Viable Toxoplasma Gondii Research Articles

PREVALENCE OF VIABLE TOXOPLASMA GONDII IN BEEF, CHICKEN, AND PORK FROM RETAIL MEAT STORES IN THE UNITED STATES: RISK ASSESSMENT TO CONSUMERS

The prevalence of viable Toxoplasma gondii was determined in 6,282 samples (2,094 each of beef, chicken, and pork) obtained from 698 retail meat stores from 28 major geographic areas of the United States. Each sample consisted of a minimum of 1 kg of meat purchased from the retail meat case. To detect viable T. gondii, meat samples were fed to T. gondii-free cats and feces of cats were examined for oocyst shedding. Initially, 100 g of meat from 6 individual samples of a given species were pooled (total, 600 g), fed to a cat over a period of 3 days, and feces were examined for oocysts for 14 days; the remaining meat samples were stored at 4 C for 14 days (until results of the initial cat fecal examination were known). When a cat fed pooled samples had shed oocysts, 6 individual meat samples from each pool were bioassayed for T. gondii in cats and mice. Toxoplasma gondii isolates were then genetically characterized using the SAG2 locus and 5 hypervariable microsatellite loci. In all, 7 cats fed pooled pork samples shed oocysts. Toxoplasma gondii oocysts were detected microscopically in the feces of 2 of the cats; 1 isolate was Type II and the second was Type III. Analyzed individually, T. gondii was detected by bioassay in 3 of the 12 associated samples with genetic data indicating T. gondii isolates present in 2. The remaining 5 pooled pork samples had so few oocysts that they were not initially detected by microscopic examination, but rather by mouse bioassay of cat feces. Two were Type I, 1 was Type II, and 2 were Type III. None of the cats fed chicken or beef samples shed oocysts. Overall, the prevalence of viable T. gondii in retail meat was very low. Nevertheless, consumers, especially pregnant women, should be aware that they can acquire T. gondii infection from ingestion of undercooked meat, and in particular, pork. Cooking meat to an internal temperature of 66 C kills T. gondii.

High Prevalence of Viable Toxoplasma gondii Infection in Market Weight Pigs from a Farm in Massachusetts

High Prevalence of Viable Toxoplasma gondii Infection in Market Weight Pigs from a Farm in Massachusetts

Isolation of Viable Toxoplasma gondii from Naturally Infected Aborted Bovine Fetuses

Isolation of Viable Toxoplasma gondii from Naturally Infected Aborted Bovine Fetuses

High prevalence of viable Toxoplasma gondii infection in market weight pigs from a farm in Massachusetts.

The ingestion of uncooked infected meat is considered important in the epidemiology of Toxoplasma gondii infection in humans and little is known of the prevalence of viable T. gondii in meat used for human consumption in the United States. In the present study, viable T. gondii was isolated from 51 out of 55 pigs destined for human consumption. Hearts and tongues (500 g) from fifty-five 6-mo-old pigs from a farm in Massachusetts were bioassayed for T. gondii by feeding them to T. gondii-free cats. Feces of these cats were examined for shedding of T. gondii oocysts. Fifty-one of 55 cats fed pig tissues each shed 25-810 million T. gondii oocysts in their feces. Two of these cats consumed tissues of pigs that were shown to be seronegative with the Sabin-Feldman dye test, the modified agglutination test, and the Western blot. Results indicate that until examination of meat for T. gondii infection is implemented in slaughterhouses, all meat should be cooked according to industry guidelines before human consumption.

Isolation of viable toxoplasma gondii from ready-to-eat cured meat

Most mammalian immune systems and parasites have co-evolved over the millennia, interacting within a common environment and communicating through a common language. This language is comprised of copious dialects in which a variety of host innate and acquired immune pathways actively interact with a multitude of parasite-specific survival strategies. Nonetheless, a simplified language is likely present since the same basic molecular and cellular mechanisms are associated with resistance or susceptibility to parasite infection. Protective immunity against protozoa within the phylum Apicomplexa (e.g. Cryptosporidia, Eimeria, Neospora, Plasmodia and Toxoplasma) is generally CD4+ T cell-dependent and elicited along the IL-12/IFN-γ/iNOS effector axis. This simplified language can be decoded in part by significant advances in understanding naı̈ve T cell activation, differentiation and generation of immunologic memory. Vaccine adjuvants and new immunisation strategies for generation of more potent immunity can also be viewed through this common language lens. The aim of this paper is to summarise recently published fundamental immunology studies, their relevance through examples in specific coccidian-host immune dialects, and how this simplified language can be used for the more rationale design of parasite vaccine control strategies.

Prevalence of Viable Toxoplasma gondii Tissue Cysts and Antibodies to T. gondii by Various Serologic Tests in Black Bears (Ursus americanus) from Pennsylvania

During the hunting season of 1993, hearts from 28 black bears (Ursus americanus) from Pennsylvania were examined for Toxoplasma gondii infection. Serum samples from heart blood were examined for T. gondii antibodies by the use of the modified agglutination test (MAT), the Sabin-Feldman dye test (DT), the latex agglutination test (LAT), and the indirect hemagglutination test (IHA). One-hundred grams of myocardium from each bear were bioassayed in mice. Approximately 500 g of myocardium from 11 bears were fed to 11 cats, and feces from those cats were examined for T. gondii oocysts. Toxoplasma gondii MAT antibodies (> or = 1:40) were found in 22 bears in titers of 1:40 (4 bears), 1:80 (3 bears), 1:160 (7 bears), 1:320 (4 bears), and > or = 1:2,000 (4 bears). Antibodies to T. gondii by DT (> or = 1:10), LAT (> or = 1:32), and IHA (> or = 1:64) tests were found in 21, 9, and 6 bears, respectively. All 6 bears that did not have T. gondii antibodies in MAT were also negative in DT, IHA, and LAT. Viable T. gondii was isolated from 3 bears by bioassays in mice and from an additional 7 bears by bioassays in cats. All 10 bears that had viable T. gondii had MAT and DT antibodies but only 6 and 5 of them had antibodies by LAT and IHA, respectively.

A fluorescence phase contrast study of the interaction between Toxoplasma gondii and lysosomes in living cells.

Lysosomes of peritoneal macrophages, selectively pinpointed by aminoacridine-induced fluorescence, do not fuse with vacuoles containing viable Toxoplasma gondii RH strain.

Toxoplasma gondii: Immunopathology of cutaneous hypersensitivity reactions in guinea pigs injected with living parasites

Intradermal skin tests, consisting of viable Toxoplasma gondii organisms, were injected into normal guinea pigs and guinea pigs chronically infected with Toxoplasma. Subsequent gross and histological observations of the reaction sites were made. Whereas erythema and induration were present at the reaction site in normal animals, these criteria of delayed hypersensitivity (DH) were markedly increased in Toxoplasma-infected guinea pigs. Histologically, rapid mononuclear cell infiltration occurred early in the development of DH in immune animals, suggesting the appearance of a classical tuberculin DH reaction. The presence of numerous intracellular Toxoplasma organisms in the reaction sites of normal guinea pigs contrasted sharply with the inability to demonstrate any parasites at the site of infection in Toxoplasma-immune animals.