Introduction

The first case of human cryptosporidiosis was seen in 1976 related in a 3-year-old girl from rural Tennessee who suffered severe gastroenteritis for 2 weeks [1]. Cryptosporidium was later recognized as a waterborne pathogen during an outbreak in Braun Station, Texas, where more than 2000 individuals were afflicted with cryptosporidiosis [2]. The parasite continues to cause a number of waterborne disease outbreaks in the USA and other countries every year [2–4]. More recently, Cryptosporidium has emerged as an important enteric pathogen worldwide [5], and a growing population of immunocompromised persons and the continued outbreaks of cryptosporidiosis in recreational water have placed an even greater emphasis on this pathogen. The parasite defies water and health authorities by its ability to withstand chlorine disinfection and filtration [5, 6]. Cryptosporidium is primarily transmitted by either direct fecal oral route or ingestion of food or water contaminated with Cryptosporidium oocyst. Both the anthroponotic (Cryptosporidium hominis and Cryptosporidium parvum) and zoonotic (C. parvum) species present unique public health challenges. These two species show geographic differences (Table 1) in their distribution as a cause of human infection; for example, C. parvum is reported to be more common in the UK while C. hominis is more common in the USA [3]. Cryptosporidium infections have gained more attention in the past 20 years as clinically important human pathogens.

Table 1 Worldwide distribution of some of the cases and surveillance data reported
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The taxonomic status of Cryptosporidium has been undergoing rapid changes because of new information that is supported primarily by molecular data [4]. Molecular data suggests that Cryptosporidium may be more closely related to gregarines, a group of apicomplexans in invertebrate that share a similar life cycle (see Fig. 1 Korpe et al., 2015) than other intestinal coccidians (such as Cyclospora and Cystoisospora) [2]. There are 26 species classified within the Cryptosporidium genus [7]. However, due to the similar spherical shape of the oocyst, microscopic size, and obscurity of internal structures, morphology is not reliable for delineating species within the Cryptosporidium genus [8]. In fact, the oocyst morphology trait is regarded as insufficient in the absence of biological and molecular data [9].

Fig. 1
figure 1

Oocysts of Cryptosporidium in MZN staining (×100 objective)

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The infectivity of Cryptosporidium oocysts has shown to be very high although it is still not clear what the exact dose required to induce infection is. The probability of transmission from a small amount of contamination is fairly high as supported by DuPont et al. (1995) who determined that the infective dose of Cryptosporidium is only 132 oocysts for healthy individuals with no previous serological immunity to cryptosporidiosis [10]. In a comparative study by Haas and Rose (1994) of oocyst levels in treated water during identified waterborne outbreaks and conditions under which no outbreaks were detected, they suggested that action be taken at a level of 10–30 oocysts or higher per 100 L of treated water [11]. In a different study by DuPont et al. (1995), it was found that the median infective dose in 29 healthy volunteering subjects was 132 oocysts [12]. However, Haas and Rose (1994) further suggested that some individuals may develop cryptosporidiosis after ingestion of only one oocyst. The latter could be attributed to the autoinfection stages of the life cycles of Cryptosporidium leading to low of infective doses required to induce infection [11].

Propagation of Cryptosporidium in Reservoir Hosts

Cryptosporidium species affect primarily the ileum of humans and livestock with the potential to cause severe enteric diseases [13]. Humans and animals function as both definitive and reservoir hosts for Cryptosporidium. Figure 1 shows oocysts recovered from stool samples and identified using modified Ziehl-Neelson (MZN) acid-fast staining method, which is a commonly used differential staining method along with safranin-methylene blue stain, modified Kinyoun’s acid-fast method, and DMSO-carbol fuchsin stain [14]. Infection begins when the ingested oocysts release sporozoites, which attach, adhere, and then invade the intestinal epithelial cells where replication occurs. The parasite possesses a number of surface glycoproteins, which are thought to play a role in the parasite pathogenesis including importance for attachment and invasion into the host cell (see accompanying article by Ludington and Ward).

Mechanisms whereby propagation and eventual shedding occur remain uncertain but have been investigated using in vitro systems. Cell damage in enterocyte monolayers is caused due to disruption of tight cell junctions, a loss of barrier function, the release of lactate dehydrogenase, and increased amount of cell death [15]. Several molecules may aid in direct tissue damage, such as phosholipases, proteases, and hemolysins [11, 15]. Proteases play an important role in the initial stages of Cryptosporidium infection [16, 17] and mediate protein degradation, invasion of host tissues, and evasion of host immunity. Distinct protease such as aminopeptidase, cysteine protease, and serine protease have been found in Cryptosporidium sporozoites, which are found during excystation process. Proteases Hemolysin H4 has similar sequence to the hemolysin of enterohemorrhagic Escherichia coli O157:H7. The main function of H4 is still unknown, but it disrupts cell membranes, suggesting that it aids in cellular invasion, which permit merozoites to exit the parasitophorous vacuole and spread to adjacent cells [15].

Global Epidemiology of Cryptosporidium in Humans and Animals

The prevalence of Cryptosporidium varies widely from country to country and from one region to another. Although cryptosporidiosis is prevalent in tropical countries, few studies have been conducted to accurately identify and characterize Cryptosporidium spp. using molecular tools. Enteric parasites are a very common source of diarrhea in many developing countries, and Cryptosporidium has been proved as one of the most persistent [14]. Human cryptosporidiosis is mainly caused by C. hominis and C. parvum which is found in both immunocompetent and immunocompromised individuals, but their occurrence differs in different parts of the world [18]. Macroepidemiological analyses depicted that C. hominis is more prevalent in North and South America, Australia, and Africa, while C. parvum causes more human infections in Europe, especially in the UK. C. hominis was more prevalent in infants under 1 year and in females aged 15 to 44 years. C. parvum occurrence peaks in spring, while C. hominis during the late summer and early autumn. Geographical patterns of these parasites were seen among the countries (Uganda, Serbia, Turkey, Israel, UK, USA, and New Zealand), due to various prevailing ecological determinants of transmission [18].

Infections by Cryptosporidium parasites are estimated to be around 500 million annually in developing countries. In Africa, about 20–35 % people are infected with the organism and about 32.5 to 40 % are infected in the Sub-Saharan Africa [19]. A cryptosporidiosis prevalence survey done in Kenya over a year period reported a prevalence of 4 % in Kenya [20]. Animals, like humans, when infected, exhibit similar symptoms. According to Del Coco and colleagues, clinical illness and diarrhea caused by Cryptosporidium have been reported for different species of young animals including calves as young as 4 days. In Kwa-Zulu Natal, east coast of South Africa [16], Cryptosporidium was found to be endemic with a laboratory-confirmed prevalence ranging from 2.9 to 3.7 % and 2.9 to 3.0 % of cases submitted for analysis, respectively [21]. The Vhembe district of the Limpopo province in South Africa is reported to have cryptosporidiosis as the second most prevalent infection [15, 22]. Moreover, Obi and Bessong (2002) showed that the infection rate of Cryptosporidium was varying between 1.2 to 20.9 % according to season, with the highest prevalence in the summer months in the Venda region [15].

Prevalence of Cryptosporidium in Animals

Cryptosporidium infection is well known as a major cause of morbidity and mortality particularly in young animals [23]. Reported studies in the USA have estimated the incidence of cryptosporidiosis in cattle to be approximately 45.5 %, 24.5 % incidence in the UK, 26 % in Russia, 40 % in Germany, and 27 % in Hungary [24] whereas in India, the first encounter of cryptosporidiosis was among buffaloes and zebu cattle [25]. A study conducted in cattle farms in the Iringa and Tanga regions of Tanzania reported a prevalence rate of 20 and 21 %, respectively, in these regions. From their data, they further reported that the probability of cattle having Cryptosporidium-positive stools declined with increase in age, and this finding led them to conclude that Cryptosporidium is most prevalent in young animals [26]. To substantiate this finding, Ayinmode and Fagbeni (2010), in a study conducted in the south west Nigeria, reported a 27.4 % prevalence of Cryptosporidium in cattle younger than 6 months of age, 28.1 % prevalence for cattle between 7 and 12 months of age, and 19.9 % for cattle older than 12 months [27]. Interestingly, Ayinmode and Fagbeni (2010) further reported an infection rate of 38.1 % in female cattle compared to a 17.7 % in male cattle. Study surveys show that up to 38.5 % of cats and 44.8 % of dogs are infected with Cryptosporidium spp. [27]. A study done in China in the Shanghai and Shaoxing regions on the molecular epidemiology of Cryptosporidium in pigs reported a 14.3 and 25.0 %, respectively [28]. The prevalence of Cryptosporidium in sheep is also well documented; in Turkey in the Aydin province, a 46.5 % infection rate was reported among lambs [29]. The information communicated by Ulutas and Voyvoda (2004) [29] in their report resonate with other similar reports which concluded that cryptosporidial infections decrease with an increase in age [27].

Prevalence and Effects of Cryptosporidium in Children

Like in animals, cryptosporidiosis seems to be most prevalent in children mainly because of their immune system that is not fully developed [30]. A Yemeni study reported an overall prevalence rate of 43.7 % among children of ages between 1 and 12 months with a higher infection rate recorded in males (36.2 %) as compared to the lowest infection rate of 32.7 % which was observed in females [31]. In a reported study done among HIV-positive and HIV-negative children admitted to Uganda’s Mulago National Referral Hospital for persistent diarrhea which lasted for over 2 weeks, Cryptosporidium infection was detected in only 6 % of HIV-negative children and 74 % of children who were HIV-positive [32]. In contrast to HIV, the immunological deficiencies that increase the risk of infection in malnourished children are unknown, but there exists a clear association between cryptosporidiosis and malnutrition [30]. In South Africa, studies conducted in Pretoria among children below 36 months and Johannesburg among children below 24 months reported a 25 and 20 % infection rate, respectively (Geyer et al., 1993) [33]. Another study done in the Vhembe region of the Limpopo province in South Africa reported a prevalence rate of 28.6 % among children between 2 and 5 years [14]. In Uganda, approximately 75 % of diarrheal cases are due to C. hominis and only 20 % is due to C. parvum [34]. C. hominis seems to be very dominant in the sub-Saharan Africa and America and Australia, whereas elsewhere, in European countries, C. parvum seems to be very predominant [35].

Prevalence of Cryptosporidium in HIV-Positive Patients

Cryptosporidium is reportedly the most frequent microorganism that causes chronic diarrhea in HIV-positive patients and is coupled by manifestations such as nonbloody stools, abdominal pains, and loss of weight [36]. In a study conducted in southwest Nigeria, Cryptosporidium was found to have the highest prevalence (52.7 %) among HIV-positive patients compared to 11.3 % for Ascaris, 10 % for Entamoeba histolytica, 3.3 % for hookworm, and 2 % for Trichuris [37]. In Kenya, a 3.2 % prevalence of Cryptosporidium was reported with C. hominis being the most dominant genotype followed by C. parvum and, then, Cryptosporidium meleagridis [38]. In India, a 32.6 % infection rate of C. parvum was reported among HIV patients [27] whereas in Iran, a 26.7 % prevalence rate was reported among HIV-positive patients [39, 40].

Control and Prevention

Reservoir characteristics and environmental factors influence the epidemiology and transmissibility of Cryptosporidium spp. Although infectious following shedding by the host, oocysts are sensitive to inactivation by numerous unfavorable environmental conditions before an appropriate new host is found [41, 42]. Moreover, higher temperatures, age, and desiccation are other parameters that are critical in the survival and infectivity of the parasites’ oocysts [43]. Exposure to sunlight for long hours renders oocysts entirely noninfective and nonviable [44, 45]. UV light has been reported to be germicidal for Cryptosporidium spp. oocysts, and recent advances in UV research have allowed for the application of UV disinfection technology in large-scale potable water treatment plants [46–48]. Solar photocatalytic disinfection (SPCDIS) using titanium-oxide-coated plastic inserts improves oocyst inactivation in water under overcast conditions [44].

Control measures need to be directed at reducing and/or preventing transmission of the infective oocysts to both humans and animals [49]. The tough nature of the oocyst makes traditional water treatment processes such as coagulation/flocculation, sedimentation, filtration, and disinfection insufficient to remove the parasite. Furthermore, chlorination has been found to be inadequate and not sufficient in the removal of the parasite species [50]. Recently, efforts are being directed toward developing vaccines for animals [51]. Moreover, Finch and Belosevic (2011) found that using modern microbial reduction process design techniques such as the integrated disinfection design framework (IDDF) ensured the provision of drinking water with a low risk of transmitting human pathogens to the public [52]. Separation of animal reservoir hosts from water supply provides an option for reducing and minimizing the oocyst burden and therefore reducing transmission. The construction of wetlands to treat wastewater and runoff from confined animal feeding operations has been found to be not only an efficient and effective process in the removal of pathogens like Cryptosporidium spp. but also very cost-effective [53]. People at risk should be made aware of activities such as swimming in community pools, consumption of freshwater plants, and unguarded contact with infected people and/or animals that may increase their likelihood of becoming infected with Cryptosporidium spp. and how to avoid those activities. Hand washing, education and point of use water treatment (mainly in developing countries), boiling of water before drinking, consumption of safe bottled water, and the use of filtration units can minimize and significantly reduce the risk of transmission of the infective oocysts and significantly improve diarrhea rates [54].

Anti-cryptosporidial pharmaceutical agents could reduce disease transmission. Cryptosporidium enteritis history of treatment has always been inadequate and unreliable. Against this background, relapses are often seen following treatment with agents such as paromomycin, nitazoxanide, and azithromycin. Thus, there is a great need to develop new anti-cryptosporidial agents (see accompanying article by Sparks et al.). Currently, nitazoxanide is the only FDA-approved drug for the treatment of the disease cryptosporidiosis. While reportedly used during outbreaks [55], the role of nitazoxanide or other chemotherapeutic agents to reduce transmission in resource-limited settings akin to anti-helminthic therapies is presently cost-prohibitive and has not been thoroughly studied. Furthermore, although nitazoxanide has shown improvements in both the clinical and microbiological cure rates, the drug is ineffective in HIV-positive and AIDS patients [37, 56] and studies in malnourished children are mixed. Abubakar et al. (2007) concluded from many different studies that current chemotherapy did not have a role for the management of cryptosporidiosis in immunocompromised individuals [22]. It is clear that restoring the immune status using anti-retroviral drugs is the most important therapy option in immunocompromised and HIV/AIDS individuals infected with Cryptosporidium spp. [57] and may therefore indirectly reduce transmission. In a murine model of Cryptosporidium infection, nitazoxanide did not decrease stool shedding during malnutrition [58], whereas supplementation with the di-peptide alanyl-glutamine did [59], suggesting similarly that supporting host defenses during malnutrition may be another strategy of reducing parasite shedding.

In addition to conventional pharmaceuticals, various trials are designed by numerous research groups worldwide investigating the potency of traditional medicinal plants and their extracts for treating cryptosporidiosis [60]. In a recent study, investigating the anti-parasitic effectiveness of Allium sativum (garlic) in the treatment of Cryptosporidium infections in experimentally infected immunocompetent and immunosuppressed mice, Gaffar (2012) concluded that garlic has good efficacy as a prophylactic and a promising therapeutic agent against Cryptosporidium [60]. Furthermore, Al-Hamairy et al. (2012) examined that the effect of six plant extracts on the shedding of oocysts in experimental mice was well illustrated where there was a marked decrease of the shedding of Cryptosporidium oocysts in mice by using 250 mg/kg body weight. It was shown that Peganum harmala (68.6 %) showed highest anti-parasitic activity followed by Artemesia herba-alba (60.0 %), Ricinus communis (36.8 %), while Allium sativum and Thymus vulgaris show the lowest activity 18.6 and 20.5 %, respectively. Moreover, Al-Hamairy and his group showed that the efficacy of plant extracts at a dose of 500 mg/kg body weight was higher than 250 mg/kg body weight in shedding of the parasite oocysts [61]. Studies have also shown that garlic plant and indinavir are effective in treatment of cryptosporidiosis [62]. Toulah et al. (2012) treated 145 immunosuppressed infected Wister rats with garlic plant and indinavir. The rats aging 3 weeks were divided into five groups: (1) normal control, (2) indinavir-treated control, (3) immunosuppressed infected, (4) garlic-treated immunosuppressed infected, and (5) indinavir-treated immunosuppressed infected rats. All were subjected to clinical, parasitological, and histopathological examination at different days postinfection. The results showed that in immunosuppressed infected rats, all rats had diarrhea, loss of appetite, weakness, and limited movement, with 51.4 % death rate. In both treated groups, some rats regained activities, with death rate of 33.3 %. There was a significant decrease in the number of excreted oocysts at day 5 and 10 posttreatment in treated groups. One week posttreatment, the number of excreted oocysts had continued in decreasing among garlic-treated immunosuppressed infected rats while among Indinavir-treated immunosuppressed infected rats, it insignificantly increased. Since oocysts excreted till the end of the experiment, no cure rate was detected among both treated groups. The histopathological changes improved in treated groups in spite of the presence of some parasites on the epithelial surfaces of ileum [62]. In a separate recent study, Majeed et al. (2015) evaluated the effect of aqueous alcohol Artemisia herba-alba and T. vulgaris extract on the Cryptosporidium parvum and there compared with spiromycine drug in the infected white mouse (BALB/C). Results obtained showed more clear effects in aqueous alcohol Artemisia herba-alba- and T. vulgaris-extract-treated groups and continued till reaching negligible degree or no oocyst detection at 10th and 14th to 17 days posttreatment, but spiromycine drug continues oocyst excretion until the end of the experiment with a significant difference (p > 0.05). Thus, it was concluded that administration of Artemisia herba-alba or T. vulgaris extract was protective against infections with C. parvum [63].

Currently, there are no vaccines against Cryptosporidium infections (see accompanying article by Ludington and Ward). For now, the lack of active therapy and vaccine prevention highlights the need to ensure that infection is avoided and prevented through public education, appropriate hygiene, and proper water management and treatment.

Determining Cryptosporidium Viability/Deactivation

Crucial in determining the effectiveness of new approaches to deactivating Cryptosporidium in water-treatment strategies is the accurate assessment of Cryptosporidium viability. The most common methods for testing Cryptosporidium viability are through in vitro fluorogenic vital assays and excystation assays. These methods evaluate oocyst viability by examining the integrity of the oocyst wall and metabolic activity of sporozites under conditions most favorable to infection [6, 64, 65]. To directly test viability and infectivity of Cryptosporidium oocysts, in vivo animal testing is the reference standard method. However, many in the field revert to in vitro viability assays because animal infectivity models require specialized laboratory facilities making them costly and time-consuming, which can be challenging in resource-limited settings. Furthermore, in the context of evaluating disinfection methods, viability assays are ideal because they enable researchers to study infectivity potential of an individual oocyst in environmental samples [66, 67].

The most common fluorogenic vital assays use 6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI) dyes to determine the integrity of the oocyst wall. DAPI is a permeable fluorescent stain that binds to nucleic acids, labeling intact sporozoites. PI is an impermeable fluorescent dye that stains the cytoplasm and DNA only when the cell wall is permeable or damaged [64, 65, 68, 69]. Therefore, DAPI staining will be present and PI staining will be absent among viable oocysts because their oocysts walls will be intact. Among nonviable oocysts, PI and DAPI staining will be present since the oocyst wall will have lost its integrity and the PI dye will be able to stain the cytoplasm.

Often, fluorogenic assays are used in conjunction with in vitro excystation assays to evaluate viability [65, 66, 69]. As fluorogenic assays determine the integrity of the oocyst wall, excystation assays evaluate the ability of sporozites to excyst from the oocyst under conditions favorable to infectivity. Excystation assays are designed to recreate infectious environments, such as highly acidic environments found in the mammalian gastrointestinal system, under which oocysts release sporozoites for infection. If the oocyst wall is damaged or the sporozoites are not intact, sporozoites will not excyst and thus are no longer infective. However, if the oocyst wall is intact and the sporozoites are able to excyst under highly acidic conditions, the oocyst is considered viable and infectious [66, 68].

Previous studies have compared in vitro excystation assays to in vivo animal infectivity testing and demonstrated strong correlations between excystation and infectivity [64, 66, 68]. As a result, in vitro assays are used to evaluate oocyst viability and efficacy of novel disinfection methods. Since in vitro assays directly evaluate individual infectivity potential of oocysts, the disinfection mechanisms at the cellular level can be investigated, while also being cost-effective and feasible assay to perform in resource-limited settings [66]. In this manner, molecular approaches, such as detection of inducible hsp70 mRNA from viable oocysts, could be further validated in field studies [70].

Developing Collaborations to Design Practical, Cost-Effective, Innovative Strategies

A key factor in addressing the challenges and furthering innovative strategies for interruption of Cryptosporidium transmission in resource-limited settings is through global partnerships among researchers across disciplines. Through the Water and Health in Limpopo Program (WHIL), researchers at the University of Virginia in Charlottesville, Virginia, USA, and the University of Venda in Limpopo Province, South Africa, have been working together to design practical, cost-effective innovative strategies to reduce incidences of waterborne illnesses. The WHIL program is an interdisciplinary program that has allowed a rich exchange of knowledge and expertise, resulting in development of innovative solutions to address some of the most challenging developing world challenges, including detection and disinfection of C. parvum oocysts in drinking water sources. From this collaborative program, researchers have discovered disinfecting capabilities of silver against C. parvum oocysts [69, 71]. They have also developed novel laboratory methods to quantify oocyst viability, which until now has only been measured through qualitative microscopic analysis of fluorogenic and excystation assays [69]. Finally, they have developed and field-tested a low-cost, novel porous ceramic tablet embedded with silver nanopatches for water purification at the household level in resource-limited settings [72, 73]

A study that emerged from the WHIL collaboration was that by Shawel et al. (2013), where the efficacy of ceramic water filters in reducing gastrointestinal infections among an HIV-positive cohort in Limpopo Province, South Africa, was evaluated [71]. Results demonstrated that ceramic water filters were effective in reducing rates of diarrheal diseases and C. parvum oocyst shedding in stool samples among participants in the intervention group [71]. These encouraging findings led to further investigation of the mechanisms by which ceramic water filters may be interrupting transmission of Cryptosporidium. Ceramic water filters purify drinking water by two mechanisms: (1) removal of pathogens through physical filtration and (2) chemical disinfection by silver nanoparticles embedded within the ceramic media. The results from Shawel et al. (2013) prompted further collaboration within the WHIL program, leading researchers to investigate the disinfection efficacy of silver on C. parvum oocysts. Studies conducted by Su et al. (2014) used in vitro excystation and fluorogenic assays to examine disinfection capabilities of silver nanoparticles on C. parvum oocysts [69]. They validated their findings through in vivo animal infectivity assays, where they found almost two orders of magnitude reduction in oocyst shedding among mice that had been fed silver-nanoparticle-treated oocysts relative to the untreated oocysts. These results correlated with excystation results, where a decrease in oocyst viability was observed in response to silver nanoparticle treatment. Prior to this, no published studies have attempted to quantify the antimicrobial effects of silver nanoparticles or ionic silver for C. parvum. Su et al. (2014) went on to also develop the first quantitative in vitro oocyst viability assay that applies dielectrophoretic sensing methodology (DEP) to detect subtle changes in the oocyst due to changes in cellular functions or oocyst wall integrity [69, 74].

These encouraging results led WHIL researchers to investigate practical and low-cost methods to embed silver in porous ceramic media in order to develop water purification technologies at the household level and thus preventing the transmission of Cryptosporidium through contaminated drinking water. Ehdaie et al. (2014) discovered a low-cost method to form metallic nanopatches in porous ceramic media in the form of a tablet for applications in water purification. The low-cost silver-embedded ceramic tablet purifies water at the household by slowly releasing silver ions into the water, providing residual disinfection. Laboratory tests have demonstrated a 3-log reduction in E. coli after 8 h for 10 L of water. Results also suggest the silver-embedded ceramic tablet is reusable for at least 6 months [73]. As a result, this novel purification method would only cost $0.002 per liter of treated water, making it the most inexpensive water purification technology currently available [73, 75, 76].

Currently, researchers in the WHIL program are completing laboratory testing to investigate disinfection efficacy of silver through in vitro viability assays, excystation, and DAPI/PI staining. Early results have been encouraging showing loss of viability among oocysts treated with the silver-embedded ceramic tablet. These results lend support to observations made by Su et al. (2014) of silver as potential chemical disinfectant agent against C. parvum oocysts and the novel silver-embedded ceramic tablet as an effective method to treat water in order to reduce transmission of Cryptosporidium [69].

Of course, additional research, such as a human health studies or animal infectivity models, needs to be conducted to directly measure efficacy against Cryptosporidiosis which researchers in the WHIL project are planning to do. However, preliminary studies have provided encouraging results. Due to the exchange of research and expertise across disciplines through the WHIL program, researchers have been able to discover novel disinfectant agents, develop innovative strategies to quantify oocyst viability, and interrupt transmission of Cryptosporidium through development of novel water purification technologies.

Conclusion

Cryptosporidium ssp., due to environmental hardiness, a unique life cycle and immune evasion within the host, resistance to available antimicrobial therapies in the most susceptible hosts, and diverse human and animal reservoirs, represent a major challenge in disease prevention—particularly in endemic settings where resources are often limited. To continue striving forward in overcoming the global challenges of Cryptosporidium transmissions, global partnership will be imperative. Overcoming global challenges requires global partnerships, similar to that of the WHIL program in order to develop innovative and effective solutions for resource-limited settings.