Commercial kitten moist food inactivated Toxoplasma gondii tissue cysts instantaneously

Toxoplasmosis is an important parasitic disease for human and animal health. Felines are the definitive hosts, with great importance in the epidemiology of this parasitosis. The present report is part of an ongoing project for the development of a new product for controlling feline toxoplasmosis. Swiss albino mice have been inoculated subcutaneously with 25 ME49 tissue cysts, obtained from the brain of previously inoculated mice. They were euthanized with isoflurane, 42 days post inoculation (dpi), and approximately 22,400 bradyzoite cysts were harvested from their brains. Aliquots of 800 cysts were distributed in 12 labelled microtubes, with the volume adjusted to 500 µl with sterile saline. All the infective material was kept at 4 °C. Twelve seronegative kittens were experimentally infected by oral route, with those 800 bradyzoite cysts of T. gondii ME49 strain, on Study Day 0. The inoculum doses were placed over a small portion (one spoon) of moist cat food (Kelcat Alimento Úmido Lata, Peixe com Ervilha e Cenoura 280g, Kelco). All kittens ingested 100% of the material. This procedure was chosen based on animal welfare. After inoculation, fecal samples from each kitten were collected and examined daily, for 28 days, by a coproparasitological fluctuation test in sucrose solution (S.G. ≥ 1.27). Blood samples were collected from the kittens at 7, 14, 28 and 35 dpi. Serum samples were tested by immunofluorescence antibody test (IFAT). None of the kittens shed oocysts, neither seroconverted with this initial inoculation. On 35 dpi, the remaining material collected from the mice brain was used to produce aliquots containing 200 tissue cysts, with the volume adjusted to 500 µl with sterile saline. The kittens were then inoculated by intranasal (IN) route, with a nasogastric tube no 4, on the same day. All samplings and tests were repeated as before. The kittens began to shed oocysts on 41 dpi (6 days after IN inoculation (daii)), and were shedding up to 47 dpi (12 daii). All kittens were seropositive by 49 dpi (14 daii). These results demonstrated that the kitten moist food was able to inactivate the tissue cysts instantaneously, even without mixing or any other preparation with the inoculum. Further experiments will be carried out with distinct components of the commercial food, in order to identify the specific substances that inactivated the T. gondii cysts with that single contact.