Surveillance of Coxiella burnetii Shedding in Three Naturally Infected Dairy Goat Herds after Vaccination, Focusing on Bulk Tank Milk and Dust Swabs

Detection of Coxiella burnetii in the mammary gland of a dairy goat

The zoonotic bacterium Coxiella (C.) burnetii can be excreted by infected goats through birth products and milk. The detection of C. burnetii DNA in the mammary gland tissue of infected dairy goats and intermittent milk shedders has been reported, but confirmation of C. burnetii bacteria in the udder remained pending. The pathogen caused abortions in a 152-head dairy goat herd, resulting in the vaccination against C. burnetii of the entire herd with annual boosters. To monitor the C. burnetii shedding at herd level, monthly bulk tank milk (BTM) samples were analyzed using PCR (IS1111). Despite vaccination, C. burnetii DNA was detected in BTM samples within the first 16 months of the study. Therefore, individual milk samples were tested on four different occasions several months apart to identify potential intermittent milk shedders. Only one goat (#67455) tested positive three times. This goat was necropsied to investigate the presence of C. burnetii in the udder and other organs. PCR detected C. burnetii DNA solely in both mammary glands and the left teat cistern. Immunohistological examination identified C. burnetii antigen in mammary gland tissue, confirmed by the detection of C. burnetii bacteria in the mammary epithelial cells using fluorescence in situ hybridization. The removal of goat #67455 led to negative BTM samples until the end of the study. The findings demonstrate the occurrence of C. burnetii in the mammary gland of a naturally infected and vaccinated goat. The presence possibly contributed to intermittent milk shedding of goat #67455, and the mammary gland tissue may serve as a replicative niche for C. burnetii.

Interdisciplinary studies on Coxiella burnetii: From molecular to cellular, to host, to one health research

The Q-GAPS (Q fever GermAn interdisciplinary Program for reSearch) consortium was launched in 2017 as a German consortium of more than 20 scientists with exceptional expertise, competence, and substantial knowledge in the field of the Q fever pathogen Coxiella (C.) burnetii. C. burnetii exemplifies as a zoonotic pathogen the challenges of zoonotic disease control and prophylaxis in human, animal, and environmental settings in a One Health approach. An interdisciplinary approach to studying the pathogen is essential to address unresolved questions about the epidemiology, immunology, pathogenesis, surveillance, and control of C. burnetii. In more than five years, Q-GAPS has provided new insights into pathogenicity and interaction with host defense mechanisms. The consortium has also investigated vaccine efficacy and application in animal reservoirs and identified expanded phenotypic and genotypic characteristics of C. burnetii and their epidemiological significance. In addition, conceptual principles for controlling, surveilling, and preventing zoonotic Q fever infections were developed and prepared for specific target groups. All findings have been continuously integrated into a Web-based, interactive, freely accessible knowledge and information platform (www.q-gaps.de), which also contains Q fever guidelines to support public health institutions in controlling and preventing Q fever. In this review, we will summarize our results and show an example of how an interdisciplinary consortium provides knowledge and better tools to control a zoonotic pathogen at the national level.

Impact of Coxiella burnetii vaccination on humoral immune response, vaginal shedding, and lamb mortality in naturally pre-infected sheep

Introduction

Sheep are considered to be one of the main reservoirs for Coxiella burnetii, a gram-negative bacterium with high zoonotic potential. Infected sheep shed tremendous amounts of the pathogen through birth products which caused human Q fever epidemics in several countries. Information about the impact of an inactivated C. burnetii Phase I vaccine on humoral immune response, vaginal shedding, and lamb mortality in naturally pre-infected sheep is scarce.

Methods

Two identically managed and naturally C. burnetii-infected sheep flocks were examined for two lambing seasons (2019 and 2020). One flock (VAC) received a primary vaccination against Q fever before mating and the second flock served as control (CTR). In each flock, one cohort of 100 ewes was included in follow-up investigations. Serum samples at eight different sampling dates were analyzed by C. burnetii phase-specific ELISAs to differentiate between the IgG Phase I and II responses. Vaginal swabs were collected within three days after parturition and examined by a C. burnetii real-time PCR (IS1111). Lamb losses were recorded to calculate lamb mortality parameters.

Results

After primary vaccination, almost all animals from cohort VAC showed a high IgG Phase I response up until the end of the study period. In cohort CTR, the seropositivity rate varied from 35.1% to 66.3%, and the Phase I and Phase II pattern showed an undulating trend with higher IgG Phase II activity during both lambing seasons. The number of vaginal shedders was significantly reduced in cohort VAC compared to cohort CTR during the lambing season in 2019 (p < 0.0167). There was no significant difference of vaginal shedders in 2020. The total lamb losses were low in both cohorts during the two investigated lambing seasons (VAC 2019: 6.8%, 2020: 3.2%; CTR 2019: 1.4%, 2020: 2.7%).

Discussion

Neither the C. burnetii vaccine nor the C. burnetii infection seem to have an impact on lamb mortality. Taken together, the inactivated C. burnetii Phase I vaccine induced a strong IgG Phase I antibody response in naturally pre-infected sheep. It might also reduce vaginal shedding in the short term but seems to have little beneficial impact on lamb mortality.

Screening for Coxiella Burnetii in Dairy Cattle Herds in Poland

Introduction

The intracellular bacterium Coxiella burnetii is the aetiological agent of Q fever, a zoonosis affecting many animal species worldwide. Cattle and small ruminants are considered the major reservoirs of the bacteria and they shed it through multiple routes.

Material and Methods

A total of 2,180 sera samples from 801 cattle herds in all Polish voivodeships were tested by ELISA for the presence of specific antibodies. Milk samples were obtained from seropositive cows in 133 herds as part of a separate study. The milk samples were examined by ELISA and real-time PCR tests.

Results

Seroprevalence at the animal level was 7.06% and true positive seroprevalence was 6.0% (95% confidence interval (CI) 1.1-9.4). Seroprevalence at the herd level was estimated at 11.1% and true positive seroprevalence was 10.5% (95% CI 3.2-15.8). Shedding of the pathogen in milk was detected by real-time PCR in 33 out of 133 tested herds (24.81%, 95% CI 17.74-33.04%) and the presence of C. burnetii antibodies was confirmed in 85 of them (63.9%, 95% CI 55.13-72.05%). The highest level of conformity between ELISA and real-time PCR results was obtained for bulk tank milk samples.

Conclusion

Coxiella burnetii infections are quite common in cattle herds across the country, which emphasises the crucial roles of surveillance and adequate biosecurity measures in the prevention and limitation of Q fever spread in Poland.