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

The Critical Role of the Cytoskeleton in the Pathogenesis of Giardia

Giardia lamblia is a flagellated parasite of the gut and causes significant morbidity worldwide. Novel druggable targets are sorely needed due to Giardia’s prevalence and the growing threat of antibiotic resistance. Giardia’s conserved and unique cytoskeletal features, such as its eight flagella and ventral disc, are required for host colonization by facilitating motility, attachment, and cell division. Therapies that target these processes could interfere with trophozoite colonization, reduce the time or severity of the infection, and reduce the number of infectious cysts shed into the environment. This requires vetting and prioritizing critical cellular processes and identifying specific Giardia proteins in those processes as targets. It is time to leverage the wealth of data gathered through genome sequencing and proteomic studies, and new insights on the cytoskeleton of Giardia to design effective new drugs to treat giardiasis

Giardia

The intestinal protozoan parasite Giardia duodenalis (syn. Giardia lamblia , Giardia intestinalis ) causes diarrhoea in humans and animals worldwide. The life cycle of G. duodenalis consists of two stages, the fl agellated trophozoite proliferating in the upper part of the small intestine and the non proliferative cyst representing the infectious stage of the parasite. Both stages can be handled in vitro and in vivo. Trophozoites are pear-shaped, motile cells exhibiting a convex dorsal and a concave ventral side. The cell body is formed by a microtubule cytoskeleton. The whole genome contained in two diploid nuclei per trophozoite has been sequenced and characterised. It has some prokaryote-like features such as short promoter sequences. Moreover, some key enzymes of energy and intermediate metabolisms share common features with prokaryotic enzymes and may have been acquired by lateral transfer. Giardia does not contain mitochondria and peroxisomes, but mitosomes, most likely an evolutionarily reduced version of a mitochondrion. The energy metabolism is chemoheterotrophic and works under anaerobic or semiaerobic conditions with glucose as main energy and carbon source and arginine as another important energy source. The present book chapter selectively reviews current knowledge in Giardia research highlighting its basic genetic, physiological and, to a lower extent, its immunological properties. Furthermore, this chapter also shows that G. duodenalis is a suitable cellular model system for the investigation of fundamental biological principles