One-health approach on the future application of snails: a focus on snail-transmitted parasitic diseases.

Snails are fascinating molluscs with unique morphological and physiological adaptive features to cope with various environments. They have traditionally been utilized as food and feed sources in many regions of the world. The future exploitation of alternative nutrient sources, like snails, is likely to increase further. Snails, however, also serve as an intermediate host for several zoonotic parasites. A category of parasitic infections, known as snail-transmitted parasitic diseases (STPDs), is harmful to humans and animals and is mainly driven by various trematodes, cestodes, and nematodes. The environment plays a crucial role in transmitting these parasites, as suitable habitats and conditions can facilitate their growth and proliferation in snails. In light of diverse environmental settings and biologically categorized snail species, this review evaluates the dynamics of significant STPDs of zoological importance. Additionally, possible diagnostic approaches for the prevention of STPDs are highlighted. One-health measures must be considered when employing snails as an alternative food or feed source to ensure the safety of snail-based products and prevent any adverse effects on humans, animals, and the environment.

Parasite Spillover from Domestic Sheep to Wild Reindeer-The Role of Salt Licks.

Attraction sites are important for environmental pathogen transmission and spillover. Yet, their role in wildlife disease dynamics is often poorly substantiated. Herein, we study the role of salt licks as potential attraction sites for the spillover of gastrointestinal parasites from domestic sheep to wild reindeer. Eggs from the introduced sheep nematode Nematodirus battus were found in faecal samples of both species, suggestive of spillover. DNA metabarcoding of soil, collected at salt licks, revealed that N. battus, in addition to Teladorsagia circumcincta, were the most frequently occurring parasitic nematodes, with a significantly higher prevalence of nematodal DNA in salt lick soil compared to soil from control sites nearby. The finding of similar DNA haplotypes of N. battus in sheep, reindeer, and salt lick soil supports the hypothesis of spillover to reindeer via salt licks. More detailed investigation of the genetic diversity of N. battus across these hosts is needed to draw firm conclusions. Infection with these sheep nematodes could potentially explain a recently observed decline in the calf recruitment rate of the Knutshø reindeer herd. This study also supports the hypothesized role of artificial salt licks as hot spots for the transmission of environmentally persistent pathogens and illustrates the importance of knowledge about such attraction points in the study of disease in free-roaming animals.

Movement of Chronic Wasting Disease Prions in Prairie, Boreal and Alpine Soils.

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy negatively impacting cervids on three continents. Soil can serve as a reservoir for horizontal transmission of CWD by interaction with the infectious prion protein (PrPCWD) shed by diseased individuals and from infected carcasses. We investigated the pathways for PrPCWD migration in soil profiles using lab-scale soil columns, comparing PrPCWD migration through pure soil minerals (quartz, illite and montmorillonite), and diverse soils from boreal (Luvisol, Brunisol) and prairie (Chernozem) regions. We analyzed the leachate of the soil columns by immunoblot and protein misfolding cyclic amplification (PMCA) and detected PrP in the leachates of columns composed of quartz, illite, Luvisol and Brunisol. Animal bioassay confirmed the presence of CWD infectivity in the leachates from quartz, illite and Luvisol columns. Leachates from columns with montmorillonite and prairie Chernozems did not contain PrP detectable by immunoblotting or PMCA; bioassay confirmed that the Chernozemic leachate was not infectious. Analysis of the solid phase of the columns confirmed the migration of PrP to lower layers in the illite column, while the strongest signal in the montmorillonite column remained close to the surface. Montmorillonite, the prevalent clay mineral in prairie soils, has the strongest prion binding ability; by contrast, illite, the main clay mineral in northern boreal and tundra soils, does not bind prions significantly. This suggests that in soils of North American CWD-endemic regions (Chernozems), PrPCWD would remain on the soil surface due to avid binding to montmorillonite. In boreal Luvisols and mountain Brunisols, prions that pass through the leaf litter will continue to move through the soil mineral horizon, becoming less bioavailable. In light-textured soils where quartz is a dominant mineral, the majority of the infectious prions will move through the soil profile. Local soil properties may consequently determine the efficiency of environmental transmission of CWD.

Characterizing parasitic nematode faunas in faeces and soil using DNA metabarcoding.

BACKGROUND: Gastrointestinal parasitic nematodes can impact fecundity, development, behaviour, and survival in wild vertebrate populations. Conventional monitoring of gastrointestinal parasitic nematodes in wild populations involves morphological identification of eggs, larvae, and adults from faeces or intestinal samples. Adult worms are typically required for species-level identification, meaning intestinal material from dead animals is needed to characterize the nematode community with high taxonomic resolution. DNA metabarcoding of environmental samples is increasingly used for time- and cost-effective, high-throughput biodiversity monitoring of small-bodied organisms, including parasite communities. Here, we evaluate the potential of DNA metabarcoding of faeces and soil samples for non-invasive monitoring of gastrointestinal parasitic nematode communities in a wild ruminant population. METHODS: Faeces and intestines were collected from a population of wild reindeer, and soil was collected both from areas showing signs of animal congregation, as well as areas with no signs of animal activity. Gastrointestinal parasitic nematode faunas were characterized using traditional morphological methods that involve flotation and sedimentation steps to concentrate nematode biomass, as well as using DNA metabarcoding. DNA metabarcoding was conducted on bulk samples, in addition to samples having undergone sedimentation and flotation treatments. RESULTS: DNA metabarcoding and morphological approaches were largely congruent, recovering similar nematode faunas from all samples. However, metabarcoding provided higher-resolution taxonomic data than morphological identification in both faeces and soil samples. Although concentration of nematode biomass by sedimentation or flotation prior to DNA metabarcoding reduced non-target amplification and increased the diversity of sequence variants recovered from each sample, the pretreatments did not improve species detection rates in soil and faeces samples. CONCLUSIONS: DNA metabarcoding of bulk faeces samples is a non-invasive, time- and cost-effective method for assessing parasitic nematode populations that provides data with comparable taxonomic resolution to morphological methods that depend on parasitological investigations of dead animals. The successful detection of parasitic gastrointestinal nematodes from soils demonstrates the utility of this approach for mapping distribution and occurrences of the free-living stages of gastrointestinal parasitic nematodes.

Global Goat! Is the Expanding Goat Population an Important Reservoir of Cryptosporidium?

Goats are a primary or additional income source for many families in resource-poor areas. Although often considered inferior to other livestock, the resilience of goats and their ability to thrive in a range of environments means that that they are of particular value. Furthermore, goats emit less methane than other livestock species. In these same areas, it is well-documented that cryptosporidiosis has a substantial impact on infant morbidity and mortality, as well as reducing child growth and development. As Cryptosporidium also causes diarrheal disease in goats, the question arises whether goats may represent a reservoir of infection to humans. Epidemiological studies regarding the potential for transmission of Cryptosporidium between goats and humans have largely concluded that Cryptosporidium species infecting goats are not zoonotic. However, these studies are mostly from developed countries, where goat husbandry is smaller, management routines differ greatly from those of developing countries, contact between goats and their owners is more limited, and cryptosporidiosis has less impact on human health. In this article, background information on goat husbandry in different countries is provided, along with information on Cryptosporidium prevalence among goats, at both the species and sub-species levels, and the potential for zoonotic transmission. The intention is to indicate data gaps that should be filled and to increase awareness of the role of goats as providers for low-income families, often living in areas where cryptosporidiosis is endemic and where appropriate baseline interventions could have a positive impact, regardless of species of goat or parasite.

Occurrence of faecal endoparasites in reindeer (Rangifer tarandus) in two grazing areas in northern Norway.

BACKGROUND: Semi-domesticated reindeer represent an important livestock industry and livelihood for a proportion of the human population in northern Fennoscandia. Reindeer husbandry is considered an extensive animal husbandry, where the animals are kept mostly on natural pastures, although sometimes kept in fenced areas for shorter periods. These reindeer may harbour a variety of parasites that may affect animal health and production. The relatively limited close contact between herds and owners gives limited opportunities for diagnosis and treatment of diseases in general. Furthermore, the effects of subclinical parasitism in livestock are commonly expressed as a reduction in productivity rather than clinical disease and mortality. Thus, specific knowledge of endoparasites and parasitic infections in these herds is scarce. This study investigated the occurrence of various endoparasites in reindeer by analysis of a total of 114 faecal samples from winter-slaughtered reindeer from two different grazing areas in Troms and Finnmark, Norway. RESULTS: Using a McMaster method, a Baermann technique, and a direct immunofluorescent antibody test, the following parasites were identified in the faecal samples with the occurrence data given as percentages: Strongylid eggs (62%), Nematodirinae spp. eggs (24%), Capillaria sp. eggs (42%) and Moniezia spp. eggs (17%), Dictyocaulus spp. larvae (14%) protostrongylid larvae (40%), Eimera spp. oocysts (23%), and Giardia duodenalis cysts (5%). Cryptosporidium oocysts were not detected. Parasite eggs, oocysts, and cysts were quantified. Molecular analysis revealed G. duodenalis sub-assemblage AI, a potentially zoonotic genotype not previously reported in reindeer from this region. Morphological analyses of Eimeria oocysts identified two species, Eimeria mayeri and Eimeria rangiferis, and molecular analyses of the cytochrome C oxidase I (coi) gene and 18 s rRNA (18SSU) gene of Eimeria confirmed the presence of Eimeria species that are specific to reindeer. CONCLUSIONS: A high prevalence, but low burden, of endoparasites was detected in samples from these semi-domesticated reindeer. The samples were collected during winter, when adult gastrointestinal parasites usually produce only low numbers of transmission stages. Therefore, together with the low number of samples, detailed and definitive conclusions regarding parasite status of semi-domesticated reindeer are avoided. Nevertheless, these data provide a snapshot overview of parasite occurrence in a semi-domesticated animal group vulnerable to the various environmental changes to which they are exposed.

Surface waters as a potential source of Giardia and Cryptosporidium in Serbia.

Giardiasis and cryptosporidiosis are recognized by the WHO as important emerging diseases of the 21st century. Symptoms are similar and include diarrhoea and vomiting, which may be severe, even life-threatening, for the immunocompromised and children under five years of age. Between 2013 and 2017, the Institute for Public Health in Serbia recorded 10 waterborne epidemics that manifested as gastrointestinal disease. Routine testing for enteropathogenic bacteria and viruses did not identify the aetiological agents of these outbreaks. As water is not examined for the presence of protozoa in Serbia, we performed a pilot study to analyse samples from four major rivers and their tributaries using a newly implemented methodology for detection of Giardia and Cryptosporidium, based on the ISO 15553:2006 standard. Using immunofluorescence microscopy, Giardia was detected in 10 out of the 31 samples, Cryptosporidium in five, while two samples were positive for both. Presence of G. duodenalis gDNA was confirmed by amplification of the ß-giardin gene in eight samples, of which one and two, respectively, were identified by RFLP as potentially zoonotic assemblages A and B. The results suggest that surface water in Serbia may be a potential source of infection and call for more in-depth studies using sophisticated molecular tools.

Correction to: Goats in the city: prevalence of Giardia duodenalis and Cryptosporidium spp. in extensively reared goats in northern India.

In the original publication of this article [1] the supplementary file was missing two primers for the PCR reaction and the PCR conditions of Giardia and Cryptosporidium. In this correction article the updated additional file (Additional file 1) is available, in which the two primers are included.

Parasite contamination of berries: Risk, occurrence, and approaches for mitigation.

Fresh fruits and vegetables, including berries, are essential components of a healthy diet and are relevant in the prevention of chronic non-communicable diseases such as cancer and heart disease. Associations between diet and health are becoming an increasing focus of consumers, and, in response, consumption of fresh berries has been increasing rapidly in recent decades. However, increased consumption of berries may be associated with an increased risk of acquiring foodborne infections, including parasites. In this review, we describe how parasite contamination of berries may occur at several points on the farm-to-fork pathway, starting from the use of contaminated water for irrigation and pesticide application, and contact with animal and human faeces during cultivation, through contaminated harvesting equipment, and including unhygienic practices of berry pickers in the production field or others handling berries prior to consumption. Parasite transmission stages tend to be robust and therefore likely to survive from contamination in the field, through the various stages of harvesting, packaging, and sale, until consumption. We describe outbreaks of parasitic disease associated with consumption of berries - so far only described for Cyclospora and Trypanosoma cruzi, both of which are briefly introduced - but also show from survey data summarised in this review that sporadic infections or undetected outbreaks associated with contaminated berries may also occur. In addition, we describe methods for assessing whether berries are contaminated with parasite transmission stages, with emphasis on the challenges associated with analysing this particular matrix. Emphasis on current possibilities for mitigation and control are addressed; avoidance of contamination and implementation of good management practices and a hazard analysis and critical control points (HACCP) approach are essential.

Not just a walk in the park: Occurrence of intestinal parasites in dogs roaming recreational parks in Chandigarh, Northern India.

Chandigarh, a city in North-west India, has numerous parks and recreational areas where stray dogs roam freely and pet dogs are exercised. This allows for extensive human-dog interaction, which may pose a public health threat. The aim of this study was to determine the occurrence of gastrointestinal parasites of public health importance, and their seasonal variation, in canine faecal samples obtained from recreational parks in Chandigarh. A total of 212 samples were collected from 10 parks during the winter (January 2015; N = 107) and monsoon season (September 2015; N = 105), to assess the prevalence of intestinal zoonotic parasites and any seasonal variations. The samples were analysed for helminth eggs using McMaster counting chambers. Immunofluorescent antibody testing was used to analyse samples for Cryptosporidium oocysts and Giardia cysts. The Giardia-positive samples were genotyped by conventional multi-locus PCR to determine their assemblage and zoonotic potential. Among the 212 samples, strongyle-type eggs were found in 34 (16.0%), Toxocara spp. eggs were found in 6 (2.8%), taeniid eggs in 1 (0.5%), Cryptosporidium spp. oocysts in 4 (1.9%) and Giardia duodenalis cysts in 49 (23.1%). Trichuris eggs were not detected. The majority of the successfully amplified Giardia isolates belonged to canid-specific assemblages. The prevalence of Giardia cysts in faecal samples was significantly higher during winter than in the monsoon season, whereas helminth-egg prevalence unaffected by season. The prevalence of strongyle-type eggs and Giardia cysts in dog faeces was lower in more affluent areas of the city than those of less affluence. There was no significant difference in the intensity of infection between the seasons. The results indicate that faeces from dogs contaminating parks in Chandigarh do not usually contain parasite transmission stages that pose a significant risk to human health. However, the importance of minimising contamination of public parks with dog faeces is highlighted.

Prevalence and zoonotic potential of intestinal protozoans in bovines in Northern India.

Bovines, and especially cattle, have a dual position of appreciation in India, being both important in the food industry as providers of dairy products, and, culturally, being considered as holy creatures that must not be harmed, killed or eaten. This status means that cattle have a paradoxical existence in India; as they are worshipped and protected, they are able to roam freely among humans, but they are also often left to fend for themselves. The water buffalo represents a significant contributor to the Indian agricultural economy as well as general social development, and are in this way somehow replacing the indigenous cattle. The vast numbers of roaming cattle without clear owners are difficult to look after in terms of veterinary healthcare and appropriate interventions when necessary, and have no regular supply of food. This article describes an investigation of the occurrence of Cryptosporidium spp. and Giardia duodenalis in bovines either roaming the streets or being kept in animal holdings in and around Chandigarh, a city in Northern India, and addresses the zoonotic potential of these protozoan parasites shed from bovines living in close contact with humans. 294 animals of all ages were sampled, and the majority of the positive samples were found from calves. The overall prevalence of Giardia was 8.2% and Cryptosporidium was 2.4%. Non-zoonotic assemblages were predominantly found in the case of the Giardia - positive samples, and in the case of Cryptosporidium, as well as non-zoonotic genotypes, zoonotic subgroups previously described from infected human infections in this area, were identified, indicating that there may be sharing of intestinal parasites in these settings, where cattle live in close contact with humans.

Goats in the city: prevalence of Giardia duodenalis and Cryptosporidium spp. in extensively reared goats in northern India.

BACKGROUND: Various characteristics of goats mean they are highly suitable livestock for backyard rearing by people with limited resources. They are a popular livestock choice in India, where they are often kept to supplement an already scarce income. In these settings, hygiene and sanitation standards tend to be low, and weakens the interface between humans and animals, thus reducing the barrier between them and thereby increasing the likelihood that zoonotic and anthroponotic infections will occur. RESULTS: This study reports an investigation of the occurrence of Cryptosporidium spp. and Giardia duodenalis in goats being reared in different settings in urban and peri-urban areas in northern India, and addressed the zoonotic potential of these important protozoan parasites shed from goats living close to humans. The overall prevalence of G. duodenalis was 33.8 and 0.5% for Cryptosporidium spp.; the relatively low prevalence of cryptosporidiosis may reflect that most samples were derived from adult animals. The prevalence of G. duodenalis excretion was found to be similar to that reported in other studies. However, although other studies have reported a predominance of non-zoonotic Assemblage E in goats, in this study potentially zoonotic Assemblages predominated [Assemblage A (36%) and Assemblage B (32%)]. CONCLUSIONS: The results of this study indicate that in this area where goats and humans are living in close proximity, there may be sharing of intestinal parasites, which can be detrimental for both host species.

Checking the detail in retail: Occurrence of Cryptosporidium and Giardia on vegetables sold across different counters in Chandigarh, India.

Fresh produce has been recognized as a vehicle of infection for protozoan parasites, particularly Cryptosporidium, and, to a lesser extent, Giardia. For both parasites, outbreaks associated with fresh produce have been documented. Although documented outbreaks tend to be from industrialized countries, contamination of fresh produce with these parasites is a global issue. In developing countries, infections with these parasites are often endemic in the community, and basic infrastructure and hygiene measures may be inadequate, thus the likelihood of contamination of fresh produce with these parasites may be higher. Realization of the importance of this transmission route comes against a backdrop of raw salads and more Western culinary habits gaining a foothold, and fresh produce being encouraged as part of the diet due to their associated health benefits. However, if consumption of uncooked fresh produce is going to increase its market sector in India, it is important that it is safe. In this study, various types of fresh produce obtained from three types of vendors in Chandigarh, a major city in Northern India, were analyzed for contamination with Cryptosporidium oocysts and Giardia cysts using a method that has been previously validated in inter-laboratory spiking experiments. A total of 284 samples of different fresh produce items were analyzed, obtained from the different retailers situated in different societal layers of the city. The overall prevalence of contamination of fresh produce with these parasites was just under 11%, with 6% of the vegetables contaminated with Cryptosporidium oocysts, and 5% with Giardia cysts. Contaminated vegetables included turnip, cabbage, carrot, chili, coriander, cucumber, radishes, and tomatoes. Molecular analyses identified contamination with Cryptosporidium parvum and Giardia duodenalis of Assemblage A and Assemblage D, indicating that contamination from animals may be of relevance. Although the prevalence of contamination is similar to those reported in previous studies, the levels of contamination on some items of fresh produce were relatively high. Although the different socioeconomic areas of Chandigarh from which the samples were obtained was not associated with likelihood of contamination, fresh produce from supermarkets had heavier contamination with Cryptosporidium oocysts than fresh produce purchased through other sales outlets. The results are discussed in relation to the fresh produce chain and sales models in Chandigarh, both in terms of where contamination may occur and the potential importance of fresh produce as a transmission vehicle.

Keeping it cool: Survival of Giardia cysts and Cryptosporidium oocysts on lettuce leaves.

Fresh produce has been recognized as a vehicle for transmission of protozoan parasites for many years, and there are numerous publications regarding their occurrence on such foodstuffs, indicating their potential importance as foodborne parasites. Nevertheless, few studies have been published regarding the effectiveness of this transmission route, and whether contamination is likely to result in transmission. The purpose of this study was to assess the viability of Cryptosporidium oocysts and Giardia cysts, two protozoa associated with both waterborne and foodborne transmission, by spiking fresh produce (lettuce leaves) with viable transmission stages and determining changes in viability. These investigations were performed under different conditions and over time spans that may be used in a regular household; a fridge at 4°C, under ambient temperatures exposed to natural cycles of light during night and day, and inside a cupboard to ensure no light exposure, for a duration of up to two weeks, or as long as the produce remained visually palatable. The major finding from this study is that whereas both Cryptosporidium oocysts and Giardia cysts survive well when kept moist and refrigerated, survival of Giardia cysts was abrogated on lettuce at room temperature. Indeed, almost 50% die-off of Giardia cysts was recorded within the first 24h. Cryptosporidium oocysts had a stable viability throughout the experiment under all the conditions investigated, indicating that fresh produce is a suitable transmission vehicle for Cryptosporidium, even if contamination occurs on-farm and the parasites are exposed to non-favourable storage conditions, as may be common in developing countries. Giardia cysts were not as robust as Cryptosporidium oocysts, and would be probably unlikely to survive under ambient storage conditions on-farm, during sale, or at home. However, if kept refrigerated, then some contaminating Giardia cysts may remain viable and therefore may pose a threat to the consumer. Thus, as the cold chain for transport and storage of fresh produce improves, it is important that similar improvements are implemented to reduce the contamination of fresh produce with parasite transmission stages.

Keeping parasitology under the One Health umbrella.

The One Health concept is no longer new, but remains an accepted concept in modern disease control - where the interactions between animal health, human health, and the environment in which we live are recognised as being of importance. However, emerging infectious diseases often garner the greatest attention and resources. Parasitic infections, many of which are zoonotic but cannot truly be considered as emerging, must ensure that they retain their place under the One Health umbrella.