Effects of drinking-water filtration on Cryptosporidium seroepidemiology, Scotland

Waterborne Cryptosporidium species and Giardia duodenalis in resources of MENA: A systematic review and meta-analysis

This review explores our understanding of Cryptosporidium species and Giardia duodenalis distribution in Middle East and North African (MENA) water resources. Results emphasize that Cryptosporidium species (sp.) and G. duodenalis (oo)cysts are present in distinct categories of water in ten MENA countries. Cryptosporidium sp. proportional prevalence in the MENA region was 24.5% (95% CI 16.3-33.8), while G. duodenalis prevalence was 37.7% (95% CI 21.9-55.1). Raw wastewater and surface water were the water categories most significantly impacted. Both parasites were reported in the various types of MENA drinking waters. The most frequent species/genotypes reported were C. hominis, C. parvum, and G. duodenalis assemblage A. Despite the high prevalence of (oo)cysts reported, we should consider the absence of waterborne outbreaks. This indicates significant underestimation and underreporting of both parasites in MENA. Stakeholders should apply water contamination legislation to eradicate Cryptosporidium sp. and G. duodenalis (oo)cysts from water resources/categories.

Molecular Identification of Protozoan Sarcocystis in Different Types of Water Bodies in Lithuania

Representatives of the genus Sarcocystis are unicellular parasites having a two-host life cycle and infecting mammals, birds, and reptiles. Until now, Sarcocystis spp. have been mainly investigated in definitive and intermediate hosts. Only a few studies have been conducted on the detection of Sarcocystis parasites in water samples. The aim of this research was to examine whether the prevalence of Sarcocystis spp. parasitizing farm animals varies in different types of water bodies. Water samples (n = 150) were collected from the entire territory of Lithuania, dividing water bodies into five groups (lakes, rivers, ponds/canals, swamps, and the inshore zone of the territorial Baltic Sea area). One-liter samples were filtered and subsequently analyzed using nested PCR. At least one of the analyzed Sarcocystis spp. (S. arieticanis, S. bertrami, S. bovifelis, S. capracanis, S. cruzi, S. hirsuta, S. miescheriana, and S. tenella) was determined in all examined samples from water bodies. No significant difference in Sarcocystis spp. prevalence between different types of water sources was detected. Our research proved that selecting appropriate primers is important for the accurate identification of parasites in samples collected from water bodies.

Influence of weather and climate on cryptosporidiosis-A review

Studies have shown that climatic factors can significantly influence transmission of many waterborne diseases. However, knowledge of the impact of climate variability on cryptosporidiosis is much less certain. Associations between the incidence of cryptosporidiosis and climatic variables have been reported in several countries. Given that the identified relationships were not consistently reported across studies, it is not known whether these were country-specific observations or can be considered more globally. Variation in the disease risk in both low- and middle-income countries and high-income countries presents new challenges and opportunities to enact responsive changes in research and public health policies. Available epidemiological evidence of the influence of weather and climate on cryptosporidiosis is reviewed. Fourteen studies met the inclusion criteria, and most studies showed that the incidence of cryptosporidiosis is highly sensitive to climatic conditions, especially temperature, rainfall and relative humidity. The identified associations varied across studies, with different conditions of importance and lag times across different locations. Therefore, there is a need for countries at risk to assess Cryptosporidium transmission routes based on the spatiotemporal patterns of the disease and what role climate and other socio-ecological changes play in the transmission. Information gathering will then allow us to provide information for evidence-based control strategies and mitigation of transmission. This review offers new perspectives on the role of climate variability on Cryptosporidium transmission. It highlights different epidemiological approaches adopted and provides the potential for future research and surveillance to reduce the disease burden. By evaluating the epidemiological transmission of this organism in high-income countries, all mitigation strategies, for example filtration and water catchment management, can be used as exemplars of preventing infection in low- to middle-income countries.

Cryptosporidium Infections in Africa-How Important Is Zoonotic Transmission? A Review of the Evidence

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, especially 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, the apparent predominance of human-to-human transmission is both interesting and puzzling. In this article, 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 in different African countries, and looking for any characteristic "hot spots" where zoonotic transmission has apparently occurred. Studies where transmission networks have been investigated are particularly relevant. Finally, in a separate section, we try to gather these different strands of evidence together in order 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 in Africa reflect a relative 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 inherent genetic traits? Is the African environment-in all its variety-simply more detrimental to oocyst survival? Will the so-called hypertransmissible subtypes, currently relatively rare in Africa, be introduced from Europe or elsewhere, and, if so, will they fade out or establish and spread? Our intention with this manuscript is not only to summarize and consolidate diverse data, thereby providing an overview of data gaps, but also to provide food for thought regarding transmission of a parasite that continues to have a considerable impact on both human and animal health.

Endemic gastrointestinal illness and change in raw water source and drinking water production - A population-based prospective study

There are indications that drinking water may contribute to endemic gastrointestinal illness (GII) even when the drinking water quality meets current standards, but the knowledge is limited. In this population-based prospective study, we assessed if changes in municipal drinking water production affected the GII incidence, by collecting self-reported GII episodes among the population in two municipalities during calendar time-specific inter-annual periods. About 2600 adults in central Sweden and 2600 adults (including 700 households with children aged 0-9 years) in Southwest Sweden, were followed during a baseline and a follow-up period in 2012-2016. Monthly reports of episodes and symptoms of GII were collected by SMS. The following drinking water related changes were assessed: Change 1 (adults); a municipality with a groundwater treatment, changed to a different groundwater source with UV treatment; Change 2 (adults); a municipality with a surface water treatment changed to a groundwater source with UV treatment; and Change 3a (adults) and 3b (children): a municipality with a surface water treatment changed to a new surface water source, having a treatment with a higher pathogen reduction. We observed no evidence that changes in raw water source and/or improved pathogen removal in the drinking water treatment affected the risk of GII among adults. Among children aged 0-9 years participating in Change 3b, we observed a 24% relative risk reduction in GII incidence. These results suggest that improved water treatment may reduce the disease burden of GII in children even in settings in which water treatment efficacy meets current quality standards.

A One Health Approach to Tackle Cryptosporidiosis

Cryptosporidiosis is a significant diarrhoeal disease in both people and animals across the world and is caused by several species of the protozoan parasite Cryptosporidium. Recent research has highlighted the longer-term consequences of the disease for malnourished children, involving growth stunting and cognitive deficits, and significant growth and production losses for livestock. There are no vaccines currently available to prevent the disease and few treatment options in either humans or animals, which has been a significant limiting factor in disease control to date. A One Health approach to tackle zoonotic cryptosporidiosis looking at new advances in veterinary, public, and environmental health research may offer several advantages and new options to help control the disease.

Development and application of DNA-aptamer-coupled magnetic beads and aptasensors for the detection of Cryptosporidium parvum oocysts in drinking and recreational water resources

Environmentally stable and disinfectant-resistant oocysts of Cryptosporidium spp. shed in the feces of infected humans and animals frequently contaminate water resources and are subsequently spread via potable and recreational waters. The current monoclonal-antibody-based methods for detecting them in water are slow, labor-intensive, and demand skills to interpret the results. We have developed DNA-aptamer-based aptasensors, coupled with magnetic beads, to detect and identify the oocysts of C. parvum for monitoring recreational and drinking water sources. A sensitive and specific electrochemical aptasensor (3'-biotinylated R4-6 aptamer) was used as a secondary ligand to bind the streptavidin-coated magnetic beads. This was incorporated into a probe using gold nanoparticle modified screen-printed carbon electrodes. Square wave voltammetry allowed for specific recognition of C. parvum oocysts. The aptamer-coated probes had an oocyst detection limit of 50. It did not bind to the cysts of Giardia duodenalis, another common waterborne pathogen, thus indicating its high specificity for the target pathogen. The system could successfully detect C. parvum oocysts in spiked samples of the raw lake and river waters. Therefore, the combined use of the aptasensor and magnetic beads has the potential to monitor water quality for C. parvum oocysts in field samples without relying on monoclonal antibodies and skill-demanding microscopy.

Measuring sporadic gastrointestinal illness associated with drinking water - an overview of methodologies

There is an increasing awareness that drinking water contributes to sporadic gastrointestinal illness (GI) in high income countries of the northern hemisphere. A literature search was conducted in order to review: (1) methods used for investigating the effects of public drinking water on GI; (2) evidence of possible dose-response relationship between sporadic GI and drinking water consumption; and (3) association between sporadic GI and factors affecting drinking water quality. Seventy-four articles were selected, key findings and information gaps were identified. In-home intervention studies have only been conducted in areas using surface water sources and intervention studies in communities supplied by ground water are therefore needed. Community-wide intervention studies may constitute a cost-effective alternative to in-home intervention studies. Proxy data that correlate with GI in the community can be used for detecting changes in the incidence of GI. Proxy data can, however, not be used for measuring the prevalence of illness. Local conditions affecting water safety may vary greatly, making direct comparisons between studies difficult unless sufficient knowledge about these conditions is acquired. Drinking water in high-income countries contributes to endemic levels of GI and there are public health benefits for further improvements of drinking water safety.

Human cryptosporidiosis in Europe

Cryptosporidium has emerged as a significant cause of diarrhoeal disease worldwide, with severe health consequences for very young, malnourished children living in endemic areas and for individuals with highly impaired T-cell functions. In Europe, as elsewhere, the burden of disease has been difficult to measure as a result of the lack of appropriate, standardized surveillance and monitoring systems. The recent occurrence of large water- and foodborne outbreaks in several EU countries, as well as the results of many surveys of human and animal cryptosporidiosis, indicate that this parasite is widespread. Specific subtypes of the zoonotic Cryptosporidium parvum and the anthroponotic C. hominis are responsible for the majority of human cases in Europe. No treatment is currently available to clear the infection, but recent progress in genetic engineering of the parasite, coupled with advances in genomics, have opened important avenues for future research. Here we explore the possible reasons for underascertainment of cryptosporidiosis and the importance of accurate diagnosis in clinical management, the epidemiology of human cryptosporidiosis and key messages from recent outbreaks to highlight important interventions and emerging public health issues.