Effects of high hydrostatic pressure on Toxoplasma gondii tissue cysts in ground pork

Recipient Organization
VIRGINIA POLYTECHNIC INSTITUTE
(N/A)
BLACKSBURG,VA 24061

Performing Department
COLLEGE OF VETERINARY MEDICINE

Non Technical Summary
Toxoplasma gondii is a protozoan parasite that infects humans and most other warm-blooded animals. Humans become infected by ingesting meat containing tissue cysts. There are about 1,500,000 cases of toxoplasmosis in the US each year. Toxoplasmosis is the third leading cause of death due to food borne pathogens in the US. High pressure processing (HPP) is an emerging technology that has been shown to be an effective non-thermal means of preserving and increasing the safety of a variety of food products. The shelf-life of the products is extended and the sensory features of the food are not or only minimally effected by HPP. Our study will examine if this commercially aviable food technology is effective in killing T. gondii tissue cysts in meat and protecting the American consumer. Our study will evaluate the efficacy of the emerging technology of high pressure processing on inactivation of Toxoplasma gondii tissue cysts in pork. This non-thermal means of treating meat maybe useful in protecting meat meant for human consumption.

Animal Health Component

75%

Research Effort Categories

Basic

(N/A)

Applied

75%

Developmental

25%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
313	3530	1110	20%
313	4050	1110	20%
501	3530	1110	20%
722	3530	1110	40%

Knowledge Area
313 - Internal Parasites in Animals; 501 - New and Improved Food Processing Technologies; 722 - Zoonotic Diseases and Parasites Affecting Humans;

Subject Of Investigation
4050 - Protozoa; 3530 - Other swine products;

Field Of Science
1110 - Parasitology;

Goals / Objectives
Objective 1. To determine the minimal time and pressure needed to inactivate T. gondii tissue cysts using high pressure processing (HPP). Objective 2. to determine the structural mechanism of HPP inactivation of T. gondii tissue cysts.

Project Methods
Our project addresses this stated objective of the Animal Health and Disease program: to protect human health through control of animal diseases transmissible to humans. We believe that the emerging technology of high hydrostatic pressure (HPP) processing of food can be a safe and practical means of controlling Toxoplasma gondii in meat meant for human consumption. Toxoplasma gondii is a protozoan parasite that infects humans and most other warm-blooded animals. HPP is an emerging technology that has been shown to be an effective non-thermal means of preserving and increasing the safety of a variety of food products. The shelf-life of the products is extended and the sensory features of the food are not or only minimally effected by HPP. HPP is able to inactivate or destroy viruses, bacteria, molds, and yeasts. All studies will be done in a Quintus food press QFP 35L-600 (Flow International Corporation, Kent, Washington) located in a dedicated room in the Food Science and Technology building at Virginia Tech. Groups of 2 each, female, CD-1 mice will be used to determine the effects of high hydrostatic pressure treatment on the infectivity of T. gondii tissue cysts. All mice will be orally fed control or HHP treated tissue cysts using animal feeding needles. Impression smears will be made from the livers or lungs of mice that die and will be examined unstained by light microscopy for tachyzoites. Five to 8 wks post-inoculation (PI) all surviving mice will be bled from the retro-orbital plexus, serum collected, and assayed for antibodies to T. gondii in a modified direct agglutination assay. The brains from all mice will be examined for T. gondii tissue cysts by squash preparations. Experimentally determined killing times and pressures will be used to determine the minimal exposure time and HPP pressure needed to completely inactivate T. gondii tissue cysts in meat.

Progress 10/01/04 to 09/30/05

Outputs
Our studies demonstrate that high pressure processing eliminates infectivity of the oocyst and tissue cyst stages of T. gondii. HPP treatment of produce can be used to inactivate T. gondii oocysts. HPP can also be used to inactivate T. gondii in pork. Pressures needed for complete inactivation are readily obtainable in commercial HPP machines. Exposure times are 1 minute or less. Adverse effects on ground pork were not apparent at effective pressures. Additional studies indicate that HPP can inactivate other protozoans in juice (Encephalitozoon cuniculi) or in oysters (Cryptosporidium).

Impacts
We have demonstrated to the food processing and pork production industries that T. gondii can be eliminated from pork and other products (produce, juice) using HPP. Pressures and exposure times are with in acceptable limits for industrial use. This technology has many applications in food processing.

Publications

Lindsay, D. S., M. V. Collins, C. N. Jordan, G. J. Flick, and J.P. Dubey. 2005. Effects of high pressure processing on infectivity of Toxoplasma gondii oocysts for mice J. Parasitol. 91: 699-701.
Lindsay, D. S., M. V. Collins, G. J. Flick, and J.P. Dubey. 2005. Effects of high pressure processing on Toxoplasma gondii tissue cysts in ground pork. J. Parasitol. In press.
Jordan, C. N., A. M. Zajac, D. Holliman, G. J. Flick and D. S. Lindsay. 2005. Effects of high pressure processing on in vitro infectivity of Encephalitozoon cuniculi. J. Parasitol. In press.
Collins, M. V., G. J. Flick, S. A. Smith, R. Fayer, R. Croonenberghs, S. O'Keefe, and D. S. Lindsay. 2005. The effect of high pressure processing on infectivity of Cryptosporidium parvum oocysts recovered from experimentally exposed Eastern oysters (Crassostrea virginica). J. Eukaryot. Microbiol. In press.