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Oral inoculation of cats with tissue cysts of Neospora caninum
M M McAllister1, W R Jolley, R A Wills
1Department of Veterinary Sciences, College of Agriculture, University of Wyoming, Laramie 82070, USA.
Objective:
To test the hypothesis that cats are definitive hosts of Neospora caninum.
Animals:
6 weaned male kittens obtained from 2 sources, and several dozen outbred mice.
Procedure:
Cats were fed large numbers of 3 strains of N caninum: tissue cysts in buffered saline solution, mouse brain homogenates, and whole carcass homogenates from seropositive mice. Fecal specimens were examined for 4 weeks by use of flotation tests, and bioassays were performed in mice. One cat was inoculated parenterally with tachyzoites, to determine whether cats could respond serologically to N caninum. Tissue cysts from portions of oral inocula were cultured to verify viability. Indirect fluorescent antibody serologic testing, histologic and immunohistologic examinations, cell culture, and polymerase chain reaction procedures were performed 4 to 8 weeks after oral exposure, to seek evidence of infection of cats and mice.
Results:
None of the cats or mice seroconverted to N caninum, with the exception of the single cat inoculated parenterally. Fecal shedding of oocysts was not observed, except for Isospora felis oocysts that were shed by 2 cats beginning prior to oral challenge exposure. Evidence of infection was not detected in tissues of cats or mice, with the exception of the parenterally inoculated cat.
Conclusions:
The hypothesis that cats are definitive hosts of N caninum is not supported.
Clinical Relevance:
Extermination of cats in efforts to control bovine neosporosis is not warranted.
