Affiliation:
1. Department of Animal Health, NEIKER-Basque Institute for Agricultural Research and Development, Basque Research and Technology Alliance (BRTA), Derio, Bizkaia, Spain
Abstract
ABSTRACT
Coxiella burnetii
infection was monitored during seven kidding seasons (2017–2023) in a dairy goat herd that after an outbreak of Q fever abortions was vaccinated with an inactivated phase I vaccine. Due to the high infection rate just after the outbreak, only the replacement stock was vaccinated during the first three kidding seasons, and when the average herd immunity had decreased (fourth kidding season onwards), the whole herd was vaccinated. Vaginal swabs, feces, and milk were analyzed by PCR to monitor infection, and dust and aerosols were analyzed to measure
C. burnetii
environmental contamination. One year after the onset of the outbreak, a significant reduction in
C. burnetii
shedding loads was observed, but the percentage of shedding animals remained high until the third kidding season. By the seventh kidding season, no shedders were detected. The bacterial load excreted was significantly lower in vaccinated compared with unvaccinated animals, and in yearlings compared with multiparous.
C. burnetii
was detected by PCR in aerosols collected inside the animal premises throughout the study period except in the last season; whereas, aerosols collected outdoors tested negative in the last three kidding seasons. Viable
C. burnetii
was detectable in environmental dust collected inside the barn until the third kidding season following the outbreak. These results indicate that after an outbreak of Q fever, the risk of infection for humans and susceptible animals can remain high for at least three kidding seasons when the number of
C. burnetii
animal shedders is still high, even when bacterial excretion is low.
IMPORTANCE
Q fever is a zoonosis distributed worldwide. Ruminants are the main reservoir, and infection can cause high rates of abortion. After entering a farm,
Coxiella burnetii
infection can persist in the animal population over several lambing/kidding periods. Once infection is established in a herd, vaccination with the inactivated Phase I vaccine significantly reduces bacterial shedding, but although at low levels, excretion may continue to occur for several lambing/kidding seasons. The time that
C. burnetii
remains viable in the farm environment after an outbreak of Q fever determines the period when risk of infection is high for the people in close contact. This work showed that this period extends at least three kidding seasons after the outbreak. These results provided valuable information on the epidemiology of
C. burnetii
infection in goat herds and may help to develop guidelines for controlling the disease and reducing infection risk for susceptible people and animals.
Funder
Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria
EC | European Regional Development Fund
Ministerio de Ciencia e Innovación
Publisher
American Society for Microbiology
Cited by
2 articles.
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