“A Zoocentric Capgras Syndrome” [article in German], U. Ehrt, Psychiatrische Praxis, vol. 26, no. 1, January 1999, pp. 43–4. The authors, who are at Klinik und Poliklinik fur Psychiatrie und Psychotherapie, Halle/Saale, Germany, report that:
“We present a case of a 23-year-old women who had the delusional belief that her cat had been replaced by the cat of her former boyfriend. Reviewing the literature we found that such a case is very rare.”
(That’s an excerpt from the article “Improbable Medical Review,” Published in AIR 15:3.)