RESEARCH ON FOOD PARASITOLOGY

Ming-Qi Deng, and Dean O. Cliver

Background Information

Our research on food parasitology is focused on protozoan Cryptosporidium parvum and Giardia lamblia.

C. parvum, a coccidean species, is the leading waterborne pathogen with worldwide distribution. It causes self-limited watery diarrhea in immunocompetent persons and persistent, life-threatening diseases in immunocompromised invividuals, since there is no effective treatment. Cryptosporidiosis is considered to be a factor contributing to death in AIDS patients. The tranmissive stage (oocyst) of this organism is exceptionally resistant to most commercial disinfectants and can transmit among many animal species and between animals and humans, thus capable of causing large waterbrone outbreaks via contaminated drinking water supply. The 1993 Milwaukee outbreak, in which more than 403,000 persons were infected and about 100 persons eventually died, was the largest waterborne outbreak ever recorded in the history of U.S.A.. Contaminated food stuffs, such as raw milk, unpasteurized apple juice, and salads, have been associated with cryptosporidial infection. Person-to-person transmission has been documented. Other transmission routes have also been suggested. You can read more about this organism here.

G. lamblia (syn. G. duodenalis, G. intstinalis), a flagellate protozoa, was the number one cause of waterborne diseases in the U.S before the occurrence of the 1993 Milwaukee outbreak. Many epidemiological aspects of giardiasis are similar to those of cryptosporidiosis. Fortunately, the disease is less severe and it is treatable.

In the past years, our research on C. parvum and G. lamblia covered several differentaspects, such as concentration and separation of the organisms from environmental and food samples, detection of the organisms using (in-)direct immunofluorescence assays and polymerase chain reaction techniques, in vitro cultivation and viability determination, immunomagnetic separation, genetic fingerprinting of iolates of various origins, and inactivation studies.



Achievements to date from our work

Developed immunomagnetic separation systems for concentrating C. parvum oocysts and G. lamblia cysts from environmental and food samples;

Developed PCR methods for detecting C. parvum oocysts and G. lamblia cysts from environmental samples and PCR- based DNA fingerprinting methods (RAPD, PCR-RAPD) in differentiating isolates from various sources;

Established a semi-quantitative in vitro C. parvum infectivity assay for detection of infectious oocysts and in oocyst inactivation/survival studies;

Modeled C. parvum oocyst transmission from food contact surfaces into dairy products and oocyst survival, such information will assist in developing hazard analysis and critical control point (HACCP) systems;

Conducted research on inactivation of C. parvum by various modes, as the most recent one being biodegradation of oocysts by selectd bacterial strains.



Publications to date from our work

Deng, M. Q., D. O. Cliver, and T. W. Mariam. 1997. Immunomagnetic capture PCR to detect viable
Cryptosporidium parvum oocysts from environmental samples. Applied and Environmental Microbiology 63(8): 3134-3138.

Deng, M. Q., and D. O. Cliver. 1998. Cryptosporidium parvum development in the BS-C-1 cell line. Journal of
Parasitology 84(1): 8-15.

Deng, M. Q., and D. O. Cliver. 1998. Differentiation of Cryptosporidium parvum isolates by a simplified randomly amplified polymorphic DNA technique. Applied and Environmental Microbiology 64(5): 1954-1957.

Deng, M. Q., and D. O. Cliver. 1999. Cryptosporidium parvum studies with dairy products. International Journal of Food Microbiology 46(2): 113-121.

Deng, M. Q., and D. O. Cliver. 1999. Improved immunofluorescence assay for detection of Giardia and
Cryptosporidium from asymptomatic adult cervine animals. Parasitology Research 85(8): 733-736.

Deng, M. Q., and D. O. Cliver. 1999. Rapid DNA extraction methods and new primers for randomly amplified
polymorphic DNA analysis of Giardia duodenalis. Journal of Microbiological Methods 37(2): 193-200.

Deng, M. Q., and D. O. Cliver. 1999. Comparative detection of Cryptosporidium parvum oocysts from apple cider. In press (International Journal of Food Microbiology).

Deng, M. Q., K. M. Lam, and D. O. Cliver. 1999. Immunomagnetic separation of Cryptosporidium parvum oocysts using MACS MicroBeads and high gradient separation columns. In press (Journal of Microbiological Methods).

Deng, M. Q., R. P. Peterson, and D. O. Cliver. 1999. First findings of Cryptosporidium and Giardia in California sea lion (Zalophus californianus). Manuscript submitted (Journal of Microbiology)

Others are in preparation.

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