Viability of Toxoplasma gondii cysts in pork processed by ageing from experimentally infected animals

Abstract

Diseases caused by food intake are mostly under-diagnosed and reported to health authorities. Toxoplasma gondii is a zoonotic agent of high prevalence in almost all regions of the world and has in foods, especially in meat eaten raw or undercooked, an important route of infection for humans. T. gondii infects mammals and birds, and in Brazil, was isolated from food-producing animals, such as sheep, goats, pigs, capybaras and chickens. The meat freezing at temperatures below -12°C, baking at 60 °C, curing techniques with sodium chloride and 2% sodium lactate, and 2% gamma irradiation at a dose greater than 0.4 KGy have proven to be effective making the tissue cysts of T. gondii unviable. Treatment of meat cuts by ageing has been growing in the country. This technique allows tenderize the meat through the action of endogenous proteases in anaerobic and under refrigeration. For this, meat portions are vacuum packed and stored under refrigeration at temperatures 0°C for periods ranging from 7 to 21 days. Proteases involved in this process are mainly caspases, calpain, proteasome and cathepsin. Despite the wide distribution in retail, there are no studies to confirm this method has some action on tissue cysts of T. gondii. The objective of this project is to use the ageing technique in meat cuts from pigs experimentally infected with T. gondii and test the viability of tissue cysts of the parasite through bioassay in cats and mice. For this, swine are orally infected with oocysts and after eight weeks, when the infection reaches the chronic phase (the presence of tissue cysts) the pigs are slaughtered and half carcasses is treated by ripening method and half will be maintained untreated as a control. These meats will be submitted to bioassay in groups of cats, directly by oral ingestion, and groups of mice subcutaneously after processing by peptic digestion to confirm whether or not the coccidial infection, providing information about the viability of tissue cysts of T. gondii, helping in this way, to increase knowledge about the biology of the parasite and the adoption of preventive measures for infection control.