Correlation of feline coronavirus shedding in faeces with serum coronavirus antibody titre

Feline coronavirus (FCoV) infection is very common in multi-cat households It has been proposed that cats with higher antibody titres are more likely to shed FCoV in their faeces Aim of the study was to determine a possible correlation between FCoV serum antibody titres and faecal FCoV shedding Four faecal samples from 72 cats originating from 18 German catteries were examined for FCoV by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) Serum antibody titres were determined by immunofluorescence assay There was a weak positive correlation between height of antibody titre and mean faecal virus load (Spearman r = 0 3394;P = 0 0035) Antibody titres were significantly higher if cats shed FCoV more frequently (Kruskal Wallis test P = 0 0042) Twenty-two cats were RT-PCRnegative in all four faecal samples Those cats had significantly lower antibody titres than cats shedding continuously (in all four samples) (Dunn's test;P 0 05) When analysing FCoV-shedding cats (shedding at least once), cats that were FCoV RT-PCR-positive continuously in all four samples had significantly higher antibody titres (Mann-Whitney U test P = 0 0026) and significantly higher mean faecal virus loads (Mann-Whitney U test P = 0 0383) than cats that were FCoV RT-PCRpositive in only one, two, or three samples Eight cats had no detectable antibodies but were shedding FCoV Height of antibody titre was correlated to faecal virus load Chronic FCoV shedders had higher antibody titres and shed more virus This knowledge can be of importance for the management of FCoV infection in multi-cat environments However, measurement of serum antibodies cannot replace faecal RT-PCR