trop Dis, 2016, 10(1): e0004380. DOI:10.1371/journal.pntd.0004380
[48]
INCANI R N, FERRER E, HOEK D, et al. Diagnosis of intestinal parasites in a rural community of venezuela: advantages and disadvantages of using microscopy or RT-PCR[J]. Acta Trop, 2017, 167: 64-70. DOI:10.1016/j.actatropica.2016.12.014
[49]
RAMÍREZ J D, HERRERA G, HERNÁNDEZ C, et al. Evaluation of the analytical and diagnostic performance of a digital droplet polymerase chain reaction (ddPCR) assay to detect Trypanosoma cruzi DNA in blood samples[J]. PLoS Negl Trop Dis, 2018, 12(12): e0007063. DOI:10.1371/journal.pntd.0007063
[50]
YANG R C, PAPARINI A, MONIS P, et al. Comparison of next-generation droplet digital PCR (ddPCR) with quantitative PCR (qPCR) for enumeration of Cryptosporidium oocysts in faecal samples[J]. Int J Parasitol, 2014, 44(14): 1105-1113. DOI:10.1016/j.ijpara.2014.08.004
[51]
GRABIAS B, ESSUMAN E, QUAKYI I A, et al. Sensitive real-time PCR detection of Plasmodium falciparum parasites in whole blood by erythrocyte membrane protein 1 gene amplification[J]. Malar J, 2019, 18(1): 116. DOI:10.1186/s12936-019-2743-9
[52]
WILSON M, GLASER K C, ADAMS-FISH D, et al. Development of droplet digital PCR for the detection of Babesia microti and Babesia duncani[J]. Exp Parasitol, 2015, 149: 24-31. DOI:10.1016/j.exppara.2014.12.003
[53]
WEERAKOON K G, GORDON C A, GOBERT G N, et al. Optimisation of a droplet digital PCR assay for the diagnosis of Schistosoma japonicum infection: a duplex approach with DNA binding dye chemistry[J]. J Microbiol Methods, 2016, 125: 19-27. DOI:10.1016/j.mimet.2016.03.012
[54]
WEERAKOON K G, GORDON C A, CAI P F, et al. A novel duplex ddPCR assay for the diagnosis of schistosomiasis japonica: proof of concept in an experimental mouse model[J]. Parasitology, 2017, 144(8): 1005-1015. DOI:10.1017/S003118201700021X
[55]
WEERAKOON K G, GORDON C A, WILLIAMS G M, et al. Droplet digital PCR diagnosis of human schistosomiasis: Parasite cell-free DNA detection in diverse clinical samples[J]. J Infect Dis, 2017, 216(12): 1611-1622. DOI:10.1093/infdis/jix521
[56]
ACOSTA SOTO L, SANTÍSIMA-TRINIDAD A B, BORNAY-LLINARES F J, et al. Quantitative PCR and digital PCR for detection of Ascaris lumbricoides eggs in reclaimed water[J]. Biomed Res Int, 2017, 2017: 7515409.
[57]
SCHNEIDER R, LAMIEN-MEDA A, AUER H, et al. Validation of a novel FRET real-time PCR assay for simultaneous quantitative detection and discrimination of human Plasmodium parasites[J]. PLoS One, 2021, 16(6): e0252887. DOI:10.1371/journal.pone.0252887
[58]
FERREIRA A L C, CARREGAL V M, DE ALMEIDA FERREIRA S, et al. Detection of Leishmania infantum in 4 different dog samples by real-time PCR and ITS-1 nested PCR[J]. Diagn Microbiol Infect Dis, 2014, 78(4): 418-421. DOI:10.1016/j.diagmicrobio.2013.10.015
[59]
孙滔, 米荣升, 张烨华, 等. 基于不同靶基因的3种住肉孢子虫PCR检测方法比较[J]. 动物医学进展, 2020, 41(12): 1-6.
SUN T, MI R S, ZHANG Y H, et al. Comparison of three Sarcocystis PCR detection methods based on different target genes[J]. Progress in Veterinary Medicine, 2020, 41(12): 1-6. DOI:10.3969/j.issn.1007-5038.2020.12.001 (in Chinese)
[60]
王会品, 李欣, 孙世珺. 简并引物q-PCR法检测新疆喀什地区羊肝组织中细粒棘球绦虫[J]. 广东医学, 2022, 43(1): 46-50.
WANG H P, LI X, SUN S J, et al. Detection of Echinococcus granulosus in sheep liver from Kashi region of Xinjiang by degenerate primer q-PCR method[J]. Guangdong Medical Journal, 2022, 43(1): 46-50. (in Chinese)
[61]
ZHAO W T, PANG Q, XU R X, et al. Monitoring the prevalence of Leucocytozoon sabrazesi in southern China and testing tricyclic compounds against gametocytes[J]. PLoS One, 2016, 11(8): e0161869. DOI:10.1371/journal.pone.0161869
[62]
ANGELONE-ALASAAD S, MOLINAR MIN A, PASQUETTI M, et al. Universal conventional and real-time PCR diagnosis tools for Sarcoptes scabiei[J]. Parasit Vectors, 2015, 8: 587. DOI:10.1186/s13071-015-1204-8
[63]
詹佳飞, 宋宏宇, 王凝, 等. 基于线粒体ND6基因检测犬感染细粒棘球绦虫的粪便PCR方法[J]. 中国人兽共患病学报, 2019, 35(7): 626-632.
ZHAN J F, SONG H Y, WANG N, et al. Detection of Echinococcus granulosus infection in dogs on the mitochondrial ND6 gene by Copro-PCR assay[J]. Chinese Journal of Zoonoses, 2019, 35(7): 626-632. (in Chinese)
[64]
TELLEVIK M G, MULLER K E, LØKKEN K R, et al. Detection of a broad range of Leishmania species and determination of parasite load of infected mouse by real-time PCR targeting the arginine permease gene AAP3[J]. Acta Trop, 2014, 137: 99-104. DOI:10.1016/j.actatropica.2014.05.008
[65]
FILGUEIRA C P B, MOREIRA O C, CANTANHÊDE L M, et al. Comparison and clinical validation of qPCR assays targeting Leishmania 18S rDNA and HSP70 genes in patients with American Tegumentary Leishmaniasis[J]. PLoS Negl Trop Dis, 2020, 14(10): e0008750. DOI:10.1371/journal.pntd.0008750
[66]
KOLTAS I S, EROGLU F, UZUN S, et al. A comparative analysis of different molecular targets using PCR for diagnosis of old world leishmaniasis[J]. Exp Parasitol, 2016, 164: 43-48. DOI:10.1016/j.exppara.2016.02.007
[67]
田万年, 李荣权, 薛书江, 等. 牛卵形巴贝斯虫不同靶基因PCR检测方法的比较[J]. 中国兽医杂志, 2018, 54(2): 30-32.
TIAN W N, LI R Q, XUE S J, et al. Comparison of different PCR methods for the detection of Babesia ovata target gene[J]. Chinese Journal of Veterinary Medicine, 2018, 54(2): 30-32. (in Chinese)
[68]
曾凡胜, 何露, 何雪梅, 等. 日本血吸虫巢式PCR检测方法的建立[J]. 热带病与寄生虫学, 2017, 15(3): 136-138.
ZENG F S, HE L, HE X M, et al. Nested-PCR assay for detection of Schistosoma japonicum[J]. Journal of Tropical Diseases and Parasitology, 2017, 15(3): 136-138. DOI:10.3969/j.issn.1672-2302.2017.03.003 (in Chinese)
[69]
FUSS A, MAZIGO H D, MUELLER A. Detection of Schistosoma mansoni DNA using polymerase chain reaction from serum and dried blood spot card samples of an adult population in North-western Tanzania[J]. Infect Dis Poverty, 2021, 10(1): 15. DOI:10.1186/s40249-021-00798-4
[70]
FUSS A, MAZIGO H D, TAPPE D, et al. Comparison of sensitivity and specificity of three diagnostic tests to detect Schistosoma mansoni infections in school children in Mwanza region, Tanzania[J]. PLoS One, 2018, 13(8): e0202499. DOI:10.1371/journal.pone.0202499
[71]
JOOF E, ANDRUS P S, SOWUNMI K, et al. Comparing PCR techniques against conventional cercarial shedding methods for detecting Schistosoma mansoni infection in Biomphalaria snails[J]. Acta Trop, 2020, 212: 105716. DOI:10.1016/j.actatropica.2020.105716
[72]
BELDI N, MANSOURI R, BETTAIEB J, et al. Molecular characterization of Leishmania parasites in Giemsa-stained slides from cases of human cutaneous and visceral Leishmaniasis, eastern Algeria[J]. Vector Borne Zoonotic Dis, 2017, 17(6): 416-424. DOI:10.1089/vbz.2016.2071
[73]
PEREIRA M R, ROCHA-SILVA F, GRACIELE-MELO C, et al. Comparison between conventional and real-time PCR assays for diagnosis of visceral leishmaniasis[J]. BioMed Res Int, 2014, 2014: 639310.
[74]
MEDEIROS F A C, GOMES L I, OLIVEIRA E, et al. Development and validation of a PCR-ELISA for the diagnosis of symptomatic and asymptomatic infection by Leishmania (Leishmania) infantum[J]. J Trop Med, 2017, 2017: 7364854.
[75]
DE CÁSSIA-PIRES R, DE MELO M D F A D, BARBOSA R D H, et al. Multiplex PCR as a tool for the diagnosis of Leishmania spp. kDNA and the gapdh housekeeping gene of mammal hosts[J]. PLoS One, 2017, 12(3): e0173922. DOI:10.1371/journal.pone.0173922
[76]
NICODEMO A C, AMATO V S, TUON F F, et al. Usefulness of kDNA PCR in the diagnosis of visceral leishmaniasis reactivation in co-infected patients[J]. Rev Inst Med Trop Sao Paulo, 2013, 55(6): 429-431. DOI:10.1590/S0036-46652013000600011
[77]
SATOW M M, YAMASHIRO-KANASHIRO E H, ROCHA M C, et al. Applicability of kDNA-PCR for routine diagnosis of American tegumentary leishmaniasis in a tertiary reference hospital[J]. Rev Inst Med Trop Sao Paulo, 2013, 55(6): 393-399.
[78]
MERDEKIOS B, PAREYN M, TADESSE D, et al. Evaluation of conventional and four real-time PCR methods for the detection of Leishmania on field-collected samples in Ethiopia[J]. PLoS Negl Trop Dis, 15(1): e0008903.
[79]
DEMAS A, OBERSTALLER J, DEBARRY J, et al. Applied genomics: Data mining reveals species-specific malaria diagnostic targets more sensitive than 18S rRNA[J]. J Clin Microbiol, 2011, 49(7): 2411-2418.
[80]
COSTA G L, ALVARENGA D A M, AGUIAR A C C, et al. Improving the molecular diagnosis of malaria: Droplet digital PCR-based method using saliva as a DNA source[J]. Front Microbiol, 2022, 13: 882530.
[81]
AMARAL L C, ROBORTELLA D R, GUIMARÃES L F F, et al. Ribosomal and non-ribosomal PCR targets for the detection of low-density and mixed malaria infections[J]. Malar J, 2019, 18(1): 154.
[82]
TAJEBE A, MAGOMA G, AEMERO M, et al. Detection of mixed infection level of Plasmodium falciparum and Plasmodium vivax by SYBR Green I-based real-time PCR in North Gondar, north-west Ethiopia[J]. Malar J, 2014, 13(1): 411.
[83]
SINGH R, SINGH D P, GUPTA R, et al. Comparison of three PCR-based assays for the non-invasive diagnosis of malaria: detection of Plasmodium parasites in blood and saliva[J]. Eur J Clin Microbiol Infect Dis, 2014, 33(9): 1631-1639.
[84]
FRANCO-HERNANDEZ E N, ACOSTA A, CORTÉS-VECINO J, et al. Survey for Toxoplasma gondii by PCR detection in meat for human consumption in Colombia[J]. Parasitol Res, 2016, 115(2): 691-695.
[85]
MOUSAVI M, SARAVANI R, MODREK M J, et al. Detection of Toxoplasma gondii in diabetic patients using the nested PCR assay via RE and B1 genes[J]. Jundishapur J Microbiol, 2016, 9(2): e29493.
[86]
FALLAHI S, KAZEMI B, SEYYED TABAEI S J, et al. Comparison of the RE and B1 gene for detection of Toxoplasma gondii infection in children with cancer[J]. Parasitol Int, 2014, 63(1): 37-41.
[87]
RAHIMI ESBOEI B, KAZEMI B, ZAREI M, et al. Evaluation of RE and B1 genes as targets for detection of Toxoplasma gondii by nested PCR in blood samples of patients with ocular toxoplasmosis[J]. Acta Parasitol, 2019, 64(2): 384-389.

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