Characterization of tissue distribution and histopathological lesions in Neospora caninum experimentally infected gerbils

Gerbils (Meriones unguiculatus) were inoculated intraperitoneally (i.p.) with Neospora caninum tachyzoites to examine parasite distribution and histological lesions at different time points over a 9-day period of infection. Gerbils were sacrificed 12 h post-infection (PI), then daily intervals up to day 9 PI. The parasite was detected by PCR assay targeting the Nc5 sequence of N. caninum. The parasite was not found in any organs until day 5 PI, however, from day 8 PI onwards, they were detected in all the organs examined as demonstrated by PCR. The first target organs in acute N. caninum infection were liver, spleen, and kidney, but not the blood as was expected. Histologic lesions were detected in the liver and spleen only, no lesions were found in other organs examined until the end of the experiment. Notably, the focal miliary hepatitis was observed in the liver of infected gerbils just after 1 day post-inoculation, whereas splenic lesions were not found until day 5 PI. These results reinforce the applicability of gerbils as a suitable model of acute neosporosis and provide new insights into the response of gerbils to N. caninum intraperitoneal infection.