Abstract: Objective　To investigate the epidemiological characteristics and identify the risk factors of Giardia lamblia infections among patients with colorectal cancer in Henan Province. Methods　A cross⁃sectional study was performed for questionnaire surveys among colorectal cancer patients in Henan Cancer Hospital during the period from March to July, 2021. Patients’ stool samples were collected, and the triosephosphate isomerase (tpi) gene of G. lamblia was amplified in stool samples using nested PCR assay to characterize the parasite genotype. Univariate analysis and multivariate logistic regression analyses were employed to identify the risk factors of G. lamblia infections among colorectal cancer patients. Results　A total of 307 colorectal cancer patients were investigated, including 176 males (57.3%) and 131 females (42.7%). PCR assay detected 8.1% [95% confidential interval (CI): (0.056, 0.117)] prevalence of G. lamblia infections among the study subjects, and there was no significant difference in the prevalence between men [9.1%, 95% CI: (0.057, 0.143)] and women [6.9%, 95% CI: (0.037, 0.125)] ([χ2] = 0.495, P = 0.482). In addition, there was no age⁃specific prevalence of G. lamblia infections among the participants ([χ2] = 1.534, P = 0.675). Multivariate logistic regression analysis identified use of septic tanks [odds ratio (OR) = 3.336, 95% CI: (1.201, 9.267)], daily use of well water [OR = 3.042, 95% CI: (1.093, 8.465)] and raising livestock [OR = 3.740, 95% CI: (1.154, 12.121)] as risk factors of G. lamblia infections among colorectal cancer patients, and the prevalence of abdominal pain was significantly greater in colorectal cancer patients with G. lamblia infections than in those without infections (P = 0.017). Among the 25 patients with G. lamblia infections, assemblage A was characterized in 24 (96.0%) cases and assemblage B in one case (4.0%). Conclusions　 The prevalence of G. lamblia is high among colorectal cancer patients in Henan Province, and assemblage A is the dominant genotype of G. lamblia. Use of septic tanks, daily use of well water and raising livestock are risk factors of G. lamblia infections among patients with colorectal cancer.

Key words: Giardia lamblia, Colorectal cancer, Genotype, Risk factor, Henan Province

摘要： 目的　了解河南省结直肠癌患者蓝氏贾第鞭毛虫感染特征并分析其危险因素。方法　2021年3—7月，采用横断面调查法对河南省肿瘤医院结直肠癌患者进行问卷调查，并收集其粪便样本，采用巢式PCR法扩增蓝氏贾第鞭毛虫磷酸丙糖异构酶（tpi）基因以确定感染虫种基因型。采用单因素分析和多因素logistic回归模型分析结直肠癌患者感染蓝氏贾第鞭毛虫的危险因素。结果　共调查结直肠癌患者307例，其中男性176例（占57.3%）、女性131例（占42.7%）。巢式PCR检测粪样基因组DNA发现，蓝氏贾第鞭毛虫感染率为8.1%[25/307，95% 可信区间（CI）:（0.056，0.117）]，其中男性感染率为9.1%[16/176，95% CI:（0.057，0.143）]、女性感染率为6.9%[9/131，95% CI:（0.037，0.125）]（[χ2] = 0.495，P = 0.482）。不同年龄组结直肠癌患者蓝氏贾第鞭毛虫感染率差异无统计学意义（[χ2] = 1.534，P = 0.675）。多因素分析发现，使用粪池[比值比（OR）= 3.336，95% CI:（1.201，9.267）]、日常使用水井水[OR = 3.042，95% CI:（1.093，8.465）]及饲养家畜[OR = 3.740，95% CI：（1.154，12.121）]是结直肠癌患者感染蓝氏贾第鞭毛虫的危险因素。结直肠癌患者中，蓝氏贾第鞭毛虫感染者腹痛发生率显著高于非感染者（P = 0.017）。25例蓝氏贾第鞭毛虫感染者中，24例（占96.0%）为聚集体A型感染、1例（占4.0%）为聚集体B型感染。结论　河南省结直肠癌患者蓝氏贾第鞭毛虫感染率相对较高，感染的蓝氏贾第鞭毛虫主要基因型为聚集体A型；使用粪池、日常使用水井水及饲养家畜是结直肠癌患者感染蓝氏贾第鞭毛虫的危险因素。 　

关键词: 蓝氏贾第鞭毛虫, 结直肠癌, 基因型, 危险因素, 河南省