Category Archives: Cryptosporidium

Journal of Food Protection

Consumption of fresh fruits and vegetables is increasing thanks to the awareness to the benefits to human health. Vegetables may become contaminated by enteric pathogens (protozoan parasites, bacteria and viruses) by irrigation with contaminated water, fertilization with fresh animal manure or by infected food handlers. Cryptosporidium spp. are fecal-oral protozoan parasites, known to be highly persistent in the environment, which facilitate the transmission of the infectious oocysts. Efficient methods were developed for releasing and concentrating Cryptosporidium oocysts from leafy vegetables and sensitive and specific methods were applied for their enumeration. The aims of this review are to discuss the development and optimization of methods applied to release oocysts from leafy vegetables, the prevalence of Cryptosporidium oocysts on fresh leafy vegetables from various parts of the world and to discuss cryptosporidiosis outbreaks resulting from the consumption of leafy vegetables. Three solutions were used with comparable efficiency to release oocysts from leafy vegetables 1M glycine solution, 0.1% Alconox and filter elution buffer with an efficiency of 36.2%, 72.6% and 44%, respectively. The prevalence of Cryptosporidium oocysts was reported in developed as well as from developing countries, although simple detection methods were applied. Most of the cryptosporidiosis outbreaks were reported in developed countries, which can be related to their efficient surveillance system. Transmission of infectious pathogens, such as Cryptosporidium may be facilitated by fresh vegetables, which are imported and transferred from less developed to highly developed countries and consumed uncooked. Monitoring of Cryptosporidium oocysts by sensitive detection methods may enhance measures to prevent their transmission by freshly consumed vegetables.

Eurosurveillance

The enteric parasite Cryptosporidium, along with norovirus, Giardia, Campylobacter and rotavirus, is among the most frequent causes of waterborne disease [1,2]. In humans, transmission of Cryptosporidium occurs via the faecal-oral route, either through direct exposure to infected people (person-to-person infection) or animals (animal-to-person infection), or through ingestion of water (drinking water, recreational water such as swimming pools, water parks, lakes, rivers) or consumption of raw or undercooked food contaminated with infectious oocysts [3]. Infection may remain asymptomatic or manifest as acute gastroenteritis (> 80% of infected individuals). Symptoms occur 1 to 12 days (mean: 7 days) after exposure and usually last 6 to 9 days. The severity and duration of symptoms are linked to the immune status of the host, and cryptosporidiosis can be life threatening in immunosuppressed individuals [4].

There are many Cryptosporidium species that can infect humans, but the vast majority of cases are due to Cryptosporidium parvum, a zoonotic species that also infects young ruminants, and Cryptosporidium hominis, which is essentially only a human pathogen [5]. The environmental route of transmission is of high relevance for Cryptosporidium [6]. This is due to several factors including: (i) the high survival rate of oocysts in water (more than 24 months at 20°C), (ii) high resistance to disinfection (30 mg/L of free chlorine are needed to achieve 99% inactivation at pH 7, with a recommended value of 0.2 mg/L for drinking water) [6], (iii) low infectious dose (10–132 oocysts in healthy adults [7]) and (iv) low host specificity [5]. Oocysts lose their infectivity when frozen, boiled or heated over 60°C [6].

The ability of Cryptosporidium to survive at high chlorine concentrations [8] and, consequently, at the disinfectant concentrations commonly used in water treatment, has always been a challenge for water treatment plant operators. However, other disinfectants, such as chlorine dioxide, ozone, UV rays and filtration have proved to be rather effective in removing Cryptosporidium. Water safety mainly depends on the combination of different treatment stages, and a multi-barrier approach is a key paradigm for ensuring safe drinking water [6]. Nonetheless, in small water supplies managed by local communities that serve only few thousand people, multi-barrier treatment systems are usually not implemented. Thus, in order to ensure the safety of drinking water, more traditional treatments, e.g. disinfection, are used and water quality is checked against certain regulatory parameters.

During 2017–20, 60 waterborne outbreaks of cryptosporidiosis have been detected in Europe, the majority of which involving treated recreational water (swimming pools) as the vehicle of infection [9]. The number of outbreaks linked to contaminated drinking water has shown a notable decrease in the past decades, although, when occurring, large numbers of individuals may be involved, as exemplified by the outbreaks reported in 2010–11 in Sweden [10,11].