Anthroponotic transmission of Cryptosporidium parvum predominates in countries with poorer sanitation - a systematic review and meta-analysis

Background: Globally cryptosporidiosis is one of the commonest causes of mortality in children under 24 months old and may be associated with important longterm health effects. Whilst most strains of Cryptosporidium parvum are zoonotic, C. parvum IIc is almost certainly anthroponotic. The global distribution of this potentially important emerging infection is not clear. Methods: We conducted a systematic review of papers identifying the subtype distribution of C. parvum infections globally. We searched PubMed and Scopus using the following key terms Cryptospor* AND parvum AND (genotyp* OR subtyp* OR gp60). Studies were eligible for inclusion if they had found C. parvum within their human study population and had subtyped some or all of these samples using standard gp60 subtyping. Pooled analyses of the proportion of strains being of the IIc subtype were determined using StatsDirect. Meta-regression analyses were run to determine any association between the relative prevalence of IIc and Gross Domestic Product, proportion of the population with access to improved drinking water and improved sanitation. Results: From an initial 843 studies, 85 were included in further analysis. Cryptosporidium parvum IIc was found in 43 of these 85 studies. Across all studies the pooled estimate of relative prevalence of IIc was 19.0% (95% CI: 12.9–25.9%), but there was substantial heterogeneity. In a meta-regression analysis, the relative proportion of all C. parvum infections being IIc decreased as the percentage of the population with access to improved sanitation increased and was some 3.4 times higher in those studies focussing on HIV-positive indivduals. Conclusions: The anthroponotic C. parvum IIc predominates primarily in lower-income countries with poor sanitation and in HIV-positive individuals. Given the apparent enhanced post-infectious virulence of the other main anthroponotic species of Cryptosporidium (C. hominis), it is important to learn about the impact of this subtype on human health

Anthroponotic transmission of Cryptosporidium parvum predominates in countries with poorer sanitation - a systematic review and meta-analysis

Background: Globally cryptosporidiosis is one of the commonest causes of mortality in children under 24 months old and may be associated with important longterm health effects. Whilst most strains of Cryptosporidium parvum are zoonotic, C. parvum IIc is almost certainly anthroponotic. The global distribution of this potentially important emerging infection is not clear. Methods: We conducted a systematic review of papers identifying the subtype distribution of C. parvum infections globally. We searched PubMed and Scopus using the following key terms Cryptospor* AND parvum AND (genotyp* OR subtyp* OR gp60). Studies were eligible for inclusion if they had found C. parvum within their human study population and had subtyped some or all of these samples using standard gp60 subtyping. Pooled analyses of the proportion of strains being of the IIc subtype were determined using StatsDirect. Meta-regression analyses were run to determine any association between the relative prevalence of IIc and Gross Domestic Product, proportion of the population with access to improved drinking water and improved sanitation. Results: From an initial 843 studies, 85 were included in further analysis. Cryptosporidium parvum IIc was found in 43 of these 85 studies. Across all studies the pooled estimate of relative prevalence of IIc was 19.0% (95% CI: 12.9–25.9%), but there was substantial heterogeneity. In a meta-regression analysis, the relative proportion of all C. parvum infections being IIc decreased as the percentage of the population with access to improved sanitation increased and was some 3.4 times higher in those studies focussing on HIV-positive indivduals. Conclusions: The anthroponotic C. parvum IIc predominates primarily in lower-income countries with poor sanitation and in HIV-positive individuals. Given the apparent enhanced post-infectious virulence of the other main anthroponotic species of Cryptosporidium (C. hominis), it is important to learn about the impact of this subtype on human health

The Current Molecular Epidemiological Scenario of Cryptosporidium, Giardia and Blastocystis in Spain. Implication for Public Health

The enteric protozoan parasites Cryptosporidium spp. and Giardia duodenalis are major contributors to the burden of gastrointestinal diseases globally. Both pathogens primarily affect children living in resource-poor settings with limited or no access to clean water and sanitation facilities, but are also significant public health threats in developed countries. Additionally, Cryptosporidium spp. and G. duodenalis are common causes of waterborne and foodborne outbreaks of gastrointestinal disease globally. Besides, the Stramenopile Blastocystis sp. is the most common eukaryotic organism reported in the human gut. Although its pathogenicity is a topic of debate, there is increasing evidence demonstrating that this protist can be associated with gastrointestinal disorders (diarrhoea, irritable bowel syndrome) and extra-intestinal manifestations, including urticaria. Because Cryptosporidium spp., G. duodenalis and Blastocystis sp. share the same transmission (faecal-oral) route, are able to infect a wide range of animal species other than humans with variable host specificities, and their infective forms are environmentally resilient, the study of these pathogens should be ideally approached under the One Health umbrella. In this context, molecular-based methods including PCR and sequencing provide powerful tools to investigate the epidemiology and transmission of these parasites. In Spain, cryptosporidiosis and giardiosis, but not blastocystosis, are notifiable diseases. However, the true incidence of these infections remain largely unknown because underdiagnosing and underreporting. Symptomatic cryptosporidiosis and giardiosis disproportionally affect children under four years of age, but we know now that subclinical infections are also common in apparently healthy individuals of all age groups. However, molecular data regarding the frequency and diversity of these pathogens are limited and spatially and temporally discontinuous. This chapter aims to provide, from a public veterinary health perspective, an updated account on the epidemiology of Cryptosporidium, G. duodenalis and Blastocystis in Spain, with an emphasis on the description of the species/genotypes circulating in symptomatic and asymptomatic human populations. Current knowledge on the presence of these pathogens in production (livestock), companion (dogs and cats) and wildlife animal species is also discussed, including their potential role as natural reservoirs of human infections, and the available evidence of zoonotic (and anthroponotic) transmission events.Research summarized in this chapter and conducted at the Spanish National Centre for Microbiology was funded by the Health Institute Carlos III (ISCIII), Ministry of Economy and Competitiveness (Spain), under projects CP12/03081 and PI16CIII/00024. The funder had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.S