Distribution of Toxoplasma gondii in pigs with a high and a low dose of infection

Toxoplasma gondii continues being one of the main food safety hazards for pregnant women and immunocompromised patients. In this sense, the distribution of this protozoan within the organism and the role of the infective dose in tissue distribution are of highly interest to understand the risk associated to the parasite and to decipher the pathobiology of this infection.

To carry out this study 11 Iberian pigs (twelve-month-old, 100Kg BW, male) were randomly allocated within 3 experimental groups: (1) Control group (2 pigs); (2) High Dose (HD) (5 pigs), animals intramuscularly inoculated with 1x10⁷ tachyzoites of T. gondii strain BCR Reference TgH 00001 (PRU); and (3), Low Dose (LD) (4 pigs), animals intramuscularly inoculated with 1x10³ tachyzoites of the same T. gondii strain. Blood samples were collected one week prior to inoculation and at 0, 15 and 30 days post-infection (dpi). At 30dpi all the animals were euthanized and samples from the brain, heart, tongue, lung, liver, spleen, kidney, mesenteric lymph node, masseter muscle and a pool of shoulder, loin and ham (meat pool) were collected at the post-mortem examination. All organs were examined for gross lesions and subjected to qPCR (TOX4-TOX5) to determine the presence of the parasite.

No changes were detected in sera from control and LD animals throughout the study, but HD animals presented between 3.8 and 16.1 fold increase in the OD (ID Screen ToxopIasmosis, IDvet). No gross lesions were detected in control or infected animals along the study. T. gondii DNA was not detected in control animals. T. gondii DNA was more frequently detected from brain and meat pool samples from HD animals (80% and 80%, respectively) than LD animals (25% and 0%, respectively). On the contrary, T. gondii DNA was more frequently detected from lung, liver and spleen samples from LD animals (75%, 100% and 80%, respectively) than HD animals (40%, 40% and 40%, respectively). No differences were observed in T. gondii distribution between HD animals and LD animals in heart, tongue, masseter muscle, kidney and mesenteric lymph node samples (100%, 40%, 80%, 100% and 100% vs 75%, 50%, 100%, 75% and 75%, respectively).

Our results highlight that despite the fact that T. gondii might present different tissue tropism according to the infective dose, target skeletal muscles are similarly affected independently of the infective dose. Therefore, different organs should be analysed to clarify the pathogenesis of this infection.

Disclosure of Interest: None Declared.