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Bulk-tank milk (BTM) samples are frequently used to evaluate the health status of dairy livestock. A large-scale investigation carried out in BTM samples from dairy cattle herds from a Q fever-endemic region in Northern Spain revealed a high degree of exposure to Coxiella burnetii. This study was aimed at assessing the value of BTM samples analysis as an indicator of the C. burnetii status in dairy cattle herds. Three herds with BTM samples positive for C. burnetii by ELISA and PCR were selected, and blood, faeces and individual milk and BTM samples were analysed by serology and PCR. In spite of the high antibodies titres found in BTM samples, only one of the three farms presented an active infection by C. burnetii, as revealed by the presence of bacterial DNA in vaginal mucus and in environmental samples collected in the calving area, a seroprevalence around 40% in heifers and the seroconversion rate observed in cows. Results obtained indicated that the analysis of BTM samples is a good epidemiological tool at the population level that can be used to discriminate between seropositive and seronegative herds, but at the herd level, additional tests are necessary to evaluate whether Q fever is a potential problem in the farm. When Q fever is suspected in a cattle herd, sera from a small group of 1- to 3-year-old animals need to be analysed to investigate recent contact with C. burnetii., (© 2012 Blackwell Verlag GmbH.)

A large-scale investigation on Coxiella burnetii was carried out in dairy cattle herds from a Q fever-endemic region to evaluate the degree of exposure to C. burnetii and to estimate prevalences. This study included all of the dairy cattle herds from the province of Bizkaia, Northern Spain (n=178). Herds were visited between September 2009 and February 2010, and 100mL of bulk-tank milk (BTM) per farm was collected to be analyzed by ELISA and PCR. Blood samples were also taken from about 15 animals randomly selected from each herd. One hundred nineteen of the 178 studied herds (66.9±6.9%) were positive for the presence of anti-C. burnetii antibodies in BTM. Serum samples from 1,306 cows, 654 heifers, and 502 calves were analyzed by ELISA, and cows showed a statistically significantly higher seroprevalence (12.3±1.8%) than heifers (1.1±0.8%) and calves (0.0±0.0%). Eighty-nine herds (50.0±7.3%) had at least 1 seropositive animal, but within-herd prevalences higher than 20% were only observed in 24 herds (13.5±5.0%). A significant correlation was observed between BTM ELISA sample-to-positive control ratios and within-herd seroprevalence, being higher when considering only cows (R(2)=0.21). Animals from herds with negative BTM by ELISA showed a mean seroprevalence of 2.5%, whereas animals from herds with positive BTM samples had a statistically significantly higher seroprevalence (8.9%, F=19.7, degrees of freedom=1). The proportion of herds C. burnetii positive by BTM PCR was 51.7±7.3% (92/178). The widespread distribution of C. burnetii in cattle advocates for the implementation of Q fever control strategies., (Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Pooling samples may provide a valuable alternative to individual testing for pathogen surveillance purposes. We studied the reliability of measuring the level of antibodies against Coxiella burnetii in bulk-tank milk (BTM) to estimate the seroprevalence of C. burnetii in dairy sheep in 34 flocks. We then estimated the seroprevalence of C. burnetii in 154 dairy sheep flocks according to the level of antibodies in BTM. We tested for the accuracy of our estimation at the population level by comparing predicted mean C. burnetii flock seroprevalence with that obtained in another survey performed on the same population. Our findings showed that testing BTM by ELISA is a cost-effective and relatively good index of the seroprevalence of C. burnetii in dairy sheep and may be a useful tool for epidemiological surveillance at the population level.

There is a great need to establish effective tools to control border disease virus (BDV) in European dairy sheep flocks. Hence, our main aim was to investigate the accuracy of analyzing anti-BDV antibodies in bulk-tank milk (BTM) in detecting the real BDV seroprevalence in dairy sheep flocks. Furthermore, the relevance of BDV to reproductive performance of dairy sheep flocks prompted us to search for the association between BDV seroprevalence and reproductive parameters. For these purposes, 34 flocks were selected based on different percentages of antibody inhibition (AIP) values in BTM as estimated by ELISA. Serum samples from 10 replacement lambs older than 6 mo, 10 ewes 1 to 2 yr old, and 10 ewes > 2 yr old were collected and analyzed for the presence of anti-BDV antibodies by ELISA. A negative relationship between BDV AIP in BTM and within-flock seroprevalence was observed. Flocks with a high AIP (> 80%) had an average of 2.5% seropositive animals; flocks with a moderate AIP (46-79%) had 11.4% seropositive animals; and finally, flocks with an AIP < or = 45% showed a high flock seroprevalence (57.2%). Ten out of 34 flocks showed a high BDV seroprevalence in lambs, suggesting the presence of persistently infected animals in the flock. The observed AIP values in BTM from these likely BDV-infected flocks were indicative of a high seroprevalence. The analysis of reproductive-parameters data collected from these flocks showed no differences in fertility or prolificacy in relation to BDV circulation rates. Nonetheless, lamb mortality was significantly greater in flocks with low-moderate seroprevalence (10-30%), probably as a result of a first-time contact with BDV of previously naïve ewes. These findings suggest that testing of BTM samples may be useful in inferring the BDV seroprevalence in a flock., (2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

To estimate the prevalence of Coxiella burnetii in the dairy sheep population from the Basque Country (northern Spain), a study was carried out combining molecular and serological techniques. First, bulk-tank milk samples from 154 flocks belonging to the Latxa Breed Farmers Association were analyzed by PCR, with 22% of flocks testing positive for C. burnetii. Then, a selection of 34 flocks (7 PCR positive and 17 negative) was investigated for the presence of serum antibodies by ELISA test on 1,011 ewes (approximately 30 ewes per flock). A total of 8.9% of the animals were seropositive, 67.6% of the flocks had at least one seropositive animal, but only in 14.7% of them was seroprevalence greater than 25%. Older ewes showed a significantly greater prevalence (17.5%) compared with yearlings (7.5%) or replacement lambs (1.5%). A marginally significant association was found between seroprevalence and PCR detection of C. burnetii in bulk-tank milk. The widespread distribution of C. burnetii in the region advocates for the implementation of Q fever control strategies and highlights the potential risk of sheep as a reservoir and infection source for other domestic and wildlife species and the human population.

Bulk-tank milk (BTM) samples from 154 sheep flocks were used to estimate BDV prevalence in the Basque Country in Spain using an ELISA and a RT-PCR test. The proportion of antibody-positive flocks was 68% but varied significantly between provinces and was 93% in Araba and 54-55% in Bizkaia and Gipuzkoa. Most ELISA-positive flocks had very low antibody inhibition percentage (AIP) indicating high seroprevalence and recent BDV exposure. However, only 9% flocks were PCR-positive suggesting few infected ewes were being milked at the time of sampling. Phylogenetic analysis of the 5' NCR sequences of BDV from seven infected flocks showed that all except one clustered within the group formed by BDV type C strains from a previous study in the region, whereas the remaining isolate was closest to BDV type A. These results suggest that BDV strains in most Basque flocks have a common origin and differences in prevalence between provinces are associated to recent events affecting BDV spread such as use of communal pastures and sheep trading. The widespread distribution of BDV in the region, advocates for the implementation of BDV control strategies and highlights the potential risk of sheep as a pestivirus reservoir for other species.