Comparison of serological diagnostic tests for detection of feline herpesvirus 1 antibodies (2018) master thesis by Nicole Winter

The most important pathogens causing cat flu are the feline herpesvirus-1 (FHV-1) and the feline calicivirus (FCV). In Switzerland, vaccination against FHV-1 and FCV is routinely practiced. Nevertheless, cat flu related symptoms are frequently presented to veterinary practitioners. Various serological methods are available to test for the presence of FHV-1 antibodies in cat serum samples. The objectives of this study were 1) to compare different serological diagnostic methods for FHV-1 antibody detection including a serum neutralization test (SNT), an enzyme-linked immunosorbent assay (ELISA) and an immunofluorescence assay (IFA), and 2) to search for associations between age, sex, breed, habitat and the presence of FHV-1 antibodies in cat sera. 

The current study included 154 cat sera. 153 cat sera originated from 23 cantons in Switzerland and one serum originated from Germany. All the sera were tested by IFA, 48 sera were tested by SNT and 94 sera were tested by ELISA. FHV-1 seroprevalences measured by SNT, IFA and ELISA were 81.25%, 70.13% and 69.15%, respectively. We observed a good correlation between the results measured by SNT and IFA (correlation of 100%). However, we observed an inferior correlation when comparing the results measured by SNT and ELISA (correlation of 94%) and by ELISA and IFA (correlation of 95%). Furthermore, the antibody titers measured by SNT and ELISA varied greatly. Reasons for this variance in results might be the diagnostic sensitivity and specificity and measurement of different types of antibodies. We further found that cats above 2 years of age were significantly more often FHV-1 seropositive and had higher FHV-1 antibody titers than younger cats. Also, with increasing age, the cats had significant higher FHV-1 antibody titers. Age as a limiting time factor for vaccination and contact with the pathogen as well as slowly rising neutralizing antibody titers could be contributing reasons why young cats were tested FHV-1 seronegative more often. Additionally, if a young cat that still possesses maternally derived antibodies (MDA) gets vaccinated, the development of an endogen immune response can be prohibited. 
Sex, breed and habitat were not found to be associated with the presence of FHV-1 antibodies in cat sera.