Further studies on the transmission of Hammonia hammondi in cats.

Sporulated Hammondia hammondi oocysts were fed to 66 mice. Beginning the 1st day after feeding and continuing for 11 days, 6 mice were killed each day and fed to a different cat. Feces of cats fed mice were examined for oocysts. The first 9 cats, fed 6 mice each from day 1 to 9, did not shed oocysts within 50 days. Cats fed mice on days 10 and 11, shed H. hammondi oocysts after 6 days. These data indicate that tachyzoites are not infectious to cats and that the cysts are formed by the 10th day in mice fed oocysts. In other experiments, it was shown that in mice fed oocysts, H. hammondi occurred less frequently in the spleen, liver, lungs, and mesenteric lymph nodes than in the brain and muscle. Muscle was found to be more heavily infected than brain. Further, pregnant mice were fed H. hammondi oocysts and the mice delivered were raised by their mothers, weaned, and then fed to cats. The cats did not shed oocysts indicating the absence of congenital infection. H. hammondi oocysts were noninfectious to chickens.