Mirage de tuberculose in the 21st century.

The occurrence of transient culture positivity for Mycobacterium tuberculosis (MTB), known as mirage de tuberculose, poses significant challenges in understanding its spectrum and implications. Here, we report a case of transient culture positivity, oscillating between detectable and non-detectable MTB cultures with minimal radiological features and review the literature on this phenomenon. The scarcity of scientific literature on this subject stems from the inherent impossibility of systematically studying mirage de tuberculose. Ethical and public health concerns prevent withholding treatment to monitor spontaneous reversion to negative cultures. Based on the literature, we estimate that mirage de tuberculose occurs in approximately one-third of individuals infected with MTB who exhibit no symptoms. Despite the inherently limited nature of these findings, they suggest that the significance of mirage de tuberculose may be greater than currently perceived. Managing cases of mirage de tuberculose presents formidable challenges from a public health perspective. Striking a balance between prompt treatment initiation to prevent transmission and the risk of unnecessary treatment requires careful consideration. In conclusion, mirage de tuberculose remains a poorly understood clinical entity with very limited literature available. Advancing research and interdisciplinary collaborations are essential to unravel the intricacies of this phenomenon and develop effective strategies to address its public health challenges.

L'apparition d'une culture transitoire positive pour Mycobacterium tuberculosis (MTB), connue sous le nom de mirage de tuberculose, pose des défis importants dans la compréhension de son spectre et de ses implications. Nous rapportons ici un cas de positivité transitoire des cultures, oscillant entre des cultures MTB détectables et non détectables avec des caractéristiques radiologiques minimales et passons en revue la littérature sur ce phénomène. La rareté de la littérature scientifique sur ce sujet provient de l'impossibilité inhérente d'étudier systématiquement le mirage de tuberculose. Des préoccupations éthiques et de santé publique empêchent l'interruption du traitement pour surveiller le retour spontané à des cultures négatives. Sur la base de la littérature, nous estimons que le mirage de tuberculose survient chez environ un tiers des personnes infectées par le MTB qui ne présentent aucun symptôme. Malgré la nature intrinsèquement limitée de ces résultats, ils suggèrent que l'importance du mirage de tuberculose pourrait être plus grande que ce que l'on perçoit actuellement. La prise en charge des mirages de tuberculose présente des défis considérables du point de vue de la santé publique. Il faut trouver un équilibre entre l'instauration rapide du traitement pour prévenir la transmission et le risque d'un traitement inutile. En conclusion, le mirage de tuberculose reste une entité clinique mal comprise et la littérature disponible est très limitée. L'avancement de la recherche et les collaborations interdisciplinaires sont essentiels pour démêler les subtilités de ce phénomène et élaborer des stratégies efficaces pour relever ses défis en matière de santé publique.

An outbreak of multi-drug-resistant Acinetobacter baumannii on a burns ICU and its control with multi-faceted containment measures.

BACKGROUND: Patients in burns centres are at high risk of acquiring multi-drug-resistant organisms (MDROs) due to the reduced skin barrier and long hospital stay. METHODS: This study reports the investigation and control of an outbreak of MDR Acinetobacter baumannii in a burns centre. The 27 patients hospitalized in the centre during the outbreak were screened regularly, and a total of 132 environmental samples were analysed to identify a potential source. Fourier-transform infra-red (FT-IR) spectroscopy and multi-locus sequence typing were applied to characterize the outbreak strain. RESULTS: Between August and November 2022, the outbreak affected eight patients, with 11 infections and three potentially related fatal outcomes. An interdisciplinary and multi-professional outbreak team implemented a bundle strategy with repetitive admission stops, isolation precaution measures, patient screenings, enhanced cleaning and disinfection, and staff education. FT-IR spectroscopy suggested that the outbreak started from a patient who had been repatriated 1 month previously from a country with high prevalence of MDR A. baumannii. Environmental sampling did not identify a common source. Acquisition of the outbreak strain was associated with a higher percentage of body surface area with burn lesions ≥2a [per percent increase: odds ratio (OR) 1.05, 95% confidence interval (CI) 0.99-1.12; P=0.09], and inversely associated with a higher nurse-to-patient ratio (per 0.1 increase: OR 0.34, 95% CI 0.10-1.12; P=0.06). CONCLUSIONS: Burn patients with a higher percentage of body surface area with burn lesions ≥2a are at high risk of colonization and infection due to MDROs, particularly during periods of high workload. A multi-faceted containment strategy can successfully control outbreaks due to MDR A. baumannii in a burns centre.

An intensive care unit outbreak with multi-drug-resistant Pseudomonas aeruginosa - spotlight on sinks.

BACKGROUND: Pseudomonas aeruginosa and other Gram-negative bacteria have the ability to persist in moist environments in healthcare settings, but their spread from these areas can result in outbreaks of healthcare-associated infections. METHODS: This study reports the investigation and containment of a multi-drug-resistant P. aeruginosa outbreak in three intensive care units of a Swiss university hospital. In total, 255 patients and 276 environmental samples were screened for the multi-drug-resistant P. aeruginosa outbreak strain. The environmental sampling and molecular characterization of patient and environmental strains, and control strategies implemented, including waterless patient care, are described. RESULTS: Between March and November 2019, the outbreak affected 29 patients. Environmental sampling detected the outbreak strain in nine samples of sink siphons of three different intensive care units with a common water sewage system, and on one gastroscope. Three weeks after replacement of the sink siphons, the outbreak strain re-grew in siphon-derived samples and newly affected patients were identified. The outbreak ceased after removal of all sinks in the proximity of patients and in medication preparation areas, and minimization of tap water use. Multi-locus sequence typing indicated clonality (sequence type 316) in 28/29 patient isolates and all 10 environmental samples. CONCLUSIONS: Sink removal combined with the introduction of waterless patient care terminated the multi-drug-resistant P. aeruginosa outbreak. Sinks in intensive care units may pose a risk for point source outbreaks with P. aeruginosa and other bacteria persisting in moist environments.

Longitudinal increase in the detection rate of Mycobacterium chimaera in heater-cooler device-derived water samples.

BACKGROUND: Colonization with Mycobacterium chimaera and other non-tuberculous mycobacteria (NTM) has been reported for heater-cooler devices (HCDs) produced by several manufacturers. Up until now, exclusively LivaNova (London, UK) HCDs have been associated with M. chimaera infections after cardiac surgery. The vast majority of studies on HCD colonization were cross-sectional. AIM: We were interested in longitudinal dynamics of mycobacterial growth in HCD water samples and analysed data of a prospective mycobacterial surveillance of five LivaNova 3T HCDs. METHODS: Five LivaNova HCDs were subjected to prospective mycobacterial surveillance. For each HCD and the total of HCDs, results of mycobacterial detection were analyzed. Logistic regression was applied to model the association between growth of any NTM or M. chimaera and duration of HCD use. RESULTS: Non-tuberculous mycobacteria were isolated in 319 (48.0%, 21 water samples grew more than one mycobacterial species) of a total of 665 water samples. The most frequently detected species were M. chimaera (N = 247/319, 77.4%), Mycobacterium gordonae (46/319, 14.4%) and Mycobacterium paragordonae (34/319, 10.7%). Detection rates increased prospectively for any NTM (odds ratio (OR) per year in use: 1.60, 95% confidence interval (CI) 1.17-2.24, P<0.001) and for M. chimaera (OR per year in use: 1.67, 95% CI 1.11-2.57, P<0.01). CONCLUSION: Longer duration of HCD use was associated with higher detection rates for any NTM and M. chimaera, respectively.

Surgical site infections after simultaneous pancreas kidney and pancreas transplantation in the Swiss Transplant Cohort Study.

BACKGROUND: Among hospital-acquired infections, surgical site infections (SSIs) are frequent. SSI in the early post-transplant course poses a relevant threat to transplant recipients. AIM: To determine incidence, risk factors for SSI and its association with post-transplant outcomes and pancreas transplant (P-Tx) recipients. METHODS: Adult simultaneous kidney-pancreas transplantation (SPK-T) and P-Tx recipients with a follow-up of at least 90 days were identified in the Swiss Transplant Cohort Study (STCS) dataset. Except for the categorization of SSIs according to Centers for Disease Control and Prevention (CDC) criteria, all other data were prospectively collected. Risk factors for SSI were investigated with logistic regression. A Weibull accelerated failure-time model was applied to address the impact of SSI on length of stay, correcting for transplant-related complications and delayed graft function. FINDINGS: Of 130 transplant recipients, 108 SPK-Tx and 22 P-Tx, 18 (14%) individuals developed SSI within the first 90 days after transplantation. Deep incisional (seven, 38.9%) and organ/space infections (eight, 44.4%) predominated. In the majority of SSIs (11, 61.1%; two SSIs with simultaneous identification of fungal pathogens) bacteria were detected with Enterococcus spp. being most frequent. The median duration of hospitalization after transplantation was significantly longer in recipients with SSI (median: 26 days; interquartile range (IQR): 19-44) than in patients without SSI (median: 17 days; IQR: 12-25; P = 0.002). In multivariate analysis, SSI was significantly associated with increased length of stay and prolonged the duration of hospitalization by 36% (95% confidence interval: 4-79). CONCLUSION: SSI after SPK-Tx and P-Tx occurred at a frequency of 14%. Among pathogens, Enterococcus spp. predominated. SSI was independently associated with a longer hospitalization after transplantation.

Implementation of daily chlorhexidine bathing in intensive care units for reduction of central line-associated bloodstream infections.

BACKGROUND: Daily chlorhexidine bathing has been associated with a reduction in central line-associated bloodstream infections (CLABSI). In the setting of an already established CLABSI surveillance system and an implemented CLABSI prevention bundle, we analysed the effect of daily chlorhexidine bathing in ICU patients on CLABSI incidence and its causative pathogens. METHODS: This was a before-and-after study in intensive care units (ICUs) at a tertiary-care centre in Switzerland. Prospective surveillance of CLABSIs and their aetiologies was established. The intervention consisted of daily chlorhexidine bathing of ICU patients with a central venous catheter. A baseline period of 19 months was followed by an intervention period of 9 months. FINDINGS: A total of 5008 patients were included. In the baseline period a mean CLABSI rate of 2.45/1000 catheter days (95% confidence interval (CI) 1.93-3.07) was observed, followed by 1.00/1000 catheter days (95% CI 0.55-1.67; P<0.001) in the intervention period. Introduction of chlorhexidine bathing was independently associated with a reduced risk of CLABSI (adjusted odds ratio 0.47, 95% CI 0.26-0.84, P=0.011). We did not observe a significant change in aetiology except for an increase of Serratia marcescens in the intervention period. CONCLUSIONS: Introduction of daily chlorhexidine bathing resulted in a decline in CLABSI incidence on ICUs. Starting from a baseline CLABSI rate that can be considered standard in a high-income setting and several measures for CLABSI prevention implemented, chlorhexidine bathing proved helpful for a further reduction.

Diversity of nontuberculous mycobacteria in Heater-Cooler Devices - results from prospective surveillance.

OBJECTIVE: The international outbreak of cardiac surgery-associated Mycobacterium chimaera infections was traced back to infectious aerosols originating from contaminated water reservoirs of heater-cooler devices (HCD). In general, nontuberculous mycobacteria (NTM) frequently colonize water systems and can contaminate medical devices. Data on detection of NTM other than M. chimaera in samples gathered from HCDs are scarce. The present study summarizes prospective mycobacterial surveillance of five HCDs over more than four years. METHODS: A cohort of five, in 2014 factory-new acquired, LivaNova 3T (London, UK) HCDs were prospectively followed. Until mid-April 2014 HCDs were maintained according to the manufacturer's recommendations, subsequently according to an intensified in-house protocol including exhaust air evacuation. Mycobacterial surveillance cultures consisted of monthly water samples gathered from patient and cardioplegia circuits, as well as airflow samples. RESULTS: Out of 441 water samples, 170 (38.6%) revealed NTM growth. The most frequently detected NTM were Mycobacterium chimaera (n=120 (67.4%)), Mycobacterium gordonae (n=35 (19.7 %)), and Mycobacterium paragordonae (n=17 (9.6%)). Growth of NTM, M. chimaera and M. paragordonae was significantly more common in water samples derived from the patient than the cardioplegia circuit of the HCD. Three (2.0%) out of 150 air samples grew NTM. CONCLUSION: Growth of NTM in HCD water samples was frequent. Diverse NTM species were detected, with M. chimaera being most common. The majority of air samples remained negative. The relevance of NTM other than M. chimaera contaminating HCDs is poorly defined, but a recent report on a HCD-associated outbreak with Mycobacterium abscessus confirms a potential threat.

International Society of Cardiovascular Infectious Diseases Guidelines for the Diagnosis, Treatment and Prevention of Disseminated Mycobacterium chimaera Infection Following Cardiac Surgery with Cardiopulmonary Bypass.

Mycobacterial infection-related morbidity and mortality in patients following cardiopulmonary bypass surgery is high and there is a growing need for a consensus-based expert opinion to provide international guidance for diagnosing, preventing and treating in these patients. In this document the International Society for Cardiovascular Infectious Diseases (ISCVID) covers aspects of prevention (field of hospital epidemiology), clinical management (infectious disease specialists, cardiac surgeons, ophthalmologists, others), laboratory diagnostics (microbiologists, molecular diagnostics), device management (perfusionists, cardiac surgeons) and public health aspects.

Development and validation of a semi-automated surveillance system-lowering the fruit for non-ventilator-associated hospital-acquired pneumonia (nvHAP) prevention.

OBJECTIVES: Conducting manual surveillance of non-ventilator-associated hospital-acquired pneumonia (nvHAP) using ECDC (European Centre for Disease Prevention and Control) surveillance criteria is very resource intensive. We developed and validated a semi-automated surveillance system for nvHAP, and describe nvHAP incidence and aetiology at our hospital. METHODS: We applied an automated classification algorithm mirroring ECDC definition criteria to distinguish patients 'not at risk' from patients 'at risk' for suffering from nvHAP. 'At risk'-patients were manually screened for nvHAP. For validation, we applied the reference standard of full manual evaluation to three validation samples comprising 2091 patients. RESULTS: Among the 39 519 University Hospital Zurich inpatient discharges in 2017, the algorithm identified 2454 'at-risk' patients, reducing the number of medical records to be manually screened by 93.8%. From this subset, nvHAP was identified in 251 patients (0.64%, 95%CI: 0.57-0.73). Sensitivity, negative predictive value, and accuracy of semi-automated surveillance versus full manual surveillance were lowest in the validation sample consisting of patients with HAP according to the International Classification of Diseases (ICD-10) discharge diagnostic codes, with 97.5% (CI: 93.7-99.3%), 99.2% (CI: 97.9-99.8%), and 99.4% (CI: 98.4-99.8%), respectively. The overall incidence rate of nvHAP was 0.83/1000 patient days (95%CI: 0.73-0.94), with highest rates in haematology/oncology, cardiac and thoracic surgery, and internal medicine including subspecialties. CONCLUSIONS: The semi-automated surveillance demonstrated a very high sensitivity, negative predictive value, and accuracy. This approach significantly reduces manual surveillance workload, thus making continuous nvHAP surveillance feasible as a pivotal element for successful prevention efforts.

Accuracy of Sensititre YeastOne echinocandins epidemiological cut-off values for identification of FKS mutant Candida albicans and Candida glabrata: a ten year national survey of the Fungal Infection Network of Switzerland (FUNGINOS).

OBJECTIVES: Echinocandins represent the first-line treatment of candidaemia. Acquired echinocandin resistance is mainly observed among Candida albicans and Candida glabrata and is associated with FKS hotspot mutations. The commercial Sensititre YeastOne™ (SYO) kit is widely used for antifungal susceptibility testing, but interpretive clinical breakpoints are not well defined. We determined echinocandins epidemiological cut-off values (ECV) for C. albicans/glabrata tested by SYO and assessed their ability to identify FKS mutants in a national survey of candidaemia. METHODS: Bloodstream isolates of C. albicans and C. glabrata were collected in 25 Swiss hospitals from 2004 to 2013 and tested by SYO. FKS hotspot sequencing was performed for isolates with an MIC≥ECV for any echinocandin. RESULTS: In all, 1277 C. albicans and 347 C. glabrata were included. ECV 97.5% of caspofungin, anidulafungin and micafungin were 0.12, 0.06 and 0.03 µg/mL for C. albicans, and 0.25, 0.12 and 0.03 µg/mL for C. glabrata, respectively. FKS hotspot sequencing was performed for 70 isolates. No mutation was found in the 52 'limit wild-type' isolates (MIC=ECV for at least one echinocandin). Among the 18 'non-wild-type' isolates (MIC>ECV for at least one echinocandin), FKS mutations were recovered in the only two isolates with MIC>ECV for all three echinocandins, but not in those exhibiting a 'non-wild-type' phenotype for only one or two echinocandins. CONCLUSION: This 10-year nationwide survey showed that the rate of echinocandin resistance among C. albicans and C. glabrata remains low in Switzerland despite increased echinocandin use. SYO-ECV could discriminate FKS mutants from wild-type isolates tested by SYO in this population.

Detection limit of Mycobacterium chimaera in water samples for monitoring medical device safety: insights from a pilot experimental series.

BACKGROUND: A growing number of Mycobacterium chimaera infections after cardiosurgery have been reported by several countries. These potentially fatal infections were traced back to contaminated heater-cooler devices (HCDs), which use water as a heat transfer medium. Aerosolization of water contaminated with M. chimaera from HCDs enables airborne transmission to patients undergoing open chest surgery. Infection control teams test HCD water samples for mycobacterial growth to guide preventive measures. The detection limit of M. chimaera in water samples, however, has not previously been investigated. AIM: To determine the detection limit of M. chimaera in water samples using laboratory-based serial dilution tests. METHODS: An M. chimaera strain representative of the international cardiosurgery-associated M. chimaera outbreak was used to generate a logarithmic dilution series. Two different water volumes, 50 and 1000mL, were inoculated, and, after identical processing (centrifugation, decantation, and decontamination), seeded on mycobacteria growth indicator tube (MGIT) and Middlebrook 7H11 solid media. FINDINGS: MGIT consistently showed a lower detection limit than 7H11 solid media, corresponding to a detection limit of ≥1.44 × 104cfu/mL for 50mL and ≥2.4cfu/mL for 1000mL water samples. Solid media failed to detect M. chimaera in 50mL water samples. CONCLUSION: Depending on water volume and culture method, major differences exist in the detection limit of M. chimaera. In terms of sensitivity, 1000mL water samples in MGIT media performed best. Our results have important implications for infection prevention and control strategies in mitigation of the M. chimaera outbreak and healthcare water safety in general.

Comparative efficacy of the Leucofeligen™ FeLV/RCP and Purevax™ RCP FeLV vaccines against infection with circulating feline Calicivirus.

BACKGROUND: Feline calicivirus (FCV) is a common virus, found worldwide, mainly responsible for chronic ulceroproliferative faucitis and periodontitis. This virus has a high mutation rate, leading to the presence of numerous FCV strains in the field. The objectives of this study was to evaluate and compare the efficacy of two vaccines (Leucofeligen™ FeLV/RCP and Purevax™ RCP FeLV), which differ by their nature (live vs. inactivated) and the vaccinal strains, against circulating FCV strains. Thirty 9-week-old specific pathogen free (SPF) kittens were thus randomised into 3 groups and were either not vaccinated (control) or vaccinated (2 injections, 3 weeks apart) with one of the vaccines. Four weeks after the second injection of primary vaccination, the cats were inoculated with a pathogenic strain representative of the ones circulating in Europe (FCV-FR4_01) and followed for 2 weeks. RESULTS: After challenge, significant differences (p < 0.05) between control cats and cats vaccinated with Leucofeligen™ FeLV/RCP or Purevax™ RCP FeLV were observed for body weight variation, rectal temperature rise and maximum clinical scores, reflecting the intensity of the signs (83% and 67% lower in the respective vaccinated groups than in the control group). Significant differences were observed between the vaccinated groups, as cats vaccinated with Leucofeligen™ FeLV/RCP had a lower temperature rise (p < 0.05 at days post-challenge 3 to 5) and lower virus shedding titres (p < 0.05 at days post-challenge 8, 9 and 11) than cats vaccinated with Purevax™ RCP FeLV. Finally, only cats vaccinated with Leucofeligen™ FeLV/RCP had a significantly lower cumulative score, reflecting the intensity and duration of calicivirosis clinical signs, than the control cats (77% lower vs. 62% lower for cats vaccinated with Purevax™ RCP FeLV). CONCLUSIONS: Both vaccines, Leucofeligen™ FeLV/RCP and Purevax™ RCP FeLV, were found to be efficacious in reducing clinical signs induced by FCV-FR4_01, a FCV strain representative of the circulating ones. However, cats vaccinated with Leucofeligen™ FeLV/RCP were able to control the infection more efficiently than those vaccinated with Purevax™ RCP FeLV, as evidenced by the shorter duration of clinical signs and lower viral titre in excretions.

Microoptical array projectors for free-form screen applications.

The system design of front-projection systems for free-form screens utilizing conventional single-aperture optical layouts always requires a trade-off between system complexity and achievable luminous output. This article presents novel slide pre-processing algorithms based on array projection technology that are able to resolve the design drawbacks for both free-form as well as strongly-inclined planar screen applications by breaking the common contradiction between system simplicity and flux. Starting from describing common design strategies and their drawbacks, the theoretical basics of the novel concept are investigated and applied to raytracing simulations. Experimental results are shown and evaluated regarding their optical performance.

Cartesian oval representation of freeform optics in illumination systems.

The geometrical method for constructing optical surfaces for illumination purpose developed by Oliker and co-workers [Trends in Nonlinear Analysis (Springer, 2003)] is generalized in order to obtain freeform designs in arbitrary optical systems. The freeform is created by a set of primitive surface elements, which are generalized Cartesian ovals adapted to the given optical system. Those primitives are determined by Hamiltonian theory of ray optics. The potential of this approach is demonstrated by some examples, e.g., freeform lenses with collimating front elements.

High mortality rate associated with bovine respiratory syncytial virus (BRSV) infection in Belgian white blue calves previously vaccinated with an inactivated BRSV vaccine.

In a group of 60 Belgian White Blue calves less than 8 months old still housed in barns, a bovine respiratory syncytial virus (BRSV) outbreak was revealed on the basis of a direct diagnosis (immunofluorescence and virus isolation) performed on the lungs of dead animals, and the kinetics of BRSV neutralizing antibodies. Clinical signs, macroscopical and microscopical pulmonary lesions were also compatible with a BRSV infection. This outbreak is peculiar because the 35 oldest calves (204 +/- 29 days old) had been vaccinated 3-4 months before with an inactivated BRSV vaccine and 30% of these animals had died of respiratory distress. While they experienced a mild respiratory symptomatology, no death was recorded among the 25 youngest calves (69 +/- 29 days old) which had been left unvaccinated. Another peculiarity was found at the histological level where a massive infiltration of eosinophils was demonstrated in the pulmonary tissues of the dead animals. Together these data parallel the dramatic story described 30 years ago in children previously vaccinated with a formalin-inactivated human RSV (HRSV) vaccine upon a natural HRSV challenge. This illustrates that an immunopathological phenomenon also takes place after BRSV vaccination in cattle.

Dynamic injury tolerances for long bones of the female upper extremity.

This paper presents the dynamic injury tolerances for the female humerus and forearm derived from dynamic 3-point bending tests using 22 female cadaver upper extremities. Twelve female humeri were tested at an average strain rate of 3.7+/-1.3%/s. The strain rates were chosen to be representative of those observed during upper extremity interaction with frontal and side airbags. The average moment to failure when mass scaled for the 5th centile female was 128+/-19 Nm. Using data from the in situ strain gauges during the drop tests and geometric properties obtained from pretest CT scans, an average dynamic elastic modulus for the female humerus was found to be 24.4+/-3.9 GPa. The injury tolerance for the forearm was determined from 10 female forearms tested at an average strain rate of 3.94+/-2.0%/s. Using 3 matched forearm pairs, it was determined that the forearm is 21% stronger in the supinated position (92+/-5 Nm) versus the pronated position (75+/-7 Nm). Two distinct fracture patterns were seen for the pronated and supinated groups. In the supinated position the average difference in fracture time between the radius and ulna was a negligible 0.4+/-0.3 ms. However, the pronated tests yielded an average difference in fracture time of 3.6+/-1.2 ms, with the ulna breaking before the radius in every test. This trend implies that in the pronated position, the ulna and radius are loaded independently, while in the supinated position the ulna and radius are loaded together as a combined structure. To produce a conservative injury criterion, a total of 7 female forearms were tested in the pronated position, which resulted in the forearm injury criterion of 58+/-12 Nm when scaled for the 5th centile female. It is anticipated that these data will provide injury reference values for the female forearm during driver air bag loading, and the female humerus during side air bag loading.

Prevalence of bovine virus diarrhoea virus infection in Belgian white blue cattle in southern Belgium.

A study was conducted in Southern Belgium to determine the prevalence of bovine viral diarrhoea virus (BVDV) infection in Belgian White Blue herds. Blood samples were taken from 9685 cattle, representing all the stock on 61 farms, by local veterinarians to screen for persistently infected animals and to determine their serological status against BVDV. Some of the herds (42.5%) were selected because of a prior positive diagnosis of BVDV or on the grounds of suspicion of BVD. A capture enzyme-linked immunosorbent assay (ELISA) was used to test for antigen. The prevalence of persistently infected animals was 0.75% overall and 1.46% in the 27 herds with at least one persistently infected animal. The prevalence of seropositive animals was determined with a competitive antibody ELISA and was found to be 65.5% for the animals as a whole but 53.8% for the herds without positively infected animals and 76.6% for the herds with at least one such animal. All the herds contained seropositive animals.