Cryptosporidium, a protozoan parasite in the phylum Apicomplexa, is the etiological agent of cryptosporidiosis, an intestinal infection characterized by profuse watery diarrhea. Over 30 species of Cryptosporidium are recognized, some host specific whereas others infect a broader host range. Cryptosporidium hominis and Cryptosporidium parvum are the species most commonly associated with human infection; C. hominis is largely associated only with human infections, but C. parvum is also associated with infection in animals, particularly young ruminants. In some regions, cryptosporidiosis is a serious veterinary problem, particularly for calves and lambs. Many outbreaks of human cryptosporidiosis have been associated with zoonotic transmission following contact with infected animals. In Africa, where cryptosporidiosis is a major contributor to pediatric morbidity and mortality, evidence suggests transmission is principally anthroponotic. Given the frequent close contact between humans and animals in Africa, this apparent predominance of human-to-human transmission is both interesting and puzzling. Here, after a brief “text book” introduction to the parasite, we consider in separate sections the different aspects of relevance to Cryptosporidium transmission in African countries; describing different aspects of the various species and subtypes in human and animal infections, considering livestock management practices, and looking for any “hot spots” where zoonotic transmission has apparently occurred. Finally, we gather these different strands of evidence together to assess the reasons behind the apparent predominance of anthroponotic transmission in Africa. Reviewing the available evidence provides an opportunity to re-think transmission pathways, not only in Africa but also elsewhere, and also to pose questions. Does the predominance of human-to-human transmission reflect an absence of zoonotic C. parvum in African livestock? Are Africans less susceptible to zoonotic Cryptosporidium infection, perhaps resulting from early immunostimulation by C. hominis or due to genetic traits? Is the African environment simply more detrimental to oocyst survival? Will the hypertransmissible subtypes, currently relatively rare in Africa, be introduced, and, if so, will they fade out or establish? Our intention is not only to summarize and consolidate diverse data, but also to provide food for thought regarding transmission of a parasite that exerts a considerable impact on both human and animal health.
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机译：Cryptosporidium，Phylumpolemplexa的原生动物寄生虫，是隐孢子虫病的病因，其特征在于细腻的水性腹泻。超过30种隐孢子虫被认识到，一些宿主特定，而其他宿主则感染更广泛的主机范围。 Cryptosporidium hominis和Cryptosporidium parvum是最常见的人类感染的物种; C. hominis在很大程度上仅与人类感染相关，但C.Parvum也与动物感染有关，特别是年轻反刍动物。在一些地区，密码孢子虫病是严重的兽医问题，特别是对于小牛和羔羊。在与受感染动物接触后，许多人的隐孢子虫病与人畜共患病有关。在非洲，密码孢子虫病是对儿科发病率和死亡率的主要贡献者，证据表明传播主要是人为的。鉴于非洲人类与动物之间的频繁接触，人对人类传播的表观占优势既有趣又令人费解。在这里，在简要的“教科书”介绍寄生虫之后，我们考虑在单独的部分中，与非洲国家的密码孢子率相关的不同方面;考虑到牲畜管理实践，并寻找任何“热点”，描述了人类和动物感染中的各种物种和亚型的不同方面。最后，我们将这些不同的证据集中在一起，评估非洲人为症状变速器明显占主导地位的原因。审查可用证据提供了重新思考传输途径的机会，不仅在非洲，而且还在其他地方，以及造成问题。人对人类传输的主要职位是否反映了非洲牲畜中的缺乏子宫的C.Parvum？非洲人是否易于敏感到动物孢子虫感染，也许是由C. hominis或因遗传性状的早期免疫刺激而导致的？非洲环境是否简单地对卵囊存活率更加有害？将介绍超务杀的亚型，目前在非洲相对罕见，介绍，如果是的话，他们会淡出或建立吗？我们的意图不仅总结和巩固了各种数据，而且还提供了对寄生虫的思考的思考，以对人类和动物健康产生相当大的影响。
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