Tissue tropism of Toxoplasma gondii in turkeys (Meleagris gallopavo) after parenteral infection

Abstract

Turkeys are known to be natural hosts for the zoonotic protozoan parasite Toxoplasma gondii. The objective of the present study was to gain further knowledge of possible predilection sites of T. gondii infection in this species after parenteral application of tachyzoites. A total of 38 turkeys were infected with different doses of T. gondii tachyzoites. Birds were killed either 6 to 8 or 10 to 12weeks after the experimental infection. Fourteen different tissues per bird were investigated by a nested polymerase chain reaction (PCR) for the presence of the parasites' DNA. T. gondii DNA was found in any type of tissue analysed; in 86.1% of all infected birds, at least one sample was tested positive. Over all intravenously infected birds, 15.4% of all analysed samples contained T. gondii DNA. Most frequently affected tissues were liver (43.3% positive samples), breast muscle (26.7% positive samples) and heart (20.0% positive samples), while the brain was less frequently positive (6.7%). The number of positive tissues varied from zero to seven tissues per animal with at least one T. gondii-positive edible tissue sample in 80% of all intravenously infected birds. Still, the results did not indicate defined target tissues or a cyst distribution pattern. Nonetheless, edible organs were most frequently parasitised. The number of positive findings did not differ between the early and the late examination time points. Therefore, a persistence of the tissue stages until the end of the study (12weeks after infection) is concluded.