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| Author(s): |
Yara Souza Clemes
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2022-05-12 |
| Examining board members: |
Hilda Fátima de Jesus Pena;
Igor da Cunha Lima Acosta;
Herbert Sousa Soares
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| Advisor: | Hilda Fátima de Jesus Pena |
| Abstract | |
Toxoplasmosis is a disease of zoonotic importance caused by the protozoan Toxoplasma gondii. The two main routes of transmission of T. gondii to humans are the ingestion of sporulated oocysts and the ingestion of raw or undercooked meat that contain viable tissue cysts of the agent. The dry ageing process can be a means of controlling toxoplasmosis acquired through meat ingestion. The objective of this study was the refinement of the dry ageing process in the non-viability of T. gondiicysts in cuts of loin (m. longissimus) of experimentally infected pigs. Six pigs with approximately 90 days of age and seronegative for T. gondii (titer < 64 by Indirect Fluorescent Antibody TEST IFAT) were orally infected with 3×103 oocysts of the T. gondii isolate TgCkBr57. Oocysts were obtained after reactivation of the isolate in mice and oral infection of a cat aged approximately five months and seronegative for T. gondii (titer < 16 by IFAT). One seronegative swine was maintained as a control throughout the experiment. The seven pigs were followed up weekly for anti-T. gondii antibodies through RIFI for eight weeks. At slaughter (swine aged 150 days and weighing approximately 80 kg), the carcasses of the six pigs were divided into six pairs. After separation of the cuts, the left loins were vacuum packed and submitted to the dry ageing process for 16, 18 or 21 days (two loins per period) in a refrigerated chamber (-1 to 0ºC). All loins, aged and non-aged, were submitted to the process of peptic digestion of tissues and bioassay in mice (300 mice for aged loins and 300 for non-aged loins), in their respective periods, to observe the infection by T. gondii. Diaphragm and tongue of all pigs were also collected at slaughter for the mouse bioassay (10 mice per pig) as an infection control. The mice were monitored daily for signs of toxoplasmosis, when they were euthanized and examined for the presence of tachyzoites and/or T. gondii cysts in their tissues. Animals surviving for six weeks post- inoculation were euthanized and examined for the presence of T. gondii. Seroconversion was observed in the six infected pigs, with the presence of IgM and IgG anti-T. gondii antibodies. The number of mice infected with loins aged for 16 days (69/100) was close to the respective non-aged loins (80/100); this number was lower in the groups inoculated with loins aged for 18 days (28/100), in relation to the respective non-aged group (73/100), suggesting a decrease in the number of cysts with 18 days of dry ageing. There was no infection in mice inoculated with loins aged for 21 days (0/100), while in the respective non-aged group there was 68/100 infected. The present study did not allow the refinement of the dry ageing process for swine loins using the periods of 16 and 18 days but confirmed the non-viability of T. gondii cysts with 21 days of dry ageing vacuum-packed pork under the experimental conditions presented. (AU) | |
| FAPESP's process: | 19/15962-9 - Refinement of the dry ageing vaccuum-packed pork for the inactivation of Toxoplasma gondii cysts from experimentally infected pigs |
| Grantee: | Yara Souza Clemes |
| Support Opportunities: | Scholarships in Brazil - Master |