Distribution of Schmallenberg Virus and Seroprevalence in Belgian Sheep and Goats

A serological survey to detect Schmallenberg virus (SBV)‐specific antibodies by ELISA was organized in the Belgian sheep population to study the seroprevalence at the end of the epidemic. One thousand eighty‐two sheep samples which were collected from 83 herds all over Belgium between November 2011 and April 2012 were tested. The overall within‐herd seroprevalence and the intraclass correlation coefficient were estimated at 84.31% (95% CI: 84.19–84.43) and 0.34, respectively. The overall between‐herd seroprevalence was 98.03% (95% CI: 97.86–98.18). A spatial cluster analysis identified a cluster of six farms with significantly lower within‐herd seroprevalence in the south of Belgium compared with the rest of the population (P = 0.04). It was shown that seroprevalence was associated to flock density and that the latter explained the presence of the spatial cluster. Additionally, 142 goat samples from eight different herds were tested for SBV‐specific antibodies. The within‐herd seroprevalence in goats was estimated at 40.68% (95% CI: 23.57–60.4%). The results of the current study provided evidence that almost every Belgian sheep herd has been in contact with SBV during 2011 and should be taken into consideration as part of comprehensive SBV surveillance and control strategies.     

Follow‐up of the Schmallenberg Virus Seroprevalence in Belgian Cattle

Schmallenberg virus (SBV), which emerged in Northwestern Europe in 2011, is an arthropod‐borne virus affecting primarily ruminants. Based on the results of two cross‐sectional studies conducted in the Belgian ruminant population during winter 2011–2012, we concluded that at the end of 2011, almost the whole population had already been infected by SBV. A second cross‐sectional serological study was conducted in the Belgian cattle population during winter 2012–2013 to examine the situation after the 2012 transmission period and to analyse the change in immunity after 1 year. A total of 7130 blood samples collected between 1st January and 28 February 2013 in 188 herds were tested for the presence of SBV‐specific antibodies. All sampled herds tested positive and within‐herd seroprevalence was estimated at 65.66% (95% CI: 62.28–69.04). A statistically significant decrease was observed between the beginning and the end of 2012. On the other hand, age‐cohort‐specific seroprevalence stayed stable from 1 year to the other. During winter 2012–2013, calves between 6 and 12 months had a seroprevalence of 20.59% (95% CI: 15.34–25.83), which seems to be an indication that SBV was still circulating at least in some parts of Belgium during summer–early autumn 2012. Results showed that the level of immunity against SBV of the animals infected has not decreased and remained high after 1 year and that the spread of the virus has slowed down considerably during 2012. This study also indicated that in the coming years, there are likely to be age cohorts of unprotected animals.     

Evidence of extensive renewed Schmallenberg virus circulation in Belgium during summer of 2016 – increase in arthrogryposis‐hydranencephaly cases expected

A seroprevalence study carried out between June and September 2016 in the Belgian sheep population showed a significant increase in overall (from 25% to 62%) and between‐herd (from 60% to 96%) seroprevalence against Schmallenberg virus (SBV) during this period, indicating the most extensive recirculation of SBV since its original emergence in 2011. SBV recirculation was confirmed by the detection of SBV RNA‐positive Culicoides obsoletus complex midges collected in the region of Antwerp in August 2016, reaching a minimum infection rate of 3%. The recirculation of SBV in the largely unprotected ruminant population during summer 2016 will likely cause an increase in the number of arthrogryposis‐hydranencephaly cases in newborn ruminants during the coming months.     

Schmallenberg Virus beyond Latitude 65°N

Extensive and rapid spread of Schmallenberg virus (SBV) in Sweden was detected by consecutive serological bulk milk surveys conducted before and after the vector season of 2012. Whereas <0.2% of cattle herds tested positive in a first survey in spring 2012, SBV‐specific antibodies were detected in almost 75% of 723 bulk milk samples randomly collected all over the country 6 months later, beyond the 65th northern latitude, and with an observed spatial distribution suggesting multiple introductions of the virus. Circulation of virus was later confirmed by the detection of SBV in malformed lambs and calves starting from November 2012 and January 2013, respectively. These observations suggest SBV circulation starting from July 2012, with a peak in transmission between August and October. A local heterogeneity of within‐herd seroprevalence was found, indicating that SBV‐naïve animals remain also in highly infected areas enabling the re‐emergence of the infection in the coming vector season.     

Significant re‐emergence and recirculation of Schmallenberg virus in previously exposed dairy herds in Ireland in 2016

Schmallenberg virus (SBV) circulation was investigated in 25 previously exposed dairy herds in Ireland in 2016. A population of 1,550 spring‐2014‐born animals, which had been monitored for SBV infection in 2014 and 2015 as part of a previous SBV surveillance study, were resampled for evidence of SBV infection during 2016. A total of 366 blood samples were collected in the 25 study herds (15 samples per herd) between 3 March 2017 and 10 March 2017 (before the 2017 vector‐active season) and analysed for SBV antibodies using a competitive ELISA kit (IDVet). A total of 256 animals tested seropositive, an AP of 69.9% (95% CI: 65.1–74.4) and TP of 77.7% (95% CI: 72.3%–82.8%) when correcting for imperfect test characteristics. These results demonstrate that a new epidemic of SBV circulation occurred in these previously exposed herds in Ireland in 2016.     

Serological Screening Suggests Presence of Schmallenberg Virus in Cattle,Sheep and Goat in the Zambezia Province,Mozambique

Schmallenberg virus (SBV) is a novel Orthobunyavirus within the family Bunyaviridae belonging to the Simbu serogroup. Schmallenberg virus infects ruminants and has since its discovery in the autumn 2011 been detected/spread to large parts of Europe. Most bunyaviruses are arboviruses, and SBV has been detected in biting midges in different European countries, suggesting that they may play a role in the transmission of the virus. It is not known how SBV was introduced to Europe and if SBV is present in countries outside of Europe. Thus, in this study, we conducted a serological screening for SBV antibodies in cattle (no. 79), sheep (no. 145) and goat (no. 141) in the Zambezia Province in Mozambique during September 2013. The results show a high percentage of antibody‐positive animals. All farms tested had seropositive animals; cattle displayed the highest prevalence with 100% positive animals. Sheep and goat also displayed high number of positive animals with a 43–97% and 72–100% within‐herd seroprevalence, respectively. This initial serological screening suggests that SBV is present on the African continent. However, cross‐reactivity with other members of the Simbu serogroup cannot be ruled out, and further studies are needed to identify and characterize the virus responsible for the antibody‐positive results.     

Large‐Scale Cross‐Sectional Serological Survey of Schmallenberg Virus in Belgian Cattle at the End of the First Vector Season

A cross‐sectional survey was conducted in the Belgian cattle population after the first period of infection of the emerging Schmallenberg virus. A total number of 11 635 cattle from 422 herds sampled between 2 January and 7 March 2012 were tested for the presence of Schmallenberg‐specific antibodies using an ELISA kit. Between‐herd seroprevalence in cattle was estimated at 99.76% (95% CI: 98.34–99.97) and within‐herd seroprevalence at 86.3% (95% CI: 84.75–87.71). An Intraclass Correlation Coefficient of 0.3 (P < 0.001) was found, indicating that the correlation between two animals within a herd with respect to their serological status was high. Those results corroborate the conclusion that the Schmallenberg virus was widespread in Belgium during winter 2011. Seroprevalence was shown to be statistically associated to the animal's age (P < 0.0001): with 64.9% (95% CI: 61.34–68.3) estimated for the 6–12 months of age, 86.79% (95% CI: 84.43–88.85) for the 12–24 months of age and 94.4% (95% CI: 93.14–95.44) for the animals older than 24 months. Based on the results of the described serological survey, we can conclude that after the first Schmallenberg virus episode, almost every Belgian cattle has already been in contact with the virus. In consequence, the vast majority of the host animals should have developed post infection protective immunity against the virus.     

Two Years After the Schmallenberg Virus Epidemic in the Netherlands: Does the Virus still Circulate?

Two years after the introduction of the Schmallenberg virus in north‐western Europe, it is unknown whether the virus is still circulating in countries that were the first to be confronted with it. When the population‐level immunity declines in Europe, reintroduction or the re‐emergence of SBV in Europe might eventually result in an outbreak of similar magnitude of that seen in 2011–2012. The Netherlands was part of the primary outbreak region of SBV in 2011. The aim of this study was to determine whether SBV circulated amongst dairy herds in the Netherlands in 2013, and if so, to which extent. For this purpose, the presence of SBV‐specific antibodies in naive cattle was investigated. A total of 394 dairy farms were sampled between October and December 2013 by collecting five serum samples per herd. Antibodies were detected in 1.1% [95% confidence interval (CI): 0.7–1.7)] of the animals. All seropositive animals were single reactors per herd and were at least 8 months old at sampling. As these results were inconclusive in demonstrating freedom of SBV circulation, a more in‐depth investigation was initiated to provide more insight: an additional sample of 20 youngstock within the same age category (including the five initially sampled animals) was collected from 17 of the 21 positive herds and tested for SBV‐specific antibodies. This resulted in 9 antibody‐positive test results of 316 samples. Again, the positive samples were single reactors within the sample obtained from each farm, which is unlikely given the characteristics of SBV. Therefore, assuming the single reactors as false‐positive, this survey showed with 95% confidence that the maximum possible prevalence of herds with SBV circulation in the Netherlands was <1% in 2013.     

Serosurvey of Schmallenberg Virus Infections in Sheep and Goat Flocks in Lower Saxony,Germany

Schmallenberg virus (SBV) infections can cause congenital musculoskeletal and vertebral malformations as well as neurological failures in foetuses of several ruminant species if susceptible mother animals were infected during early gestation. Blood samples gained from 17 goat and 64 sheep flocks in Lower Saxony (LS), Germany (January–May 2012), which is located in the core region of the 2011/2012 epidemic were tested for antibodies against SBV by ELISA to detect past exposure to SBV. A SBV‐specific questionnaire was raised in all flocks. The calculated median within‐herd prevalence was 43.8% (min–max: 5.6–93.3%) for goats and 58.7% (min–max: 6.5–100%) for sheep, showing that small ruminants in LS, especially goats, are still at risk of novel SBV infections in the following lambing seasons as not all animals have seroconverted yet. Statistical analysis revealed that goats have a significantly lower risk of SBV infections than sheep which might be explained by different host preferences of Culicoides ssp. as main vectors for SBV and different housing conditions.     

Serological status for BTV‐8 in French cattle prior to the 2015 re‐emergence

Undetected in Europe since 2010, bluetongue virus serotype 8 (BTV ‐8) re‐emerged in August 2015 in Central France. To gain insight into the re‐emergence on the French territory, we estimated the seroprevalence in cattle before the detection of BTV ‐8 in 2015, in areas differentially affected by the current outbreak. A retrospective survey based on the analysis of stored sera was thus conducted in the winter preceding the re‐emergence in seven French departments including the one where the virus was first detected. A total of 10,066 sera were retrieved from animals sampled in 444 different herds in winter 2014/15. Between‐herd seroprevalence revealed the presence of seropositive animals in almost all herds sampled (97.4%). The animal‐level seroprevalence averaged at 44%, with a strong age pattern reflecting the cumulative exposure to both natural infection and to vaccination. A multivariable analysis allowed separating the respective effects of both exposures. A higher proportion of seropositivity risk was attributed to vaccination (67.4%) than to exposure to natural infection (24.2%). The evolution of seroprevalence induced by the two main risk factors in 74 mainland departments was reconstructed between the vaccination ban (2013) and the re‐emergence (2015). We showed a striking decrease in seroprevalence with time after the vaccination ban, due to population renewal, which could have facilitated virus transmission leading to the current outbreak situation.     

Seroprevalence of brucellosis in goats and sheep in Thailand: Results from the Thai National Brucellosis Surveillance System from 2013 to 2015

In Thailand, brucellosis re‐emerged in humans in 2003 and is considered a public health risk to goat farmers as the disease is endemic in small ruminants. The Thai Department of Livestock Development (DLD ) established a nationwide surveillance system for brucellosis in goats and sheep in 1997. Using data from this surveillance system, we describe the seroprevalence of brucellosis from 2013 to 2015 in small ruminants and the spatial distribution of the disease throughout Thailand. Surveillance data collected included the number of animals and herds tested, the province of the animal and herd and the laboratory results. Seroprevalence was estimated at both the animal and herd levels. During the 3‐year period, 443,561 goats and sheep were tested for brucellosis by the DLD throughout Thailand using the Rose Bengal Plate Test (RBPT ) and the enzyme‐linked immunosorbent assay test for Brucella . Among the 3 years, 2013 had the highest proportion of herds that tested positive for brucellosis at 13.80% (95% CI, 12.52, 15.16). Overall, this study found that brucellosis seroprevalence in small ruminants is decreasing throughout Thailand. However, there is variability in the spread of the disease with provinces in the eastern and western regions of Thailand having higher proportions of animals and herds testing positive. Overall provinces in the south had the lowest proportion of animals and herds testing positive for brucellosis. Periodic review of surveillance data documents the impact of the current brucellosis control programme and supports a targeted response in higher prevalence regions when there are limited financial resources for control measures.     

First report of Schmallenberg Virus Infection in Cattle and Midges in Poland

Two outbreaks of Schmallenberg virus (SBV) infection that coincided with the introduction of two bulls imported from France into two herds located in West Pomerania and Silesia provinces in Poland are described in detail. The first SBV real‐time RT‐PCR‐positive result was obtained during routine testing of one of the imported bulls. The second bull and the affected farms were tracked by further investigation. Transmission of SBV into Polish cattle herds where the bulls were imported was confirmed by viral RNA detection in real‐time RT‐PCR, virus isolation followed by immunoperoxidase (IPX) staining and seroconversion. SBV RNA was detected also in Culicoides obsoletus pools caught in a trap located 5 km from one of the outbreaks. Testing nearly 900 samples collected prior to the two outbreaks from the same areas or provinces neighbouring with Germany where SBV cases had previously been detected gave negative results for the presence of SBV or specific antibodies. These cases are the first ones detected in cattle in Poland and provide evidence of recent transmission of the pathogen into the country and involvement of midge vectors.     

Post‐epidemic investigation of Schmallenberg virus in wild ruminants in Slovenia

Schmallenberg virus (SBV) is a vector‐borne virus belonging to the genus Orthobunyavirus within the Bunyaviridae family. SBV emerged in Europe in 2011 and was characterized by epidemics of abortions, stillbirths and congenital malformations in domestic ruminants. The first evidence of SBV infection in Slovenia was from an ELISA‐positive sample from a cow collected in August 2012; clinical manifestations of SBV disease in sheep and cattle were observed in 2013, with SBV RNA detected in samples collected from a total of 28 herds. A potential re‐emergence of SBV in Europe is predicted to occur when population‐level immunity declines. SBV is also capable of infecting several wild ruminant species, although clinical disease has not yet been described in these species. Data on SBV‐positive wild ruminants suggest that these species might be possible sources for the re‐emergence of SBV. The aim of this study was to investigate whether SBV was circulating among wild ruminants in Slovenia and whether these species can act as a virus reservoir. A total of 281 blood and spleen samples from wild ruminants, including roe deer, red deer, chamois and European mouflon, were collected during the 2017–2018 hunting season. Serum samples were tested for antibodies against SBV by ELISA; the overall seroprevalence was 18.1%. Seropositive samples were reported from all over the country in examined animal species from 1 to 15 years of age. Spleen samples from the seropositive animals and serum samples from the seronegative animals were tested for the presence of SBV RNA using real‐time RT‐PCR; all the samples tested negative. Based on the results of the seropositive animals, it was demonstrated that SBV was circulating in wild ruminant populations in Slovenia even after the epidemic, as almost half (23/51) of the seropositive animals were 1 or 2 years old.     

Herd‐Level Risk Factors for the Seropositivity to Mycoplasma hyopneumoniae and the Occurrence of Enzootic Pneumonia Among Fattening Pigs in Areas of Endemic Infection and High Pig Density

The aim of the present study was to identify potential risk factors for the occurrence of enzootic pneumonia (EP) in herds situated in a region of high pig density, where a majority of herds is endemically infected with Mycoplasma hyopneumoniae. Between 2006 and 2010, overall 100 herds were enrolled in a case–control study. Data were collected through personal interview with the farmers, clinical examination of pigs and their environments, and serological testing for M. hyopneumoniae, swine influenza virus and porcine reproductive and respiratory syndrome virus. There were 40 case herds (coughing index high, seroprevalence high) with a mean coughing index of 4.3 and a seroprevalence of 86.6%. There were two control groups. Control group I consisted of 25 herds (coughing index low, seroprevalence low) with mean values of 0.7 and 11.2%, and 35 herds were allocated to control group II (coughing index low, seroprevalence high) where the mean coughing index was 0.9 and seroprevalence 86.3%. Case herds and control II herds had an increased age of piglets at weaning compared to control I herds. Any contact between fattening pigs of different age during restocking of compartments increased the risk for the occurrence of EP in a herd. Finally, farms that use living animals for the exposure to gilts during the acclimatization and farms that had increased number of weaned piglets per sow and year were less likely to test positive for M. hyopneumoniae and less likely to develop clinical symptoms of EP in fattening pigs.     

Exposure of Wildlife to the Schmallenberg Virus in France (2011–2014): Higher,Faster, Stronger (than Bluetongue)!

The Schmallenberg virus (SBV) has recently emerged in Europe, causing losses to the domestic livestock. A retrospective analysis of serodata was conducted in France for estimating seroprevalence of SBV among six wildlife species from 2011–2012 to 2013–2014, that is during the three vector seasons after the emergence of the SBV in France. Our objective was to quantify the exposure of wildlife to SBV and the potential protective effect of elevation such as previously observed for bluetongue. We also compared the spatiotemporal trends between domestic and wild animals at the level of the departments. We tested 2050 sera using competitive ELISA tests. Individual and population risk factors were further tested using general linear models among 1934 individuals. All populations but one exhibited positive results, seroprevalence up to 30% being observed for all species. The average seroprevalence did not differ between species but ranged from 0 to 90% according to the area and period, due to the dynamic pattern of infection. Seroprevalence was on average higher in the lowlands compared to areas located up to 800 m. Nevertheless, seroprevalence above 50% occurred in areas located up to 1500 m. Thus, contrary to what had been observed for bluetongue during the late 2000s in the same areas, SBV could spread to high altitudes and infect all the studied species. The spatial spread of SBV in wildlife did not fully match with SBV outbreaks reported in the domestic livestock. The mismatch was most obvious in mountainous areas where outbreaks in wildlife occurred on average one year after the peak of congenital cases in livestock. These results suggest a much larger spread and vector capacity for SBV than for bluetongue virus in natural areas. Potential consequences for wildlife dynamics are discussed.     

Clinical and Serological Dynamics of Besnoitia besnoiti Infection in Three Endemically Infected Beef Cattle Herds

The dynamics of bovine besnoitiosis were studied in an area where the disease is endemic. A four‐year longitudinal study was conducted for the first time in three infected beef cattle herds located in the Urbasa‐Andía Mountains (Navarra, Spain). Each herd was visited four to seven times, and clinical and serological prevalence rates and incidence rates were estimated. Clinical inspections to identify compatible clinical signs with the disease stages were conducted at the beginning and end of the study. Serological assessment was initially performed by ELISA. Seronegative animals with clinical signs and seropositive animals with relative index per cent (RIPC) values lower than 30 that did not increase during the study period were analysed by Western blot to optimize the sensitivity and specificity of the ELISA test. Clinical prevalence rates were slightly higher (62% on average) than the seroprevalence rates (50% on average), and tissue cysts located in the vestibulum vaginae and sclera were the most frequently detected clinical signs. The proportion of seropositive animals with clinical signs varied from 16.7% to 73.6% among the herds, and 17% of cattle with clinical signs proved to be seronegative by both serological tests. An average 22% serological incidence rate was also reported in addition to clinical incidence rates that varied from 12.5% to 16.7%. Additionally, parasitemia was investigated in the herd that showed the highest clinical and seroprevalence rates. Only one PCR positive blood sample was detected. Thus, the role that blood may play in parasite transmission needs to be further investigated. Infected herds maintained both high prevalence and incidence rates in the absence of control measures and a high number of parasite carriers. Finally, economic impact studies on reproductive and productive losses associated with besnoitiosis need to be performed to implement a cost–benefit control programme.     

Evaluation of Coxiella burnetii Status in Dairy Cattle Herds with Bulk‐tank Milk Positive by ELISA and PCR

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.     

Coxiella burnetii Infections in Small Ruminants and Humans in Switzerland

The recent Q fever epidemic in the Netherlands raised concerns about the potential risk of outbreaks in other European countries. In Switzerland, the prevalence of Q fever in animals and humans has not been studied in recent years. In this study, we describe the current situation with respect to Coxiella (C.) burnetii infections in small ruminants and humans in Switzerland, as a basis for future epidemiological investigations and public health risk assessments. Specific objectives of this cross‐sectional study were to (i) estimate the seroprevalence of C. burnetii in sheep and goats, (ii) quantify the amount of bacteria shed during abortion and (iii) analyse temporal trends in human C. burnetii infections. The seroprevalence of C. burnetii in small ruminants was determined by commercial ELISA from a representative sample of 100 sheep flocks and 72 goat herds. Herd‐level seroprevalence was 5.0% (95% CI: 1.6–11.3) for sheep and 11.1% (95% CI: 4.9–20.7) for goats. Animal‐level seroprevalence was 1.8% (95% CI: 0.8–3.4) for sheep and 3.4% (95% CI: 1.7–6) for goats. The quantification of C. burnetii in 97 ovine and caprine abortion samples by real‐time PCR indicated shedding of >10⁴ bacteria/g in 13.4% of all samples tested. To our knowledge, this is the first study reporting C. burnetii quantities in a large number of small ruminant abortion samples. Annual human Q fever serology data were provided by five major Swiss laboratories. Overall, seroprevalence in humans ranged between 1.7% and 3.5% from 2007 to 2011, and no temporal trends were observed. Interestingly, the two laboratories with significantly higher seroprevalences are located in the regions with the largest goat populations as well as, for one laboratory, with the highest livestock density in Switzerland. However, a direct link between animal and human infection data could not be established in this study.     

Q Fever Dairy Herd Status Determination Based on Serological and Molecular Analysis of Bulk Tank Milk

Ruminants are recognized as the main reservoirs of Coxiella burnetii. EFSA highlighted the lack of knowledge about Q fever prevalence in many European countries. A cross‐sectional study was carried out in randomly selected dairy herds (n = 109) from central Portugal to screen for C. burnetii infection and to correlate it with herd factors. Bulk tank milk (BTM) samples from cattle (n = 45) and small ruminant (n = 64) herds were tested by ELISA and PCR. The apparent seroprevalence of Q fever was estimated in 45.9% (95% CI: 36.3–55.7) being higher in small ruminants (51.6; 95% CI: 39.6–63.4) than in cattle (37.8; 95% CI: 25.1–52.4). The shedding of C. burnetii in BTM was detected in 11.9% (95% CI: 7.1–19.4) of BTM, and it was higher in cattle (20%; 95% CI: 10.9–33.8) than in sheep and mixed herds (6.3%; 95% CI: 2.5–15). A high bacterial load (≥ 3 × 10³ bacteria/ml) was observed in 85% of PCR‐positive BTM. A significant correlation was found between the bacterial load and positive samples on ELISA (P < 0.001). Antibody positivity was significantly associated with the increased herd size (P < 0.01) and the occurrence of abortion (P < 0.05), whereas the shedding of C. burnetii was significantly associated with the report of infertility (P < 0.05). The results highlight that serological and molecular methods in combination are a useful tool to screen for Q fever and to clarify the herd infection status. The shedding of C. burnetii through milk is important, especially in dairy cattle, and thus, the role of milk as a potential source of infection among dairy workers should not be neglected. To our knowledge, this is the first study reporting C. burnetii infection in dairy livestock in Portugal showing that Q fever is significant in dairy herds, leading to economic losses and being a risk for public health, which highlights the need of implementation of control measures.     

Control of Bovine Brucellosis from Persistently Infected Holdings Using RB51 Vaccination with Test‐and‐Slaughter: A Comparative Case Report from a High Incidence Area in Portugal

Bovine brucellosis due to Brucella abortus infection causes significant reproductive and production losses in cattle and is a major zoonosis. Eradication of this disease has proved difficult to achieve in Portugal where it still occurs in some regions despite an ongoing national eradication programme. In 2004, the Alentejo region, a major cattle producing area, reported one of the highest levels of bovine brucellosis in the country, especially in one divisional area. In that area, bovine brucellosis was particularly problematic in a holding of ten herds, the largest extensive cattle unit in the country, which remained infected despite an extensive test‐and‐slaughter programme and depopulation of five herds. A 5‐year programme of RB51 vaccination with biannual test‐and‐slaughter was thus implemented in 2004. The apparent animal seroprevalence decreased from 19% (646/3,400) to 3% (88/2930) on the third herd‐level test and remained below 0.8% (27/3324) after the fourth test. After the tenth test, the holding had a prevalence of 0.1% (2/2332) and only one herd remained positive with a within‐herd prevalence of 1.1% (2/177). The results were compared to all other herds (n = 10) in the divisional area that were also persistently infected but were subject only to test‐and‐slaughter before being depopulated. In these herds, the strategy of test‐and‐slaughter did not reduce the prevalence, which remained significantly higher than the vaccinated group (median = 0.48% and 8.5% in vaccinated versus non‐vaccinated herds; Wilcoxon rank sum test; P < 0.01). The success of this pilot programme in continental Portugal provided a valuable case study to the official veterinary services by illustrating the value of RB51 vaccination with parallel testing and improved biosecurity as a comprehensive and sustainable strategy for bovine brucellosis control in persistently infected herds.