Feasibility Study on Coxiella burnetii Phase-Specific Antibody Tests and Interferon-?-Recall Assay in Dairy Cattle - Abstract
The zoonotic pathogen Coxiella burnetii (C. burnetii) is characterized by two antigenic phases (PhI and II). PhI- and PhII-antibody tests and a PhII-IFN-?-recall assay (IFN-?-RA) with neutralization of IL-10 were developed for ruminants. Cows in an endemically infected farm were monitored for shedding of C. burnetii by quantitative polymerase chain reaction (qPCR) in milk (MS) and puerperal fluid (PS) samples over a period of two years. Subsequently, blood was collected. According to the shedding pattern cows were allocated to four groups: (1) MS+/PS+ (n=16), (2) MS+/PS- (n=36), (3) MS-/PS+ (n=17), and (4) Non-S (n=37, non-shedder). A fifth group consisted of primiparous cows that had been vaccinated as heifers prior tobreeding and thatwere tested after calving ((5) H/Vacc, n=11). As an additional parameter, the time since last detection of C. burnetii (< 6 months, ? 6 months) was also included in the analysis.
Group 1 was characterized by a higher level of PhI/PhII-antibodies and a lower level of IFN-? compared to group 3, which was characterized by high level of IFN-?, a moderate level of PhII-antibodies and absence or low level of PhI-antibodies. An inverse relationship of parameters of cellular and humoral immunity was observed for these two groups. An intermediate position was observed for group 2, i.e., cows with recent detection of C. burnetii tended to show a pattern similar to group 1, while those shedding C. burnetii more than 6 months ago were similar to group 3. Vaccinated heifers were characterized by strong IFN-?-reactivity, moderate PhII-antibodies and absence of PhI-antibodies; low level shedding was observed in heifers despite vaccination.