The effect of water source and soil supplementation on parasite contamination in organic vegetable gardens

Abstract The objective of this study was to determine factors associated with vegetable contamination with zoonotic protozoan. Samples of water, soil and vegetables were collected from July/2014 to May/2016, totaling 83 samples, 21 properties of Londrina region, Paraná, Brazil. DNA amplification of Toxoplasma gondii, Cryptosporidium spp. and Giardia intestinalis in the samples was conducted using polymerase chain reaction (PCR). The PCR results were positive for T. gondii in 12.9% (8/62), Cryptosporidium spp. in 11.3% (7/62) and G. intestinalis in 25.8% (16/62) of the samples. DNA sequencing identified C. parvum in five samples and G. intestinalis Assemblage E in three. The statistical associations demonstrated greater probability of positive samples for T. gondii and for at least one of the three protozoa when the source of irrigation water was the river; a greater chance of positive samples for Cryptosporidium spp. when deer were present on the property; and a smaller chance of positive samples for at least one of the three etiologic agents when soil was supplemented with limestone. The results expose some critical contamination points, providing support for training farmers on good management practices during the production process.

摘要
本研究旨在明确蔬菜受人畜共患原生动物污染的相关影响因素。研究于2014年7月至2016年5月期间，在巴西巴拉那州隆德里纳地区的21处种植场地采集水样、土壤样本及蔬菜样本，共计83份。采用聚合酶链式反应（polymerase chain reaction, PCR）对样本中的刚地弓形虫（Toxoplasma gondii）、隐孢子虫属（Cryptosporidium spp.）以及蓝氏贾第鞭毛虫（Giardia intestinalis）进行DNA扩增检测。PCR检测结果显示，样本中刚地弓形虫阳性率为12.9%（8/62），隐孢子虫属阳性率为11.3%（7/62），蓝氏贾第鞭毛虫阳性率为25.8%（16/62）。经DNA测序确认，5份样本呈微小隐孢子虫（C. parvum）阳性，3份样本呈蓝氏贾第鞭毛虫群E型（G. intestinalis Assemblage E）阳性。统计学关联分析结果表明：当灌溉水源为河水时，刚地弓形虫以及三种原生动物中至少一种呈阳性的样本概率显著升高；当场地内有鹿活动时，隐孢子虫属呈阳性的样本概率显著升高；而当土壤施加石灰时，三种病原中至少一种呈阳性的样本概率显著降低。本研究结果明确了若干关键污染节点，可为农户生产过程中良好管理规范的培训工作提供理论支撑。