Comparative Infectivity for Calves of Oocysts of Feline Coccidia: Besnoitia, Hammondia, Cystoisospora, Sarcocystis, and Toxoplasma

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Abstract
Oocysts of 6 spp. of feline coccidia were fed to calves in their grain ration. Calves were observed daily for clinical signs of infection for 26-115 days after feeding. Neither gross lesions, microscopic lesions nor parasites were found in any of the experimental animals. A mixture of organs from each calf was fed to cats to determine if viable parasites were present. Besnoitia wallacei, Hammondia hammondi and Sarcocystis muris were not pathogenic for calves, and did not establish patent infections that could be transmitted back to cats. Although Cystoisospora felis and C. rivolta were not pathogenic for calves, oocysts were shed by cats that had ingested organs from calves infected with a mixture of C. felis and C. rivolta oocysts. Cats that ingested organs from other calves housed in the same isolation barn as those infected with C. felis and C. rivolta also shed oocysts of these species, but cats fed organs from a control calf housed in another isolated barn shed no oocysts. Some control calves and some calves infected with other feline coccidia may have acquired natural infections with C. felis and C. rivolta. Three strains of T. gondii were infectious for calves. Infectivity and pathogenicity of T. gondii for cattle varied with the strain. Infective strains were slightly to moderately pathogenic, with 2 strains producing diarrhea, anorexia, poor weight gain, depression, weakness, fever and dyspnea. Cats fed organs from these calves shed T. gondii oocysts.