[Long-term follow-up of a Coxiellosis outbreak in a goat flock]

In January 2020 Coxiella (C.) burnetii was detected in a small goat flock after the observation of a weak born kid, an abortion as well as a malformed kid.

All animals older than 3 months were subsequently primarily vaccinated with Coxevac (2x three weeks apart) until May 2020 and were revaccinated once in October/November 2020 and in May 2021. Young animals were primarily vaccinated annually except for 2023. Surveillance was performed by qPCR-testing of milk samples, vaginal and preputial (genital swabs, GT), nasal (NT) and environmental swabs (UT). Vaccination was controlled by blood and milk samples which were analyzed for phase-(PhI, PhII)-specific antibodies. Data were compared with those that had been collected in a seronegative goat herd in the course of vaccination.

The load of C. burnetii steadily decreased in all types of samples until June 2020. Weak positive samples were detected until November (milk) and December 2020 (GT). Two NT tested weak-positive (5 C.b./NT) in May and December 2021. No persistent infection was observed. The detection rate in UT was high until April 2020 (24/24), remained stable during the rest of the year (31/40) and slowly decreased during the following years: 12/24 (2021), 5/16 (2022), 2/8 (2023), 1/8 (2024), and 0/8 (2025).

Unexpectedly, vaccination only significantly increased the PhI-titers while PhII-titers remained stable. In contrast, in seronegative kids in the case- and adults in the control-herd vaccination induced a significant increase of PhII- titers while almost no PhI- titers were observed.

No short-term effect of vaccination was observed, therefore prophylactic vaccination is very important. A quantitative interpretation is required for environmental samples, these samples are valuable to verify the lack of infection. Positive results may be confirmed by NT or GT. NT are equivalent to GT, and they are collected more easily.