Prevalence of <i>Cryptosporidium parvum</i>, <i>Giardia duodenalis</i> and <i>Eimeria</i> spp. in diarrhoeic suckling calves from north-western Spain and analysis of their interactions

Although <i>Cryptosporidium parvum</i>, <i>Giardia duodenalis</i> and some <i>Eimeria</i> species are frequently involved in neonatal calf diarrhoea (NCD), detailed studies on their interactions are scarce. Therefore, a cross-sectional study including faecal samples from 404 diarrhoeic calves aged 0–30 days was performed. <i>Cryptosporidium</i> oocysts and <i>G. duodenalis</i> cysts were detected by immunofluorescence antibody test and positive samples were molecularly characterized. <i>Eimeria</i> oocysts were microscopically detected using the modified McMaster technique and morphometric species identification was performed. <i>Cryptosporidium</i> infections (53.7%) predominated over those by <i>G. duodenalis</i> (12.4%) and <i>Eimeria</i> spp. (6.9%). Three <i>Cryptosporidium</i> species were identified: <i>C. parvum</i> (98.0%), <i>C. bovis</i> (1.0%) and <i>C. ryanae</i> (1.0%). Eleven <i>C. parvum</i> zoonotic subtypes were detected, with IIaA15G2R1 as the most common; only <i>G</i>. <i>duodenalis</i> assemblage E was identified. Moreover, 10 <i>Eimeria</i> species were found, being <i>Eimeria ellipsoidalis</i> (96.4%), <i>Eimeria bovis</i> (85.7%), and <i>Eimeria zuernii</i> (71.4%) predominant. A significant positive association between <i>G. duodenalis</i> and <i>Eimeria</i> spp. was detected as well as a negative association between <i>C. parvum</i> and <i>Eimeria</i> spp. Our results showed that <i>C. parvum</i> wasprevalent in diarrhoeic calves under 21 days of life; <i>Eimeria</i> spp. and <i>G. duodenalis</i> were especially common in animals in their fourth week of life. Concurrent infections increased with age. Moreover, the study also revealed potential public health risks since a noticeable percentage of animals were infected with <i>C. parvum</i> zoonotic subtypes. Further studies are needed for determining the role of these parasites in co-infections with other enteropathogens and their implications in the pathogenicity of NCD.

尽管微小隐孢子虫（Cryptosporidium parvum）、十二指肠贾第虫（Giardia duodenalis）以及部分艾美耳属（Eimeria）物种常与新生犊牛腹泻（neonatal calf diarrhoea, NCD）相关，但针对这些病原体间相互作用的详细研究仍较为匮乏。因此本研究开展了一项横断面调查，共收集404份0~30日龄腹泻犊牛的粪便样本。采用免疫荧光抗体试验检测隐孢子虫卵囊与十二指肠贾第虫包囊，并对阳性样本进行分子生物学鉴定；同时使用改良麦克马斯特技术（modified McMaster technique）镜检艾美耳属卵囊，并通过形态计量学方法完成物种鉴定。隐孢子虫感染率（53.7%）高于十二指肠贾第虫感染（12.4%）与艾美耳属物种感染（6.9%）。共鉴定出3种隐孢子虫：微小隐孢子虫（98.0%）、牛隐孢子虫（C. bovis，1.0%）以及瑞安隐孢子虫（C. ryanae，1.0%）。检测到11种微小隐孢子虫人畜共患亚型，其中以IIaA15G2R1最为常见；仅鉴定出十二指肠贾第虫群E型（assemblage E）。此外，共检出10种艾美耳属物种，其中以椭圆艾美耳虫（Eimeria ellipsoidalis，96.4%）、牛艾美耳虫（Eimeria bovis，85.7%）以及祖尔艾美耳虫（Eimeria zuernii，71.4%）占比最高。本研究发现十二指肠贾第虫与艾美耳属物种感染存在显著正相关，而微小隐孢子虫与艾美耳属物种感染则呈显著负相关。研究结果显示，21日龄以下腹泻犊牛中微小隐孢子虫感染最为普遍；艾美耳属物种与十二指肠贾第虫感染则多见于犊牛第四周龄阶段。混合感染率随犊牛日龄增长而升高。此外，本研究还揭示了潜在公共卫生风险：有相当比例的犊牛感染了微小隐孢子虫人畜共患亚型。未来仍需开展进一步研究，以明确这些寄生虫与其他肠道病原体的复合感染作用，及其在新生犊牛腹泻致病性中的具体影响。