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Cryptosporidium parvum studies with dairy products
1Department of Population Health and Reproduction, and World Health Organization Collaborating Center for Food Virology, School of Veterinary Medicine, University of California-Davis, 95616-8743, USA.
International Journal of Food Microbiology
|March 23, 2000
Summary
Cryptosporidium parvum oocysts can transfer from surfaces to food, with survival varying by food type and storage. Desiccation significantly reduces oocyst viability on surfaces, while freezing eliminates it in ice cream.
Area of Science:
- Food safety
- Parasitology
- Microbiology
Background:
- Cryptosporidium parvum (C. parvum) is a significant cause of waterborne disease outbreaks.
- Understanding oocyst transfer and survival in food is crucial for preventing contamination.
Purpose of the Study:
- To model the transfer of C. parvum oocysts from contaminated water via food contact surfaces into yogurt and ice cream.
- To assess the viability and survival of C. parvum oocysts during food processing and storage.
Main Methods:
- Oocyst viability was determined using propidium iodide staining and direct immunofluorescence assay.
- Oocysts were recovered from milk products and stainless steel surfaces using sucrose flotation and rinsing methods.
- Oocyst survival was evaluated in yogurt during fermentation and storage, and in ice cream during freezing and hardening.
Main Results:
- Oocyst recovery rates varied: 82.3% from low-fat milk, 60.7% from ice cream, and 62.5% from yogurt.
- Recovery from wet stainless steel was 93.1%, decreasing to 69.0% after air-drying.
- Oocyst viability decreased significantly with desiccation on surfaces; only 5% remained viable after 4 hours of air-drying.
- Oocyst viability dropped to approximately 58% after 8 days of yogurt storage at 4°C.
- No viable oocysts were detected in ice cream after 24 hours at -20°C, compared to 8% viability in water controls.
Conclusions:
- Food contact surfaces can act as a route for C. parvum oocyst contamination into dairy products.
- Desiccation on surfaces and freezing temperatures in ice cream are effective in reducing oocyst viability.
- Further research is needed to fully understand the risk of C. parvum transmission through contaminated dairy products.