Iglesias-Piñeiro Javier, González-Warleta Marta, Castro-Hermida José Antonio, Córdoba María, González-Lanza Camino, Manga-González Yolanda, Mezo Mercedes
Departamento de Zooloxía, Xenética e Antropoloxía Física, Facultade de Bioloxía, Campus Vida, Universidade de Santiago de Compostela, 15706, Santiago de Compostela (A Coruña), Spain.
Laboratorio de Parasitología, Centro de Investigaciones Agrarias de Mabegondo, Instituto Galego de Calidade Alimentaria-Xunta de Galicia, Carretera AC-542 de Betanzos a Mesón do Vento, Km 7, 15318, Abegondo (A Coruña), Spain.
Parasit Vectors. 2016 Nov 29;9(1):610. doi: 10.1186/s13071-016-1892-8.
Paramphistomosis caused by Calicophoron daubneyi and fasciolosis caused by Fasciola hepatica are common parasitic diseases of livestock animals. Transmission of the diseases depends on the presence of intermediate hosts, i.e. freshwater gastropods such as lymnaeids. We carried out a 2-year-long study of the dynamics of the snail population acting as the intermediate host for these parasites, considering the population structure in terms of size/age and infection status. In addition, we determined the kinetics of trematode egg excretion in grazing cows. Generalized Additive Models (GAMs) were used to analyze the associations between different response variables and snail size, sampling month and weather-related variables.
Of the molluscan species examined, Galba truncatula, Radix peregra, Anisus (Anisus) leucostoma and Pisidium casertanum (n = 2802), only G. truncatula was infected with C. daubneyi or F. hepatica, at prevalence rates of 8.2% and 4.4% respectively. The probability of infection with C. daubneyi or F. hepatica was linearly related to snail size, although in different ways (negative for C. daubneyi and positive for F. hepatica). The total snail population increased in winter, when specimens of all size classes were found. Infected snails were more abundant during spring-autumn. Mature cercariae of both parasites were found in most seasons. In the statistical models, the sampling month accounted for a high percentage (71.9-78.2%) of the observed variability in snail abundance. The inclusion of climatic variables in the models moderately increased the percentage of deviance explained (77.7-91.9%). Excretion of C. daubneyi eggs in cow faeces was always higher than that of F. hepatica eggs.
Particular care should be taken to prevent pastures and the surrounding environment being contaminated with parasite eggs during winter-spring, when the number of snails susceptible to miracidial infections is maximal. This is therefore the optimal time for treating grazing animals. Nevertheless, control of trematodosis based only on chemotherapy is difficult in an area such as the study area, where environmental factors favour the regular appearance of snail populations harbouring mature cercariae.
由道氏杯殖吸虫引起的前后盘吸虫病和由肝片吸虫引起的肝片吸虫病是家畜常见的寄生虫病。这些疾病的传播取决于中间宿主的存在，即淡水腹足类动物，如椎实螺科。我们对作为这些寄生虫中间宿主的蜗牛种群动态进行了为期两年的研究，考虑了其大小/年龄和感染状况方面的种群结构。此外，我们还测定了放牧奶牛吸虫卵排泄的动力学。使用广义相加模型（GAMs）分析不同响应变量与蜗牛大小、采样月份和与天气相关变量之间的关联。
在所检查的软体动物物种中，即截口圆扁螺、梨形环棱螺、白口盖圆扁螺和卡氏豆螺（n = 2802），只有截口圆扁螺感染了道氏杯殖吸虫或肝片吸虫，感染率分别为8.2%和4.4%。感染道氏杯殖吸虫或肝片吸虫的概率与蜗牛大小呈线性相关，尽管方式不同（道氏杯殖吸虫为负相关，肝片吸虫为正相关）。蜗牛总数在冬季增加，此时发现了所有大小类别的样本。感染的蜗牛在春秋季更为常见。在大多数季节都发现了两种寄生虫的成熟尾蚴。在统计模型中，采样月份占观察到的蜗牛丰度变异性的比例很高（71.9 - 78.2%）。将气候变量纳入模型适度增加了解释的偏差百分比（77.7 - 91.9%）。奶牛粪便中道氏杯殖吸虫卵的排泄量始终高于肝片吸虫卵。
在冬春季节，对吸虫毛蚴感染敏感的蜗牛数量最多，此时应特别注意防止牧场和周边环境被寄生虫卵污染。因此，这是治疗放牧动物的最佳时机。然而，在研究区域这样的地区，仅基于化疗来控制吸虫病是困难的，因为环境因素有利于定期出现携带成熟尾蚴的蜗牛种群。
