This review analysed outbreaks of human cryptosporidiosis due to raw milk. The objective of our study was to highlight and identify underestimated and underreported aspects of transmission of the parasite as well as the added value of genotyping Cryptosporidium isolates.
We conducted a descriptive literature review using the digital archives Pubmed and Embase. All original papers and case reports referring to outbreaks of Cryptosporidium due to unpasteurized milk were reviewed. The cross-references from these publications were also included.
Outbreaks have been described in the USA, Australia, and the UK. Laboratory evidence of Cryptosporidium from milk specimens was lacking in the majority of the investigations. However, in most recent reports molecular tests on stool specimens along with epidemiological data supported that the infection was acquired through the consumption of unpasteurized milk. As the incubation period for Cryptosporidium is relatively long (days to weeks) compared with many other foodborne pathogens (hours to days), these reports often lack microbiological confirmation because, by the time the outbreak was identified, the possibly contaminated milk was not available anymore.
Cryptosporidiosis is generally considered a waterborne intestinal infection, but several reports on foodborne transmission (including through raw milk) have been reported in the literature. Calves are frequently infected with Cryptosporidium spp., which does not multiply in milk. However, Cryptosporidium oocysts can survive if pasteurization fails. Thus, pasteurization is essential to inactivate oocysts. Although cryptosporidiosis cases acquired from raw milk are seldom reported, the risk should not be underestimated and Cryptosporidium should be considered as a potential agent of contamination. Genotyping Cryptosporidium isolates might be a supportive tool to strengthen epidemiologic evidence as well as to estimate the burden of the disease.
A review of outbreaks of cryptosporidiosis due to unpasteurized milk, 15 April 2020
Cryptosporidiosis is one of the leading causes of diarrhoeal illness and mortality induced by protozoan pathogens worldwide. As a largely waterborne disease, emphasis has been given to the study of Cryptosporidium spp. in surface waters, readily susceptible to pathogenic contamination. Conversely, the status of Cryptosporidium in potable groundwater sources, generally regarded as a pristine and “safe” drinking-water supply owing to (sub)-soil protection, remains largely unknown. As such, this investigation presents the first literature review aimed to ascertain the global prevalence of Cryptosporidium in groundwater supply sources intended for human consumption.
Thirty-seven peer-reviewed studies were identified and included in the review. Groundwater sample and supply detection rates (estimated 10–20%) indicate Cryptosporidium is frequently present in domestic groundwater sources, representing a latent health concern for groundwater consumers. Specifically, sample (10.4%) and source (19.1%) detection rates deriving from comprehensive “temporal” investigations are put forward as representative of a contamination ‘baseline’ for Cryptosporidium in ‘domestic’ groundwater supplies. Proposed ‘baseline’ prevalence figures are largely applicable in preventive risk-based catchment and groundwater quality management including the formulation of Quantitative Microbial Risk Assessment (QMRA). Notwithstanding, a large geographical disparity in available investigations and lack of standardized reporting restrict the transferability of research findings.
Overall, the mechanisms responsible for Cryptosporidium transport and ingress into groundwater supplies remain ambiguous, representing a critical knowledge gap, and denoting a distinctive lack of integration between groundwater and public-health sub-disciplines among investigations. Key recommendations and guidelines are provided for prospective studies directed at more integrative and multi-disciplinary research.
Cryptosporidium spp. in groundwater supplies intended for human consumption—a descriptive review of global prevalence, risk factors and knowledge gaps, 18 March 2020
Chique; P. Hynds; L. Andrade; L. Burke; D. Morris; M.P. Ryan; J. O’Dwyer
Outbreak News Today reports that since the last report on the Cryptosporidium outbreak in Sweden about two weeks ago, health officials say the number of reported cases has decreased in recent weeks.
While cases are declining, the number of cases reported per week remains slightly higher compared to the same period in previous years. To date, some 400 Cryptosporidium cases have been recorded.
Most cases have been reported from Stockholm, Östergötland, Västra Götaland, Halland, Jönköping and Uppsala.
The Public Health Authority analyzes samples from the cases to determine what type of cryptosporidium they have become ill from. Of the 202 samples analyzed so far, 93 have been shown to belong to subtype (A) and 58 belong to subtype B of Cryptosporidium parvum. In addition to this subtype, a number of different subtypes have been detected.
The fact that different subtypes are seen indicates that there are different sources of infection for the cases reported during the fall. From the survey studies it was shown that cases with subtype A have drunk to a greater extent pre-purchased freshly squeezed fruit and vegetable drinks that are no longer on the market when the shelf life is short. The majority (almost 80%) of cases with subtype A were reported to have fallen ill.
The U.S. Centers for Disease Control reports that Cryptosporidium is the leading cause of outbreaks of diarrhea linked to water and the third leading cause of diarrhea associated with animal contact in the United States.
During 2009–2017, 444 cryptosporidiosis outbreaks, resulting in 7,465 cases were reported by 40 states and Puerto Rico. The number of reported outbreaks has increased an average of approximately 13% per year. Leading causes include swallowing contaminated water in pools or water playgrounds, contact with infected cattle, and contact with infected persons in child care settings.
What are the implications for public health practice?
To prevent cryptosporidiosis outbreaks, CDC recommends not swimming or attending child care if ill with diarrhea and recommends hand washing after contact with animals.
All those infected had drunk from the same container of self-pressed apple juice. Incubation period (1 week) and clinical signs were similar among those infected, although some experienced a more prolonged duration of symptoms (up to 2–3 weeks) than others.
The infections resulted after consumption from only one of 40 containers of juice and not from any of the other containers. It seems that although Cryptosporidium oocysts were detected in a sample from another container, the contamination did not affect the whole batch. This is perhaps indicative of a restricted contamination event, either from contaminated ground in the orchard, or during collection of the fruit, or during processing.
Although outbreaks of foodborne cryptosporidiosis have previously been associated with consumption of contaminated apple juice, most of the more recent outbreaks of foodborne cryptosporidiosis have been associated with salad vegetables or herbs. This outbreak, the first outside U.S. reported to be associated with apple juice, is a timely reminder that such juice is a suitable transmission vehicle for Cryptosporidium oocysts, and that appropriate hygienic measures are essential in the production of such juice, including artisanal (non-commercial) production.
Robertson, L. J., Temesgen, T. T., Tysnes, K. R., & Eikås, J. E. (2019). An apple a day: An outbreak of cryptosporidiosis in Norway associated with self-pressed apple juice. Epidemiology and Infection, 147. doi:10.1017/s0950268819000232
In 1999, I gave a talk to hundreds of farm leaders in Ottawa and told them that DNA fingerprinting – via PulseNet – would revolutionize foodborne illness outbreak investigations and that farmers better be prepared (the pic is from a 2003 awards ceremony where I was acknowledged for my outreach and extension efforts, the hair was fabulous).
Twenty years later and whole genome sequencing is even further piecing together disparate outbreaks.
Joanie Stiers of Farm Flavor writes that Michigan’s laboratory toolbox now includes whole-genome sequencing, allowing public health officials to stop the spread of foodborne illness faster than ever.
“With food now being distributed worldwide, illness can be spread from anywhere in the world,” says Ted Gatesy, laboratory manager of the microbiology section at Geagley Lab, which houses the whole-genome sequencing. “Using whole-genome sequencing, an illness can be tracked, for the most part, to the point in the food chain where it originated.
Cryptosporidiosis, a leading cause of diarrhea among infants, is caused by apicomplexan parasites classified in the genus Cryptosporidium. The lack of effective drugs is motivating research to develop alternative treatments. With this aim, the impact of probiotics on the course of cryptosporidiosis was investigated.
The native intestinal microbiota of specific pathogen-free immunosuppressed mice was initially depleted with orally administered antibiotics. A commercially available probiotic product intended for human consumption was subsequently added to the drinking water. Mice were infected with Cryptosporidium parvumoocysts.
On average, mice treated with the probiotic product developed more severe infections. The probiotics significantly altered the fecal microbiota, but no direct association between ingestion of probiotic bacteria and their abundance in fecal microbiota was observed. These results suggest that probiotics indirectly altered the intestinal microenvironment or the intestinal epithelium in a way that favored proliferation of C. parvum.
Probiotic product enhances susceptibility of mice to cryptosporidiosis
Applied and Environmental Microbiology, 10.1128/AEM.01408-18
According to The Canberra Times, the current drought affecting parts of Australia could lead to a spike in gastro cases around the country, a population health scientist from The Australian National University has warned.
The warning comes from the results of a study, published in the Journal of Water and Health, found reported cases of cryptosporidiosis, rose significantly in parts of Queensland and the Australian Capital Territory along the Murray Darling Basin during the drought that ended in 2009.
Lead researcher Dr Aparna Lal, from the ANU Research School of Population Health, said the study estimated the risk of the gastro bug dropped by 84 per cent in the ACT and by 57 per cent in Queensland once the drought ended.
She said 385 cases of the gastro bug were reported in the ACT and 527 in Queensland, out of 2048 cases in the Murray Darling Drainage Basin, from 2001 until 2012.
“Cryptosporidiosis is one of the most common water-related parasitic diseases in the world, and Australia reports the second highest rate of the illness in humans among many developed countries,” Dr Lal said.
Children under five years old are particularly at risk from cryptosporidiosis, and it can cause developmental problems such as stunted growth.
Dr Lal said droughts reduced river volume and flow, thereby potentially increasing the concentration of pathogens such as those that cause gastro.
“As these gastro bugs can also be spread from livestock, land-use change may also contribute to this pattern, due in part to access around waterways,” she said.
Crypto, which commonly refers to both the parasite and the diarrheal disease that it causes, cryptosporidiosis, infects humans and animals. It is a serious problem in developing countries, where it is a leading cause of life-threatening diarrhea in children under two. Now cases reported in the U.S. are increasing.
Swallowing one mouthful of crypto-contaminated water can cause illness. While most people recover after a few weeks of significant gastrointestinal upset, young children, the elderly, and the immunosuppressed can face chronic infection, wasting, cognitive impairment, and even death.
No vaccine exists, and the sole FDA-approved drug for crypto is, paradoxically, ineffective in people with weakened immune systems.
A major roadblock to developing drugs is the fact that crypto oocysts—the infectious form of the parasite that thrives in the small intestine—are impossible to cultivate under laboratory conditions, explained Saul Tzipori, distinguished professor of microbiology and infectious diseases at Cummings School, who has made the study of crypto and other intestinal diseases his life’s work.
To produce oocysts for scientific investigation, crypto must therefore be grown in host animals. The process is expensive, time-consuming, and cumbersome.
“To evaluate and optimize prototype vaccines and test them in humans we need to use the same source, age, viability, quality, and quantity of oocysts. This is impossible with available methods, which necessarily involve variation,” said Tzipori, who is also the Agnes Varis Chair in Science and Society and chair of the Department of Infectious Disease and Global Health.
Now Tzipori and his team, in collaboration with researchers at Massachusetts General Hospital, have developed a way to rapidly freeze crypto oocysts, preserve their infectiousness indefinitely, and thaw them as needed for study. The researchers recently published their discovery, which was supported by the Bill & Melinda Gates Foundation, in Nature Communications.
For the past forty years, scientists have tried to keep crypto oocysts for later use by freezing them—a process called cryopreservation—using slow cooling, “but those methods didn’t yield infectious oocysts,” explained the paper’s co-first author, Justyna Jaskiewicz, a veterinarian who is pursuing a Ph.D. in biomedical sciences as a member of Tzipori’s lab. The group discovered that the oocysts’ impermeable walls kept out cryoprotective agents—chemicals that are typically used to prevent formation of harmful ice crystals by replacing intracellular water. As a result, sharp ice crystals formed, which punctured and damaged the oocysts’ infectious interior.
To help tackle this problem, Tzipori’s team tapped the expertise of Massachusetts General’s Center for Engineering in Medicine, whose co-founder, Mehmet Toner, is widely known for advances in low-temperature biology and tissue stabilization.
The solution turned out to be bleaching the oocysts to make their walls permeable before soaking them in protective chemical agents.
Oocysts in solution were then loaded into cylindrical glass microcapillaries about three inches long and 200 microns in diameter—the diameter of about four human hairs—and plunged into liquid nitrogen at -196 degrees Celsius (about -320 Fahrenheit). Almost immediately, the oocyst solution morphed into a glasslike solid free of ice crystals.
“Unlike standard cryopreservation, where cells are slowly cooled, our technique vitrified the oocysts almost instantaneously. Vitrification is an ice-free method that cools cells so rapidly that crystals don’t form,” said Rebecca Sandlin, an investigator at the Center for Engineering in Medicine and co-first author on the paper.
Oocysts thawed three months later were 50 to 80 percent viable and still infectious in mice. The researchers believe such cryopreservation will last indefinitely. They hope to increase the volume of oocysts frozen and test the methodology with other strains of the parasite.
The discovery is just the latest from Tzipori’s far-ranging research on a host of globally important infectious diseases, from E. coli to dengue fever.
Tzipori believes ultrafast cooling will benefit scientists worldwide in addition to advancing his own work on crypto drug discovery and vaccine development.
“For the first time, we can produce the crypto parasite—including unique or genetically modified strains—in large quantities, without need for constant passage through animals, uniformly cryopreserved, and ship it to other investigators in liquid nitrogen that can be stored indefinitely and used at any time,” he said. “This capability has existed for other pathogens, but never for crypto.”
Cryptosporidium is a protozoan parasite that causes the diarrheal disease, cryptosporidiosis. Although many species have been identified, the majority of human disease worldwide is caused by two species; Cryptosporidium parvum and Cryptosporidium hominis.
In Australia, data from the National Notifiable Diseases Surveillance System (NNDSS) show that cryptosporidiosis outbreaks occur every few years. To better understand the transmission, trends and nature of cryptosporidiosis outbreaks in Western Australia, epidemiological and genomic data from three cryptosporidiosis outbreaks in 2003, 2007 and 2011 were reviewed.
The 2007 outbreak was the largest (n = 607) compared with the outbreaks in 2003 (n = 404) and 2011 (n = 355). All three outbreaks appeared to have occurred predominantly in the urban metropolitan area (Perth), which reported the highest number of case notifications; increases in case notifications were also observed in rural and remote areas. Children aged 0–4 years and non-Aboriginal people comprised the majority of notifications in all outbreaks. However, in the 2003 and 2007 outbreaks, a higher proportion of cases from Aboriginal people was observed in the remote areas. Molecular data were only available for the 2007 (n = 126) and 2011 (n = 42) outbreaks, with C. hominis the main species identified in both outbreaks. Subtyping at the glycoprotein 60 (gp60) locus identified subtype IbA10G2 in 46.3% and 89.5% of C. hominis isolates typed, respectively, in the 2007 and 2011 outbreaks, with the IdA15G1 subtype was identified in 33.3% of C. hominis isolates typed in the 2007 outbreak. The clustering of cases with the IdA15G1 subtype in the remote areas suggests the occurrence of a concurrent outbreak in remote areas during the 2007 outbreak, which primarily affected Aboriginal people.
Both the C. hominis IbA10G2 and IdA15G1 subtypes have been implicated in cryptosporidiosis outbreaks worldwide; its occurrence indicates that the mode of transmission in both the 2007 and 2011 outbreaks was anthroponotic. To better understand the epidemiology, sources and transmission of cryptosporidiosis in Australia, genotyping data should routinely be incorporated into national surveillance programmes.
Comparison of three cryptosporidiosis outbreaks in Western Australia: 2003, 2007 and 2011